The effect of an experimental sleep extension manipulation on timing and duration of sedentary behavior and physical activity in habitually short-sleeping and inactive adolescents: Results from a randomized crossover trial.
Davidson J, Creasy S, et al. • Sleep health • 2026
Sleep extension reduced sedentary behavior by 72 minutes and light physical activity by 13.2 minutes per day in habitually short-sleeping and inactive adolescents, with sedentary behavior decreasing predominantly in evening hours, while moderate-to-vigorous physical activity was unaffected.
Key Findings
Results
One week of sleep extension reduced sedentary behavior by 72 minutes per day compared to typical sleep conditions.
43 habitually short-sleeping, habitually inactive, healthy-weight adolescents participated in a randomized crossover trial
Participants were 16.0 ± 1.24 years old, 69.8% female, 86% White
Sleep was monitored with wrist-worn actigraphy and activity with thigh-worn accelerometer during both conditions
The study was conducted during the school year
Results
The reduction in sedentary behavior during sleep extension occurred predominantly in evening hours between 18:00 and 00:00.
Evening sedentary behavior decreased by 39 minutes during sleep extension (95% CI: -54.6, -24, p < .001)
This evening reduction accounted for the majority of the total 72-minute daily decrease in sedentary behavior
The authors concluded that 'increased sleep duration replaced time spent in SB primarily in the evening hours'
Home monitoring with accelerometry allowed time-of-day analysis of activity patterns
Results
Sleep extension significantly reduced light physical activity by 13.2 minutes per day.
Light PA (LPA) decreased by 13.2 minutes during sleep extension compared to typical sleep (95% CI: -26.4, 0.00, p = .048)
The decrease in LPA occurred primarily in the morning hours
The authors noted the amount of change was 'small and likely not clinically significant'
The borderline 95% CI (upper bound = 0.00) indicates the finding was at the margin of statistical significance
Results
Sleep extension did not produce a significant change in moderate-to-vigorous physical activity (MVPA).
There was no significant change in MVPA between sleep extension and typical sleep conditions (p > .05)
Participants were defined as habitually inactive, performing less than 3 hours of regular physical activity per week
The authors explicitly concluded that 'sleep extension did not impact MVPA'
Relationships were assessed using linear mixed models
Methods
The study used a randomized crossover design in which each participant completed one week of typical sleep and one week of sleep extension with time in bed extended by at least one hour each school night.
Participants were required to be habitually short-sleeping (≤7 h/night on school days) and habitually inactive (<3 hours of regular physical activity per week)
Sleep extension required increasing time in bed by ≥1 hour each school night
The crossover design allowed within-subject comparisons across both conditions
Both conditions were conducted during the school year to maintain ecological validity
Activity monitoring used a thigh-worn accelerometer and sleep monitoring used wrist-worn actigraphy during both conditions
What This Means
This research suggests that when teenagers who typically don't get enough sleep are given the opportunity to sleep more, the extra sleep time largely replaces time they would have spent sitting still or being sedentary in the evening — not time they would have spent being physically active. The study followed 43 adolescents who normally slept 7 hours or less on school nights and got little regular exercise. Each participant spent one week following their usual sleep schedule and one week going to bed at least an hour earlier on school nights. Wearing activity trackers on their thighs and wrists, researchers found that on nights when teens went to bed earlier, they spent about 72 fewer minutes being sedentary each day, mostly in the hours between 6 PM and midnight.
Importantly, the extra sleep did not come at the cost of meaningful physical activity. Moderate-to-vigorous exercise — the kind that most benefits health — was unchanged between the two conditions. There was a small reduction in light physical activity (such as slow walking) of about 13 minutes per day, mainly in the morning, but the researchers considered this too small to be clinically meaningful. This suggests that encouraging adolescents to go to bed earlier is unlikely to reduce their participation in exercise or sports.
This research matters because short sleep, physical inactivity, and excessive sedentary time are all common in teenagers and all linked to negative health outcomes. The findings suggest that sleep extension interventions in adolescents may simultaneously address two health concerns at once — insufficient sleep and excessive sedentary behavior — without undermining physical activity levels. However, the study involved a relatively homogeneous group (mostly White, healthy-weight teens) over just one week, so how well these results apply to more diverse populations or over longer periods remains to be determined.
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Davidson J, Creasy S, Meneses E, Brinton J, Bernard A, Bowen A, et al.. (2026). The effect of an experimental sleep extension manipulation on timing and duration of sedentary behavior and physical activity in habitually short-sleeping and inactive adolescents: Results from a randomized crossover trial.. Sleep health. https://doi.org/10.1016/j.sleh.2026.02.006