Creatine Supplementation

Assessment of intramuscular cr stores during future

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Unformatted text preview: tores during future studies of this type may help explain some of the discrepancies. Within the cycling literature, authors have also attempted to delineate the effects of Cr under conditions that might be exhibited during performance, such as dehydration and energy restriction. In one such paper, Vogel et al.[51] examined the effects of cycle performance at two levels of acute hydration. Sixteen men were randomly assigned to either a Cr group (n = 7, 20 g/day for 5 days) or a placebo group (n = 9). Subjects were required to perform five, 5-second maximal sprints on a cycle ergometer in an environmental chamber with the temperature at 32°C and 50% humidity. To induce a state of hypohydration, subjects then performed a 75-minute exercise session followed by the same sprint protocol, then an additional 75 minutes of exercise. It was determined that the two 75-minute exercise sessions elicited similar significant losses in body mass (–2.5% for the Cr group and –4% for the placebo group) as well as plasma volume (–7% for the Cr group and –9% for the placebo group) for the Cr and placebo groups. Additionally, there were no significant differences for either group for any of power measures. Reports of muscle cramping and tightness were not different between the groups and it was concluded that Cr supplementation did not appear to negatively affect hydration status during extended cycling exercise.[51] To examine the issue of Cr usage during a period of energy restriction, Rockwell et al.[48] randomly assigned 16 men to either Cr group or a placebo group. Cr was administered at 20 g/day and both the Cr and placebo group consumed a formula diet of 75.3kJ (18 kcal/kg/day; 57% carbohydrate, 21% protein and 24% fat). Subjects were then required to perform ten, 6-second maximal sprints with 30 seconds of recovery between sets. Both the Cr and placebo groups lost similar amounts of body mass and percentage body fat, but the placebo group had a significant decrease in percentage change of fat-free mass when compared with the Cr group. Nitrogen loss (tot...
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