The pulmonary vascular response to combined activation of the muscle metaboreflex and mechanoreflex.
Muscle metabo- and mechanoreflexes are known to influence systemic cardiovascular responses to exercise. Whether interplay between these reflexes is operant in the control of the pulmonary vascular response to exercise is unknown. The aim of this study was to assess the pulmonary vascular response to the combined activation of the two muscle reflexes. Nine healthy subjects performed a bout of isometric calf plantarflexion exercise during local circulatory occlusion, which was continued for 9 min postexercise (PECO). At 5 min into PECO the calf muscle was passively stretched for 180 s. A control (no exercise) protocol was also undertaken. Heart rate, blood pressure measurements and echocardiographically determined estimates of systolic pulmonary artery pressure (SPAP) and cardiac output ( ) were obtained at intervals throughout the two protocols. Elevations in SPAP (by 22.51 ± 2.61%), (by 26.92 ± 2.99%) and mean arterial pressure (by 15.38 ± 2.29%) were noted during isometric exercise in comparison to baseline (all P < 0.05). Increases in SPAP and mean arterial pressure persisted during PECO (All P < 0.05), whereas returned to resting levels. These increases in mean arterial pressure and SPAP were sustained during stretch which significantly elevated (All P < 0.05). These data suggest that activation of the muscle mechanoreflex attenuated the increases in pulmonary vascular resistance caused by metaboreflex activation. This finding has important implications for the regulation of pulmonary haemodynamics during human exercise.
School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. m.j.white@bham.ac.uk
Michael J
MJ
White
Christos K
CK
Lykidis
George M
GM
Balanos
D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology; D014655:Vascular Resistance