The purpose of this study was to analyze the effects of a single bout and repeated bouts of stretching on indirect markers of exercise-induced muscle damage. The authors conducted a randomized controlled clinical trial at a university human research laboratory. 56 untrained males were separated into four groups at random. (I) a single stretching group underwent a single bout of stretching on the quadriceps muscle; (II) an eccentric exercised group underwent eccentric quadriceps muscle contractions until exhaustion; (III) an eccentric exercise group followed by a single bout of stretching; (IV) an eccentric exercised group submitted to repeated bouts of stretching performed immediately and 24, 48, and 72 h post-exercise. Muscle stiffness, muscle soreness, maximal concentric peak torque, and plasma creatine kinase activity were assessed before exercise and 1, 24, 48, 72, and 96 h post-exercise. All exercised groups showed significant reduction in maximal concentric peak torque and significant increases in muscle soreness, muscle stiffness, and plasma creatine kinase. There were no differences between these groups in all assessed variables, with the exception of markers of muscle stiffness, which were significantly lower in the eccentric exercise group followed by single or repeated bouts. The single stretching group showed no change in any assessed variables during the measurement period.
The study found that muscle stretching performed after exercise, either as single bout or as repeated bouts, does not affect the levels of the main markers of exercise-induced muscle damage; however, repeated bouts of stretching performed during the days after exercise could have favorable effects on muscle stiffness.