title: Interaction of cardiac and muscle mechanical afferents on baroreflex control of the sinus node during dynamic exercise.
abstract: The effects of cardiopulmonary baroreceptors and muscle mechanoreceptors stimulation on cardiac baroreflex sensitivity (BRS), and heart rate variability (HRV) were evaluated by measuring continuously and non-invasively systolic blood pressure (SBP) and pulse interval (PI) during upright and supine passive cycling. BRS and HRV were evaluated with the cross-correlation method (xBRS) and in the frequency domain, respectively. At rest, the shift from upright to supine posture enhanced xBRS from 16.4+/-12.1 to 23.4+/-12.9 ms/mmHg, and the high frequency (HF, 0.15-0.4 Hz) power of HRV from 48.9+/-18.6 to 55.1+/-14.7 normalized units (NU), while it attenuated the low-frequency (LF, 0.04-0.15 Hz) power from 51.1+/-18.6 to 44.9+/-14.7 NU (P<0.05), respectively. During both upright and supine passive exercise, xBRS and the HF power were attenuated (10.0+/-8.0 and 12.5+/-9.0 ms/mmHg; 41.1+/-21.2 and 41.5+/-12.7 NU, respectively; P<0.05) and the LF power increased (58.8+/-21.2 and 58.5+/-12.7 NU, P<0.05), compared with rest. The effect of mechanoreflex activation overrides that of the cardiopulmonary baroreceptors loading resulting in decreased cardiac vagal outflow and reduced BRS during supine passive exercise.
authors.affiliation: Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex, UK. luigi.vorluni@brunel.ac.uk
authors.forename: L
authors.initials: L
authors.lastname: Vorluni
authors.forename: S
authors.initials: S
authors.lastname: Volianitis
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001696:Biomechanical Phenomena; D001794:Blood Pressure; D002302:Cardiac Output / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D005082:Physical Exertion / Q000502:physiology*; D011674:Pulse; D012849:Sinoatrial Node / Q000502:physiology*; D017833:Visceral Afferents / Q000502:physiology*