Inertial measurement units (IMU) are proven as efficient tools for swimming analysis by overcoming the limits of video-based systems application in aquatic environments. However, coaches still believe in the lack of a reliable and easy-to-use analysis system for swimming. To provide a broad view of swimmers' performance, this paper describes a new macro-micro analysis approach, comprehensive enough to cover a full training session, regardless of the swimming technique. Seventeen national level swimmers (5 females, 12 males, 19.6 ± 2.1 yrs) were equipped with six IMUs and asked to swim 4 × 50 m trials in each swimming technique (i.e., frontcrawl, breaststroke, butterfly, and backstroke) in a 25 m pool, in front of five 2-D cameras (four under water and one over water) for validation. The proposed approach detects swimming bouts, laps, and swimming technique in macro level and swimming phases in micro level on all sensor locations for comparison. Swimming phases are the phases swimmers pass from wall to wall (wall push-off, glide, strokes preparation, swimming, and turn) and micro analysis detects the beginning of each phase. For macro analysis, an overall accuracy range of 0.83–0.98, 0.80–1.00, and 0.83–0.99 were achieved, respectively, for swimming bouts detection, laps detection and swimming technique identification on selected sensor locations, the highest being achieved with sacrum. For micro analysis, we obtained the lowest error mean and standard deviation on sacrum for the beginning of wall-push off, glide and turn (−20 ± 89 ms, 4 ± 100 ms, 23 ± 97 ms, respectively), on shank for the beginning of strokes preparation (0 ± 88 ms) and on wrist for the beginning of swimming (−42 ± 72 ms). Comparing the swimming techniques, sacrum sensor achieves the smallest range of error mean and standard deviation during micro analysis. By using the same macro-micro approach across different swimming techniques, this study shows its efficiency to detect the main events and phases of a training session. Moreover, comparing the results of both macro and micro analyses, sacrum has achieved relatively higher amounts of accuracy and lower mean and standard deviation of error in all swimming techniques.

中文翻译：

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使用 IMU 传感器对主要游泳技术进行游泳分析的新型宏观-微观方法

通过克服基于视频的系统在水生环境中应用的限制，惯性测量单元 (IMU) 被证明是游泳分析的有效工具。然而，教练们仍然认为缺乏可靠且易于使用的游泳分析系统。为了提供游泳运动员表现的广泛视图，本文描述了一种新的宏观微观分析方法，其全面性足以涵盖完整的训练课程，无论游泳技术如何。17 名国家级游泳运动员（5 名女性，12 名男性，19.6 ± 2.1 岁）配备了 6 个 IMU，并要求在 25 m 的游泳技术（即前爬、蛙泳、蝶泳和仰泳）中进行 4 × 50 m 试验池，在五台二维摄像机（四台在水下，一台在水上）前进行验证。所提出的方法检测游泳比赛、圈数、以及所有传感器位置的宏观游泳技术和微观游泳阶段以进行比较。游泳阶段是游泳者从墙到墙的阶段（墙推出、滑行、划水准备、游泳和转身），微观分析检测每个阶段的开始。对于宏观分析，选定传感器位置的游泳回合检测、圈数检测和游泳技术识别的总体精度范围分别为 0.83-0.98、0.80-1.00 和 0.83-0.99，其中骶骨达到最高。对于微观分析，我们获得了推墙、滑行和转弯开始时骶骨的最低误差平均值和标准偏差（分别为-20 ± 89 ms、4 ± 100 ms、23 ± 97 ms），用于开始划水准备 (0 ± 88 ms) 的小腿和用于开始游泳 (-42 ± 72 ms) 的手腕。与游泳技术相比，骶骨传感器在微观分析过程中实现了最小范围的误差均值和标准偏差。通过在不同的游泳技术中使用相同的宏观微观方法，这项研究显示了其检测训练课程主要事件和阶段的效率。此外，比较宏观和微观分析的结果，骶骨在所有游泳技术中都实现了相对较高的准确度和较低的平均误差和标准差。该研究显示了其检测培训课程主要事件和阶段的效率。此外，比较宏观和微观分析的结果，骶骨在所有游泳技术中都实现了相对较高的准确度和较低的平均误差和标准差。该研究显示了其检测培训课程主要事件和阶段的效率。此外，比较宏观和微观分析的结果，骶骨在所有游泳技术中都实现了相对较高的准确度和较低的平均误差和标准差。