The impact of acute sleep fragmentation on muscle blood flow responses to handgrip exercise

Sleep fragmentation is reported to impair resting vascular function. The aim of this study was to test the hypothesis that acute sleep fragmentation would impair muscle blood flow during exercise. Twenty adults (10 females, 10 males) participated in a randomized crossover study that included one night of habitual sleep and one night of fragmented sleep. Sleep was assessed at home using wrist actigraphy. Arousals from sleep were increased by an audio alarm sounding every 30 minutes. The morning following each sleep condition, participants performed single handgrip contractions and rhythmic handgrip exercise at 15%, 30%, and 45% MVC. Forearm blood flow (FBF) was measured using Doppler ultrasound. Nightly awakenings and wake after sleep onset significantly increased by 18% and 43%, respectively, after fragmented sleep leading to lower sleep duration (p<0.001). Peak FBF and total hyperemic responses following single contractions were similar between sleep conditions (all p > 0.05). During rhythmic handgrip exercise, brachial artery dilation was reduced after fragmented sleep (main effect: 5.5 ± 4.8 vs. 3.3 ± 3.7 %; p=0.01) leading to a lower FBF response to rhythmic exercise (main effect: 122 ± 58 vs. 110 ± 56 mL/min; p=0.04). Endothelial sensitivity to shear rate was similar between sleep conditions (habitual vs. fragmented: 0.039 ± 0.024 vs. 0.042 ± 0.031 %/s -1 ; p=0.77). In summary, acute sleep fragmentation decreases skeletal muscle blood flow during exercise. This finding suggests that blunted oxygen delivery may be a contributing factor for exercise performance deficits after disturbed sleep.