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.