AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 4 1189-R1196, Copyright © 1994 by American Physiological Society

ARTICLES

Autonomic functions and orthostatic responses 24 h after acute intense exercise in paraplegic subjects

K. A. Engelke, J. D. Shea, D. F. Doerr and V. A. Convertino
Department of Physiology, University of Florida, Gainesville 32610.

We tested the hypothesis that a bout of graded exercise designed to elicit maximal effort would increase the sensitivity of autonomically mediated baroreflexes and enhance blood pressure (BP) stability in subjects prone to postural hypotension. Therefore, we measured heart rate (HR), BP, forearm vascular resistance (FVR), and vasoactive hormone responses before and during 15 min of 70 degrees head-up tilt (HUT) in 10 paraplegic subjects (21-65 yr) on two occasions: 1) 24 h after maximal arm-crank exercise (postexercise) and 2) without exercise (control). During HUT, HR increased 30 beats/min in both postexercise and control, but the reduction in systolic BP (SBP) during control (-12.0 +/- 4.6 mmHg) was larger (P = 0.017) than that during HUT after exercise (-0.3 +/- 4.3 mmHg). The postexercise increase in FVR from supine to HUT of 17.0 +/- 2.4 to 24.8 +/- 3.2 peripheral resistance units (PRU) was greater (P = 0.042) than the increase observed during control (18.3 +/- 3.7 to 19.5 +/- 3.1 PRU). The gain of the carotid-cardiac baroreflex was also increased (P = 0.049) after exercise. Responses in norepinephrine, vasopressin, and plasma renin-angiotensin induced by HUT were similar for control and postexercise, and there was no difference in either leg compliance or plasma volume between the two conditions. Additionally, HR and SBP responses to phases II and IV of the Valsalva maneuver, indexes of integrated baroreflex sensitivity, were increased (P < 0.05) after maximal exercise compared with control. Thus acute intense exercise eliminated orthostatic hypotension in paraplegics, was associated with increased FVR and baroreflex sensitivity, and was independent of blood volume changes.

This article has been cited by other articles:

				V. A. Convertino Evidence for altered {alpha}-adrenoreceptor responsiveness after a single bout of maximal exercise J Appl Physiol, July 1, 2003; 95(1): 192 - 198. [Abstract] [Full Text] [PDF]

				J. M. Wecht, R. E. De Meersman, J. P. Weir, A. M. Spungen, and W. A. Bauman Cardiac homeostasis is independent of calf venous compliance in subjects with paraplegia Am J Physiol Heart Circ Physiol, June 1, 2003; 284(6): H2393 - H2399. [Abstract] [Full Text] [PDF]

				J. M. Wecht, R. E. de Meersman, J. P. Weir, W. A. Bauman, and D. R. Grimm Effects of autonomic disruption and inactivity on venous vascular function Am J Physiol Heart Circ Physiol, February 1, 2000; 278(2): H515 - H520. [Abstract] [Full Text] [PDF]