Empirical Validation of a Streamlined Three-Repetition Squat Protocol Using MAI Motion

MAI Motion is a motion capture system designed to assess lower limb biomechanics during functional movements such as the squat. Determining how many repetitions are needed to obtain consistent and comparable kinematic measurements is critical for balancing data quality and participant burden. This study evaluates whether three repetitions (3×) of the squat test provide comparable kinematic data to five repetitions (5×). 3D videos of healthy adult participants (n=10) performing 5× squat movements were captured using MAI Motion. Primary measurements were the mean values of each joint angle and the coefficient of variation (CV). Statistical comparisons (paired t-tests or non-parametric equivalents) determined that differences in mean values or CV existed between 3× and 5×. Analysis revealed minimal differences in mean angles between 3× and 5×. Variability, assessed via CV, showed no clinically meaningful differences (p<0.05). Although ankle angle and knee and hip abduction had higher CV values than other metrics, 3× and 5× performed similarly. Participants reported that 3× required less effort than 5×, implying a practical advantage for clinical or research settings. These findings validate that a 3× squat may capture biomechanical data comparable to a 5× protocol using the MAI Motion system. Reducing repetitions could possibly lessen participant fatigue while preserving the consistency of kinematic outputs, making 3× a pragmatic standard for most populations.