Sprint performance and mechanical outputs computed with an iPhone app: Comparison with existing reference methods

Abstract

The purpose of this study was to assess validity and reliability of sprint performance outcomes measured with an iPhone application (named: MySprint) and existing field methods (i.e. timing photocells and radar gun). To do this, 12 highly trained male sprinters performed 6 maximal 40-m sprints during a single session which were simultaneously timed using 7 pairs of timing photocells, a radar gun and a newly developed iPhone app based on high-speed video recording. Several split times as well as mechanical outputs computed from the model proposed by Samozino et al. [(2015). A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scandinavian Journal of Medicine & Science in Sports. https://doi.org/10.1111/sms.12490] were then measured by each system, and values were compared for validity and reliability purposes. First, there was an almost perfect correlation between the values of time for each split of the 40-m sprint measured with MySprint and the timing photocells (r = 0.989-0.999, standard error of estimate = 0.007-0.015 s, intraclass correlation coefficient (ICC) = 1.0). Second, almost perfect associations were observed for the maximal theoretical horizontal force (F), the maximal theoretical velocity (V), the maximal power (P) and the mechanical effectiveness (DRF - decrease in the ratio of force over acceleration) measured with the app and the radar gun (r = 0.974-0.999, ICC = 0.987-1.00). Finally, when analysing the performance outputs of the six different sprints of each athlete, almost identical levels of reliability were observed as revealed by the coefficient of variation (MySprint: CV = 0.027-0.14%; reference systems: CV = 0.028-0.11%). Results on the present study showed that sprint performance can be evaluated in a valid and reliable way using a novel iPhone app.

Sprint versus isolated eccentric training: Comparative effects on hamstring architecture and performance in soccer players

“…However, only the sprint comprehensive training provided this potentially preventive stimulus (increase fascicle length), and at the same time induced better sprint performance and mechanical outcomes, which could be considered a practical "win-win" strategy for the management of hamstring injuries. Due to the specificity of sprint training and low cost of testing methods (all variables can now be derived from split times or slow-motion videos with a validated App [54] of the sprints and online free computation spreadsheets (https:// www.researchgate.net/publication/321767606_Spreadsheet_for_Sprint_acceleration_forcevelocity-power_profiling), both players and staff can be more compliant to this type of intervention, compared to previously proposed methods. Finally, based on the current pilot results, further studies should test whether a comprehensive sprint training offers significant injury prevention advantages, as suggested recently [41,42].…”

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

“…Thus, it appears that other types of displacement or velocity-time devices than the laser may be used, provided the almost perfect exponential fitting is verified. For example, previous studies used radar (Cross et al, 2015), photocells (Samozino et al, 2016;Romero-Franco et al, 2017), linear encoders (Cross et al, 2018), or high-speed video (Romero-Franco et al, 2017) after verification of the high-quality of fitting (correlation coefficient >0.99). In addition, this almost perfect fit was observed in loaded sprint conditions (Pantoja et al, 2018;Cross et al 2017b;Cross et al 2018) and for various levels of sprint performance and athletes' age and sex (Pantoja et al, 2016;Slawinski et al, 2017;Nagahara et al, 2017b), which tends to support its general validity to varying athlete's characteristics/levels and with external resistance.…”

Comprehensive mechanical power analysis in sprint running acceleration

“…In recent years, a simpler kinematic approach has been developed for power output computation during accelerated running . It considers the time course of a runner's velocity that can be easily measured by laser‐assisted or other time/gate devices . From the time course of BCoM velocity of our subjects, we also computed the horizontal power as proposed by Samozino et al (a) by fitting the time course of the subject's velocity with a mono‐exponential equation, which was (b) time differentiated to obtain acceleration and (c) by multiplying acceleration and velocity, mass‐specific power was obtained (W kg −1 ), (d) the mean of which was considered as horizontal power ( P horizontal ) and compared with our values (Figure ).…”