Muscle fibre conduction velocity, mean power frequency, mean EMG voltage and force during submaximal fatiguing contractions of human quadriceps.

In 5 healthy male subjects the changes in muscle fibre conduction velocity, mean power frequency, mean EMG voltage, and force in the quadriceps were measured during submaximal fatiguing contractions, ranging from 60 to 100% of maximum force. Surface EMG was recorded from vastus lateralis. The analysis was divided into 2 parts - before and after force had begun to decline (endurance point). The conduction velocity and mean power frequency declined less before the endurance point than after this point. For all forces, the mean EMG voltage increased up to the endurance point. After the endurance point, the effect of fatigue had a decreasing influence on mean EMG voltage.