Figure 1. Measurement protocols and twitch responses of elbow flexors in one subject.

A, measurements of MVC, voluntary activation and twitch forces of elbow flexors were made at 60 deg elbow flexion and then the arm was passively extended in 10 deg steps in a custom-built myograph. Measurements were continued up to 150 deg and the sequence repeated. These sequences were performed pre-exercise, 2 h after eccentric exercise reduced the MVC by 40%, and 1 and 8 days later. Each shaded bar indicates the timing of voluntary and stimulated contractions and is expanded in panel B. B, during a MVC, paired stimuli (10 ms interval) were delivered to the motor nerve of biceps and brachialis. Paired and single stimuli were delivered after the MVC. C, resting twitches evoked by paired stimuli to the motor nerve for biceps and brachialis decreased markedly and gradually recovered by day 8. D, in this subject superimposed twitches evoked by the same stimuli during MVCs were similar in size before exercise, at day 1 and day 8.