Impact of Hypohydration and Creatine Supplementation on Skeletal Muscle Performance and Metabolism.
Technical rept. Jul 95-Dec 96,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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Two studies were done using 3 iP magnetic resonance spectroscopy to examine the separate effects of hypohydration and dietary creatine supplementation on muscle metabolism and performance. Volunteers performed supine single-leg knee extension exercise in a 1.5 Tesla whole body magnetic resonance spectroscopy MRS system. For the hypohydration study, exercise was performed to exhaustion when euhydrated and 4 hypohydrated. Hypohydration reduced P 0.05 time to fatigue 15 EU 25167 HY213 52 Sec Isd. Muscle pH and PiBATP were similar during exercise and at exhaustion regardless of hydration state. It was concluded that hypohydration reduces muscle endurance and the effects appear independent of H and Pi concentration. For the creatine studies, 3 repeat bouts of high-intensity exercise were performed before and after 5 days of creatine supplementation 0.3 gkg-1-day-i. Middle-aged persons 5814 yr had lower resting PCrBATP compared to the young group 6.3610.94 vs. 7.180.93, pO.05 and a lower mean PCr resynthesis rate for bouts 1 and 2 18.13.5 vs. 23.26.0 mmolkg wet wt-1min-1, pO.05. After creatine supplementation, resting PCrBATP increased 15 p0.05 in the young group and 29 p0.05 in the middle-aged group 8.31.3 vs. 8.311.0 eliminating the difference between groups. Mean PCr resynthesis rate also increased in the middle-aged group p 0.05 during the creatine trial to a level not different from the young group 24.33.8 vs. 24.2 3.2 mmol kg wet wt- 1 min- 1. Time to exhaustion was increased in the young group after creatine supplementation 122136 vs. 16259 s, p 0.05 but did not improve in the middle-aged group 113 31 vs. 144181 s, p 0.2.
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