Short-Term Intermittent Normobaric Hypoxia Combined with Light Exercise Improves Acclimatization of Cardiorespiratory Function in Inactive Adults

Abstract

Background: Un-acclimatized individuals may experience acute altitude illness. Thus, the current study investigated the impact of short-term intermittent normobaric hypoxia (NH) combined with light exercise on the acclimatization of cardiorespiratory function to altitude in inactive adults.

Methods: This quasi-experimental study recruited 10 inactive university students (age: 26.3 ± 2.53 years). All participants were instructed to perform light exercise while exposed to intermittent NH (15%) (2 h/d) for 2 weeks continuously. The heart rate (HR), relative oxygen consumption (VO2 mL/kg/min), minute ventilation (VE), VO2/HR, and respiratory frequency (RF) were measured.

Results: Results illustrated a significant improvement in participants' cardiorespiratory functions by 10 days after exposure to NH, as compared to day 1 of exposure, based on their HR, RF, and VE responses at rest and HR, RF, VE, VO2, VO2/kg, and VO2/HR during light exercise. Resting-state values had returned to the pre-NH exposure levels after 10 days of intermittent NH exposure. Furthermore, values measured during light exercise were significantly decreased on days 10 and 14 as compared to day 1 of NH exposure.

Conclusion: This study concluded that as few as 10 days of exposure to intermittent NH (pO2 = 15%) combined with light exercise may improve the acclimation to NH of 15% pO2 in inactive adults.

Keywords: acclamation; altitude; health-related fitness; oxygen consumption; sedentary; training.

Figure 1

Resting heart rate (HR) at 1 day before exposure to hypoxia and on the 1st, 10th, and 14th day of exposure to hypoxia. * Indicates that data are significantly different from the day before exposure to hypoxia (pre-exposure to hypoxia) (P < 0.05).

Figure 2

Resting respiratory frequency (RF) on 1 day before exposure to hypoxia and during exposure to hypoxia on the 1st day, 10th day, and 14th day. * Indicates that data are significantly different from the day before exposure to hypoxia (pre-exposure to hypoxia) (P < 0.05).

Figure 3

Resting minute ventilation (VE) on 1 day before exposure to hypoxia and during exposure to hypoxia on the 1st, 10th, and 14th day. * Indicates that data are significantly different from the day before exposure to hypoxia (pre-hypoxia exposure) (P < 0.05).