Volume 4 - 2022 | <a class="ArticleLayoutHeader__info__doi" href="https://doi.org/10.3389/fspor.2022.902521">https://doi.org/10.3389/fspor.2022.902521</a>
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Performance diagnostics of finger strength is very relevant in climbing
The aim of our study was to find modalities for an intermittent finger flexor muscle endurance test that optimize the correlation of test performance with lead climbing performance
Twenty-seven female and 25 male climbers pulled with 60% MVC and a work-to-rest ratio of 7:2 s on a fingerboard until fatigue
were found for women when 9% deviation in the required force and 1 s deviation in the required pulling time was tolerated
the optimum was reached with the same time deviation and a force deviation of 6%
Together with maximum finger strength the repetitions explained 31.5% of the variance of climbing ability in women and 46.3% in men
Consequences from our results are to tolerate at least 7% force deviation for women and 5% for men and to terminate the finger endurance test quickly after the force falls below the threshold
different test devices have been used: Hand dynamometers
specially designed measuring apparatuses and the currently most common rungs or holds
Overview of measurement methods of finger flexor muscle endurance based on sustained isometric contractions
Overview of measurement methods of finger flexor muscle endurance using intermittent isometric contractions
It is a bit of a dilemma to decide when the repetition is not valid anymore
Because when worsening fatigue is being experienced
It seems reasonable to us to look for implementation modalities for frequently used tests that increase the validity of the tests
the main goal of our study was to find out which test termination criteria in intermittent finger flexor muscle endurance tests optimize the correlation of test performance with climbing performance
we wanted to find out how well the optimized endurance test together with the athletes&#x00027; maximum strength predicts lead climbing performance
Seven were left-handed and 45 were right-handed
The experiments were undertaken with the understanding and written consent of each participant
and the study conforms with Declaration of Helsinki
The Ethics Committee of the Augsburg University
approved our research (approval number 20/104
we conducted a maximum finger flexor muscle strength test and an endurance test on a fingerboard
The participants started with a standardized 15-min warm-up consisting of a general warm-up of the involved muscles and a specific warm-up on the fingerboard
They performed 3 series of 5 repetitions of intermittent pulling (7 s pulling
The first two series were performed two-handed
We took the body weight because the maximum force was not known yet
The intermittent pulling within the warm-up served at the same time for familiarization for the following endurance test
2 preparatory trials for the maximum strength test were performed
the athletes were able to pull 51.9 &#x000B1; 11.9 kg
which corresponds to 76.1% &#x000B1; 14.2% of their body weight
Participants could stop the test at any time if they felt uncomfortable or if they could not manage another repetition
the test was terminated by the experimenter as soon as the force exerted by the athlete dropped 10% below the the required force for an extended period longer than 2 s in two consecutive trials
Participant standing on Entralpi&#x000A9; force plate
the recorded data were evaluated retrospectively
To analyze which criterion one should apply in order to obtain the greatest correlation of the test with climbing performance
we calculated bilateral correlations between the lead climbing ability and the number of repetitions for different criteria for a valid repetition
all possible constellations of negative deviation from the required 60% MVC in one-percent increments up to a maximum of 10% undercutting and a deviation from the required pull duration of 7 s in 1-s decrements were considered
only the time within the respective force target zone was taken into account
the time at the beginning of the pulling was not taken into account until the target zone was reached
Lead climbing ability was assessed using the self-reported value on the IRCRA-scale as shown above
To determine both the proportion of endurance and of maximum strength in lead climbing performance
the data met the assumptions for regression analysis
All variables had equal variance and were found to be homoscedastic and normally distributed
The inclusion method was used with the best value from the above endurance test analysis for women and men
and the value of the relative maximum strength
The beta coefficient was consulted as an indicator of the level of influence on climbing performance
Analyses were performed using SPSS software (IBM SPSS
The level of significance was set at &#x003B1; &#x0003C; 0.05 for each procedure
<a href="#T4">Tables 4</a>, <a href="#T5">5</a> show the number of repetitions on the fingerboard for women and men
for different criteria for a repetition to be counted as a valid repetition
the number of repetitions is lower when the criteria are stricter
the number of repetitions is reduced when the period of time over which the force must be applied during the pull is set longer
the number of repetitions is lower if a smaller decrease of force is tolerated
there was little variation in the number of repetitions for the different tolerated decreasaes in pulling time
Considering that the force is mostly built up within the first second at the beginning of the repetition this means that the requirement to pull for 7 s was basically followed quite well by the women
With regard to the tolerated force deviation
it can be seen that the women hardly succeeded in meeting the specified force exactly
they achieved just under 5 repetitions; if 10% deviation was tolerated
Number of repetitions for different criteria of a &#x0201C;valid&#x0201D; repetition in women
Number of repetitions for different criteria of a &#x0201C;valid&#x0201D; repetition in men
the repetition numbers increased even further when more than 3 s of time deviation was tolerated
This means that in some attempts they have just met half of the specified time period of 7 s
almost twice as many repetitions were valid in the men when tolerating 10% force deviation than without any tolerance
the men already achieved almost the same value at 5% tolerated deviation as at 10% tolerated deviation
In <a href="#T6">Table 6</a> the results of the correlations between the lead climbing ability and the number of repetitions are shown for women and for men
Since the number of repetitions hardly differed between the tolerated time deviation of 3 and more seconds
the results for all force conditions and for time deviations up to 3 s are presented
Results of the correlations of the intermittent finger flexor muscle endurance test with lead climbing performance for different tolerated deviations of time and force
irrespective of the tolerated deviation for the pulling time
the correlation became higher the more force deviation was tolerated
a ceiling effect was found at about 8% force deviation for women and about 5% force deviation for men
for the men no matter which criterion one used
the correlation with lead climbing performance was always above 0.50
For the women, test performance did not correlate significantly with climbing performance unless at least a 7% force deviation was tolerated. The highest correlation, R = 0.429, was found for the condition of a tolerance of the pulling time of up to 1 s with a tolerated force deviation of 9%. According to <a href="#B5">Cohen (1988)</a>
a small correlation is found in the women from a force deviation of 3%
the choice of force deviation tolerance was not quite so decisive
Except for the 0% condition all correlations were higher than 0.6 and thus represented a large correlation
the strictest criterion for the pulling time improved their respective correlation
was found for the condition of a tolerated decrease in pulling time of 1 swith a decrease of force of 6%
the correlation between the number of repetitions in the endurance test and lead climbing performance is much higher than in women
This means that endurance is clearly more relevant for men than for women concerning lead climbing performance
lead climbing performance is predicted by almost 70%
whereas in women it is predicted by no more than 50%
The regression analyses revealed that lead performance is additionally strongly influenced by relative maximum strength in women
the R2 for the overall model was 0.315 (adjusted R2 = 0.255)
The beta coefficient of endurance at 9% tolerated force deviation and 1 s deviation in pulling time was 0.388 (P = 0.035)
while the beta coefficient of maximum strength was 0.414 (P = 0.025)
The explained lead climbing performance for men was higher than for women
the beta coefficient of endurance at 6% tolerated force deviation and 1 s deviation in pulling time was 0.682 (P &#x0003C; 0.001)
whereas the beta coefficient of maximum strength was &#x02212;0.003 (P = 0.988)
a very similar correlation value as ours (R = 0.656) was obtained for a similar climbing level of the male participants
They did not consider the number of repetitions
the test was performed with a contraction relief ratio of 8:2 s at 60% MVC
The criterion for the termination of the test was
when the force dropped by more than 10% below the target force for more than 1 s
which is pretty much in line with the recommendations we derive from our results
Comparative results for female participants are not yet available
In the studies on sustained contractions listed above, correlations are sometimes higher (<a href="#B3">Bal&#x000E1;&#x00161; et al., 2012</a>; <a href="#B18">L&#x000F3;pez-Rivera and Gonz&#x000E1;lez-Badillo, 2012</a>), sometimes similar (<a href="#B4">Bergua et al., 2018</a>; <a href="#B23">Michailov et al., 2018</a>; <a href="#B1">Bal&#x000E1;&#x00161; et al., 2021</a>) and sometimes lower (<a href="#B25">Ozimek et al., 2016</a>, <a href="#B24">2017</a>)
as the climbing levels of the test participants vary greatly
one can be quite content if a single test already explains 50&#x02013;70% of the variance in climbing ability
relative grip strength explained more than 50% of lead climbing performance but &#x0003C;30% for men
we can make the following recommendations for intermittent finger flexor muscle endurance testing when using 60% MVC and 7:2 s contraction-rest ratio: For women
we propose to tolerate at least 7% up to 10% force deviation in relation to the predetermined force (significant moderate correlations)
Since women pull fewer kilograms in absolute terms
the test measures not so much endurance as the ability to target the prescribed load very precisely
The highest correlation value was reached for 6%
but all considered deviations showed strong correlations
the threshold could be set to 10% for both genders for user friendliness
leads to a reduced correlation with lead climbing performance
we think that the application of our recommendations can increase the intermittent tests&#x00027; validity with respect to climbing performance and climbing specific endurance
A limitation of the study is that in the intermittent test
participants could choose whether or not to shake their arms during the 2-s rest after each load phase
as this compromises the standard conditions
there were hardly any cases in which the participants did not put their arms down and shake them briefly
so we assume that the influence on the results is not too great
We did not tell the participants in our study that we were applying different criteria retrospectively as to when a repetition was valid
They assumed that they had to pull the given force over the 7 s
we could do it the other way around and give participants different target zones to stay within
we think that in practice it is quite difficult to target an exact force value and therefore it makes sense to prescribe an exact value but to tolerate a certain deviation
further studies could investigate the effects of prescribing different target zones
Further research could also be conducted to further increase the intermittent test&#x00027;s validity
we did not analyze different combinations of contraction and relaxation phases (e.g.
we focused only on the final phase for test termination
One could also consider the initial phase of the test as a criterion for test termination
The only dependent variable we considered in our study was the number of repetitions
rather than time till task failure and force-time integral
This is because our approach of calculating a valid repetition retrospectively makes these values constants rather than variables
these two parameters should also be used as performance criteria
A relatively large number of participants took part in the study
the external validity of the findings can only refer to athletes of the climbing levels included in the study
in our case mainly advanced and intermediate athletes
findings on the validity of performance tests would also be highly desirable
The original contributions presented in the study are included in the article/supplementary materials
further inquiries can be directed to the corresponding author
The studies involving human participants were reviewed and approved by University Augsburg
The patients/participants provided their written informed consent to participate in this study
and SK: conception and preparation of the manuscript
All authors contributed to the article and approved the submitted version
This work was supported by the German Federal Institute for Sport Science under Grant ZMVI4-070705/20-21
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations
Any product that may be evaluated in this article
or claim that may be made by its manufacturer
is not guaranteed or endorsed by the publisher
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Winkler M and K&#x000FC;nzell S (2022) Optimization of an Intermittent Finger Endurance Test for Climbers Regarding Gender and Deviation in Force and Pulling Time
Received: 23 March 2022; Accepted: 29 April 2022; Published: 23 May 2022
Copyright &#x000A9; 2022 Augste, Winkler and K&#x000FC;nzell. This is an open-access article distributed under the terms of the <a rel="license" href="http://creativecommons.org/licenses/by/4.0/" target="_blank">Creative Commons Attribution License (CC BY)</a>
distribution or reproduction in other forums is permitted
provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited
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&#x0002A;Correspondence: Claudia Augste, <a id="encmail">Y2xhdWRpYS5hdWdzdGVAdW5pLWEuZGU=</a>
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Volume 4 - 2022 | <a class="ArticleLayoutHeader__info__doi" href="https://doi.org/10.3389/fspor.2022.790336">https://doi.org/10.3389/fspor.2022.790336</a>
The analysis of the load structure in competitions is essential to develop performance structure models from which sport-specific testing and training protocols can be derived
The aim of this study was to characterize the external load structure of competitive climbing at an international level in the disciplines of speed
and Olympic combined based on video recordings of top athletes
the route was completed by women with a median of 11 moves and by men with 9 moves that required 0.73 and 0.60 s per move
Bouldering competitions are characterized by various bouts of activity with resting periods in between
a median of 3 times in the qualification and semi-final rounds and 4 times in the final round with an average attempt duration of 27.0 s
the load structure is characterized by an average climbing time of 4:09 min and 4:18 min
and reach times of 1.4 s and 1.6 s for women and men
Olympic combined competitions combine all 3 single disciplines starting with speed followed by bouldering and lead and are characterized by high competition loads
and relatively short resting periods in between
be assessed free of repercussion on the athlete&#x00027;s performance and obtained from real competitions
studies investigating the load structure based on external parameters are uncommon in comparison to those that investigate internal parameters
Today&#x00027;s present competition climbing disciplines are speed, lead, bouldering, and Olympic combined (<a href="#B16">International Federation of Sport Climbing, 2020</a>)
representative values of external measured parameters from current competitive climbing on an international level are still missing
The aim of our study was therefore to analyze the external load structure to determine the general characteristics of competitive climbing at an international level in today&#x00027;s present competition climbing disciplines
For the analysis of the discipline-specific load structure
video recordings of international climbing competitions were used
we selected a 2018 World Cup and the 2018 World Championship
one 2018 World Cup was analyzed; for the Olympic combined discipline
The discrepancies regarding the number of analyzed competitions are rooted in the standardization of the route in speed climbing and the rarity of Olympic combined as an international competition format
The analyzed videos were either obtained from the International Federation of Sport Climbing (IFSC) YouTube channel or were the respective competition&#x00027;s own recordings (Casio EXILIM EX-F1 Cameras
Videos were analyzed using Kinovea (Version 0.8.15) software
The variables analyzed were those considered relevant to describing the load structure in each respective discipline
If the athlete reacts to the start signal in less than 0.01s
the measurement device is a so-called starting pad for one foot
which means that it is possible for motor action of the hips to commence before the start signal (negative values) without being considered as false start as long as the foot maintains contact with the starting pad for the required time
Due to the high temporal resolution of the camera (300 Hz)
it was possible to accurately capture the beginning of the movement
For the purpose of measuring the number of actions
an action was determined to be a visible displacement of the limb across the phase of the loss and regaining of contact between holds
Contact times were calculated as the time span between the first contact with the climbing holds or the climbing wall and its complete loss of contact
were calculated as the difference between the loss of contact and the start of the next contact
observation time as the time between the start of the climbing period and the beginning of the first attempt
attempt duration differentiated between successful and not successful attempts and average attempt duration
climbing time per boulder as the sum of attempt durations per boulder
resting time between attempts and resting time between boulders
resting time per boulder as the observation time plus the sum of resting times between attempts
and the ratio of climbing and resting time per boulder
Olympic combined: In the Olympic combined event
athletes compete against each other in the abovementioned single disciplines
athletes compete in all three single disciplines within one competition
the athletes have to do either 1 or 3 runs depending on whether they advance to the next stage or not
the bouldering and lead parts follow the final round format of standard competitions in the disciplines described above
Observation time in each discipline takes place during the resting time between events
The final ranking is determined based on multiplying the athlete&#x00027;s result in each respective discipline
the analysis of the overall duration of the competition and the resting times between the single disciplines was prioritized because it was assumed that the load structure of the single disciplines is similar to the load structure of the single disciplines carried out within the Olympic combined competition
The overall duration of the competition was measured as the time span between the beginning of the first attempt of the first speed run and the end of the lead attempt
The resting time between runs in speed was measured as the time span between the end and the start of the consecutive speed run
the resting time between speed and bouldering as the time span between the end of the last speed attempt and the beginning of the first climbing period in bouldering and
the resting time between bouldering and lead
as the end of the last attempt in bouldering and the beginning of the lead attempt
Further details are described in the respective section of the single disciplines
Subjects were elite athletes competing at international climbing competitions in 2018 and represent the best climbers of the respective competition:
Speed: The 20 fastest runs with available video recordings were analyzed while considering only the 2 fastest runs per athlete
In cases where an athlete completed more than 2 of the 20 fastest runs
runs from the next fastest athlete were selected to enhance variability
The selected runs were scored from 12 women and 14 men athletes
The runs were analyzed regardless of the round of competition
and final round from the World Cup and the final round of the World Championship
the courses of the semi-finalists (each round: 20 per gender)
the courses of the finalists (each final round: 6 per gender) were analyzed
As some athletes participated in the selected rounds of both competitions
video recordings of 20 different female athletes and 24 different male athletes were analyzed
37 attempts from female and 43 attempts from male athletes were analyzed
These data represent 8 attempts per gender in both the semi-final and final rounds of the World Cup (16 attempts in total per gender)
6 attempts per gender from the finals of the World Championship
and those 10 attempts by women and 16 attempts by men in which the route was topped in the qualification round
some athletes participated in both competitions
which means that the attempts were obtained from 12 different female and 25 different male athletes
Olympic combined: Only the final round of the World Championship was analyzed as the qualification round is already covered by studies of the single disciplines
which means that the load structure was obtained from the 6 female and the 6 male finalists
Inter-rater reliability of the analyzed dependent variables used for load structure determination
The inter-rater reliability was very high across all disciplines for almost all of the analyzed parameters. This conclusion can be drawn from the fact that the relative reliability coefficients (ICC) exceeded the 0.81 benchmark in almost all cases, which according to Hopkins (<a href="#B14">Hopkins, 2000</a>) indicates high reliability
where the ICC for the number of actions of the lower extremities was 0.38
This may be due to the fact that the two raters disagreed as to whether short contacts with the wall are a sufficient criterion to rate them as separate actions
standard deviation [SD] = 2.12) and the ICC could be largely influenced by the small number of observations (n = 8)
A general high reliability is in line with existing studies in this field (<a href="#B27">Sch&#x000E4;dle-Schardt, 1998</a>; <a href="#B33">White and Olsen, 2010</a>; <a href="#B1">Arbulu et al., 2015</a>)
This further confirms time-motion analysis as a reliable tool to analyze kinematic parameters in the context of load structure determination
IBM&#x000AE; SPSS&#x000AE; Statistics (<a href="https://scicrunch.org/resolver/RRID:SCR_019096">RRID:SCR_019096</a>
Version 26) was used for all statistical analyses
and therefore statistical tests for analyzing group differences were applied: t-tests to calculate group differences between genders for the assessed independent variables start time
and contact and reach times for upper and lower limbs
Statistical significance was accepted at p &#x0003C; 0.05 level
Due to the dependency of the load structure on route characteristics and climbing style of the athletes
The load structure in speed climbing is determined by two attempts in the qualification round and one attempt in each stage of the final round. Each attempt is characterized by the start time, the number of actions, and the contact and the reach times of the upper and lower limbs. Statistics from those variables are presented in <a href="#T2">Table 2</a>
Statistics of international speed climbing competitions
Group comparison showed significant differences between the load characteristics of women and men for all of the analyzed parameters
longer durations were found in the women&#x00027;s than in the men&#x00027;s category
The structure of bouldering competitions consists of a course of boulders (5 in the qualification round and 4 in the semi-final and final round) which have to be climbed within a fixed time period
the athletes attempted a boulder problem 3 times in the qualification-/semi-final round and 4 times in the final round at a median with an average attempt duration of 27.0 s and an average resting time between attempts of 32.2 s
the resting time between boulders was around 8 min in the qualification-/semi-final round and 22 min in the final round
Details about the load structure in bouldering are presented in <a href="#T3">Table 3</a>
Statistics of international bouldering competitions
and the number of actions at international lead climbing competitions
The average durations of contact and reach times were equal between the left and the right bodyside for both the upper and lower limbs
Reach times of the upper limbs were further subdivided: reaching directly (grabbing only) for the next hold occurred most frequently (54.9%) and lasted up to 1 s in 90.8% of the cases
reaching directly for the next hold occurred either alone or in combination with the other categories
Shaking alone or in combination with other categories (&#x0201C;shaking any&#x0201D;) were occurred in 24.5% of the actions
&#x0201C;clipping any&#x0201D; in 21.3% and &#x0201C;chalking any&#x0201D; in 19.5%
a different frequency distribution pattern of the durations had been found in comparison to &#x0201C;grabbing only&#x0201D; with the majority of the reach times lasting longer than 3 s for &#x0201C;shaking any,&#x0201D; longer than 2 s for &#x0201C;clipping any,&#x0201D; and longer than 5 s for &#x0201C;chalking any.&#x0201D;
Regarding finger grip positions: In the women&#x00027;s category
the crimp grip was applied in 66.5% of the cases and the open hand grip in 33.5% whereas
the crimp and open hand crimp were applied in 36.7 and 63.3% of the cases
The load structure of the final round of Olympic combined is considered apart from that of the single disciplines and is characterized by the resting time between the runs in speed, the resting time between speed and bouldering and between bouldering and lead, and the total duration of the competition. Statistics are presented in <a href="#T5">Table 5</a>
Statistics of international Olympic combined climbing competitions
The median number of actions was varied between 9 and 12 for the upper and the lower limbs
with men carrying out fewer actions than women
These gender-related differences are caused by the fact that men tend to skip hold 7 referring to numbering all holds that include footholds in an ascending order from the ground
This is well known as the so-called &#x0201C;Tomoa Skip.&#x0201D; Higher up
women used hold 18 with their right hand whereas men directly went from hold 14 to 19 skipping hold 18
very low SDs show that the movement sequences of the top athletes are very standardized
Movement speed can be derived from the sum of contact and reach times resulting in an average movement time for the upper and lower limbs of 0.74 and 0.72 s in the women&#x00027;s and 0.62 and 0.59 s for the men&#x00027;s category
Not considering the differentiation between the upper and lower limbs
the average movement time was 0.73 s in the women&#x00027;s and 0.60 s in the men&#x00027;s category
Men carried out fewer actions than women and therefore had to cover a greater distance per action and nonetheless also had significantly shorter contact and reach times
this is hardly surprising given that men and women compete on an identical route despite having different constitutions
who observed a significant reduction in latent reaction time due to time anticipation within a single experiment
The ability to precisely anticipate and appropriately coordinate the movement start may imply a high-performance benefit
In terms of practical application, the recommended number of repetitions for sport-specific testing and training protocols should reflect the median number of actions, which varies from 9 and 12. Furthermore, the movement speed of around 0.73 and 0.6 s for women and men, respectively, serves as an additional training parameter and biometric feedback tool for training control (<a href="#B32">Weakley et al., 2021</a>)
minimizing starting times holds the potential to significantly reduce speed running times
The current study updates and expands existing knowledge due to its relatively large sample size and its analysis of all rounds of current competition bouldering when compared to the study of a national competition by <a href="#B33">White and Olsen (2010)</a> and to the study of World Cups 5 years earlier by <a href="#B21">Medernach et al. (2016)</a>. The comparison of concrete results with the study of <a href="#B21">Medernach et al. (2016)</a>
who analyzed a competition that was held in the same format
shows that in our study women executed fewer attempts (M = 3.2 vs
M = 5.1) but with longer durations (M = 28 s vs
Men executed fewer attempts as well (M = 3.4 vs
M = 4.3) and rested longer in between them (M = 34 s vs
This indicates a trend toward executing fewer but more well-planned attempts while focusing on recovery between them in order to increase success
This underlines the necessity of up-to-date competition analyses in order to map the load structure correctly and help athletes to be prepared in the best way possible
As recovery ability is paramount in bouldering
recovery strategies targeting the different resting times found in bouldering competitions should be developed and practiced
The current study provides valuable insights into the current load structure in competitive lead climbing
Since reaching directly for the next hold (&#x00022;grabbing only&#x0201D;) accounts for only 54.9% of the cases, contact and reach times are highly influenced by the frequencies and durations of shaking, clipping, and chalking of the athletes, which might contribute to the much shorter durations reported above in comparison to the findings of Sch&#x000E4;dle-Schardt (<a href="#B27">Sch&#x000E4;dle-Schardt, 1998</a>) and <a href="#B1">Arbulu et al. (2015)</a>
Short contact and reach times and high climbing speed might positively influence the climbing economy if the route requirements tend to exceed the athlete&#x00027;s critical force (<a href="#B12">Giles et al., 2021</a>) and maintaining a stronger pace throughout the attempt has been shown to be beneficial for competition climbing success (<a href="#B1">Arbulu et al., 2015</a>; <a href="#B19">Kotchenko, 2017</a>)
women had to face difficulties of around 8b in the qualification round and 8b&#x0002B;/8c in the final rounds whereas men faced difficulties of 8b&#x0002B;/8c in the qualification and 8c&#x0002B; in the final rounds
A practical implication, which can be derived from the load structure in lead climbing for performance analysis, for example, is the assessment of climbing-specific intermittent finger endurance. Different test protocols have been used but the ones that are representative of the load structure of current competition climbing should be prioritized (<a href="#B24">Michailov et al., 2018</a>)
this would mean a 6 s work to 2 s rest ratio representing the overall averages of contact and reach times
The combination of all 3 single disciplines within the final round of Olympic combined climbing competitions results in a higher competition load as compared to the single disciplines
The average resting time between the runs in speed climbing was 6:24 min (SD = 1:29)
Minimal and maximal resting times were 3:19 and 8:34 min
This relatively large deviation could be explained by the competition format
The same accounts for the resting times between speed and bouldering and between bouldering and lead
Due to the starting order of the subsequent disciplines being in reverse order with respect to ranking up until this point in the competition
the differences between the minimal and maximal resting times were roughly 13 and 10 min between speed and bouldering and 24 and 21 min between bouldering and lead in the women&#x00027;s and men&#x00027;s category
Given the high competition loads and the relatively short resting times between disciplines
a practical application of this study&#x00027;s result may be that athletes should not only train in a way to maximize performance in the single disciplines but to also handle the required high load
and short resting times of the combined format
Crucial aspects for targeting this are tailored fueling (<a href="#B23">Michael et al., 2019</a>) and recovery strategies
The latter must be highly effective and at the same time require a very limited amount of time
the resting times can only partially be used for recovery due to fact that the observation period of the following discipline (4 times 2 min for bouldering and 6 min for lead)
and other activities take place during this period
Evidence indicates that a few minutes of active recovery either by walking or easy climbing (<a href="#B6">Draper et al., 2006</a>; <a href="#B30">Valenzuela et al., 2015</a>) lead to improved recovery and therefore are considered a tailored recovery strategy. For cold water immersion, in contrast, only durations of 20 min have been evaluated (<a href="#B13">Heyman et al., 2009</a>) while the benefit of shorter periods remains unclear
The main limitation of the current study is the dependency of load structure on route characteristics
These vary greatly from competition to competition and even from boulder/route to boulder/route and therefore it is generally difficult to derive a universally valid load structure
Single influences were reduced by a broader data basis
which was derived from the selection of different routes and courses of competitions from different competitions
the current study is limited in regard to the chosen sample and by virtue of not considering a wider range of competitions
load structure is dependent on an athlete&#x00027;s climbing style
By analyzing the world&#x00027;s best climbers in each discipline
the presented load structure tends to be more valid for high-level athletes who compete at international climbing competitions than for lower level climbers who have different climbing abilities and might not be able to use the same methods (e.g.
the so-called Tomoa skip in speed climbing)
These athletes should therefore use load structures that represent the requirements of their own climbs and climbing abilities
Another limitation arises from the constant development of climbing and route setting styles
which means that the presented load structure based on 2018 competitions does not necessarily represent the requirements of current competitions
This is especially true of the Olympic combined where a new format will be applied in the 2024 Olympic Games
a retrospective approach is an inherent problem of this research area
The raw data supporting the conclusions of this article will be made available by the authors
The studies involving human participants were reviewed and approved by Commitee for Ethics University of Augsburg
Written informed consent from the participants&#x00027; legal guardian/next of kin was not required to participate in this study in accordance with the national legislation and the institutional requirements
All authors conceived of and designed the analysis
MW performed the data and statistical analysis and took lead in writing and editing the manuscript
By providing critical feedback and revising the initial manuscript
CA and SK helped shaped the final manuscript
This study was part of the research project Development of a scientifically based performance diagnostics in sports climbing which was founded by the German Federal Institute of Sport Science (BISp ZMVI4-070707/18-19)
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Received: 06 October 2021; Accepted: 21 February 2022; Published: 22 March 2022
Copyright &#x000A9; 2022 Winkler, K&#x000FC;nzell and Augste. This is an open-access article distributed under the terms of the <a rel="license" href="http://creativecommons.org/licenses/by/4.0/" target="_blank">Creative Commons Attribution License (CC BY)</a>
&#x0002A;Correspondence: Marvin Winkler, <a id="encmail">bWFydmluLndpbmtsZXJAc3BvcnQudW5pLWF1Z3NidXJnLmRl</a>
Biomechanics and Control of Human Movement
Volume 2 - 2020 | <a class="ArticleLayoutHeader__info__doi" href="https://doi.org/10.3389/fspor.2020.559277">https://doi.org/10.3389/fspor.2020.559277</a>
The float serve is an effective weapon to impede the attack of the opposing team
Because of its great importance in indoor and beach volleyball
we measured and quantified the float effect
We recorded 24 float serves of 12 top athletes in beach volleyball and indoor volleyball
We determined the 3D trajectories of the ball flight and developed two measures to describe the size of the float effect
the mean residuals and the anticipation error
These measures suggest that the float effect is greater in the vertical plane than in the horizontal plane
Analyses of ball release velocities suggest that a certain ball release velocity is a necessary
A validation of the float measurements with subjective expert ratings showed a correlation with the horizontal deviations
This study provides a new approach to analyze floating in on-court volleyball serves and broadens the knowledge for float effects in sports
should then be made more difficult and error prone
the effectiveness of float serves in volleyball should be related to distance between the expected and the actual position of the ball during the flight time
the horizontal acceleration changes in a jerky manner at a certain point during the ball flight
A float serve can also lead to an unpredictable path in the vertical direction
perceived as a sudden &#x0201C;falling&#x0201D; of the ball
Prototypical ball trajectories of served balls
All figures are presented from a bird&#x00027;s eye view to depict changes in the lateral direction
(A) Straight serve: The horizontal acceleration is zero
The ball moves with constant velocity in the horizontal plane
(B) Serve with side spin: The horizontal acceleration is constant yet not zero
The ball travels with increasing velocity in the horizontal plane
(C) Float serve: The horizontal acceleration changes unexpectedly at a certain location
initially traveling with a constant velocity in the horizontal plane
experiences sudden accelerations in the horizontal plane
and deviates from the originally straight path (dotted line)
Using an impact-type ball-ejection device, <a href="#B1">Asai et al. (2010)</a> assessed float effects of ball trajectories with ball-flight velocities near the Reynolds number and calculated the deviation of the landing points&#x00027; 2D coordinates of repeated trials as a measure of aerodynamic instability
kinematic data of on-court ball trajectory served by athletes is still lacking
the purpose of the present study is to implement a measurement procedure for quantifying the extent of float of volleyball serves
The main objective is to establish kinematic-based measures by recording and analyzing ball flight curves generated by experienced volleyball players close to competition conditions
The method was applied in beach volleyball as well as in indoor volleyball
as the float serve is a relevant technique in both sports
we test the hypotheses that (1) ball release velocity is a predictor of the extent of floating and (2) that objectively
kinematic-based measures correlate with expert&#x00027;s subjective ratings of the perceived extent of floating of the ball
To quantify the extent of random movement (float effect) in the ball flight trajectories of serves by experienced volleyball players, two studies (beach volleyball, study 1; indoor volleyball, study 2) were carried out. Five young elite beach volleyball players (3 males) and one senior volleyball player (male) participated in study 1. According to a taxonomy suggested by <a href="#B21">Swann et al. (2015)</a>
three of the young players were competitive elite
and the senior was a world-class elite player
Six successful elite indoor volleyball players (all females) participated in study 2
the ball flight paths of 24 float serves were analyzed using video
Each participant performed two series of 12 float serves using his or her individually preferred float serve technique (float serve or jump float serve)
the parameters of the ball flight (ball velocity
and release height) were determined and a measure was calculated that quantifies the unpredictable portion of the movement trajectory
the subjectively perceived floating of the ball was documented from the perspective of the reception player and the coach
The study was not an experimental intervention
data were collected during a usual training session on request of the national coach
The serves were performed at the beginning of the training following a standardized warm-up routine
The participants are voluntary members of the national team and
participate voluntarily in the training session
With regard to the task assigned to the participants (2 &#x000D7; 12 float serves)
we did not see any special requirements from the study that goes beyond the normal training load and that would make a vote by an ethics committee necessary
in research projects with German sports associations (here the German Volleyball Association)
the ethical adequacy for the welfare of the athletes is ensured bilaterally and jointly
Study 1 was carried out on an indoor beach volleyball court at the Olympic training center, Stuttgart, Germany; study 2 took place at the Olympic training center, Berlin, Germany. Set up of the cameras was similar in both studies (see <a href="#F2">Figure 2</a>)
The court dimensions were in accordance with the official volleyball rules (INDOOR: 9 &#x000D7; 18 m; BEACH: 8 &#x000D7; 16 m)
The net heights were 2.24 m for the INDOOR court and 2.35 m for the BEACH court
Officially approved balls were used (INDOOR: MIKASA MVA 200; BEACH: MIKASA Beach-Volleyball-Beach-Champ VLS 200 Micro)
Camera setup and coordinate system from a bird&#x00027;s eye view
The origin of the coordinate system is located in the right corner of the base line of the serving player&#x00027;s court
seen from the server&#x00027;s perspective
five video cameras (Basler Aviator) were used to record the trajectory of the ball flight
the cameras allow a spatial resolution of 1,600 &#x000D7; 400 pixels
which was adequate for reliably digitizing the center of the ball
An additional video camera (camera 6) was placed in a way to record the sagittal motion of the float serve movement
Both indoor courts offered sufficient light conditions allowing short shutter speeds (&#x02264;1/250 s)
For 3D reconstruction of the ball trajectory
a reference system with 32 pass points was used
Reference system was introduced by using a 5-m telescopically extendable leveling rod made from aluminum profiles (NESTLE GmbH
Germany) that was mounted vertically on a tripod on which clearly visible reference points were marked at fixed distances
At a total of eight locations within the capture volume
and then the positions of the reference points relative to the origin were measured using a laser rangefinder (GLM40
Vertical alignment was achieved by means of spirit levels and optical bearing
the leveling rod was carefully adjusted according to the guidance of two observers from two different viewing angles (perpendicular to each other)
who visually controlled for exact alignment of the rod with reference to clearly visible vertical house edges
From each measuring position of the leveling rod
a video frame was captured from each camera perspective
The calibration images needed for each camera were then generated by video overlay (software Gimp 2.6) of the respective video frames
The athletes got together in pairs to participate in the investigation. While one of the two players performed 12 float serves, the other player acted as a rater (R1). Together with the volleyball coach (<a href="#F2">Figure 2</a>, R2), the rater was positioned behind the opposite service line (see <a href="#F2">Figure 2</a>) and rated each float serve of his or her partner
A second coach (R3) was positioned inclined behind the float server and also was asked to evaluate the serves in terms of the magnitude of floating
All participants independently rated the magnitude of the ball floating on a 5-point scale from 0 (&#x0201C;no floating at all&#x0201D;) to 4 (&#x0201C;very strong floating&#x0201D;)
They were instructed to evaluate the &#x0201C;overall impression&#x0201D; of a perceived floating of the ball
The server was instructed to serve within a 3-m-wide area and to hit a target corridor in the rear section of the opposing field (i.e., in x-coordinates between 1.5 and 5.5 m) (see <a href="#F2">Figure 2</a>)
The target corridor was illustrated to the players on a tactical board
but there were no reference lines on the court
Whether or not the players served the ball into the target area was determined afterward based on the 3D coordinates of the ball flight curve
All serves that hit the target corridor were included in the analysis
The synchronized video recordings of the ball flight were triggered by the record stop of the takes
which was handled manually when the ball touched the ground
The last 4 s of the video data prior to the record were stored
Data storage of the six video files at a time took &#x0007E;40 s
the three raters documented their perceived floating of the ball curve
The required time period for data acquisition of a series of 12 float serve per server was &#x0007E;10 min
For the acquisition of the kinematic data of the ball
the 2D coordinates of the center of the ball were manually tracked in the videos of all cameras at each frame
a circular mask was superposed to the video display
using the center of the circular mask as a reference for the center of the ball
These mask completely enframed the ball and
allowed precise determination of the 2D positions of the ball center
Tracking started five frames prior to ball-hand-contact of the serve and was finished five frames after ball-ground contact
the 3D coordinates of a series of float serves are plotted
Representative trajectories of a series of float serves in beach volleyball
Shown are the 3D coordinates of the ball flights from a bird&#x00027;s eye view (above) and from the side view (below)
a nonlinear regression was applied using the function for projectile motion
The fit was done for the 3D ball coordinates projected to the ball flight direction
which is given by the direction from the start to the end position of the ball flight
where g represents gravity and ydir the distance covered by the ball in the flight direction
this would cause an acceleration in the horizontal direction resulting in a curved ball trajectory
we do not compute linear regressions because a continuously curved trajectory is not classified (due to its predictability) as a floating ball
The curvature of such a ball trajectory in the horizontal plane is also best described by a quadratic regression
We computed two measures of the deviation, the mean residuals (x.R) and the spatial distance at the locus of reception (&#x0201C;anticipation error&#x0201D;). In <a href="#F4">Figure 4</a>
both measures are illustrated using a hypothetical data set
It shows a curved ball trajectory (x = 0.005&#x0002A;y2 &#x0002B; 0.3) from a bird&#x00027;s eye view (horizontal plane) without any random movement over the first 7 m (open circles)
we assume that there was no measurement error when capturing the 3D coordinates of the ball flight
Illustration of the floating measures using a hypothetical data set
Flight path without ball floating (open circles) and after the ball receives an additional acceleration (gray circles)
Mean residuals: Ball floating is indicated by a worse fit of the position data of the entire trajectory (solid line)
Mean deviation from the regression line (x.R) is used to quantify the extent of ball floating
Anticipation error (AE): Based on the polynomial regression of the first 7 m of the ball trajectory
the flight path is extrapolated (dash-dotted line) to the (&#x0201C;anticipated&#x0201D;) locus of reception and the horizontal and vertical distance to the actually measured locus of reception is computed
The mean residuals were calculated for the vertical (mR_vertical) and horizontal plane (mR_horizontal) separately
for a &#x0201C;combined&#x0201D; mean residual measure
mR_vertical and mR_horizontal were summed up
The second measure to describe the random proportion of the ball-flight path maps the situation of the reception player
We assume that the player observes the approaching ball for a certain path length and then predicts the (anticipated) locus of reception
We define the locus of reception as the position in space where the ball path enters a plane 70 cm above and parallel to the floor
Based on the polynomial regression of the first 7 m of the ball trajectory
we extrapolate the flight path to the defined (&#x0201C;anticipated&#x0201D;) locus of reception (dash-dotted line)
The horizontal and vertical distance between the point of intersection actually measured and the anticipated locus of reception is the anticipation error
The &#x0201C;combined&#x0201D; anticipation error results from the Euclidean distance between the point of intersection actually measured and the anticipated locus of reception
The interrater reliability of the experts rating the perceived ball floating was examined using the intraclass correlation coefficients (ICC, model: two-way random-effects, type: mean of k raters, definition: consistency). ICC estimates and their 95% confident intervals were calculated (<a href="#B13">Koo and Li, 2016</a>)
The Spearman rank order correlation coefficients were calculated to determine the relationship between the expert rating and the kinematic ball floating measures (mean residuals
A nonparametric statistical measure was used because the ratings are data on an ordinal scale
In order to analyze whether release velocity differs between individual athletes
one-way ANOVAs were calculated separately for INDOOR and BEACH
Bivariate regression analysis was used to establish the strength of the relationship between release velocity and both dependent variables
The statistical significance level was set to p &#x0003C; 0.05
Statistical calculations were run with SPSS 23
six players with 24 serves each) could be analyzed
The remaining serves were either net balls or &#x0201C;out&#x0201D;
In both studies, the magnitude of perceived floating was mostly consistent between the three raters (beach: ICC = 0.71 (CI: 0.60&#x02013;0.80), n = 94; indoor: ICC = 0.79 (CI: 0.70&#x02013;0.86), n = 92). ICC estimates indicate moderate to good reliability. Since average judgments are generally more reliable and valid than individual judgments, sufficient agreement is assumed (<a href="#B3">Bortz and D&#x000F6;ring, 2002</a>)
the average of the three ratings was calculated
Somewhat surprisingly, only few serves were judged as &#x0201C;strongly floating.&#x0201D; In study 1 (beach), just 18 serves (19.1%) were scored in this category; in study 2 (indoor), even less, only 8 out of 92 serves (8.7%). A comparison of the rating results for individual players (see <a href="#T1">Table 1</a>) indicates that the ability to produce a floating ball path differs widely across players
The highest rating with mean = 2.3 points was found in the beach study (participant 1) and the lowest rating with mean = 0.5 points in the indoor study (participant 12)
The mean residuals represent the deviation between the observed ball path and the ball path estimated by a quadratic regression on the horizontal and the vertical plane, respectively. Overall (see <a href="#F5">Figures 5A,B</a>)
the mean residuals in the vertical plane (mR_vertical) are higher than in the horizontal plane (mR_horizontal)
mR_vertical (mean = 3.04 cm) is more than twice as high as mR_horizontal (mean = 1.44 cm)
and for beach volleyball mR_vertical (mean = 2.70 cm) is approximately twice as high as mR_horizontal (mean = 1.46 cm)
(A,B) Mean residuals for each participant of the beach volleyball (left) and indoor volleyball study (right)
Bars are grouped due to deviations in the horizontal (light gray) and vertical (dark gray) planes
Overall, and similar to the mean residual measure, the anticipation error, too, indicates higher floating for the vertical plane compared to the horizontal plane (see <a href="#F6">Figures 6A,B</a>)
the actually measured locus of reception deviates 0.39 m (SD = 0.27 m
indoor) from the &#x0201C;anticipated&#x0201D; locus of reception
The largest measured anticipation error of a single float serve in the vertical plane was 1.50 m (INDOOR
anticipation error was 0.26 m (SD = 0.21 m
the maximum measured anticipation error was 0.99 m (INDOOR
(A,B) Anticipation error for each participant of the beach volleyball (left) and indoor volleyball study (right)
Bars are grouped for horizontal (light gray) and vertical (dark gray) deviations
the ratings were correlated with the &#x0201C;combined&#x0201D; float measures
the mean residuals correlate significantly with the expert rating (rs = 0.238
whereas no correlations were found for the anticipation error
the ratings were correlated with the vertical and horizontal components of the respective dependent measures
Rank correlations of expert rating with mean residuals in the horizontal plane show a moderate relationship for both studies (Spearman-Rho; BEACH: rs = 0.277
no significant correlations were found (BEACH: rs =0.115
a moderate but significant correlation with the expert rating was found for the horizontal plane
Rank correlation of anticipation error with expert rating was rs =0.232 (p = 0.024
no significant correlations were found (BEACH: rs = 0.050
due to the larger court in indoor volleyball
mean release velocities of indoor float serves (x = 17.79 m/s
n = 92) were higher than beach float serves (x = 15.14 m/s
Both indoor and beach volleyball release velocities differed significantly between individual athletes (Beach: F(5/93) = 14.4
there was a notable correlation between release velocity and expert rating in both studies (beach: rs = 0.392
there was no corresponding relationship between release velocity and objective
Regression analysis revealed that release velocity did not predict the extent of floating in the horizontal plane
For both dependent variables (mean residuals
the coefficient of determination was very small (all r2 &#x0003C; 0.033)
a significant effect of release velocity on ball floating was found with more floating related to lower velocities
explained variance was quite low (r2 = 0.126 for mean residuals and r2 = 0.086 for anticipation error)
The aim of the present study is to analyze the kinematics of ball-flight trajectories of volleyball float serves from elite level players and to develop a measure to quantify float effects
we investigated whether the objectively measured float effect also corresponds to the subjective perception of experts
upon performing each serve by every player
the other co-player and the two coaches rated their perceived floating of the ball
Even though there was no complete congruence between the expert raters
there was a high correlation in judging the float effect of float services
Some of the differences between the raters could be due to the slightly different viewing perspectives
only a few serves were rated as heavily floating
and not a single serve was consistently rated as very heavily floating by all three raters
there was a surprisingly low quota (65%) of valid serves
the pressure to produce a heavy float effect and the missing penalization of service errors led the athletes to take a higher risk in serving
we introduce a measure that describes the distance between the actually measured and the anticipated locus of reception
This measure seems appropriate and useful as the random proportion of the ball flight trajectory is expressed as a spatial deviation that is directly linked to the perceptual and motor demands of the reception player
we conclude that the anticipation error is a useful tool to represent the quality of the float serve
since it is associated with the raters&#x00027; perception
Values for single serves up to 1.0 m for the horizontal and up to 1.5 m for the vertical plane illustrate the high demands on fast closed loop corrections of the locus of reception resulting from a successful float serve
Due to the longer indoor court and therefore
to the longer ball path length compared to beach volleyball
anticipation errors are somewhat higher because extrapolation of the flight path on the (&#x0201C;anticipated&#x0201D;) locus of reception was required for longer distances
Whereas the anticipation error quantifies the effect of random movement (floating) on the prediction of the further course of the ball flight path
the mean residual measure quantifies to which extent the ball curve is unpredictable regarding the entire trajectory
float effects expressed as mean residuals are more pronounced in the flight direction compared to the crosswise direction (horizontal plane)
Although the study was designed to capture float effects close to competition conditions
it should be noted that in the BEACH study
a net height was used for organizational reasons that differed slightly from the respective competition heights
not be excluded that the&#x02014;although small&#x02014;deviations from the competition heights have an influence on the execution of the float serves and
we assume that this influence is only marginal
which was conducted at competition net height
the compromise height chosen in the BEACH study did not lead to a lower number of balls actually floating
While we could only demonstrate a correlation between the mean residuals and the subjective ratings when looking at the overall floating effect
an analysis broken down by different planes revealed a significant correlation at the horizontal plane for both INDOOR and BEACH and both floating measures
with no corresponding correlations for the vertical plane
that from the perspectives of the three raters
left/right discrepancies related to the anticipated ball flight trajectory are easier to detect than discrepancies related to the &#x0201C;length&#x0201D; of the ball flight trajectory
The combination of the two plane-specific measures leads to a dilution of the overall correlation between the ratings and the overall measures because the objective floating effect that is added from the vertical plane is not perceived subjectively
The lack of correlation between the expert ratings and the mean residuals in the vertical plane can be explained in two ways
quadratic regression could be erroneous because the flight curve could significantly deviate from a parabola due to drag forces
Although the use of a quadratic regression is a simplification
we believe that it is still suitable for detecting the random deviations due to the float effect
the ball is slowed down by the air resistance during the flight
so the residuals calculated by the quadratic regression are systematically somewhat overestimated
we do not see any alternative to our approach
Modeling drag is very difficult and error prone because of the complex relationships between airspeed
and the constantly changing position of the valve in the ball
a float effect in the vertical plane could be harder to detect from a position far behind the baseline&#x02014;the position from where the experts rated the ball trajectories
Both reasons would lead to lower correlations between objective measures and expert ratings and could have additive effects
unexpected deviations can easier be perceived if the observer is positioned on the field
This has implications for the practice of training
If coaches want to reliably detect the float effect in the vertical direction
We recommend the center of the side line of the receiving team&#x00027;s field as the best position for observing the ball floating in the vertical direction
The release velocities measured in the indoor study are, on average, slightly lower, but of the same order of magnitude as the values reported by Huang and Hu (2007; x = 19.7 m/s, SD = 3.7 m/s). The release velocities are also in accordance with the ones <a href="#B2">Beyer et al. (2013)</a> recommend to enable sudden excursions of the ball&#x00027;s flight (between 15 and 20 m/s)
In order to simulate flight path characteristics and thereby float effects
they conducted a wind tunnel study to gather lift and drag data (on two different models of volleyballs) based on indoor volleyball conditions
how strongly the ball flight curve actually floats
depends to a large extent on the characteristics of further parameters (e.g.
Furthermore, it should be noted that the ball release velocity variation in our study is small. Compared, for example, with the study by <a href="#B10">Huang and Hu (2007)</a> the standard deviation is less than one third
players show a very high repeatability in the execution of the serve movement with regard to an appropriate ball release velocity
if the variable used as predictor (ball release velocity) varies only very little
there can hardly be any covariation in the calculation with the criterion (ball floating)
Similar to our results, standard deviation for landing points of a dimple-type volleyball (Mikasa MVA200) ejected from an impact-type ball ejection device (<a href="#B1">Asai et al., 2010</a>) with an initial speed of 15 m/s was higher in the flight direction (SD = 1.14 m) than for horizontal dispersion (SD = 0.71 m)
compared to the float effects (anticipation error) in our study
they found larger effects in both directions
These differences can be explained by the fact that in our measures
the predictable proportion of the ball trajectory is considered by applying polynomial regressions
3D-coordinates of the ball trajectories are required
What we present here is&#x02014;to the best of our knowledge for the first time&#x02014;data that allow a realistic estimate of the magnitude of the float effect in volleyball
With regard to the relevance for competitive volleyball
it should be emphasized that the analyzed ball flight curves originated from very experienced beach and indoor volleyball players
There is broad consensus in volleyball that the float effect is a performance-relevant phenomenon both in indoor and beach volleyball. The effectiveness of a float serve depends largely on the player hitting the ball in such a way that the release parameters necessary for the float effect are realized. There are practical recommendations on how this can be achieved (<a href="#B7">Czimek, 2017</a>)
there is a lack of evidence as to whether the biomechanical constellations targeted by this technique actually cause the intended float effect and to what extent the respective float effect occurs
the question of the impact of different ball flight parameters on the ball floating can now be investigated
a measurement system can now be developed that provides a reliable and fast measurement of release angle
The precise and reliable control of these parameters is obviously difficult even for highly skilled players
One reason for this may be that the internally available information on the execution of the movement is incomplete or &#x0201C;noisy&#x0201D; due to short contact times
This justifies the need for objective feedback
The effectiveness of the volleyball float serve lies in the fact that the unpredictability of the ball flight trajectory significantly increases the difficulty of its reception
The greater the deviations from the anticipated locus of reception
the greater the corrective movements required
The suggested regression analysis of the ball trajectories has shown to be an adequate approach to capture the complexity of the float effect and allows to calculate objective measures of ball floating
With the mean residual measure and the anticipation error
two different aspects of ball-flight trajectories of float serves from elite volleyball players were analyzed
We could give evidence&#x02014;to our knowledge
for the first time in a setting close to competition&#x02014;that the float effect can cause a significant deviation error
in our study of up to 1.5 m in the vertical and about 1 m in the horizontal direction
All relevant data is contained within the article
The authors declare that all experiments performed in the study do comply with the current laws of Germany
and KZ contributed in the conception and design of the study
SKi organized the database and performed the calculations together with MR
MR and SK&#x000FC; performed the statistical analysis
MR wrote the first draft of the manuscript
The present study was funded by the German Federal Institute of Sport Science (IIA1-070602/11)
We thank the coaching staff and the athletes of the Germany&#x00027;s youth national volleyball team for their help in this project
We thank Heiko Maurer for his helpful advice in the data analysis and Michael Joch for his support in creating the figures
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Received: 05 May 2020; Accepted: 27 August 2020; Published: 06 October 2020
Copyright &#x000A9; 2020 Reiser, Zentgraf, Kindermann and K&#x000FC;nzell. This is an open-access article distributed under the terms of the <a rel="license" href="http://creativecommons.org/licenses/by/4.0/" target="_blank">Creative Commons Attribution License (CC BY)</a>
&#x0002A;Correspondence: Mathias Reiser, <a id="encmail">bWF0aGlhcy5yZWlzZXJAc3BvcnQudW5pLWdpZXNzZW4uZGU=</a>
Volume 8 - 2017 | <a class="ArticleLayoutHeader__info__doi" href="https://doi.org/10.3389/fpsyg.2017.02241">https://doi.org/10.3389/fpsyg.2017.02241</a>
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The goal of this study was to investigate the effect of predictability on dual-task performance in a continuous tracking task
Participants practiced either informed (explicit group) or uninformed (implicit group) about a repeated segment in the curves they had to track
In Experiment 1 participants practices the tracking task only
dual-task performance was assessed after by combining the tracking task with an auditory reaction time task
Results showed both groups learned equally well and tracking performance on a predictable segment in the dual-task condition was better than on random segments
reaction times did not benefit from a predictable tracking segment
To investigate the effect of learning under dual-task situation participants in Experiment 2 practiced the tracking task while simultaneously performing the auditory reaction time task
No learning of the repeated segment could be demonstrated for either group during the training blocks
in contrast to the test-block and retention test
where participants performed better on the repeated segment in both dual-task and single-task conditions
Only the explicit group improved from test-block to retention test
reaction times while tracking a predictable segment were no better than reaction times while tracking a random segment
We concluded that predictability has a positive effect only on the predictable task itself possibly because of a task-shielding mechanism
For dual-task training there seems to be an initial negative effect of explicit instructions
but the advantage of explicit instructions was demonstrated in a retention test
This might be due to the explicit memory system informing or aiding the implicit memory system
When casually observing motor behavior of humans in everyday situations however
it becomes apparent that seemingly successful dual-tasking is a common occurrence: walking down a busy street while talking
or driving a car while listening to the radio for instance
We argue that a key feature of such successful multi-tasking is the predictable nature of at least one of the tasks
for instance going down a familiar set of stairs
and there is no mismatch between expected consequences and results
movements are largely automatic (they occur without awareness or attentional control)
it would be highly disadvantageous if we were aware of every eye movement or postural adjustment
we hypothesize that automaticity and by extension dual-task performance is dependent on the predictability of a task
The role of implicit and explicit knowledge in dual-task performance therefore remains unclear
we would argue that predictability could be a crucial factor in facilitating optimal dual-task performance
and accepting that implicit and explicit knowledge constitute predictability
Therefore we may find reduced learning in Experiment 2 but possibly better performance in dual-task conditions compared to single-task conditions after learning
Participants were 37 university students that were divided into two groups: the implicit group had 20 participants (M = 25.0 years old
SD = 2.2) and the explicit group had 17 participants (M = 25.1 years old
All participants reported normal or corrected-to-normal vision and no reported neurological disorders
All participants gave informed consent prior to the start of the experiment and received remuneration of 20&#x20AC; after completing the experiment
The research was approved by the local ethics committee of the University of Augsburg
We asked participants to sit at a table in front of a joystick (Speedlink Dark Tornado) and a 24&#x2033; computer screen (144 Hz
1920 &#x00D7; 1080 pixel resolution) which were 40 cm apart
The tracking program ran on a Windows 7 computer and data was recorded at 120 Hz
The stimuli of the auditory go/no-go task were delivered via Sennheiser stereo headphones and we recorded responses with a foot pedal (f-pro USB-foot switch
To ensure that tracking performance was not influenced by moving the joystick through the resting zone
which causes an irregularity in resistance
we made sure that the motion required to position the cursor from the upper to the lower edge of the screen fell within the upper half of the range of motion of the joystick on the y-axis
The pursuit tracking task was replicated from <a href="#B21">K&#x00FC;nzell et al. (2016)</a>. Random tracking segments were created from three segments j (left segment), k (middle segment) and l (right segment), with j &#x2260; k, k &#x2260; l, and j &#x2260; l. The formula used to create the segments was taken from <a href="#B46">Wulf and Schmidt (1997)</a>:
A trial consists of two random outer segments and a repeating middle segment connected by interpolated segments
Participants tracked a target that moved along the curves
the curves themselves were not visible during the experiment
The secondary task was an auditory go/no-go reaction time task, similar to studies investigating implicit sequence learning in SRT tasks (e.g., <a href="#B17">Heuer and Schmidtke, 1996</a>)
Participants pressed a pedal for high-pitched tones and ignored low-pitched tones (1086 and 217 Hz
On each trial the number of target sounds was 19 or 20 and the number of distractor sounds varied between 13 and 20
The minimum duration between sounds was 1001 ms and no sounds were placed earlier than 500 ms after the start of the trial or 500 ms before the end of the trial
participants sat at the table and adjusted their seat and pedal
We explained that the cursor and the target moved automatically from left to right along a sinusoidal curve
and the goal was to keep the cursor as accurately as possible on the target by moving the joystick forward and backward (along the x-axis cursor movement was coupled to the target)
Every five trials feedback reflecting average performance of the last five trials appeared on the screen
the implicit group answered a questionnaire to determine how aware they were of the repeated middle segment
The questionnaire contained seven questions designed to gradually probe participants about their knowledge of the repeated middle segment
The questions were: (1) Did you notice anything special during the experiment
(2) Was there something that helped or hindered you while performing the tracking
(4) Did you notice anything special concerning the path of the target
(7) Which segment was the repeated segment
Both pretests were done for familiarization and stimuli were randomized to prevent learning
The break between training blocks was about a minute
the single-task trials with a random middle segment and the dual-task trials were nested within blocks with trials identical to those of the training blocks to minimize fatigue effects
The other 2 &#x00D7; 2 &#x00D7; 2 ANOVA included Condition (single-task vs
The differences in performance between the repeated segment and the outer segments within the dual-task condition were tested using a paired-samples t-test
to test the effect of the tracking on reaction times (RTs) we performed a 2 &#x00D7; 2 analysis of variance (ANOVA) on reaction times
with factors Task (single or dual) and Group (implicit vs
A Greenhouse&#x2013;Geisser correction was used when the assumption of sphericity was violated
Mean root mean square error (RMSE) scores throughout the training blocks
Training blocks 1&#x2013;4 had repeating middle segments while the pre-test had random segments in the middle
An interaction between Condition and Group (implicit vs
explicit) indicated that the difference in performance with a repeating segment in the middle compared to a random segment in the middle was greater for the explicit group than for the implicit group (M = 0.18 cm
Results of the test-block for the implicit and explicit group together
comparing the effect of putting a random segment in the middle and of dual-tasking with a repeating middle segment
To test the effect of dual-tasking we compared the single task Condition with a repeated segment in the middle with the dual-tasking, see Figure <a href="#F4">4</a>
A main effect of Condition (Single-task vs
Dual-task) showed that performance in the dual-task condition deteriorated
A main effect of Segment indicated better performance on the middle segment
and a paired samples t-test revealed that during dual tasking
performance on the repeated segment (M = 1.47
SD = 0.23) was better than on the outer segments [M = 1.59
RTs lower than 200 ms and higher than 1000 ms were discarded
We found a significant main effect of Condition
because RTs were significantly slower in the dual-task condition (M = 558 ms
SD = 58) than in the audio-only pre-test (M = 510 ms
and no Condition &#x00D7; Group interaction was found
In another ANOVA no significant effect of Segment
indicating a repeating tracking segment did not lead to better performance on the reaction time task
We did not find a significant Group &#x00D7; Segment effect
Participants of the implicit group could not verbalize explicit knowledge about the repeated middle segment during the first five probing questions
For question 6 two participants said they noticed a repeating segment but for question 7 only one of them correctly identified the middle one as repeating
where participants were asked to say which segment was repeating even if they did not notice a repeating segment in question 6
The design of the current study does not allow us to determine the contribution of implicit knowledge for the explicit group however
the results of the questionnaire do indicate that during the training and test-block participants were unaware of the repeating middle segment
The design of the current study does not allow for a complete dissociation of implicit and explicit knowledge
therefore it cannot be determined if the positive effect found in the explicit condition in dual-tasking is due to explicit knowledge itself or caused by the implicit learning system being unimpeded by the explicit instructions
who did not find an advantage of a learned repeating sequence in an SRT task on the reaction times of a simultaneous go/no-go auditory task with random tones
Further study is needed but it could be that predictability does not influence the mechanisms that produce dual-task interference
rather it improves dual-task performance by facilitating the predictable task only
it could be argued that motor learning rarely takes place in single-task conditions; there usually are distractions or multiple tasks to be performed in many sports for instance
we now turn to the question what happens with implicit and explicit learning under dual-task conditions
since we didn&#x2019;t find an effect of informing participants about the repeating middle segment for single-task training we need to assess whether this information is beneficial or detrimental in a more demanding learning environment
further clarifying the role of implicit and explicit knowledge
In the second experiment we investigated whether a repeated tracking segment could still be learned under dual-task conditions
depending on whether instructions about the repeating middle segment were given or not
For comparable results we kept the setup and experimental procedure of Experiment 1 but asked participants to perform the training blocks under dual-task condition
The implicit group contained 19 participants (M = 24.0 years old
SD = 2.5) and the explicit group had 20 participants (M = 23.76 years old
All participants had normal or corrected-to-normal vision and no reported neurological disorders
All participants gave informed consent prior to the start of the experiment and received remuneration of 20&#x20AC; or course credit after completing the experiment
task and display were identical to Experiment 1
The procedure of Experiment 2 differed from Experiment 1 in that participants performed the training of the tracking task always together with the auditory reaction time task (see Figure <a href="#F5">5</a> for the complete protocol)
The pre-test included single task and dual-task trials
Participants were asked to try their best on both tasks equally throughout the experiment
Another difference with Experiment 1 is that the training blocks contained 20 trials instead of the 40 trials because we found in a pilot that fatigue played a much larger role in the dual-task training than the single task training
the test-block was expanded to contain both testing under single and dual task conditions
The retention test was exactly the same as the test-block and was added to see if learning was consolidated and test performance without the possibly confounding effect of fatigue resulting from putting the test-block at the end of multiple training blocks
Note that tracking curves in the pre-test did not contain a repeating segment
the single-task and dual-task trials with a random middle segment were nested within blocks with trials with a repeating segment to minimize fatigue effects
we chose the first option and analyzed RMSE scores with a 2 &#x00D7; 2 &#x00D7; 2 &#x00D7; 2 ANOVA with within-subjects factors Test (test-block vs
Dual-task) and between-subjects factor Group (Implicit vs
Similarly we submitted reaction times to a 2 &#x00D7; 2 &#x00D7; 2 ANOVA with within-subjects factors Test
Condition (Repeating segment in the middle vs
To check for the existence of dual-task costs during the test-block and retention test we performed another 2 &#x00D7; 2 &#x00D7; 2 ANOVA with within-subjects factors Test (Test-block vs
Condition (Dual-task with repeating segment in the middle vs
Root mean square error scores for the training blocks
Block 1 and Block 2 were completed on 1 day
Block 3 and Block 4 were completed on another day
The questionnaires revealed that one participant in the implicit group discovered the repeating middle segment
During the training blocks participants improved, F(1.57,58.05) = 7.21, p = 0.003, &#x03B7;p2 = 0.16, and performance on the repeated segment was better than on the random segments, F(1,37) = 11.45, p = 0.002, &#x03B7;p2 = 0.24, but crucially we could not demonstrate an interaction effect between Block and Segment, F(2.19,80.98) &#x003C; 1, p = 0.672, indicating that learning of the repeating segment was not better than learning of the random segments, see Figure <a href="#F6">6</a>
No difference between the implicit and explicit group could be found
In the test-block and retention test, see Figure <a href="#F7">7</a>
we found better tracking of a constant segment
No significant dual-task costs could be found although it almost reached significance
We did not find a significant interaction between Condition (dual-task vs
There was a significant interaction effect of Test and Group (test-block vs
indicating that the explicit group improved from test-block to retention-test while the implicit group did not
Root mean square error scores for the test-block and the retention test performed 1 week later
No difference in reaction times between the repeating segment (M = 538 ms
SD = 69) and random segment was found (M = 538 ms
nor was there a difference between the implicit (M = 531 ms
We did find better performance on the retention-test (M = 527 ms
SD = 66) compared to the test-block performed earlier (M = 557 ms
Dual-task costs were still present at the test-block and retention test when comparing dual-task performance on the repeated segment (M = 538 ms
SD = 69) with single task performance (M = 482 ms
a significant interaction effect between Condition and Group
indicated that the difference in reaction times between Dual-task with a repeating segment and Single-task was greater for the explicit group (M = 76 ms
SE = 8) than the implicit group (M = 39 ms
This raises the question what the content of the learned information was for the explicit group
In the current experiment we cannot say whether the explicit group made use of explicit knowledge or that for them implicit knowledge was also helpful
whereas the interviews clearly prove that the implicit group did not make use of explicit knowledge
the results for the explicit group are consistent with the view that explicit knowledge is helpful for learning but the expression is suppressed during dual-tasking
But the results also concur with the view that only implicit learning occurs under dual-task conditions and that the explicit group in the current study acquired implicit knowledge in addition to the in dual-task situations harmful explicit knowledge
Our results are compatible with both these views since we did not give explicit instructions on how to perform the tracking movements
rather the explicit instructions more likely had the effect of focusing attention to the repeating segment aiding implicit learning
If the strategy during the current experiment was to decouple the tasks there is no reason to assume that predictability of one task influences performance on the other task
The influence the two tasks might have on each other
is exactly what participants learned to avoid
Another explanation is that predictability does not transfer between modalities
in line with the idea of multiple resources
The visual-manual system may not share resources with the auditory-pedal system and a reduction of resource usage for predictability does not help the other system
The finding of both experiments suggests there is a beneficial but limited role of predictability in multitasking performance. Our task differs from the SRT task used in similar investigation but there seems to be converging evidence that in dual-task situations explicit knowledge of a sequence is not as beneficial as implicitly learned movement sequences (<a href="#B17">Heuer and Schmidtke, 1996</a>; <a href="#B14">Frensch et al., 1998</a>)
Although the effect was not statistically significant
our results agree with this: after single-task training both explicitly instructed and implicitly trained participants performed better on predictable segments of the tracking segment whereas after dual-task training
initially only the implicit group demonstrated learning effects in the dual-task condition
when tested again a week later the explicit group demonstrated similar learning effects and a larger overall improvement in performance compared to the implicit group
A possible explanation is that explicit instructions aid implicit motor learning but initially interfere with the expression of knowledge
Another explanation is that explicit instructions fatigued the participants more
the test-block was performed after two training blocks while the retention test was performed on a different day without any training blocks
where each item is always uniquely followed by a certain other item
can be learned in the presence of attentional distraction
whereas sequences that lacked such an item to item connection could not
As such our findings are in agreement with the idea of a non-attentional and an attentional learning system
This study was carried out in accordance with the recommendations of the ethical guidelines of the ethics committee of the University of Augsburg
All subjects gave written informed consent in accordance with the Declaration of Helsinki
The protocol was approved by the Augsburg University
All authors listed have made a substantial
direct and intellectual contribution to the work
This research was supported by a grant within the Priority Program
SPP 1772 from the German Research Foundation [Deutsche Forschungsgemeinschaft (DFG)]
The authors would like to thank Bettina Rathke and Isabella Schedel for helping with data collection
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*Correspondence: Harald E. Ewolds, <a id="encmail">aGFyYWxkLmV3b2xkc0BzcG9ydC51bmktYXVnc2J1cmcuZGU=</a>
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