Effect of hypobaric hypoxia on heart rate variability during exercise: a pilot field study

Abstract

The influence of hypoxia on heart rate variability (HRV) has been studied under resting conditions with mixed results. Differences have been found in physiological responses to normobaric versus hypobaric hypoxia. Our aim was to study the influence of hypobaric hypoxia on HRV during physical exercise to determine whether HRV changes due to the exercise-induced heart rate (HR) increase or whether hypoxia itself exerts an influence. We tested nine healthy non-acclimatised white males (age = 43 +/- 7 years) at 400 and 4,200 m during exercises. At 400 m HRV was measured at 50% and 75% maximal oxygen uptake (VO(2) max). At 4,200 m HR was kept equal as during exercise at 400 m by adjusting the intensity of step testing. The Poincaré plot as a non-linear method of HRV analysis was used, where the shape of the ellipse depending on HRV is expressed by two parameters, SD1 and SD2 (correlating to parasympathetic activity and both sympathetic and parasympathetic activity, respectively). We established a decrease in SD2 and an insignificant decrease in SD1 at medium HR at 4,200 m compared to 400 m. Both parameters showed similar tendencies during high-intensity exercise. Our results indicate that hypobaric hypoxia itself exerts an influence on HRV at a moderate HR.

Circadian and Sex Differences After Acute High-Altitude Exposure: Are Early Acclimation Responses Improved by Blue Light?

“…All these results are indicative of activation of the sympathetic tone and a vagal withdrawal response, in agreement with previous work on acute hypoxia at rest. [58][59][60][61] Apart from a significant reduction in SDNN in men at night after 3 hours of hypobaric exposure, in the present study we did not find any clear-cut trend in the effect of bLED illumination on HRV. These findings suggest a negligible effect of blue light on HRV, at least in the first 3 hours of exposure.…”

Effects of hypoxia and hypercapnia on human HRV and respiratory sinus arrhythmia

“…Low (LF: 0-0.04 Hz), middle (MF: 0.04-0.15 Hz) and high (HF: 0.15-0.4 Hz) frequency bands form part of this variability and are often determined by spectral analysis of an R-R interval tachogram using fast Fourier transform (FFT). The influence of both hypoxia and hypercapnia on resting HRV has been studied at rest, but with equivocal results regarding changes in the frequency domain (37). Hypoxia may decrease HRV total power (TP) (6,14,29) and decrease both MF and HF power (3,6,21,23,24,29).…”

Serum and Stimulated Saliva C-reactive Protein Changes in Altitude Chamber

“…Acute hypobaric hypoxia in altitude chamber causes tachycardia and increases cardiac output in aviators (4). This can cause a significant increase in serum cardiac markers.…”

“…This training has a significant effect on prevention of air accidents because 75% of air accidents are human-dependent (3). Hypobaric hypoxia also increases heart rate and cardiac output (4). However, the most important effect of hypoxia is cerebral impairment due to a decrease in neurons sensitivity.…”