August 1, 1995Acta Physiologica Scandinavica
Cardiovascular response to exercise in humans following acclimatization to extreme altitude
Why the study?
How does acclimatization to extreme altitude affect cardiovascular responses to exercise under vagal/adrenergic blockade and acute normoxia?
Population
14 climbers on an expedition to the Himalayas, studied at a lower base camp following 56-81 days at…
Comparison
Vagal and adrenergic blockade and acute… vs Baseline exercise in chronic hypoxia without…
Design
Other
Follow-up
56-81 days (acclimatization period)
Authors
Discussion
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Implication
Blunted post-acclimatization HRpeak may affect exercise testing interpretation in returnees; leaves open sympathetic mechanisms in broader hypoxia cohorts.
Key Points
- To assess how prolonged acclimatization to extreme altitude alters cardiovascular responses during one- and two-legged maximal exercise, using autonomic blockades and acute oxygen restoration.
- Studied 14 Himalayan expedition climbers at 5,250 m following 56–81 days of acclimatization between 5,250 m and 8,700 m.
- Evaluated responses during maximal one- and two-legged cycling with vagal blockade (atropine), beta-1 adrenergic blockade, and acute 60% oxygen inhalation.
- Peak heart rate ranged from 113 to 168 beats min⁻¹ and was lowest after returning from higher camps, with acute 60% oxygen inhalation increasing peak heart rate by 5 to 35 beats min⁻¹ most markedly in participants with the lowest baseline peaks.
- Heart rate responses to beta-1 blockade increased alongside higher peak heart rates, whereas responses to atropine were lowest in subjects displaying higher peak heart rates.
- Peak heart rate, peak oxygen uptake, and noradrenaline levels were similar between one- and two-legged cycling, whereas peak plasma lactate reached higher concentrations during the one-legged protocol.
Structured PICO
How does acclimatization to extreme altitude affect cardiovascular responses to exercise under vagal/adrenergic blockade and acute normoxia?
P
Population
14 climbers on an expedition to the Himalayas, studied at a lower base camp (5250 m) following 56-81 days at altitudes between 5250 and 8700 m.
I
Intervention
Vagal and adrenergic blockade (beta-1 blockade, atropine) and acute restoration of normoxia (60% O2 inhalation) during maximal one- and two-legged cycling.
C
Comparator
Baseline exercise in chronic hypoxia without blockade/normoxia.
O
Outcome
Peak heart rate (HRpeak), oxygen uptake (VO2peak), noradrenaline (NA), and peak plasma lactate.surrogate
Acclimatization to extreme altitude reduces peak heart rate during exercise, which is linked to the severity of hypoxemia and attenuated cardiac sympathetic activation.
Cite This Study
Savard et al. (1995) studied this question.