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The impact of sleeping with reduced glycogen stores on immunity and sleep in triathletes.
Louis, J, Marquet, LA, Tiollier, E, Bermon, S, Hausswirth, C, Brisswalter, J
European journal of applied physiology. 2016;116(10):1941-54
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Plain language summary
Endurance athletes are increasingly using training strategies focused on low glycogen availability in attempt to improve performance. It is well known, however, that increasing training stress could influence immune function and increase the risk of illness or injury. In endurance sports, training load, nutrient intake and sleep are key factors in modulating immune function. The aim of this study was to investigate the effects of a 3-week training strategy involving lowered glycogen availability overnight on immune function, upper respiratory tract infections and sleep patterns in 21 trained endurance athletes. This study found that reduced glycogen availability resulted in significantly faster 10km running times, and found no significant changes in the recorded immunity markers. Based on this study, the authors conclude that reduced glycogen availability has no deleterious impact on immune function.
Abstract
PURPOSE We investigated the effects of a 3-week dietary periodization on immunity and sleep in triathletes. METHODS 21 triathletes were divided into two groups with different nutritional guidelines during a 3-week endurance training program including nine twice a day sessions with lowered (SL group) or maintained (CON group) glycogen availability during the overnight recovery period. In addition to performance tests, sleep was monitored every night. Systemic and mucosal immune parameters as well as the incidence of URTI were monitored every week of the training/nutrition protocol. Two-ways ANOVA and effect sizes were used to examine differences in dependent variables between groups at each time point. RESULTS The SL group significantly improved 10 km running performance (-1 min 13 s, P < 0.01, d = 0.38), whereas no improvement was recorded in the CON group (-2 s, NS). No significant changes in white blood cells counts, plasma cortisol and IL-6 were recorded over the protocol in both groups. The vitamin D status decreased in similar proportions between groups, whereas salivary IgA decreased in the SL group only (P < 0.05, d = 0.23). The incidence of URTI was not altered in both groups. All participants in both groups went to bed earlier during the training program (SL -20 min, CON -27 min, P < 0.05, d = 0.28). In the SL group, only sleep efficiency slightly decreased by 1.1 % (P < 0.05, d = 0.25) and the fragmentation index tended to increase at the end of the protocol (P = 0.06). CONCLUSION Sleeping and training the next morning regularly with reduced glycogen availability has minimal effects on selected markers of immunity, the incidence of URTI and sleeping patterns in trained athletes.
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Sleep restriction for 1 week reduces insulin sensitivity in healthy men.
Buxton, OM, Pavlova, M, Reid, EW, Wang, W, Simonson, DC, Adler, GK
Diabetes. 2010;59(9):2126-33
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Short sleep duration is associated with an increased risk of many chronic diseases including diabetes, however the effects of sleep restriction on insulin sensitivity have not yet been established. The aim of study was to assess the effects of decreased sleep duration on insulin sensitivity in a controlled environment. This 12-day inpatient study included 20 healthy men who were randmoised to receive a wakefulness-promoting drug, modafinil, or placebo during the sleep restriction phase. This study showed that sleep restriction for one week significantly reduces insulin sensitivity. These findings raise concerns about chronic insufficient sleep on the development of metabolic diseases and promote further research into these effects.
Abstract
OBJECTIVE Short sleep duration is associated with impaired glucose tolerance and an increased risk of diabetes. The effects of sleep restriction on insulin sensitivity have not been established. This study tests the hypothesis that decreasing nighttime sleep duration reduces insulin sensitivity and assesses the effects of a drug, modafinil, that increases alertness during wakefulness. RESEARCH DESIGN AND METHODS This 12-day inpatient General Clinical Research Center study included 20 healthy men (age 20-35 years and BMI 20-30 kg/m(2)). Subjects spent 10 h/night in bed for >or=8 nights including three inpatient nights (sleep-replete condition), followed by 5 h/night in bed for 7 nights (sleep-restricted condition). Subjects received 300 mg/day modafinil or placebo during sleep restriction. Diet and activity were controlled. On the last 2 days of each condition, we assessed glucose metabolism by intravenous glucose tolerance test (IVGTT) and euglycemic-hyperinsulinemic clamp. Salivary cortisol, 24-h urinary catecholamines, and neurobehavioral performance were measured. RESULTS IVGTT-derived insulin sensitivity was reduced by (means +/- SD) 20 +/- 24% after sleep restriction (P = 0.001), without significant alterations in the insulin secretory response. Similarly, insulin sensitivity assessed by clamp was reduced by 11 +/- 5.5% (P < 0.04) after sleep restriction. Glucose tolerance and the disposition index were reduced by sleep restriction. These outcomes were not affected by modafinil treatment. Changes in insulin sensitivity did not correlate with changes in salivary cortisol (increase of 51 +/- 8% with sleep restriction, P < 0.02), urinary catecholamines, or slow wave sleep. CONCLUSIONS Sleep restriction (5 h/night) for 1 week significantly reduces insulin sensitivity, raising concerns about effects of chronic insufficient sleep on disease processes associated with insulin resistance.