The effect of creatine supplementation and sleep deprivation, with
intermittent moderate-intensity exercise, on cognitive and psychomotor
performance, mood state, effort and salivary concentrations of cortisol
and melatonin were examined. Subjects were divided into a creatine
supplementation group and a placebo group. They took 5 g of creatine
monohydrate or a placebo, dependent on their group, four times a day for
7 days immediately prior to the experiment. They undertook tests
examining central executive functioning, short-term memory, choice
reaction time, balance, mood state and effort at baseline and following
18-, 24- and 36-h sleep deprivation, with moderate intermittent
exercise. Saliva samples were taken prior to each set of tests. A group
× time analysis of covariance, with baseline performance the covariate,
showed that the creatine group performed significantly (p < 0.05) better
than the placebo group on the central executive task but only at 36 h.
The creatine group demonstrated a significant (p < 0.01) linear
improvement in performance of the central executive task throughout the
experiment, while the placebo group showed no significant effects. There
were no significant differences between the groups for any of the other
variables. A significant (p < 0.001) main effect of time was found for
the balance test with a linear improvement being registered. Cortisol
concentrations on Day 1 were significantly (p < 0.01) higher than on Day
2. Mood significantly (p < 0.001) deteriorated up to 24 h with no change
from 24 to 36 h. Effort at baseline was significantly (p < 0.01) lower
than in the other conditions. It was concluded that, during sleep
deprivation with moderate-intensity exercise, creatine supplementation
only affects performance of complex central executive tasks.
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