Abstract

Electrical activity and soreness in the quadriceps muscles were examined during a 48-h period after eccentric (EC) and concentric contraction (CC) to study the amplitude and frequency characteristics of the electrical signal after exercise and to study the relationship between the electrical signal and muscle soreness. The exercise protocol included a step test performed for 15 min using a 46-cm step in which one quadriceps contracted eccentrically and one contracted concentrically. Electrical activity was quantified by computing both root mean square electromyograph and mean power frequency of the myoelectrical signal during low-level contractions of the muscles. Recordings of muscle activity were made before, immediately after, 1, 12, 24 and 48 h after exercise in 12 volunteer subjects. Recordings were made with the subject seated, holding the leg being tested slightly off the ground. Subjects were given a subjective pain rating scale. The results suggest that an increase in the electrical activity of muscles is needed to produce the same pre-exercise contraction after performing eccentric exercise. However, this increase in activity is not associated with a shift in frequency, thus suggesting that motor units with similar activation characteristics are utilized to generate force both before and after exercise. Muscle soreness only occurred in the muscles that had contracted eccentrically and did not occur at the time of greatest electrical change. Verf.-Referat (gekuerzt)