Exercise intensity typical of mountain climbing does not exacerbate acute mountain sickness in normobaric hypoxia

Abstract

Physical exertion is thought to exacerbate acute mountain sickness (AMS). In this prospective, randomized, crossover trial, we investigated whether moderate exercise worsens AMS in normobaric hypoxia (12% oxygen, equivalent to 4,500 m). Sixteen subjects were exposed to altitude twice: once with exercise [3 × 45 min within the first 4 h on a bicycle ergometer at 50% of their altitude-specific maximal workload (maximal oxygen uptake)], and once without. AMS was evaluated by the Lake Louise score and the AMS-C score of the Environmental Symptom Questionnaire. There was no significant difference in AMS between the exposures with and without exercise, neither after 5, 8, nor 18 h (incidence: 64 and 43%; LLS: 6.5 ± 0.7 and 5.1 ± 0.8; AMS-C score: 1.2 ± 0.3 and 1.1 ± 0.3 for exercise vs. rest at 18 h; all P > 0.05). Exercise decreased capillary Po(2) (from 36 ± 1 Torr at rest to 31 ± 1 Torr), capillary arterial oxygen saturation (from 72% at rest to 67 ± 2%), and cerebral oxygen saturation (from 49 ± 2% at rest to 42 ± 1%, as assessed by near-infrared spectroscopy; P < 0.05), and increased ventilation (capillary Pco(2) 27 ± 1 Torr; P < 0.05). After exercise, the increase in ventilation persisted for several hours and was associated with similar levels of capillary and cerebral oxygenation at the exercise and rest day. We conclude that moderate exercise at ~50% maximal oxygen uptake does not increase AMS in normobaric hypoxia. These data do not exclude that considerably higher exercise intensities exacerbate AMS.

Acute high-altitude sickness

“…People aged >40-60 years tend to develop AMS less than younger adults [27]. Recent studies examining the hypothesis that exercise enhances AMS yielded controversial results [29][30][31].…”

“…Avoiding overexertion following ascent is another commonly recommended measure, although studies have reported varying results about the relationship between exertion and risk of AMS [29,30,113]. Abrupt cessation of caffeine intake in chronic users of caffeinated beverages may provoke withdrawal symptoms that mimic those of AMS [114].…”

Comparison of capillary and venous blood in the analysis of concentration and function of leucocyte sub-populations

“…The higher expression of adhesion molecules observed in both capillary-drawn samples (Fig. 1) may also suggest that the routinely used methods adopted in this research to increase blood flow to these sampling sites, either via action of nonivamide and butoxyethyl nicotinate containing cream-Finalgon ® (Zavorsky et al 2005;Schommer et al 2012;Beneke and Alkhatib 2015) or submersion of limb in hot water, may have contributed to neutrophil activation. Nonivamide has been described to, when applied to the skin, induce release of vasodilative polypeptides such as calcitonin-gene-related peptide (CGRP) and substance P (Stucker et al 1999).…”

Cerebral Water and Ion Balance Remains Stable when Humans Are Exposed to Acute Hypoxic Exercise

“…Also, it should be considered that the study hypothesis was based on observation of AMS symptoms developed when hypoxic exposure is combined with moderate (Roach et al, 2000) and intense (Wu et al, 2012) exercise at altitude. However, mild to moderate intensity exercise apparently does not worsen AMS (Schommer et al, 2012;Rupp et al, 2013). In the present study, a 30 min high-intensity exercise protocol was applied.…”

“…Less than 1 h of hypoxic exposure can increase cerebral blood volume by 2 mL and brain parenchyma volume by 8 mL in a resting person (Dubowitz et al, 2009). Symptoms of AMS are more severe when hypoxic exposure is combined with exercise (Roach et al, 2000) and seems to be more frequent when intense (Wu et al, 2012) rather than moderate physical activity (Schommer et al, 2012) is carried out at altitude. Thus, even brief intense exercise in hypoxia may provoke the initial events that eventually lead to AMS.…”