Heart rate variability in men subjected to 30 hours of exercise and sleep deprivation

Introduction: Heart rate variability (HRV) is considered to be a factor determining condition of the heart, especially its fatigue and possible overtraining. Impact of ultra-endurance exercise, additionally involving sleep deprivation, on HRV is poorly investigated so far. Objective: To evaluate whether prolonged physical activity combined with complete sleep deprivation might alter the cardiac autonomic control in healthy young men. Methods: Indices of HRV (HRV SDNN, pNN50, rMSSD and LF/HF ratio) were assessed in 11 endurance trained men before (trial B) and after (trial A) 30 hours of prolonged exercise combined with complete sleep deprivation using infrared sensor fitted in BioCardio Mouse (Poland). Results: The values of heart rate (HR) were significantly higher and the HRV time domain indices were significantly lower in trial A as compared to the results obtained in trial B (pNN50 10.6 [+ or -] 2.3 ms vs.18.3 [+ or -] 2.0 ms, P < 0.001; rMSSD 45 [+ or -] 6 ms vs.66 [+ or -] 6 ms, P < 0.05 and SDNN 53 [+ or -] 7 ms vs.74 [+ or -] 5 ms, P < 0.01, respectively). The LF/HF ratio was significantly lower in trial A than in trial B (1.12 [+ or -] 0.11 vs. 1.38 [+ or -] 0.11, P < 0.05). Conclusions: Ultra-endurance exercise (30-hours adventure race) combined with complete sleep deprivation seems to affect cardiac autonomic response (lower rMSSD, pNN50, SDNN and LF/HF ratio), thus reflecting a sustained sympathetic outflow during recovery from prolonged exercise. The new, simple and cheap BioCardio Mouse delivered consistent and reliable results of several factors determining HRV. Automatically generated reports are easy to follow and raw results can easily be used in everyday monitoring of athletes. Key words: heart rate variability, ultra-endurance exercise, sleep deprivation