Muscle Oxygen Delivery in the Forearm and in the Vastus Lateralis Muscles in Response to Resistance Exercise: A Comparison Between Nepalese Porters and Italian Trekkers.

Vittore Verratti,Gabriele Mulliri,Antonio Crisafulli,Danilo Bondi,Paolo Cerretelli,Maria Erika Marinozzi,Giovanna Ghiani,Tiziana Pietrangelo

doi:10.3389/fphys.2020.607616

Abstract

Altitude ascending represents an intriguing experimental model reproducing physiological and pathophysiological conditions sharing hypoxemia as the denominator. The aim of the present study was to investigate fractional oxygen extraction and blood dynamics in response to hypobaric hypoxia and to acute resistance exercises, taking into account several factors including different ethnic origin and muscle groups. As part of the “Kanchenjunga Exploration & Physiology” project, six Italian trekkers and six Nepalese porters took part in a high altitude trek in the Himalayas. The measurements were carried out at low (1,450 m) and high altitude (HA; 4,780 m). Near-infrared spectroscopy (NIRS)-derived parameters, i.e., Tot-Hb and tissue saturation index (TSI), were gathered at rest and after bouts of 3-min resistive exercise, both in the quadriceps and in the forearm muscles. TSI decreased with altitude, particularly in forearm muscles (from 66.9 to 57.3%), whereas the decrement was less in the quadriceps (from 62.5 to 57.2%); Nepalese porters were characterized by greater values in thigh TSI than Italian trekkers. Tot-Hb was increased after exercise. At altitude, such increase appeared to be higher in the quadriceps. This effect might be a consequence of the long-term adaptive memory due to the frequent exposures to altitude. Although speculative, we suggest a long-term adaptation of the Nepalese porters due to improved oxygenation of muscles frequently undergoing hypoxic exercise. Muscle structure, individual factors, and altitude exposure time should be taken into account to move on the knowledge of oxygen delivery and utilization at altitude.

Highlights

Traveling at high altitude (HA) is nowadays very popular, but it requires medical advice in respect to altitude tolerance and acclimatization (Schommer and Bärtsch, 2011)
Oxygen saturation decreased with altitude in all participants, ranging from 80 to 92% at high altitude; all participants showed values in the normal physiological range at low altitude (LA)
Model fit measures suggested that tissue saturation index (TSI) had a better fit of the current analyses compared to Tot-Hb

Summary

Introduction

Traveling at high altitude (HA) is nowadays very popular, but it requires medical advice in respect to altitude tolerance and acclimatization (Schommer and Bärtsch, 2011). Common traveling conditions with Caucasian tourists along with local porters may have practical implications. It may help in unraveling differences between native lowlanders and highlanders in response to hypobaric hypoxia (Magliulo et al, 2020), thereby shedding light on the physiological adaptation to living permanently or working occasionally at altitude. With regard to exercise physiology, most of the plans for altitude training were based on oxygen delivery and supply adaptations, with a faster response of O2 muscular uptake (Doria et al, 2011), an enhanced vascular endothelial growth factor (Vogt et al, 2001), along with a detrimental effect on muscle tissue over the period of typical Himalayan expeditions (Vogt and Hoppeler, 2010)

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