Abstract
The evidence that physical exercise lowers metabolic and cardiovascular risk is undisputed. Normobaric hypoxia training has been introduced to facilitate the effects of exercise. We tested the hypothesis that hypoxia training augments exercise‐related effects. We randomized 23 men with metabolic‐syndrome to single‐blinded exercise at normoxia (FiO2 21%) or hypoxia (FiO2 15%). Six weeks endurance training on a treadmill, 3 days per week, over 60 min at 60% VO 2max was required. The study included the following: (1) metabolic phenotyping by indirect calorimetry and adipose and muscle tissue microdialysis to gain insight into effects on resting, postprandial, and exercise metabolism, (2) cardiac imaging, and (3) biopsies. Primary endpoint was the change in cardiorespiratory fitness; secondary endpoints were as follows: changes in body weight, waist circumference, blood pressure, cardiac dimensions, and adipose and muscle tissue metabolism and gene expression. Our subjects reduced waist circumference and improved several cardiovascular risk markers including blood pressure. However, these effects were similar in both training groups. Cardiac dimensions were not influenced. We focused on glucose metabolism. After an oral glucose load, adipose tissue metabolism was significantly shifted to a more lipolytic state under hypoxia, whereas muscle metabolism was similar under both conditions. Postprandial energy expenditure was significantly increased under hypoxia, whereas activity energy expenditure was improved under normoxia. Gene expression was not consistently influenced by FiO2. Adipose tissue triglyceride lipase, leptin, and hypoxia‐inducible factor‐alpha expression were increased by normoxia but not hypoxia.
Highlights
In a recent clarion call, the Global Burden of Metabolic Risk Factors for Chronic Diseases Collaboration emphasized that the cardiometabolic disease and risk factor epidemic at the beginning of the 21st century are high blood pressure and an increasing effect of obesity and the metabolic syndrome leading to type-2 diabetes (Global Burden of Metabolic Risk Factors for Chronic Diseases C, 2014)
Primary endpoint was the change in cardiorespiratory fitness; secondary endpoints were as follows: changes in body weight, waist circumference, blood pressure, cardiac dimensions, and adipose and muscle tissue metabolism and gene expression
After an oral glucose load, adipose tissue metabolism was significantly shifted to a more lipolytic state under hypoxia, whereas muscle metabolism was similar under both conditions
Summary
In a recent clarion call, the Global Burden of Metabolic Risk Factors for Chronic Diseases Collaboration emphasized that the cardiometabolic disease and risk factor epidemic at the beginning of the 21st century are high blood pressure and an increasing effect of obesity and the metabolic syndrome leading to type-2 diabetes (Global Burden of Metabolic Risk Factors for Chronic Diseases C, 2014). Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society Normobaric hypoxic conditioning is defined as exposure to systemic and/or local hypoxia at rest (passive) or combined with exercise training (active) (Workman and Basset 2012). Our group has conducted two controlled studies of hypoxic training in subjects without metabolic abnormalities that gave encouraging results (Haufe et al 2008; Wiesner et al 2010). Tested the hypothesis that a similar study in male subjects with the metabolic syndrome would show benefit of hypoxia training
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