Fatigue of the medial gastrocnemius induces a proximal shift and decrease in peak muscle activity during walking

Fatigue of skeletal muscles reduces their ability to prevent injuries to their corresponding tendons. For example, Achilles tendinopathy often results when the tendon is overloaded due to fatigue of the triceps surae. To better understand this occurrence, we used a high-density array of electrodes to measure electromyographical signals from the medial gastrocnemius during walking before and after a fatiguing task. Muscle fatigue induced a proximal shift in the distribution of muscle activity and caused overall muscle activity to decrease. This shift in muscle activity likely indicates that the muscle recruits different motor units and muscle fibers when it is fatigued than when it is not fatigued.