Acute Effects of Multi-Joint Eccentric Exercise on Lower-Extremity Muscle Activation Measured During Land and Water Walking.

Falls are a leading cause of injury and loss of independence in older adults, often linked to deficits in lower-limb muscle function and gait mechanics. Eccentric exercise can improve muscular resilience, while aquatic walking offers a safe, supportive environment to retrain gait; however, little is known about how these modalities interact at the neuromuscular level. This study compared lower-limb muscle activation during gait on land and in water, before and after an acute bout of eccentric exercise, in healthy young adults. Surface electromyography was collected from the tibialis anterior (TA), gastrocnemius medialis (GM), vastus lateralis (VL), and biceps femoris (BF) during treadmill walking on land and at equivalent speeds in chest-deep water. Results showed that aquatic walking consistently altered activation patterns relative to land walking, with increased TA activity (28%, Cohen's d = 0.69) and reduced GM activity (-27%, Cohen's d = -0.48) during swing, reduced VL activity during stance (-20%, Cohen's d = -0.43), increased VL activity during swing (46%, Cohen's d = 0.72), and increased BF activity during stance (51%, Cohen's d = 0.63). These changes produced distinct co-activation patterns between the shank and thigh. Eccentric exercise had limited effects overall but increased thigh co-activation during swing in land walking. Findings suggest that eccentric exercise can be safely combined with aquatic walking and highlight the potential of this multimodal approach for enhancing gait mechanics relevant to fall prevention.