A simple method for computing sprint acceleration kinetics from running velocity data: Replication study with improved design

Abstract

Measuring the ground reaction forces (GRF) underlying sprint acceleration is important to understanding the performance of such a common task. Until recently direct measurements of GRF during sprinting were limited to a few steps per trial, but a simple method (SM) was developed to estimate GRF across an entire acceleration. The SM utilizes displacement-or velocity-time data and basic computations applied to the runner's center of mass and was validated against compiled force plate (FP) measurements; however, this validation used multiple-trials to generate a single acceleration profile, and consequently fatigue and error may have introduced noise into the analyses. In this study, we replicated the original validation by comparing the main sprint kinetics and force-velocity-power variables (e.g. GRF and its horizontal and vertical components, mechanical power output, ratio of horizontal component to resultant GRF) between synchronized FP data from a single sprinting acceleration and SM data derived from running velocity measured with a 100 Hz laser. These analyses were made possible thanks to a newly developed 50-m FP system providing seamless GRF data during a single sprint acceleration. Sixteen trained male sprinters performed two all-out 60-m sprints. We observed good agreement between the two methods for kinetic variables (e.g. grand average bias of 4.71%, range 0.696±0.540-8.26±5.51%), and high inter-trial reliability (grand average standard error of measurement of 2.50% for FP and 2.36% for the SM). This replication study clearly shows that when implemented correctly, this method accurately estimates sprint acceleration kinetics.

Team sport players individual acceleration-speed profile in-situ: a proof of concept in professional football

“…1), which is consistent with the fact that even at the very first steps of a standing or starting-block start, the center of mass velocity raises quickly above 3 m/s within the first step (e.g. Morin et al, 2019;Nagahara et al, 2014). A first linear regression was fitted to these speed-acceleration points (~70 data points depending on the individuals).…”

“…In other words, the AS profile represents the maximal forward acceleration capability of a player (resulting from propulsive force in the direction of running, according to Newtonian laws of motion) over the range of their running velocity spectrum. Conceptually, the information provided by the in-situ AS profile is close to the sprint forcevelocity profile explored during specific testing (linear sprint acceleration from zero to maximal running speed) (Morin et al, 2019;Samozino et al, 2016). The aim of this proof-of-concept study is to present a simple method to derive team sport players individual acceleration-speed profile from global positioning system (GPS) data collected over several training sessions.…”

“…Gold standard methods for ground reaction force measurement during sprint acceleration require instrumented treadmills or track-embedded multiple force plate systems, which is inaccessible to most athletes. For this reason, a simple field method based on position-time data and Newtonian laws of motion applied to the athlete's center of mass has been recently presented (Morin et al, 2019;Samozino et al, 2016). Due to a good ratio between overall validity and the overall reliability and simplicity of the model inputs (i.e.…”

Differences in the Force Velocity Mechanical Profile and the Effectiveness of Force Application During Sprint-Acceleration Between Sprinters and Hurdlers

“…It should be noted, that the female athletes which involved in the current study were in the top national-level, and participated in the finals of the national championships in athletics competitions. Beyond that, the inverse dynamic model used in our study (Samozino et al, 2008(Samozino et al, , 2016Morin et al, 2019) has limitations such as estimating the horizontal aerodynamic drag force from only stature, body mass and a fixed drag coefficient (Arsac and Locatelli, 2002), as well as having the assumption of a quasi-null center of mass vertical acceleration over the sprintacceleration phase. The latter assumption is more pronounced when using starting blocks and less when starting from a threepoint crouching position.…”

“…The Rate of decrease in RF (DRF) computed as the slope of the linear RF-V relationship, as the velocity increases until the end of the acceleration. The parameters derived with this method have been validated compared to force plate measurements and a low absolute bias (≤6%) was found while a high reliability (coefficients of variation (CV) and standard errors of measurement <5%) was observed as well (Samozino et al, 2016;Morin et al, 2019). For the vertical F-V profile, the best trial of each jumping condition was used to determine the components of the mechanical F-V profile (VTC-F 0 .…”