The purpose of this investigation was to examine the correlation between the maximal isometric strength of the biceps femoris (caput longum) and semitendinosus muscles measured through a dynamometer fitted with a load cell and the corresponding electromyographic activity recorded for each muscle. Nine female volunteers (19-23 years old), of similar anthropometry and with no antecedents of skeletal muscle diseases were enrolled in this study. The protocol consisted of maximal isometric contractions of the biceps femoris (caput longum) and semitendinosus muscles, in which the volunteers remained in ventral decubitus with a knee flexed to 90º. Maximal isometric strength was generated against the load cell for 6 s followed by a 2 min rest. The contractions were repeated for as long as possible. The root mean square values of the biceps femoris (caput longum) and semitendinosus muscles tended to increase with decreasing force as a function of the number of repetitions. This electromyographic fatigue was confirmed by the positive correlation between these two variables. The protocol described here may provide an useful index for measuring neuromuscular fatigue.