Autonomic adaptations in andean trained participants to a 4220-m altitude marathon.
OBJECTIVE
Both training and chronic hypoxia act on the autonomic nervous system. Because trained Andean high-altitude natives could perform a high-altitude marathon (4220 m above sea level) in 02:27:23 h, we hypothesized that living in chronic hypoxia does not limit the training-induced benefits on the autonomic modulation of the heart.


METHODS
Trained (N=13) and sedentary (N=11) Andean high-altitude natives performed an active orthostatic test. Eight of the trained subjects repeated the test 6-8 and 20-24 h after the end of a high-altitude marathon. Resting heart rate (HR) and the autonomic modulation of the heart were assessed by time domain and spectral analysis of HR variability (HRV): sympathetic (RR low frequency (LF)) and parasympathetic (RR high frequency (HF)) modulations, and sympathovagal balance (RR-LF:HF ratio).


RESULTS
Trained subjects exhibited a higher total power of HRV and a lower resting HR (+30%, P<0.005) than sedentary subjects secondary to a higher and dominant parasympathetic modulation on sympathetic activity (RR-HF, RR-LF:HF ratio). At 6-8 h after the marathon, total power of HRV decreased (-69%), whereas resting HR increased from basal level (+22%), mainly because of a rise in sympathetic modulation (RR-LF, RR-LF:HF ratio). From 8 to 24 h of recovery, sympathetic modulation fell (RR-LF, RR-LF:HF ratio) and all HRV parameters were restored. Responses to the active standing position did not change between each recording session.


CONCLUSIONS
Living in chronic hypoxia does not limit the training-induced benefits on the autonomic control of the cardiovascular system in Andean high-altitude natives. The sympathetic predominance on the heart observed 6-8 h after the high-altitude marathon disappeared after 1 d of recovery. Therefore, living at high altitude does not impair the autonomic response to training.
Cornolo
Jérémy
J
University Paris 13, ARPE, Laboratory of Functional and Cellular Responses to Hypoxia, Bobigny, FRANCE.
Brugniaux
Julien V
JV
Macarlupu
Jose-Luis
JL
Privat
Catherine
C
León-Velarde
Fabiola
F
Richalet
Jean-Paul
JP
D000222:Adaptation, Physiological; D000328:Adult; D000531:Altitude; D001341:Autonomic Nervous System / Q000502:physiology*; D016022:Case-Control Studies; D015444:Exercise / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010568:Peru; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013997:Time Factors