Reliability of the spatiotemporal determinants of maximal sprint speed in adolescent boys over single and multiple steps

The purpose of this study was to examine the reliability of the spatiotemporal determinants of maximal sprinting speed in boys over single and multiple steps. Fifty-four adolescent boys (age = 14.1 ± 0.7 years [range = 12.9-15.7 years]; height = 1.63 ± 0.09 m; body mass = 55.3 ± 13.3 kg; -0.31 ± 0.90 age from Peak Height Velocity (PHV) in years; mean ± s) volunteered to complete a 30 m sprint test on 3 occasions over a 2-week period. Speed, step length, step frequency, contact time, and flight time were assessed via an optical measurement system. Speed and step characteristics were obtained from the single-fastest step and average of the 2 and 4 fastest consecutive steps. Pairwise comparison of consecutive trials revealed the coefficient of variation (CV) for speed was greater in 4-step (CV = 7.3 & 7.5%) compared with 2-step (CV = 4.2 & 4.1%) and 1-step (CV = 4.8 & 4.6%) analysis. The CV of step length, step frequency and contact time ranged from 4.8 to 7.5% for 1-step, 3.8-5.0% for 2-step and 4.2-7.5% for 4-step analyses across all trials. An acceptable degree of reliability was achieved for the spatiotemporal and performance variables assessed in this study. Two-step analysis demonstrated the highest degree of reliability for the key spatiotemporal variables, and therefore may be the most suitable approach to monitor the spatiotemporal characteristics of maximal sprint speed in boys.