Goal: The countermovement jump (CMJ) is commonly used to measure lower-body explosive power. This study evaluates how accurately markerless motion capture (MMC) with a single smartphone can measure bilateral and unilateral CMJ jump height. Methods: First, three repetitions each of bilateral and unilateral CMJ were performed by sixteen healthy adults (mean age: 30.87$\pm$7.24 years; mean BMI: 23.14$\pm$2.55 $kg/m^2$) on force plates and simultaneously captured using optical motion capture (OMC) and one smartphone camera. Next, MMC was performed on the smartphone videos using OpenPose. Then, we evaluated MMC in quantifying jump height using the force plate and OMC as ground truths. Results: MMC quantifies jump heights with ICC between 0.84 and 0.99 without manual segmentation and camera calibration. Conclusions: Our results suggest that using a single smartphone for markerless motion capture is promising. Index Terms - Countermovement jump, Markerless motion capture, Optical motion capture, Jump height. Impact Statement - Countermovement jump height can be accurately quantified using markerless motion capture with a single smartphone, with a simple setup that requires neither camera calibration nor manual segmentation.

翻译：目的：反向运动跳跃（CMJ）常用于测量下肢爆发力。本研究评估了使用单部智能手机进行无标记动作捕捉（MMC）测量双侧和单侧CMJ跳跃高度的准确性。方法：首先，16名健康成年人（平均年龄：30.87±7.24岁；平均BMI：23.14±2.55 kg/m²）在测力台上分别完成三次双侧和单侧CMJ，并同时使用光学动作捕捉（OMC）和一部智能手机摄像头进行记录。随后，利用OpenPose对智能手机视频进行无标记动作捕捉分析。最后，以测力台和OMC为基准，评估MMC量化跳跃高度的性能。结果：无需手动分割和相机标定，MMC量化跳跃高度的组内相关系数（ICC）介于0.84至0.99之间。结论：研究结果表明，使用单部智能手机进行无标记动作捕捉具有良好应用前景。关键词：反向运动跳跃，无标记动作捕捉，光学动作捕捉，跳跃高度。影响声明：通过单部智能手机进行无标记动作捕捉，可在无需相机标定和手动分割的简易设置下，准确量化反向运动跳跃高度。