Insufficient sleep and inadequate amounts of physical activity (PA) are common lifestyle behaviors, but there is a paucity of research examining the interaction between insufficient sleep and PA.
PURPOSE: To establish how sleep restriction affects PA, and the role this plays in sleep restriction-induced insulin resistance (IR) in overweight adults.
METHODS Thirteen overweight adults, who regularly sleep 7-9 h/night, underwent two study conditions; 5 days of modest sleep restriction (6-h time-in-bed, SR), and 5 days of SR+exercise (SREX), followed by a weekend recovery period (WR). Sleep (Actigraphy) and PA (Actigraph) were monitored for 7 days prior to each condition, throughout each condition, and during WR. Blood samples were collected during a mixed meal tolerance test (MT) after baseline (B), SR/SREX, and WR. Daily exercise, SREX, was 45 minutes of treadmill walking (65% VO₂peak).
RESULTS Subjects slept 8.0±0.2 h during B weekdays compared to SR and SREX (5.9±0.1 h; 5.9±0.0 h, respectively) and 7.4±0.2 hours on weekend (7.4±0.3; 8.2±0.4, respectively). Steps were maintained during SR compared to B (B-SR, 8276±622; SR, 7656±676 steps/day) but were increased during SREX (B-SREX, 8550±776; SREX 13182±789 steps/day, p<0.001). Steps during the B weekend period were reduced compared to B (p<0.001) and during WR following SR±EX (SR, p<0.01;SREX, p<0.001). Subjects performed less light (LT) PA during SR±EX (p=0.001). Sedentary (SED) PA tended to be higher during SR compared to B (p=0.07) but tended to be reduced during SREX (p=0.09). Moderate-vigorous PA (MVPA) was elevated during SREX (p<0.001) and reduced during SR (p<0.05) compared to B. During MT, glucose and insulin response did not differ by condition or across time. Matsuda calculations tended to also show improvements in IR (time, p=0.06), where WR improved compared to B (p<0.05), no differences between B and SR±EX.
CONCLUSION Overweight adults maintained steps during SR, but reduced time spent performing MVPA. When subjects performed EX daily (SREX), SED was replaced with MVPA with no changes in LTPA observed. Subjects increased SED and decreased LTPA and MVPA during WR compared to B weekend, likely due to the reduced step counts. Modest SR did not induce IR in overweight adults, but despite reduced PA during WR, IR was improved compared to B.