Efficacy of intermittent hypoxic training on hemodynamic function and exercise performance in competitive swimmers

Abstract

[Purpose]Hemodynamic function is a parameter indicating oxygen delivery and utilization capacity and is an important determinant of exercise performance. The present study aimed to determine whether intermittent hypoxic training (IHT) ameliorates hemodynamic function and exercise performance in competitive swimmers.[Methods]Twenty competitive swimmers (10 men, 10 women) volunteered to participate in the study. Participants were divided into the normoxic training (NT) group and the hypoxic training (HT) group and were subjected to training in a simulated altitude of 3000 m. We evaluated hemodynamic function profiles over 30 min of submaximal exercise on a bicycle and exercise performance before and after 6 weeks of training, which involved continuous exercise at 80% maximal heart rate (HRmax) for 30 min and interval exercise at 90% of HRmax measured before training for 30 min (ten rounds comprising 2 min of exercise followed by 1 min of rest each round).[Results]Significant changes in oxygen consumption (decrease) and end-diastolic volume (increase) were observed only in the HT group. Heart rate (HR), cardiac output (CO), and ejection fraction (EF) were significantly reduced in both groups, but the reduction rates of HR and CO were greater in the HT group than in the NT group. Exercise performance measures, including maximal oxygen consumption and 400-m time trial, were significantly increased only in the HT group.[Conclusion]Our findings suggested that 6 weeks of IHT, which involved high-intensity continuous and interval exercise, can effectively improve exercise performance by enhancing hemodynamic function in competitive swimmers.

Interval Hypoxic Training Enhances Athletic Performance and Does Not Adversely Affect Immune Function in Middle- and Long-Distance Runners

“…The oxygen transport capacity in systemic conditions is most often evaluated using VO 2 max [8]. Exercise training in a hypoxic condition may increase exercise performance by inducing various biochemical and structural adaptive changes in the skeletal and cardiac muscles, which favor the oxidative process and can enhance non-hematological parameters, such as exercise economy, acid-base balance, and metabolic response during submaximal exercise, ultimately leading to improved oxygen delivery and utilization capacity [1,[8][9][10][11]13]. Among the various LLTH methods, IHT consists of repeated exposures to 5-7 min of steady or progressive hypoxia, interrupted by equal periods of recovery; it can modify oxygen transport and energy utilization and induce permanent modifications in the cardiac function [12].…”

“…However, research findings on IHT as an effective hypoxic training method for enhancing athletic performance at sea level are inconclusive [8]. In various previous studies, the difference in the enhancement of athletic performance, via the IHT method, was attributed to the intensity of the exercise performed in the hypoxic conditions [8,9,34]. There are also some differences in the type of exercise.…”

“…There are also some differences in the type of exercise. Park and Lim [8] evaluated the effects of six weeks of hypoxic training on exercise performance in moderately trained competitive swimmers and reported that a moderate intensity of continuous and interval training in a hypoxic condition for six weeks resulted in an unclear change in the aerobic and anaerobic performance compared to normoxic training. They also argued that the unclear improvement after hypoxic training was attributed to the relatively low exercise intensity.…”

“…Currently, altitude/hypoxic training is a common and popular practice for enhancing athletic performance in normoxic conditions among various athletes [8]. The most typical altitude/hypoxic training regimens proposed include living high-training high (LHTH), living high-training low (LHTL), and living low-training high (LLTH) methods.…”

“…Among the various LLTH methods, IHT consists of repeated exposures to 5-7 min of steady or progressive hypoxia, interrupted by equal periods of recovery; it can modify oxygen transport and energy utilization and induce permanent modifications in cardiac function [12]. Short-term repeated exposure to hypoxic conditions with high-intensity exercise enhances athletic performance via the metabolic and oxygen utilizing capacity [11,[13][14][15]. However, some studies have not supported the enhancing effect of high-intensity training in hypoxic conditions on athletic performance [16][17][18][19].…”