Inertial measurement unit systems (IMU) are increasingly used in sports. However, no algorithm evaluating the instantaneous swimming velocity has been validated on the four swimming strokes, or on dive start. Our objective is to develop and validate a new method to measure instantaneous swimming velocity on athletes presenting various musculoskeletal and neurological impairments and swimming one of the four swimming strokes. Seven Paralympic athletes were involved and performed a total of 18 trials of 50 m in real conditions. All trials were recorded with a 3-axis accelerometer, a tethered device and a video camera. The instantaneous velocity was computed by drift-free integration of the forward acceleration. For all trials, Bland–Altman analyses showed a bias of 0.03–0.06 m.s⁻¹ with the tethered device, with 95% LOA lower than 0.31–0.80 m.s⁻¹, RMSE was 0.14–0.39 m.s⁻¹, and ICC amounted 0.494–0.941. No significant difference was found for the mean 50 m velocities between the accelerometer, the tethered device and the video camera. The results obtained for freestyle were comparable to those obtained with GPS in outdoor pools. Those obtained for backstroke, breaststroke and butterfly were very encouraging. Our method is simple, reliable, advantageous compared to tethered devices, and could be easily used in the field by coaches.

惯性测量单位系统（IMU）越来越多地用于体育运动中。但是，在四个游泳行程或潜水开始时，尚未验证评估瞬时游泳速度的算法。我们的目标是开发和验证一种新方法，该方法可测量出现各种肌肉骨骼和神经功能障碍以及游泳四个泳道之一的运动员的瞬时游泳速度。七名残奥会运动员参与其中，并在真实条件下进行了18次50 m的试验。所有试验均使用3轴加速度计，系留装置和摄像机记录。通过向前加速度的无漂移积分来计算瞬时速度。对于所有试验，Bland–Altman分析显示偏差为0.03–0.06 ms ^-1使用系留装置时，95％的LOA低于0.31-0.80 ms ^-1，RMSE为0.14-0.39 ms ^-1，而ICC为0.494-0.941。加速度计，系留设备和摄像机之间的平均50 m速度没有发现显着差异。自由泳获得的结果与室外游泳池中GPS获得的结果相当。仰泳，蛙泳和蝶泳获得的成绩令人鼓舞。与系留装置相比，我们的方法简单，可靠，具有优势，并且教练可以在野外轻松使用。