Effect of High-Intensity Training in Normobaric Hypoxia on Thoroughbred Skeletal Muscle.

Hiroshi Nagahisa,Hajime Ohmura,Kazutaka Mukai,Hirofumi Miyata,Toshiyuki Takahashi

doi:10.1155/2016/1535367

Hiroshi Nagahisa, Hajime Ohmura + Show 3 more

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https://doi.org/10.1155/2016/1535367

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Abstract

Hypoxic training is believed to increase endurance capacity in association with hypoxia inducible factor-1α (HIF-1α), a modulator of vascular endothelial growth factor-A (VEGF-A), and to influence activation of satellite cells (SCs). However, the effect of hypoxic training on SC activation and its relation to angiogenesis has not been thoroughly investigated. Eight Thoroughbred horses were subjected to normoxic (FIO2 = 21%) or hypoxic (FIO2 = 15%) training for 3 days/week (100% ) for 4 weeks. Incremental exercise tests (IET) were conducted on a treadmill under normoxia and the maximal oxygen consumption () and running distance were measured before and after each training session. Muscle biopsy samples were obtained from the gluteus medius muscle at 6 scheduled times before, during, and one week after IET for immunohistochemical analysis and real-time RT-PCR analysis. Running distance and , measured during IET, increased significantly after hypoxic training compared with normoxic training. Capillary density and mRNA expression related to SC activation (e.g., myogenin and hepatocyte growth factor) and angiogenesis (VEGF-A) increased only after hypoxic training. These results suggest that increases in mRNA expression after training enhance and prolong SC activation and angiogenesis and that nitric oxide plays an important role in these hypoxia-induced training effects.

Highlights

Hypoxic training is commonly used to increase endurance capacity in athletes [1,2,3]
Many studies at the cellular level demonstrated that hypoxia inducible factor-1α (HIF-1α) had an important role in structural and metabolic adaptation to hypoxia and that hypoxia has been mainly investigated in association with HIF-1α, which stabilizes under hypoxia and leads to angiogenesis via upregulation of VEGF-A [5, 6]
These results suggest that immediate upregulation of transcription of VEGF-A mRNA after training is associated with increased translation and that the increase of VEGF-A protein is essential for angiogenesis

Summary

Introduction

Hypoxic training is commonly used to increase endurance capacity in athletes [1,2,3]. As a method of utilizing hypoxic training without this negative effect, the “live-low, train-high” theory has been proposed [1]. This type of training is intended to gain synergistic training effects through intensive metabolic stress combined with exercise and hypoxia. A previous study, based on this theory, demonstrated improvements in maximal oxygen consumption (V O2max) and increased capillary density related to the upregulation of vascular endothelial growth factor-A (VEGFA) expression [1]. Many studies at the cellular level demonstrated that hypoxia inducible factor-1α (HIF-1α) had an important role in structural and metabolic adaptation to hypoxia and that hypoxia has been mainly investigated in association with HIF-1α, which stabilizes under hypoxia and leads to angiogenesis via upregulation of VEGF-A [5, 6].

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