The effects of sleep deprivation on performance and perceived fatigability

Cognitive-motor performance is impaired and mental fatigue is increased when subjected to acute sleep deprivation (SD). However, the immediate effects of SD on the mechanisms of performance fatigability compared to a well-rested state are less understood. Therefore, examining performance fatigability in combination with systematic testing of various sites of the neuromuscular system can allow for the characterization of how SD limits physical function. PURPOSE: To determine if healthy, young females exhibit greater increases in perceived and performance fatigability of the elbow flexors following an acute 24-hour bout of SD compared to a well-rested state. Further, the study attempted to identify the neuromuscular factors that may account for the presumed increases in perceived and performance fatigability during acute SD. METHODS: Nine healthy females (22.8 ± 2.7 years) performed a 20-min sustained, isometric elbow flexion equivalent to the muscle activity of a 25% maximal voluntary contraction (MVC) in a SD and well-rested condition. Perceived fatigue and ratings of perceived exertion (RPE), MVC and submaximal torque, voluntary activation, muscle relaxation rate, as well as motor cortical, motoneuronal and peripheral excitability were assessed prior to, during and following the fatiguing elbow flexion task. RESULTS: At task termination, elbow flexor MVC torque was ~30% less, RPE was ~82% greater, and perceived fatigue scores were ~137% greater in the SD condition than control. However, maximal rate of relaxation, submaximal torque and voluntary activation were not different between conditions. Motor cortical excitability increased for both conditions with no differences detected during the fatigue task or throughout recovery. Surprisingly, at task termination, peripheral excitability decreased by ~7% for SD, but was unaltered for the control. Motoneuronal excitability decreased similarly for both conditions by task termination compared to pre-fatigue and remained depressed up to 5 min into recovery for SD, but recovered within 3 min for control. CONCLUSION: Following an acute 24-hour bout of SD, females had greater MVC reductions and experienced greater perceived fatigability. Although central fatigue and supraspinal factors may not be contributing factors, peripheral and motoneuronal excitability are likely candidates for the greater performance fatigability.Health and Social Development, Faculty of (Okanagan)Health and Exercise Sciences, School of (Okanagan)Graduat