Chemoreflex and metaboreflex control during static hypoxic exercise.
To investigate the effects of muscle metaboreceptor activation during hypoxic static exercise, we recorded muscle sympathetic nerve activity (MSNA), heart rate, blood pressure, ventilation, and blood lactate in 13 healthy subjects (22 +/- 2 yr) during 3 min of three randomized interventions: isocapnic hypoxia (10% O(2)) (chemoreflex activation), isometric handgrip exercise in normoxia (metaboreflex activation), and isometric handgrip exercise during isocapnic hypoxia (concomitant metaboreflex and chemoreflex activation). Each intervention was followed by a forearm circulatory arrest to allow persistent metaboreflex activation in the absence of exercise and chemoreflex activation. Handgrip increased blood pressure, MSNA, heart rate, ventilation, and lactate (all P < 0.001). Hypoxia without handgrip increased MSNA, heart rate, and ventilation (all P < 0.001), but it did not change blood pressure and lactate. Handgrip enhanced blood pressure, heart rate, MSNA, and ventilation responses to hypoxia (all P < 0.05). During circulatory arrest after handgrip in hypoxia, heart rate returned promptly to baseline values, whereas ventilation decreased but remained elevated (P < 0.05). In contrast, MSNA, blood pressure, and lactate returned to baseline values during circulatory arrest after hypoxia without exercise but remained markedly increased after handgrip in hypoxia (P < 0.05). We conclude that metaboreceptors and chemoreceptors exert differential effects on the cardiorespiratory and sympathetic responses during exercise in hypoxia.
Houssiere
Anne
A
Dept. of Physiology, Faculty of Medicine, Erasme University Hospital, 808 Lennik Rd., B-1070 Brussels, Belgium.
Najem
Boutaina
B
Ciarka
Agniezka
A
Velez-Roa
Sonia
S
Naeije
Robert
R
van de Borne
Philippe
P
D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D002628:Chemoreceptor Cells / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000502:physiology
D002245:Carbon Dioxide