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Unformatted text preview: ed the effects of Cr
supplementation on muscle properties and sprint
performance. Twenty-three well trained rowers
were randomly assigned to either a Cr group (n = 11;
20 g/day for 6 days) or a placebo group (n = 12).
Testing consisted of 40 consecutive electrical stimulations of the quadriceps at an activation frequency
of 150Hz, which was equal to 30% of maximal
voluntary isometric peak torque. Repeated measures
ANOVA indicated that there was a significant increase in body mass for the Cr group compared with
the placebo group. However, there was no group
difference for maximal voluntary torque generation,
muscle activation as elicited by electrical stimulation, and recovery from the electrically stimulated
exercise. Additionally, there were no differences
between groups peak power, time to peak power, or
work to peak power during the sprint tests.
Wiroth et al. examined the potential ergogenic
effects of Cr supplementation on maximal pedalling
performance by recruiting three groups of subjects
(G1 = sedentary, n = 14, mean age 70.1 years; G2 =
trained cyclists, n = 14, mean age 66.4 years; and G3
= young sedentary, n = 14, mean age 26.0 years).
Within each group, Cr was administered (5g three
times daily for 5 days) using a double-blinded,
randomised design. Subjects performed five maximal 10-second sprints with 60 seconds of passive
recovery between each sprint, with power output,
work done and heart rate being recorded during each
sprint. Maximal power was significantly increased
only for G1 and G3, suggesting that Cr was beneficial in previously untrained older and younger populations but not in previously trained individuals.
This is in contrast to the findings of Rawson et al.
who reported no significant increases in force or
power output in older subjects during an isokinetic
test following 5 days of Cr loading. It is possible that
the increased training status of the trained cyclist
Sports Med 2005; 35 (2) The Effects of Creatine in Sport and Exercise group may have reduced the responsiveness to Cr
loading. Assessment of intramuscular Cr s...
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