Effects of various acute hypoxic conditions on metabolic parameters and cardiac function during exercise and recovery.

Hwang-Woon Moon,Sub Sunoo,Sang-Seok Nam,Hun-Young Park,Dong-Jun Lee

doi:10.1186/s40064-016-2952-4

Hwang-Woon Moon, Sub Sunoo + Show 3 more

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https://doi.org/10.1186/s40064-016-2952-4

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Abstract

PurposeEvaluation of metabolic parameters and cardiac function is important to determine the decrease in aerobic exercise capacity under hypoxic conditions. However, the variations in metabolic parameters and cardiac function and the reasons for the decrease in aerobic exercise capacity under hypoxic conditions have not been clearly explained. The purpose of this study was to compare the responses between sea level and various acute normobaric hypoxic conditions on metabolic parameters and cardiac function during exercise and recovery in order to evaluate aerobic exercise capacity.MethodsTen healthy male participants (21.3 ± 3.06 y) performed submaximal bicycle exercise (116.7 ± 20.1 W and 60 rpm) at sea level (20.9 % O2) and under various normobaric hypoxic conditions (16.5 % O2, 14.5 % O2, 12.8 % O2, and 11.2 % O2) in a random order. Metabolic parameters (arterial oxygen saturation; SPO2, oxygen consumption; VO2, blood lactate level) and cardiac function (heart rate; HR, stroke volume; SV, end-systolic volume; ESV, end-diastolic volume; EDV, ejection fraction; EF, cardiac output; CO) were measured at rest, during exercise (30 min), and recovery (30 min). We compared the responses on metabolic parameters and cardiac function between the different oxygen partial pressure conditions during exercise and recovery.ResultsThe various acute normobaric hypoxic conditions did not affect VO2 and SV during exercise and recovery. SPO2 decreased (p < .05) and blood lactate level increased (p < .05) as the oxygen partial pressure decreased. HR, EF, CO increased (p < .05) and EDV, ESV decreased (p < .05) at oxygen partial pressures of 14.5 % O2 and below compared with 20.9 and 16.5 % O2 during exercise and recovery.ConclusionA decrease in the oxygen partial pressure to 14.5 % O2 and below might be associated with significant changes in metabolic parameters and cardiac function during exercise and recovery. These changes are an acute compensation response to reduced aerobic exercise capacity by decreased oxygen delivering and utilizing capacities under hypoxic conditions.

Highlights

In 1968, the Olympic Games were held at high altitude in Mexico City, and since the effects of hypoxic conditions at high altitude on exercise performance haveUnder hypoxic conditions, oxygen partial pressure decreases owing to low atmospheric pressure, and this results in the reduction of the alveolar oxygen partial pressure, arterial blood oxygen saturation (SpO2), and arteriovenous oxygen difference, diminishing the capacity for oxygen delivery and utilization (Bhaumik et al 2008; Brutsaert 2008)
There were some changes in metabolic parameters and cardiac function at rest, during exercise, and recovery as it is shown in Figs. 1 and 2
Blood lactate level increased at 16.5 % O2, 14.5 % O2, 12.8 % O2, and 11.2 % O2 (p < .05) compared with 20.9 % O2 during exercise and recovery, and it was increased at 11.2 % O2 (p < .05) compared with all other oxygen levels

Summary

Introduction

In 1968, the Olympic Games were held at high altitude in Mexico City, and since the effects of hypoxic conditions at high altitude on exercise performance haveUnder hypoxic conditions, oxygen partial pressure decreases owing to low atmospheric pressure, and this results in the reduction of the alveolar oxygen partial pressure, arterial blood oxygen saturation (SpO2), and arteriovenous oxygen difference, diminishing the capacity for oxygen delivery and utilization (Bhaumik et al 2008; Brutsaert 2008). Results have been inconsistent regarding stroke volume (SV), end-systolic volume (ESV), end-diastolic volume (EDV), ejection fraction (EF), systemic vascular resistance (SVR), and CO (Thomson et al 2006; Hsu et al 2006; Hainsworth and Drinkhill 2007; Yan et al 2007; Fukuda et al 2010) These inconsistencies might have resulted from differences in the study design, extent of hypoxia, exercise type, intensity, and duration (Thomson et al 2006; Lawler et al 1988; Sunoo et al 1997; Morton and Cable 2005; Hinckson et al 2006; Friedmann et al 2007; Adamos et al 2008; Elstad et al 2009). Variations in metabolic parameters and cardiac function, and decrease in aerobic exercise capacity under hypoxic conditions have not been explained clearly

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