Reliability of the OptoJump Next system for measuring temporal values in elite racewalking

Racewalking is an Olympic event where athletes are not permitted a visible loss of contact, with the result that competitors try to minimise flight times. The accuracy of measurements taken during testing is dependent on valid and reliable systems to determine temporal values. The aim of the study was to compare different methodologies used to measure contact and flight times in overground and treadmill racewalking. Eighteen racewalkers completed overground and instrumented treadmill trials at 5 speeds, during which flight and contact times were measured using the OptoJump Next photocell system (1000 Hz), high-speed videography (500 Hz), and force plates (1000 Hz). Results from OptoJump Next were extracted using 5 settings based on the number of light emitting diodes (LEDs) activated (GaitIn_GaitOut), and annotated as 0_0, 1_1, 2_2, 3_3 and 4_4. Regarding flight time measurements for the overground condition, the 2_2 LED setting had the best 95% confidence interval (95% CI) for Intraclass Correlation Coefficient (ICC) (0.978 – 0.988), the least bias (0.000 s), and the lowest random error (0.008 s). For the treadmill condition, the 0_0 LED setting had the best 95% CI for ICC (0.890 – 0.957), the least bias (0.004 s), and the lowest random error (0.017 s). Although high-speed videography also provided highly reliable results, the equally reliable and quicker availability of results using OptoJump Next is beneficial in laboratory-based testing. Coaches and researches are advised to alter the system’s LED settings as appropriate, and to report these settings with their findings.