Abstract
Free radicals, highly reactive molecules that can cause extensive cellular damage, have been shown to increase following both aerobic and resistance-type exercise. Regular aerobic exercise (i.e. training) has been reported to strengthen the antioxidant defense system, thereby possibly protecting against free radical-mediated damage following exercise. However, the effect of regular resistance exercise on free radical production is unclear. PURPOSE To determine the effects of resistance training status on selected indices of serum free radical production and muscle damage following an acute whole-body resistance exercise bout. METHODS Twelve males (23.1 ± 4.4 yrs) that were recreationally resistance trained (RT) and twelve untrained (UT) males (22.6 ± 2.4 yrs) that did not have resistance exercise experience in the past year participated in this study. All subjects completed an eight-exercise circuit resistance exercise protocol consisting of three sets of ten repetitions at 73.5% of one repetition maximum for each exercise. Blood samples were obtained pre-exercise, immediately post-exercise, and at, 6, 24, and 48 hours post-exercise, and were analyzed for malondialdehyde (MDA) and creatine kinase (CK). RESULTS At pre-exercise, MDA (nmol/ml) averaged 3.41 ± .76 (RT) and 3.20 ± .98 (UT) and did not differ either between groups or over time. CK activity (IU/L) was significantly (p < 0.05) elevated immediately post-exercise (170.6 ± 123.5), 6h post-exercise (290.3 ± 164.9), 24h post-exercise (365.5 ± 239.5), and 48h post-exercise (247.5 ± 184.8) as compared to pre-exercise (126.4 ± 97.0) for both groups. There was no difference in CK activity between groups. CONCLUSION This study indicated that free radical production was unaffected by intense whole-body resistance exercise and training status. However, both groups experienced a significant level of skeletal muscle membrane damage following exercise as demonstrated by CK elevation.
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