Reliability of Sprint Time and Force-Velocity Profiles During Sprint Acceleration in Elite Rugby Union Players: Inter-Trial Reliability of Linear Encoder, GPS, Timing Gates and Video Analysis.

This study aimed to test the reliability of measurements obtained using different technologies for sprint time and force-velocity profiles during sprint running. Seventeen elite rugby union players completed three experimental sessions, separated by one week. During each session, players completed two 30 m sprints and measurements were performed simultaneously with a linear encoder, a 10 Hz GPS unit, timing gates and video analysis. Split time (5, 10, 15, 20, 25 and 30 m), maximal velocity (VMAX, m·s-1) and force-velocity variables (maximal power, PMAX, W·kg-1; theoretical maximal force, F0, N·kg-1; theoretical maximal velocity, V0, m·s-1; maximal ratio of force, RFMAX, percentage) from the best sprint of each session were computed. Statistical significance was set at p < 0.05 for all analyses. Linear encoder and video analysis showed moderate-to-very-high reliability for sprint time (intraclass correlation coefficient (ICC) = 0.68 to 0.94; standard error of measurement (SEM) = 0.95 to 2.59%), while timing gates showed poor-to-high reliability (ICC = 0.23 to 0.85; SEM = 1.80 to 7.23%). Linear encoder showed very-high reliability for maximal velocity (ICC = 0.94) and force-velocity variables for PMAX (ICC = 0.90), high reliability for V0 (ICC = 0.88) as well as RFMAX (ICC = 0.75), and moderate reliability for F0 (ICC = 0.66). Linear encoder (ICC = 0.66 to 0.94) and video analysis (ICC = 0.50 to 0.94) were the most reliable methods to measure sprint times while linear encoder, due to a higher sampling frequency, was the most reliable to establish the force-velocity profile.