Effects of Resistance Training in Hypobaric vs. Normobaric Hypoxia on Circulating Ions and Hormones.

Rafael Timon,Belen Feriche,Cristina Benavente,Paulino Padial,Blanca De La Fuente,Ismael Martínez-Guardado,Juan Bonitch-Góngora,Guillermo Olcina

doi:10.3390/ijerph19063436

Abstract

Hypobaric hypoxia (HH) seems to lead to different responses compared to normobaric hypoxia (NH) during physical conditioning. The aim of the study was to analyze the hormonal and circulating ion responses after performing high-intensity resistance training with different inter-set rest under HH and NH condition. Sixteen male volunteers were randomly divided into two training groups. Each group completed two counterbalanced resistance training sessions (three sets × ten repetitions, remaining two repetitions in reserve), with both one- and two-minute inter-set rest, under HH and NH. Blood samples were obtained to determine hormones and circulating ions (Ca2+, Pi, and HCO3−) at baseline and after training sessions (5, 10, and 30 min). Resistance training with one-minute rest caused greater hormonal stress than with two-minute rest in cortisol and growth hormone, although the hypoxic environmental condition did not cause any significant alterations in these hormones. The short inter-set rest also caused greater alterations in HCO3− and Pi than the longer rest. Additionally, higher levels of Ca2+ and Pi, and lower levels of HCO3−, were observed after training in HH compared to NH. Metabolic and physiological responses after resistance training are mediated by inter-set rest intervals and hypoxic environmental condition. According to the alterations observed in the circulating ions, HH could cause greater muscular fatigue and metabolic stress than NH.

Highlights

Various studies on resistance training under hypoxic conditions have been performed, both to assess acute physiological responses [1–3] and long-term adaptations [4,5]
Previous studies have shown that resistance training under hypoxic conditions enhances the buildup of metabolites [6], which clearly have an important role in muscle growth
Lactate values after training were significantly higher in all conditions when comparing Hypobaric hypoxia (HH) with Normobaric hypoxia (NH)

Summary

Introduction

Various studies on resistance training under hypoxic conditions have been performed, both to assess acute physiological responses [1–3] and long-term adaptations [4,5]. Previous studies have shown that resistance training under hypoxic conditions enhances the buildup of metabolites [6], which clearly have an important role in muscle growth. Resistance training performed under hypoxia lead to a significant oxidative and hormonal stress [6,7]. Increases in anabolic hormones [8,9] and reactive oxygen species [10], as well as alterations in circulating ions (Pi, Na+ , and H+ ) [3,11], have been observed after the resistance training. There is no unanimity in the results obtained regarding the physiological responses caused since factors such as the type (hypobaric hypoxia [HH] or normobaric hypoxia [NH]) and the severity of the hypoxia Feriche et al [3] observed significant increases in growth hormone (GH) and Ca2+

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