THE ADDITION OF SARCOMERES IN SERIES IS THE MAIN PROTECTIVE MECHANISM FOLLOWING ECCENTRIC EXERCISE

Abstract

Sore muscles following unaccustomed eccentric exercise is a common experience. One remarkable aspect of this is the rapid training. A single bout of exercise can provide significant protection against muscle damage and soreness from subsequent bouts. Several studies have shown that such training also increases the optimum muscle length and/or the number of sarcomeres. The present study aimed to test whether this accounts for all the protection. Rats were trained for up to 30 minutes per day on a treadmill, either inclined to 16° (concentrically biased exercise) or declined to 16° (eccentrically biased exercise) for one week. The decline rats were found to have smaller optimum knee angles, or longer muscle lengths, for torque generation by vastus intermedius muscles than the incline rats. When test eccentric contractions were given over the same range of knee angles for each training group, the decline rats showed less damage. When the differences in the optimum length were accounted for and the eccentric contractions were given over the same portion of the torque angle curve, there was no difference between the two groups in the amount of damage that they suffered, suggesting that the shift in optimum was responsible for all of the protection.