Mahdi Hamidi Rad

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Technical evaluation of swimming performance is an essential factor in preparing elite swimmers for their competitions. Inertial measurement units (IMUs) have attracted much attention recently because they can provide coaches with a detailed analysis of swimmers' performance during training. A coach can obtain a quantitative and objective evaluation from IMU. The purpose of this study was to validate the use of a new phase-based performance assessment with a single IMU worn on the sacrum during training sessions. Sixteen competitive swimmers performed five one-way front crawl trials at their maximum speed wearing an IMU on the sacrum. The coach recorded the lap time for each trial, as it remains the gold standard for swimmer's performance in competition. The measurement was carried out once a week for 10 consecutive weeks to monitor the improvement in the swimmers' performance. Meaningful progress was defined as a time decrease of at least 0.5 s over a 25 m lap. Using validated algorithms, we estimated five goal metrics from the IMU signals representing the swimmer's performance in the swimming phases (wall push-off, glide, stroke preparation, free-swimming) and in the entire lap. The results showed that the goal metrics for free-swimming phase and the entire lap predicted the swimmer's progress well (e.g., accuracy, precision, sensitivity, and specificity of 0.91, 0.89, 0.94, and 0.95 for the lap goal metric, respectively). As the goal metrics for initial phases (wall push-off, glide, stroke preparation) achieved high precision and specificity (& GE;0.79) in progress detection, the coach can use them for swimmers with satisfactory free-swimming phase performance and make further improvements in initial phases. Changes in the values of the goal metrics have been shown to be correlated with changes in lap time when there is meaningful progress. The results of this study show that goal metrics provided by the phase-based performance evaluation with a single IMU can help monitoring swimming progress. Average velocity of the lap can replace traditional lap time measurement, while phase-based goal metrics provide more information about the swimmer's performance in each phase. This evaluation can help the coach quantitatively monitor the swimmer's performance and train them more efficiently.

FRONTIERS MEDIA SA2022

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Swimming coaches provide regular timed and technical feedback to swimmers and guide them efficiently in training sessions. Due to the complexity of swimmers' performance, which is not visible in qualitative observation, quantitative and objective performance evaluation can better assist the coach in this regard. Inertial measurement units (IMUs) are used in swimming for objective performance evaluation. In this study, we propose a new performance evaluation feedback (SmartSwim) using IMU and investigate its effects on the swimmer's weekly progress. Measurements were conducted each week with 15 competitive swimmers for 10 weeks using a Sacrum IMU. The SmartSwim report included a comprehensive representation of performance based on goal metrics of each phase extracted from the IMU signals. The swimmers were divided into two groups: the experimental and control groups. The SmartSwim report for each swimmer in the experimental group was given to the coach, who used it to adjust the training accordingly. The results showed that the experimental group outperformed the control group when comparing each swimmer, each session and the whole sessions. At the level of each individual, more members of the experimental group showed significant downward trend of average lap time (Mann-Kendall trend test, 95% confidence level). While comparing the sessions, the experimental group showed significantly lower lap time than the control group from the sixth session onwards (p-value < 0.05 from t-test). Considering all sessions, the experimental group showed significantly higher progress, lower average lap time, and more consistent records (Mann-Whitney U test at 95% confidence level) than the control group. This study demonstrated that SmartSwim can assist coaching by quantitatively assessing swimmers' performance, leading to more efficient training.

MDPI2022

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As one of the three most popular sports in the Summer Olympics, competitive swimming has always been an attractive subject of study for sports scientists. The intricate nature of the swimmer's movements and the variety of techniques have led coaches to require analysis systems to gain a more detailed understanding of swimmers' performances. Surveys have shown that despite recent technological advances in sports, swimming coaches still need a measurement device that is accessible, easy to use, and provides easy-to-understand results. Conventional analysis systems such as high-resolution cameras, while accurate, are too time-consuming and cumbersome for daily use. With the advent of wearable sensors, especially inertial measurement units (IMU), motion analysis has gained the ability to not only study new aspects of motion, but also cover in-field applications. However, researchers focused primarily on extracting features rather than using them to evaluate performance and provide feedback in the field. Free-swimming is the phase that has been most studied with IMUs, and among the major swimming styles, front crawl has attracted more attention. Therefore, a comprehensive analysis approach based on IMUs covering all swimming styles and phases can provide the swimming community with deeper insight into swimmers' performance and a better solution to training needs. This thesis presents a novel methodology for swimming analysis based on inertial wearable sensors. The proposed method uses a unified macro-micro analysis approach that scans the entire training session for swimming bouts and then narrows down to separating the swimming phases from wall to wall. The method is implemented using the IMU data from different sensor positions on the swimmer's body for comparison. Based on the results of the developed algorithms, sacrum position was determined to be optimal for detecting all swimming phases. As a result, the analysis then detects a set of spatio-temporal and kinematic parameters based on the IMU data on the sacrum at each phase, which are used for the swimmers' phase-based performance evaluation. Furthermore, the extracted parameters were shown to reflect different aspects of the swimmer's performance, such as propulsion, posture, or efficiency. The developed performance evaluation method estimates a set of velocity-based goal metrics, validated against the reference system, that represent how well the swimmer performed during the corresponding phase. Finally, the system is used to provide weekly feedback to a team of young swimmers to evaluate the application of feedback in practice and its impact on swimmers' progress. Overall, this thesis proposes a new approach to swimming performance evaluation based on IMUs, with a broader scope of application to all phases and styles of swimming. It aims to expand the application of IMUs in swimming by providing spatio-temporal and kinematic parameters that represent critical aspects of swimming and objectively evaluate swimmers' performance. The estimated goal metrics are sensitive to swimmers' progress during weeks of training. In addition, the potential of such an analysis system for in-field training sessions is tested and showed promising results. Finally, coaches can obtain a more detailed view of swimmers' techniques at both macro and micro levels using a single IMU sensor on a daily basis.

EPFL2022

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