The effect of Normabaric Hypoxia on skeletal muscle oxygenation in 400m and endurance runners

Abstract

Skeletal muscle adaptations are known to occur when chronic physiological stress such as training occurs. Type I to type II transitions have been verified by research going in both directions. With the high oxygen uptake of type I fibres it can be understood that this can cause and increase in systemic O2 reduction during exercise, with it being exemplified in hypoxia. Leading to a hypothesis that a lower incidence of type I fibres, could allow for greater O2 management in hypoxic conditions. EN and SPR represented type I and type II muscle fibres respectively, due to their self reported training modality. During this study of 7 EN (mean age 29± 4.93 yr, height 180.86±6.09 cm, body mass 76.56±4.98 kg) and 5 SPR (mean age 21.8±2.86 yr, height 181.94±1.99 cm, body mass 74.86±2.72 kg), a supine cycling, sub-maximal protocol was followed. NIRS was utilised to measure THC and SmO2 of the VL. It was observed that there was no main effect of training status (p>0.05) on THC in both hypoxia and normoxia. SmO2 in hypoxia presented no significant difference in all statistical testing (p>0.05). Normoxic conditions presented an inclination to a relationship between SmO2 and training status (p=0.0688), graphically identifying SPR attaining lower SmO2. These findings support the hypothesis that in hypoxia, a high incidence of type I fibres causes a greater reduction in SmO2. And infers that due to a lower prevalence of type I in SPR, they can perform in hypoxia to a greater extent as a result of a lower rate of O2 utilisation. As a result of these findings, sports performers could be informed about the possible effects of their training on their ability in hypoxia. Allowing for modifications prior to performance such as an increase in anaerobic exercise.