Purpose: Experts have recommended exercise for improved sleep, but often with the caveat that one should avoid nighttime exercise. The aim of this study was to challenge this recommendation in a sample who might be most prone to sleep impairment after nighttime exercise. The secondary aims were to assess whether or not post-treatment sleep was correlated with anxiolytic effects or downregulation of body temperature.
Methods: Twelve sedentary adults with insomnia completed two treatments (separated by 2-5 days) in counterbalanced order: (1) 30 min of moderate treadmill exercise (60-70% maximum heart rate) + 15 min of moderate resistance exercise and (2) a control treatment (reading). Each treatment was completed 2 h before bedtime and followed by a 10-min shower, a light snack, 8 h of polysomnographic recording, and a sleep questionnaire. State anxiety was assessed before and 30 min after each treatment and 10 min before bedtime. Body temperature was assessed from pre-exercise to wake time.
Results: No significant treatment differences in sleep were found, and Hedges g paired comparisons indicated small effect sizes; however, two participants had severely disturbed objective sleep following exercise. Significant correlations were found between change in state anxiety from pre-exercise to bedtime and TST (r = 0.69, p = 0.03). Stage 1 (r = 0.67, p = 0.03), WASO (r = 0.69, p = 0.03), and sleep efficiency (r = 0.66, p = 0.02). No significant correlations were found of sleep with temperature decline.
Conclusions: Profound sleep disturbance after exercise in some participants, and no marked sleep improvement in the others, provides some support for caution regarding late-night exercise for sedentary individuals with insomnia.
Keywords: Insomnia; Night exercise; Sleep; State anxiety.
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