Hierarchical clustering approach to movement smoothness and temporal adaptation in rhythmic step aerobics training in middle aged women

This study examined the effects of rhythmic step aerobics on movement smoothness and core dynamics in middle-aged women, focusing on forward and reverse stepping. While step aerobics enhances balance and musculoskeletal function, its impact on kinematics-especially movement smoothness and synchronization-remains underexplored. This study analysed centre of mass motion using inertial measurement units in three dimensions. Nine middle-aged women (age: 53.38 years, BMI: 24.45 Formula: see text) completed 24 training sessions, with evaluations every 12 sessions. Step detection was performed using continuous wavelet transform, stance-to-swing ratio assessed temporal adaptation, and jerk cost analysis quantified movement smoothness. Hierarchical clustering (Ward's method) identified motor adaptation patterns. Results showed significant kinematic adaptations, particularly in backward stepping, with increased stance duration and smoother motion. Notably, the third step (first backward step) reflected adaptation, especially from the 12th to 24th sessions, suggesting the central nervous system prioritized this particular step for initial stability. In contrast, no significant adaptation was observed in the fourth step, indicating asymmetry in lower limb trainability. Alternating the leading step every minute may reduce asymmetry. These findings highlight rhythmic step aerobics as a promising intervention for mobility enhancement, with stance-to-swing ratio and smoothness as valid trainability metrics for prehabilitation and rehabilitation programs.