How Much ExerciseExercising at moderate intensity for at least a half an hour each morning, seven days per week produced the best effect. Those who used stretching also had less trouble falling asleep
When to ExerciseOnly the women who exercised in the morning had the beneficial effects on sleep. Those who exercised in the evening actually had more trouble falling asleep. "Postmenopausal women commonly report sleep problems. Exercise may help to alleviate these problems, as long as it is performed early in the day," said principal investigator Anne McTiernan, M.D., Ph.D., a member of Fred Hutchinson's Public Health Sciences Division.
Why Does Morning Exercise Help Sleep?
One possible explanation, the researchers note, is that morning versus evening exercise may affect the body's daily "circadian" rhythms that affect sleep quality. Morning exercise may get the body clock in alignment, and evening exercise upset it. More research is needed to confirm this theory.
SOURCE: Shelley S. Tworoger, PhD1,2; Yutaka Yasui, PhD1; et. al. "Effects of a Yearlong Moderate-Intensity Exercise and a Stretching Intervention on Sleep Quality in Postmenopausal Women." SLEEP. 2003. Vol. 26, Issue 7, pages 830-836.