Changes in surface EMG during static fatiguing contractions in the upper trapezius muscle

The effect of contraction levels on muscle fiber conduction velocity (MFCV), median frequency (MDF) and mean amplitude of surface electromyography (EMG) was examined in the trapezius of 10 healthy male students. The subjects performed shoulder elevation at 5% (30 min), 15% (10 min), 30% (5 min) and 50% (1 min) to the maximum voluntary contraction (MVC). MFCV and MDF decreased during the contraction. Mean amplitude of EMG increased during 50% MVC, it decreased in other contractions during exercise. These results suggested that MFCV and MDF are affected by the muscle fatigue during static contractions.