Acute Sleep Reduction Impairs Heart Rate Variability and Heart Rate Recovery Following Aerobic Exercise in Healthy Adults

INTRODUCTION: According to the CDC, ~35% of American adults are receiving an inadequate amount of sleep (/night). PURPOSE: This study aimed to investigate the effects of acute sleep reduction on heart rate variability (HRV) and heart rate recovery (HRR) following aerobic exercise. METHODS: Healthy, active adults (n=11; 26.4±5.4 yr; 45% female) were screened to ensure eligibility (i.e., meeting the CDC’s sleep recommendations of 7-9hr/night, apparently healthy, recreationally active, and non-smoking), characterize body composition via DXA and measure maximal cardiovascular capacity (VO2max). Utilizing a within subjects, repeated measures design, participants completed an initial 7d period of habitual sleep (CON) followed by a 7d period of sleep reduction (SR; sleeping ~3hr less per night). Sleep habits were assessed throughout via accelerometry (Actigraph wGT3X-BT) and sleep diary. Following CON and SR, participants completed a laboratory visit, in which 5min of supine resting HR was measured (Polar H10) prior to a 45min aerobic exercise (AE) challenge on a cycle ergometer at a workload corresponding to 70% of their VO2max. Heart rate was monitored during exercise and each minute over a 5min recovery period post-exercise. HRV metrics were analyzed via Kubios HRV Scientific (time and frequency domains). RESULTS: Sleep was reduced 31% during SR (CON: 8.1±0.3 hr/night; SR: 5.4±0.2 hr/night, p£0.05). Sleep efficiency increased (5±2%), while average number of awakenings (42±4%) and sleep fragmentation index (24±8%) decreased in SR (p£0.05). In the time domain, SR reduced SDNN 13% (CON: 68.3±1.7, SR: 59.5±1.1 ms, p£0.05), whereas RR, RMSSD, and pNN50 did change (p>0.05). In the frequency domain, SR reduced low frequency (LF) power 28% (CON: 2233.4±100.6, SR: 1607.4±93.1 ms2), LF/HF power 47% (CON: 2.5±0.2, SR: 1.3±0.1, p£0.05), and total power 27% (CON: 4535.0±210.4, SR: 3291.2±130.0, p£0.05). Very low frequency (VLF) and high frequency (HF) power did not change following SR (p>0.05). Peak exercising HR was similar between visits (CON: 158±2, SR: 157±2, p>0.05). HRR during the first minute post-exercise tended to decrease 15% after SR (CON: 42±1, SR: 36±1, p£0.10). CONCLUSION: Short term acute sleep reduction appears to reduce HRV and HRR immediately following moderate intensity exercise.