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Sustained sympathetic activity in altitude acclimatizing lowlanders and high‐altitude natives
Author(s) -
Lundby C.,
Calbet J.,
Hall G.,
Saltin B.,
Sander M.
Publication year - 2018
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.12976
Subject(s) - effects of high altitude on humans , acclimatization , altitude (triangle) , hypoxia (environmental) , heart rate , microneurography , blood pressure , acute exposure , sympathetic nervous system , medicine , altitude sickness , anesthesia , biology , baroreflex , chemistry , anatomy , oxygen , botany , geometry , mathematics , organic chemistry
Combined results from different independent studies suggest that acclimatization to high altitude induces a slowly developing sympathetic activation, even at levels of hypoxia that cause no acute chemoreflex‐mediated sympathoexcitation. We here provide direct neurophysiological evidence for this phenomenon. In eight Danish lowlanders, we quantified mean arterial blood pressure ( MAP ), heart rate ( HR ), and muscle sympathetic nerve activity ( MSNA ), twice at sea level (normoxia and with acute hypoxic exposure to 12.6% O 2 ) and twice at high altitude (after 10 and 50 days of exposure to 4100 m). Measurements were also obtained in eight Bolivian highlanders on one occasion at high altitude. Acute hypoxic exposure caused no increase in MSNA (15 ± 2 vs 16 ± 2 bursts per min, respectively, and also MAP and HR remained stable). In contrast, from sea level to 10 and 50 days in high‐altitude increases were observed in MAP : 72 ± 2 vs 78 ± 2 and 75 ± 2 mm Hg; HR : 54 ± 3 vs 67 ± 3 and 65 ± 3 beats per min; MSNA : 15 ± 2 vs 42 ± 5 and 42 ± 5 bursts per min, all P < .05. Bolivian subjects had high levels of MSNA : 34 ± 4 bursts per min. The simultaneous increase in MAP , HR , and MSNA suggests high altitude‐induced sympathetic activity, which is sustained in well‐acclimatized lowlanders. The high MSNA levels in the Bolivian highlanders suggest lifelong sympathetic activation at high altitude.