Short sleep duration, low physical activity (PA), and sedentary behavior (SB) are associated with negative health outcomes and highly prevalent in adolescents. This study examined changes in the amoun Show more
Short sleep duration, low physical activity (PA), and sedentary behavior (SB) are associated with negative health outcomes and highly prevalent in adolescents. This study examined changes in the amount and timing of PA and SB following a 1-week sleep extension manipulation in adolescents. Forty-three habitually short-sleeping (≤7 h/night on school days), habitually inactive (<3 hours of regular physical activity per week), and healthy-weight adolescents (16.0 ± 1.24 years, 69.8% female; 86% White) completed a randomized crossover procedure during the school year. Participants slept for 1 week on their typical school schedule (Typical Sleep, TS), and 1 week during which time in bed was extended by ≥1 hour each school night (Sleep Extension, EXT). Home-monitoring of sleep with wrist-worn actigraphy and activity with thigh-worn accelerometer was completed during both conditions. Relationships between sleep, SB, PA, and experimental manipulation were assessed with linear mixed models. SB and light PA (LPA) across the 24 days decreased significantly during EXT compared to TS by 72 minutes and 13.2 minutes, respectively (95% CI: -102, -42, p < .001; 95% CI: -26.4, 0.00, p = .048). SB decreased predominantly between the hours of 18:00-00:00 (-39 minute 95% CI: -54.6, -24, p < .001). There was no significant change in moderate-to-vigorous PA (MVPA) between conditions (p > .05). Increased sleep duration replaced time spent in SB primarily in the evening hours. While LPA decreased primarily in the morning hours, the amount of change was small and likely not clinically significant. Sleep extension did not impact MVPA. Show less