Accelerometric assessment of fatigue-induced changes in swimming technique in high performance adolescent athletes

The present study analyzed the kinematic changes under fatigue in highly trained adolescent swimmers during a 50-m all-out front cwal test. Twenty-four girls and fourteen boys aged 12-13 participated in the study. The movement of the hip rim was analyzed using a specialized inertial device equipped with a triaxial gyroscope and accelerometer to measure changes in angular velocity and acceleration. Between the first and second lengths of the pool, the following were observed: a significant (F1.36 = 63.6; p < 0.0001; η² = 0.64) increase (34%) in maximum pelvic angle, significant (F1,36 = 6.0; p = 0.0193; η² = 0.14;) increase (12.10%) in angular velocity in rotational motion around a vertical axis, and a significant (F1,36 = 11.29; p = 0.0018; η² = 0.24) increase (6.86%) in angular velocity in yaw rotation motion around the sagittal axis. Significant (F1,36 = 13.96; p = 0.0006; η² = 0.28) differences in maximum pelvic angle were observed for lap and side. As unfavourable changes in kinematics are already observed in the second half of the distance, it is therefore suspected that performing frequent high-intensity repetitions may lead to the perpetuation of unfavourable movement patterns. Taking this into account, coaches should limit maximum-speed swimming in adolescent athletes to short distances and an appropriate interval and use training methods to reduce asymmetric work such as training snorkels.