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Pugh, Michael D.1; Sawyer, Robert D.2; Loftis, Dustin C.2; Gremillion, Charles A.2; Williams, James S. FACSM2
1The University of Texas Southwestern Medical Center at Dallas, Dallas, TX. 2Texas Tech University, Lubbock, TX.
(No relationships reported)
Reactive oxygen species (ROS) or free radicals are unstable molecules that have been implicated in the processes of muscle damage and fatigue. Previous studies have shown that both exercise and hypoxia associated with altitude exposure result in increased production of ROS. Catechins in green tea extract (GTE) are powerful antioxidants capable of scavenging ROS and possibly preventing muscle damage and fatigue.
PURPOSE: To determine the effects of GTE supplementation on endurance performance and ROS production during exercise at simulated altitude.
METHODS: Ten recreationally-active (VO2max = 51.4 ± 1.2 ml/kg/min; 23.1 ± 1.5 yrs) male subjects first completed a maximal graded exercise test (GXT) on a cycle ergometer followed by three time-trial (TT) performances. The first TT served as a practice session and was followed by two experimental TT performances at simulated altitude (2500 m). The experimental TT performances were randomized and all TT performances were separated by 48 hrs. Based on the maximal power output achieved on the GXT, each subject was assigned a specific amount of work (joules) to be completed as fast as possible during the experimental TT performances. Subjects ingested GTE or placebo capsules 1 hr prior to the experimental TT performances and a blood sample was obtained before the GTE or placebo ingestion and 60 min after the TT performance for the determination of ROS (malondialdehyde-MDA).
RESULTS: Cycling TT performance was significantly faster (p < 0.01) at simulated altitude with GTE supplementation compared to placebo (28.9 ± 22.2 sec). Nine of the ten subjects demonstrated an improvement in time. Mean power output for the subjects was also significantly higher at simulated altitude (p < 0.01) with GTE supplementation compared to placebo (6.97 ± 3.93 W). No significant differences (p > 0.05) were found in plasma MDA levels between conditions or time.
CONCLUSION: Supplementation with GTE improves cycling TT performance at simulated altitude however; the improvement in TT performance does not appear to be related to MDA levels.
©2009The American College of Sports Medicine
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