Sleep deprivation: cytokine and neuroendocrine effects on perception of effort

Introduction
An increased perception of effort and subjective fatigue are thought to be central to decreased exercise performance observed following disrupted sleep. However, there is limited understanding of the mechanisms which underpin these phenomena. We investigated the role of interleukin-6 (IL-6), the soluble interleukin-6 receptor (sIL-6R) and neuroendocrine factors (cortisol, adrenaline, noradrenaline and brain derived neurotropic factor (BDNF)) in mediating these responses at rest and during exercise.

Methods
In a randomized order ten healthy active males completed 3 experimental trials following different sleep conditions; a single night of sleep deprivation (DEP), partial sleep deprivation equivalent to 4-hrs of sleep (PART) and normal sleep (CON). The experimental sessions consisted of physiological and perceptual measurements of exercise intensity throughout 45-min moderate intensity and 15-min maximal effort cycling. Cytokine and neuroendocrine factors were assessed at rest and in response to exercise.

Results
Sleep deprivation resulted in increased resting IL-6, lower blood glucose, increased perceived fatigue and perception of effort, lower free-living energy expenditure, and reduced maximal exercise performance. In contrast, sleep deprivation did not alter physiological, cytokine or neuroendocrine responses to exercise. Variations in the resting concentration of IL-6 were associated with lowered blood glucose, an increased perception of effort, and impaired exercise performance. Resting concentrations of cortisol, adrenaline, noradrenaline, and BNDF showed subtle interactions with specific aspects of mood status, and performance but were not impacted by sleep deprivation. There were minimal effects of partial sleep deprivation.

Conclusions
These findings demonstrate that cytokine and neuroendocrine responses to exercise are not altered by sleep deprivation but that changes in the resting concentration of IL-6 may play a role in altered perception of effort in this context.