Introducing the novel deceleration threshold method: comparative reliability to previous sprint deceleration analysis methods in team-sport athletes

Pre-planned deceleration assessments are vital for profiling team sport athletes as they provide a measure of the athletes' ability to implement effective performance and protection strategies to tolerate the substantial mechanical forces. Although task requirements of these linear assessments are generally consistent, current research employs low sampling technology, which limits the ability to define the deceleration start point and subsequently the reliability. Therefore, this study compared the intra- and inter-day reliability of three deceleration assessment analysis methods: set distance, peak velocity, and the novel deceleration threshold, using a motorized linear encoder device. Ten female and 10 male subjects performed three maximal effort 30 m sprint deceleration trials over two testing days. Each trial was filtered and analyzed using a customized code to calculate key deceleration metrics: distance-to-stop (DTS), time-to-stop (TTS), and average deceleration (DEC_ave) for each analysis method. Intraclass correlation coefficients (ICC) using two-way fixed effect models, coefficients of variation (CV%), and standard errors of measurement (SEM) were calculated to determine the intra-day reliability across all three trials of the first testing day, and inter-day reliability using the: best, average of best two, and average of all trials. The deceleration threshold method using the average of the best two trials from each testing day, exhibited excellent inter-day reliability for the key metrics (TTS: ICC = 0.93, CV% = 6.4; DTS: ICC = 0.97, CV% = 5.3; DEC_ave: ICC = 0.92, CV% = 7.1). To optimize reliability and sensitivity of detecting a meaningful change in sprint deceleration performance practitioners should consider using the average of two best trials analyzed with the deceleration threshold.