Np. Whitehead et al., DAMAGE TO HUMAN MUSCLE FROM ECCENTRIC EXERCISE AFTER TRAINING WITH CONCENTRIC EXERCISE, Journal of physiology, 512(2), 1998, pp. 615-620
1. It is known that a period of eccentric exercise provides protection
against damage to muscle from subsequent eccentric exercise. Here we
ask, does concentric exercise do the opposite, make muscle more prone
to damage? 2. The triceps surae muscle group of one leg in each of eig
ht human subjects was subjected to 30 min of concentric exercise per d
ay, for 5 days. At the end of the training period there was a small bu
t significant increase in passive torque in the exercised muscle (P <
0.05), with no changes in the untrained muscle. 3. After a single peri
od of eccentric exercise, angle-torque curves for muscles of both legs
shifted in the direction of longer muscle lengths, suggestive of an i
ncrease in series compliance. The shift in the concentrically trained
muscle was significantly greater over the first 48 h post-exercise (P
< 0.05). 4. The volume of the trained leg increased significantly more
than the untrained leg for five subjects over 72 h post-exercise (P <
0.05). Peak torque fell, passive stiffness increased and both muscles
became sore, but with no significant differences between the two legs
. 5. It is concluded that a period of concentric exercise increases th
e susceptibility of muscle to changes associated with the damage from
eccentric exercise.