Evaluating Relationships Between Sleep and Next-Day Physical Activity in Young Women

Background: To evaluate the relationship between sleep and next-day physical activity (PA) under free-living conditions in women. Methods: Sleep and PA were measured objectively for 7 consecutive days by accelerometry in 330 young adult women (aged 17-25 y). A structural equation model was used to evaluate the relationship between the driving factor of sleep (total sleep or morning wake time) and the amount of nonsleep sedentary (SED) and moderate to vigorous physical activity (MVPA) each day. Results: With sleep duration as the driving factor, the estimates of beta SED and beta MVPA were -0.415 and -0.093, respectively (P=.05). For every hour slept, a 24.9-minute reduction in SED time and a 5.58-minute reduction in MVPA were observed. With wake time as the driving factor, the estimates of beta SED and beta MVPA were -0.636 and -0.149, respectively. For every wake time that was 1 hour later, a 38.2-minute decrease in SED and a 8.9-minute decrease in MVPA (P =.05) were observed. Conclusions: Women who wake later or who sleep longer tend to get less MVPA throughout the day. Getting up earlier and going to bed earlier may support behaviors that improve PA and lifestyle.