Reliability of the KiSprint force starting block to evaluate different push-off variables in high-level sprinters

Abstract

This study aimed to determine the within- and between-session reliability of different variables collected during the starting block phase with the KiSprint force starting block and to identify the number of trials that maximise the reliability of the measurement. Thirty high-level sprinters (23 men and 7 women) completed two sessions separated by 1 week. The first session consisted of two sets of five sprints and the second session of one set of five sprints. Outcomes of each set were calculated as Aver3 (average of the first three sprints), Aver5 (average of the five sprints) and CENTRAL (average of the three central sprints). The instrumented sprint starting blocks (KiSprint system) served to record a total of 20 push-off variables. Within-session reliability was acceptable (coefficient of variation (CV)<15%; intraclass correlation coefficient >0.70) for 103 out of 117 comparisons and between-session reliability was acceptable for 60 out of 117 comparisons. Aver5 provided a lower CV (within-session: 4.8% ± 2.9%; between-session: 13.0% ± 6.4%) than Aver3 (within-session: 8.2% ± 6.6% (CV ratio = 1.72); between-session: 14.5% ± 7.1% (CV ratio = 1.11)) and CENTRAL (within-session: 5.3% ± 3.6% (CV ratio = 1.10); between-session: 15.2% ± 9.7% (CV ratio = 1.17)). These results indicate that the KiSprint system can collect several variables with acceptable reliability in high-level sprinters, while the Aver5 procedure is recommended to maximise the reliability of the measurement.