Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis




Kinesiology and Health Promotion

First Advisor

Dr. Lance Bollinger


Background: As little as three nights of sleep restriction reduces muscle strength. More than one-third of Americans are chronically sleep restricted (< 7.0 hours/night) and are at risk of muscle weakness (dynapenia). Presently, the mechanistic cause of sleep restriction-induced dynapenia (SRID) has not been elucidated. Rapid changes in muscle strength are typically driven by short-term changes in muscle contractility or voluntary recruitment. The purpose of this study was to investigate how sleep restriction affects muscle contractile function and voluntary recruitment. Methods: A sample of 12 subjects (age 24.8 ± 2.6y) underwent isometric and isokinetic knee extensor muscle testing following 3d of adequate sleep (SA; 8.05 ± 0.45h), 3 d of sleep restriction (SR; 5.02 ± 0.05h), and 7d of washout (WO, 8.27 ± 0.50). The morning (7-11a local time) following the last day of each sleep period, subjects performed muscle strength testing using an isokinetic dynamometer. Subjects sat upright with the dominant leg secured at 60⁰ of knee flexion to optimize maximal quadriceps torque. They then performed 3 maximal voluntary isometric contractions (MVICs) of the quadriceps. Then subjects performed 6 submaximal contractions at 15, 30, 45, 60, 75, and 90% of the greatest MVIC. Next, subjects completed an interpolated twitch experiment while on the isokinetic dynamometer to assess voluntary activation. Finally, subjects completed 5 repetitions of isometric contractions, in descending order, at speeds of 300, 240, 180, 120, and 60 degree/s. From these methods we measured the highest MVIC, calculated the voluntary activation (VA), measured twitch properties, and compared the torque-EMG relationship. One-way repeated measures ANOVA were used to compare sleep, MVIC, and VA values, two-way (time x twitch property) repeated measures ANOVA was used to compare twitch properties and the torque-EMG relationship. Results: MVIC torque decreased following SR compared to SA before and after sleep restriction (SA: 217.1 ± 69.4 Nm vs. SR: 199.4 ± 67.1 Nm, p = 0.032). MVIC after WO (219.2 ± 54.2 Nm) was significantly greater than SR (p = 0.018) but was not significantly different from SA (p = 0.991). Although peak isokinetic torque decreased with increasing velocity (p < 0.001), there was no significant effect of sleep or sleep x speed interaction. Peak twitch torque and rate of torque
development, but not relaxation rate, were significantly greater in the potentiated state, but no significant effect of sleep or sleep x time interaction was noted. Sleep 3 condition did not significantly affect voluntary activation (SA: 86.3 ± 11.1% v. SR:86.6 ± 11.9% v. WO 87.7 ± 11.1%; p = 0.695). The torque output at various levels ofelectromyography (EMG) activity was not significantly different among sleep conditions (p = 0.383). The mean power frequency (MPF) of the VL was not significantly different among sleep conditions (p = 0.241). Conclusions: Threenights of sleep restriction decreases knee extensor strength which returns to baseline after 7d of adequate sleep. However, muscle twitch properties and motor unit recruitment are unaffected by 3 nights of sleep restriction. Despite this, sleep extension significantly increased MVIC following a short bout of SR. Future research should focus on the benefits of sleep extension.

Digital Object Identifier (DOI)

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