Author(s): WANG, F., ZHANG, Q., GLAISE, P., HAUTIER, C., Institution: UNIVERSITE CLAUDE BERNARD LYON 1, Country: FRANCE, Abstract-ID: 1046

INTRODUCTION:
In modern team sports, the ability to accelerate and decelerate at high intensity is a key factor in determining the outcome of a match. Existing fixed-distance protocols may overlook critical biomechanical adjustments required at different approach velocities, as recent evidence suggests that horizontal deceleration performance is task-specific and highly dependent on the preceding approach distance and velocity [1]. Based on this evidence, the present study aims to investigate the influence of graded approach velocities 70–95% of maximal sprinting speed (MSS) on horizontal deceleration kinetics, focusing on the strategic reorganization of braking mechanics under increasing demand.
METHODS:
Thirty-three collegiate male soccer players performed a preliminary maximal 30-m sprint test to determine MSS and the specific acceleration distances required to reach target velocities (70%, 80%, 85%, 90%, and 95% of MSS). During the deceleration trials, approach velocities were regulated by adjusting the acceleration distance for each participant. Subjects were instructed to accelerate for the prescribed distance and then immediately perform a maximum horizontal deceleration to a complete stop. Approach velocity was monitored in real-time, and trials were accepted only if the speed fell within ± 5% of the target velocity. Raw speed data were captured via radar (46.875 Hz) and processed using custom MATLAB scripts [2]. Data were analyzed using a linear mixed model with Bonferroni corrections.
RESULTS:
As approach velocity increased from 70% to 95% MSS, linear momentum significantly rose by approximately 28% (from 466.41 to 596.85 kg·m/s, p < .001), whereas mean deceleration (DecMean) declined from 4.86 to 4.55 m/s2 (p < .001), and horizontal average braking force (HBFave) decreased from 5.03 to 4.80 N/kg (p = .021). This limitation in braking efficiency compelled subjects to compensate by extending deceleration distance (+3.95 m) and duration (+0.5 s) (p < .001). Phase-specific analysis indicated that early-phase DecMean significantly declined from 4.51 to 4.02 m/s2 (p < .001), whereas the late phase remained stable (5.57 to 5.56 m/s2, p > .05). Similarly, early-phase HBFave decreased by 13% (p < .001) whereas late-phase HBFave stayed unchanged (p > .05).
CONCLUSION:
The results indicate that braking efficiency during maximal deceleration is critically constrained by approach velocity. Specifically, a discrepancy emerged between surging momentum and a significant decline in early-phase mean deceleration, confirming a limitation of braking capacity in the initial phase. Consequently, to dissipate the excessive momentum despite this early inefficiency, participants were forced to adopt a compensatory strategy by prolonging deceleration distance and time. This adjustment may reflect physiological constraints linked to the force-velocity relationship or serves as a protective mechanism to reduce the risk of falling and injury.
References:
1. Philipp et al. 2023
2. Harper et al. 2020