Daily Associations Between Sleep and Physical Activity.

BACKGROUND

Research has demonstrated a correlational relationship between sleep and physical activity, though this work has been largely cross sectional and fails to demonstrate temporal relationships. The purpose of this study was to test the daily, bidirectional relationships between sleep and physical activity, and whether this varied between weekdays and weekend days.

METHOD

Fifty-four healthy, young adults wore a Fitbit Flex to measure sleep and physical activity during a 6-day study period.

RESULTS

Mixed linear models revealed that physical activity did not predict subsequent night's sleep. However, on nights when participants had longer than their own average total sleep time, and greater than their own average wake after sleep onset, this predicted less physical activity the following day.

CONCLUSION

Results suggest that, in healthy young adults, physical activity may not promote healthier subsequent sleep, but sleep duration and continuity influence physical activity in their own way. Young adults may respond differently to health promotion efforts, and a greater understanding of these temporal associations can enhance the efficacy of these efforts.