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The speed-accuracy trade-off for football kicks

Authors:

Abstract

Introduction: The speed–accuracy trade-off phenomenon is a motor skill response widely observed across human movement; as first described by Fitts (1954). Lees and Nolan (2002) investigated the speed-accuracy trade-off in professional football players kicking a stationary ball in a penalty kick simulation. A significant reduction in ball speed (of 6 m.s-1) was demonstrated when accuracy was emphasised. Accuracy measures, however, were not reported. The aim of this study was to investigate the speed–accuracy trade-off in football free kicks including assessment of both accuracy (radial offset) and ball velocity. Methods: Eight university football players performed 20 accuracy focused and 20 maximal velocity focused kicks. The instep free kicks were taken on a 3G artificial turf pitch from a 16 m distance to the goal-line and placed in front of the centre of the goal. All players wore the same boots, run up was controlled and the target was defined as the extreme top right corner of the goal. A player questionnaire and control recordings of kick type were used to exclude kicks performed with poor technique. TrackMan Football prototype (TrackMan Golf, Vedbaek, Denmark) was used to measure ball velocity. Two synchronised GoPro HERO4 Black camera (GoPro Inc., San Mateo, CA) (240 Hz, 1280x720 pixels) placed parallel and perpendicular to the goal-line were used to measure radial offset from the target as the ball crossed the goal-line. Non-parametric Mann-Witney tests were used to test for differences between accuracy and velocity (normalised to an individual’s maximum) between the accuracy focused and velocity focused kicks (with significance set at p < 0.05). Results: The accuracy focused kicks had significantly lower radial offset distance (2.08 ± 1.06 m vs 2.82 ± 1.39 m; p < 0.001) and percent of maximum velocity (74.4 ± 10.4% vs 93.1 ± 4.4%; p < 0.001) compared to the velocity focused kicks. Discussion: Quantifying the outcome of the speed-accuracy trade-off from an individual performing a free-kick, i.e. focusing on accuracy led to kicks on average being 0.64 ± 0.32 m closer to the target but with a 19.0 ± 5.8% reduction in velocity. This supports future work in this area, for example, to investigate how factors such as football boot design impact the magnitude of this trade-off and to extend the accuracy measurements to consider not just radial offset but also directional offset. This is both interesting and relevant to football boot manufacturers.
The speed-accuracy trade-off for football kicks
Okholm Kryger, K., Mitchell, S., Forrester, S.
Corresponding author:
Katrine Okholm Kryger
The Sports Technology Institute,
The Wolfson School. Mechanical, Electrical and Manufacturing Engineering,
Loughborough University,
Loughborough LE11 3TU,
UK
Telephone number = 01509564808
Email = k.okholm-kryger@lboro.ac.uk
1
ABSTRACT
Introduction:
The speed–accuracy trade-off phenomenon is a motor skill response widely observed across
human movement; as first described by Fitts (1954). Lees and Nolan (2002) investigated the
speed-accuracy trade-off in professional football players kicking a stationary ball in a penalty
kick simulation. A significant reduction in ball speed (of 6 m.s-1) was demonstrated when
accuracy was emphasised. Accuracy measures, however, were not reported. The aim of this
study was to investigate the speed–accuracy trade-off in football free kicks including
assessment of both accuracy (radial offset) and ball velocity.
Methods: Eight university football players performed 20 accuracy focused and 20 maximal
velocity focused kicks. The instep free kicks were taken on a 3G artificial turf pitch from a 16
m distance to the goal-line and placed in front of the centre of the goal. All players wore the
same boots, run up was controlled and the target was defined as the extreme top right corner
of the goal. A player questionnaire and control recordings of kick type were used to exclude
kicks performed with poor technique. TrackMan Football prototype (TrackMan Golf,
Vedbaek, Denmark) was used to measure ball velocity. Two synchronised GoPro HERO4
Black camera (GoPro Inc., San Mateo, CA) (240 Hz, 1280x720 pixels) placed parallel and
perpendicular to the goal-line were used to measure radial offset from the target as the ball
crossed the goal-line. Non-parametric Mann-Witney tests were used to test for differences
between accuracy and velocity (normalised to an individual’s maximum) between the
accuracy focused and velocity focused kicks (with significance set at p < 0.05).
Results: The accuracy focused kicks had significantly lower radial offset distance (2.08 ±
1.06 m vs 2.82 ± 1.39 m; p < 0.001) and percent of maximum velocity (74.4 ± 10.4% vs 93.1
± 4.4%; p < 0.001) compared to the velocity focused kicks.
Discussion: Quantifying the outcome of the speed-accuracy trade-off from an individual
performing a free-kick, i.e. focusing on accuracy led to kicks on average being 0.64 ± 0.32 m
closer to the target but with a 19.0 ± 5.8% reduction in velocity. This supports future work in
this area, for example, to investigate how factors such as football boot design impact the
magnitude of this trade-off and to extend the accuracy measurements to consider not just
radial offset but also directional offset. This is both interesting and relevant to football boot
manufacturers.
2
... The speed-accuracy trade-off theory by Fitts [13] claims that focusing on one of these two parameters will impact the outcome of the other. The speedaccuracy trade-off theory has been demonstrated in football shooting with increased ball velocity leading to decreased ball accuracy and vice versa [14]. Another limitation is how offset was assessed. ...
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Football boots are marketed with a specific performance feature focus, for example, power boots are marketed for optimal shooting performance. However, little evidence exists on the impact of boot design on shooting performance. This study assessed the effect of upper padding on shooting velocity and accuracy using a test-retest reliable test setup. Nine university level football players performed a protocol of shooting to: (1) maximise velocity; and (2) maximise accuracy in football boots with and without upper padding (Poron Memory foam). The protocol was completed twice; the non-padded boot results were used for test-retest validation, while the non-padded versus padding results were used to investigate the effect of padding. Velocity was assessed through actual ball velocity, percentage of maximum velocity and perceived velocity. Accuracy was assessed through radial offset, vertical offset, horizontal offset, success (goal/no goal), zonal offset and perceived accuracy. No significant differences between boots were observed in the velocity measures for either velocity or accuracy focused shots. Significant differences between boots were observed in vertical offset for both accuracy (without padding mean ± standard deviation − 0.02 ± 1.05 m, with padding 0.28 ± 0.87 m, P = 0.029) and velocity (without padding 0.04 ± 1.33 m, with padding 0.38 ± 0.86 m, P = 0.042) focused shots resulting in more missed shots above the goal for the padded boot (without padding 41-43% missed, with padding 56-72% missed). These findings suggest the addition of upper padding has a negative impact on shooting accuracy while not impacting shooting velocity.
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