Abstract
Inertial measurement units (IMUs) fixed to the lower limbs have been reported to provide accurate estimates of stride lengths (SLs) during walking. Due to technical challenges, validation of such estimates in running is generally limited to speeds (well) below 5 m·s−1. However, athletes sprinting at (sub)maximal effort already surpass 5 m·s−1 after a few strides. The present study aimed to develop and validate IMU-derived SLs during maximal linear overground sprints. Recreational athletes (n = 21) completed two sets of three 35 m sprints executed at 60, 80, and 100% of subjective effort, with an IMU on the instep of each shoe. Reference SLs from start to ~30 m were obtained with a series of video cameras. SLs from IMUs were obtained by double integration of horizontal acceleration with a zero-velocity update, corrected for acceleration artefacts at touch-down of the feet. Peak sprint speeds (mean ± SD) reached at the three levels of effort were 7.02 ± 0.80, 7.65 ± 0.77, and 8.42 ± 0.85 m·s−1, respectively. Biases (±Limits of Agreement) of SLs obtained from all participants during sprints at 60, 80, and 100% effort were 0.01% (±6.33%), −0.75% (±6.39%), and −2.51% (±8.54%), respectively. In conclusion, in recreational athletes wearing IMUs tightly fixed to their shoes, stride length can be estimated with reasonable accuracy during maximal linear sprint acceleration.
Highlights
Stride length can be estimated with inertial measurement units (IMUs) attached to the feet
We demonstrated that fairly accurate estimates of SL could be obtained during maximal sprint acceleration [10], but these estimates were indirectly obtained from the IMU-signals by combining the timing of the footfalls with the well-known monoexponential speed increase during sprint acceleration [23]
The results of the present study show that it is possible to derive reasonably accurate estimates of SL during maximal sprint acceleration using foot-mounted IMUs
Summary
Stride length can be estimated with inertial measurement units (IMUs) attached to the feet. SL determines acceleration and maximal speed, which are both important performance determining factors in athletics [5], and in team sports like football [6]. Optimization of SL (and frequency) is of interest to athletes, coaches, and scientists and, it has been measured in many studies on performance [5,7,8,9,10,11,12] and training [13,14,15,16]. Direct determination of SL from IMUs attached to the feet of athletes, similar to what has been done during walking, would be of great practical benefit for training and testing in sports
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