Effects of Inertial Load of Water on Lower Extremity Joint Moments During Landing and Cutting

Background/Objectives: This study investigated the effects of dynamic stability train-ing using inertial water load on lower limb joint moments and postural control during landing and directional changes. Given the high biomechanical demands of transition-ing from the non-dominant to dominant leg, we examined whether perturbation-based training could enhance neuromuscular control and movement efficiency. Methods: Twenty-six healthy males in their 20s were randomly assigned to an experimental group (n = 13), performing water-filled bag training for 10 weeks, or a control group (n = 13) with no training. Participants completed a landing followed by a 90° cutting maneuver, with joint moments measured via a 3D motion capture system. Analyses were con-ducted for the landing and change-of-direction phases. Results: In the landing phase, group differences were observed in hip, knee, and ankle moments, particularly in the frontal and transverse planes (p < 0.05), but none remained significant after Bonferroni adjustment. The experimental group generally showed lower hip flexion/extension (Hip Moment X) and greater knee and ankle internal/external rotation moments (Knee, Ankle Moment Z). In the cutting phase, only knee abduction/adduction (Knee Moment Y) showed a significant time effect (p = 0.007), not surviving adjustment, with a trend to-ward improved frontal plane control. Conclusions: Ten weeks of water-filled inertial load training improved neuromuscular coordination, shock absorption, and postural control patterns, especially in frontal and transverse planes. Perturbation-based training may be a sport-specific strategy to enhance movement efficiency and reduce lower-limb injury risk during rapid directional changes.