Weight Training and Muscle Damage or Repair
Injuries No Comments »Another mechanism involved in the generation of free radicals in weight trainers does not involve the physiological effects of training, but involves the effects of recovery from training, namely, free radical production in damaged muscle. As a result of intense resistance exercise, the skeletal muscle of bodybuilders, power lifters, and Olympic lifters is subjected to both mechanical and oxidative damage. This damage includes the loss of sarcoplasmic reticulum structural integrity, increased lipid peroxidation and membrane perturbations, and the release of both myoglobin and muscle enzymes into circulation. Exercise induced muscle damage can occur from both concentric and eccentric training, but eccentric contractions, or negatives, are known to cause greater structural damage and thereby increased oxidative damage. Oxidative stress in resistance training does not come from a dramatically elevated metabolic rate during the exercise bout as in aerobic trainers, but is actually part of the repair process. After muscle damage, including exercise-induced micro trauma, there is a period of neutrophil and monocyte/macrophage infiltration. The white blood cells (leukocytes) that are activated in response to muscle damage are mobilized to the damaged area in an attempt to initiate repair. Delayed-onset muscle soreness has been related to this repair process. Although this immune response appears to be proportional to z-band damage, even moderate exercise has been shown to trigger a twofold increase in neutrophil activation. As a consequence of neutrophil activation, these repair processes are well known to use oxygen radicals as a means of clearing away microscopic tissue fragments. Again, in this scenario, the healing of damaged muscle can lead to further muscle damage due to oxidative stressors brought on by the repair process. In addition to white blood cell infiltration, cell damage can lead to both muscle calcium abnormalities and the disruption of iron - containing proteins, including myoglobin. One
concluding note is necessary to put the concepts of exercise, radical production, and muscle damage into perspective. Although the research is not clear-cut when approaching the question of which came first, the radicals or the damage, it can be speculated that exercise causes a downward spiral situation. Acute bouts of aerobic and resistance exercise both cause increased free radical production, although through different mechanisms (oxygen processing and reperfusion injury). Since these free radicals are known to cause damage to cytoskeletons, membranes, and other cellular components, it can be concluded that post-exercise muscle damage is due, in part, to free radical actions. Once skeletal muscle is damaged, however, leukocyte radical production is initiated to clear away damaged fibers, leading to the subsequent release of more free radicals and further damage. Further research is required to quantify the nature of each step’s contribution to the oxidative damage seen is skeletal muscle.
Tags:delayed onset muscle soreness, Injuries, muscle damage, muscle enzymes, myoglobin, oxidative damage, oxygen radicals, power lifters, resistance exercise, sarcoplasmic reticulum weight trainers
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