Creatine Supplementation

Nitrogen loss total urinary nitrogen and estimated

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Unformatted text preview: al urinary nitrogen and estimated faecal loss 2005 Adis Data Information BV. All rights reserved. 119 relative to nitrogen content of the diet) was found to be similar in both groups. Cr and PCr concentrations were determined by muscle biopsy from the vastus lateralis and all samples were adjusted for the highest ATP concentrations at pre- and post-treatment. The Cr group had significantly greater total Cr content when compared with pre-treatment measures (15–16%), while there was no change for the placebo group. It is interesting to note that there were no significant differences or interactions between the groups, either before or after energy restriction and supplementation, for any of the cycle performance measures. The authors suggest that the brief 6-second sprints that are dependent on the phosphagen system are less affected than longer sprint periods that might rely on anaerobic glycolysis. Dealing with the issue of Cr supplementation and exercise in a hot environment, Volek et al.[49] examined the physiological responses to short-term exercise at 37°C (80% humidity) after 7 days of Cr loading. Twenty-two males were randomly assigned to either a Cr group (n = 10; 0.3 g/kg BW) or a placebo group (n = 10) in a double-blind fashion. The exercise session consisted of cycling for 30 minutes at 60–70% of peak oxygen consumption and then, immediately perform three, 10-second maximal sprints. Repeated measures ANOVA revealed no significant differences between groups for heart rate, blood pressure and sweat rate responses to exercise. Urine excretion rates for Cr, sodium and potassium obtained over 24 hours were also not different between the two groups. The exercise bouts significantly increased levels of cortisol, aldosterone, renin, angiotensin I and II, atrial peptide and arginine vasopressin for both groups but there was a significant interaction term indicating that peak power during cycling was significantly greater during all three sprints for the Cr group but unchanged for the placebo group. 2.3 Continuou...
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