Green tea extract supplementation and cycling time-trial performance at moderate altitude

Date

2008-08

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Abstract

Reactive oxygen species are unstable molecules that have been shown to cause muscle damage and possibly be involved in the skeletal muscle fatiguing process. Reactive oxygen species are generated by high intensity exercise and also exposure to altitude related hypoxia, as well as various other conditions. Green tea extract is a known, powerful antioxidant, meaning it has the ability to scavenge reactive oxygen species, possibly decreasing muscle damage and fatigue. The purpose of this research was to determine the effects of green tea extract supplementation on reactive oxygen species production, oxidative stress, and endurance exercise performance at moderate altitude.

Ten subjects performed a graded exercise test to determine maximum oxygen consumption and power output. The subjects then participated in three time trials on a fixed gear cycle ergometer. These time trials corresponded with cycling at seventy five percent of their maximum power output for twenty minutes, if the subject pedaled faster; he completed the time trial in less than twenty minutes. One hour prior to performing in the second and third time trials, a blood sample was collected from each subject and a supplement was given. The supplement consisted of either a placebo (dextrose) or green tea extract. The supplementation was administered in a random, double blind fashion, to minimize bias of the results. One hour after completion of the time trial, a blood sample was again obtained.

The results of this study show an average twenty-nine second improvement in cycling time trial performance, and corresponding increase of approximately seven watts in mean power output, with green tea extract supplementation compared to placebo. There were no significant differences in heart rate, percent of maximum heart rate, oxygen saturation, or rating of perceived exertion between the two different supplements. There also were no significant differences in the plasma malondialdehyde (marker of oxidative stress) between the two supplementations.

This study found that while green tea extract improves endurance exercise performance at moderate altitude, the mechanism by which this performance improved is not readily known, as there was no change in malondialdehyde concentrations. Further research should be completed to determine a better quantitative measure for oxidative stress and reactive oxygen species in the body.

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Keywords

Altitude, Green tea extract, Endura, Oxidative stress

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