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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. 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.
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