Modest sleep restriction does not influence steps, physical activity intensity or glucose tolerance in obese adults

Sleep restriction (SR) (<6 h) and physical activity (PA) are risk factors for obesity, but little work has examined the inter-related influences of both risk factors. In a free-living environment, 13 overweight/obese adults were sleep restricted for five nights to 6 h time-in-bed each night, with and without regular exercise (45 min/65% VO₂ max; counterbalanced design). Two days of recovery sleep followed SR. Subjects were measured during a mixed meal tolerance test (MMT), resting metabolic rate, cognitive testing and fat biopsy (n=8). SR increased peak glucose response (+7.3 mg/dl, p = .04), elevated fasting non-esterified fatty acid (NEFA) concentrations (+0.1 mmol/L, p = .001) and enhanced fat oxidation (p < .001) without modifying step counts or PA intensity. Inclusion of daily exercise increased step count (+4,700 steps/day, p < .001) and decreased the insulin response to a meal (p = .01) but did not prevent the increased peak glucose response or elevated NEFA levels. The weekend recovery period improved fasting glucose (p = .02), insulin (p = .02), NEFA concentrations (p = .001) and HOMA-IR (p < .01) despite reduced steps (p < .01) and increased sedentary time (p < .01). Abdominal adipose tissue (AT) samples, obtained after baseline, SR and exercise, did not differ in lipolytic capacity following SR. Fatty acid synthase protein content tended to increase following SR (p = .07), but not following exercise. In a free-living setting, SR adversely affected circulating NEFAs, fuel oxidation and peak glucose response but did not directly affect glucose tolerance or AT lipolysis. SR-associated metabolic impairments were not mitigated by exercise, yet recovery sleep completely rescued its adverse effects on glucose metabolism.

Associations between objective afternoon and evening physical activity and objective sleep in patients with fibromyalgia and insomnia

Patients with fibromyalgia (FM) suffer from chronic pain, which limits physical activity and is associated with disturbed sleep. However, the relationship between physical activity, pain and sleep is unclear in these patients. This study examined whether actigraphic (Actiwatch-2, Philips Respironics) afternoon and evening activity and pain are associated with actigraphic sleep. Adults with FM and insomnia complaints (n = 160, mean age [M_age ] = 52, SD = 12, 94% female) completed 14 days of actigraphy. Activity levels (i.e., activity counts per minute) were recorded, and average afternoon/evening activity for intervals 12:00-3:00 PM, 3:00-6:00 PM and 6:00-9:00 PM was computed. Multiple linear regressions examined whether afternoon/evening activity, pain (daily evening diaries from 0 [no pain sensation] to 100 [most intense pain imaginable]), or their interaction, predicted sleep onset latency (SOL), wake time after sleep onset (WASO), total sleep time (TST) and sleep efficiency (SE). Greater afternoon activity was independently associated with lower SE (B = -0.08, p < .001), lower TST (β = -0.36, standard error [SE] = 0.06, p < .001) and longer WASO (B = 0.34, p < .001). Greater early evening activity was independently associated with lower SE (B = -0.06, p < .001), lower TST (β = -0.26, SE = 0.06, p < .001) and longer WASO (B = 0.23, p < .001). Self-reported pain intensity interacted with afternoon and early evening physical activity, such that associations between higher activity and lower SE were stronger for individuals reporting higher pain. Late evening activity was not associated with sleep outcomes. Results suggest that in FM, increased afternoon and early evening physical activity is associated with sleep disturbance, and this relationship is stronger in individuals with higher pain.