A comparison between common measurement systems for quantifying spatiotemporal variables during the early sprint acceleration phase

There has been increasing interest in new measurement systems that provide instantaneous spatiotemporal data whilst being less expensive and more accessible to practitioners. The aim of this study was to examine the agreement between the OptoJump Next system (OJ), videography and force platform methods for measuring spatiotemporal variables during the acceleration phase of sprinting. Ninety-nine university students completed two maximal 20 metre sprints in which spatiotemporal parameters (contact time [CT], flight time [FT], step length [SL] and step rate) were simultaneously obtained using the OJ system (1000 Hz), videography (200 Hz), and force platforms (1000 Hz). The OJ and video systems showed high agreement for the measurement of step length (bias: 0.003-0.007 m, random error [RE]: 0.057-0.071 m). For temporal parameters, OJ tended to overestimate CT compared to the force platforms (bias: 0.012-0.014 s, RE: 0.009-0.021 s) and also underestimated FT (bias: 0.012-0.013 s, RE: 0.011-0.012 s). Despite the lower sampling rate, videography showed a closer agreement with the force platform for both CT (bias: 0.005-0.010 s, RE: 0.009-0.021 s) and FT (bias: 0.005-0.007 s, RE: 0.008-0.010 s). Although OptoJump next provides instantaneous spatiotemporal parameters, coaches may wish to adjust for the systematic overestimation of CT (0.013 s) and underestimation of FT (0.012 s) in order to obtain sprint spatiotemporal data that aligns to force platforms.