The Effects Of Green Tea Extract Supplementation On Markers Of Muscle Injury And Oxidative Stress.

Abstract

Reactive oxygen species (ROS) are key biologic radical species that oxidize molecules and impair their function. Exercise involving repeated lengthening muscle contractions (i.e. downhill running) has been shown to result in the generation of ROS. ROS are also thought to be involved in the inflammatory response to exercise. In addition, some markers of ROS induced damage exhibit a delayed response, 24 to 48 hr post-exercise, and have been correlated with delayed onset muscle soreness (DOMS). Green tea polyphenols possess antioxidant properties and have been used to counteract ROS production. PURPOSE: To test the hypothesis that the antioxidants in green tea will reduce biomarkers of oxidative stress and mechanical muscle damage following a downhill run. METHODS: Participants were young, healthy males (21 - 25 y/o) who reported running 3 - 5 days/wk. Participants were randomly assigned to a placebo (n = 6), green tea pre-exercise group (n = 5), or green tea post-exercise group (n = 5). Subjects performed a 45-min downhill treadmill run (-10°) at 60 - 65% of their VO2max. Measurements of muscle soreness (7 point Likert scale) and blood samples for the measurement of oxidative stress (malondialdehyde-MDA) and muscle damage (creatine kinase-CK) were obtained pre-exercise, immediately post-exercise, and 24 hr post-exercise. RESULTS: CK levels and muscle soreness were significantly elevated in all 3 groups at 24 hr post-exercise (p <.05). Green tea supplementation did not affect muscle damage as there were no differences in CK or soreness between the groups at any time point (p >.05). There were no significant differences (p >.05) in MDA between pre, post, and 24 hr samples for any group, however, a 36% and 24% increase in MDA occurred in the placebo and supplemented groups respectively at 24 hr post-exercise. CONCLUSIONS: This pilot study suggests that: 1) downhill running is not associated with increased oxidative stress, although there was a trend for increased MDA in the placebo group, and 2) green tea supplementation is ineffective in reducing muscle soreness/injury in response to downhill running.