Question

If a muscle contracts isometrically for a long period of time, an EMG (which records the electrical activity in the muscle) recording shows that as the amplitude (frequency of action potential) increases, the contractile force slowly decreases. What is the explanation for this?

Answer 1

During the course of a continuous isometric contraction of given strength, the electrical activity progressively increases. This is due to recruitment of motor units taking place to compensate the decrease in force of contraction occurring in the fatigued muscle fibres.

Step-by-step explanation: