Journal of Applied Physiology, Vol 79, Issue 3 805-811, Copyright © 1995 by American Physiological Society

ARTICLES

Lesser vagal withdrawal during isometric exercise with age

J. A. Taylor, J. Hayano and D. R. Seals
Hebrew Rehabilitation Center for the Aged, Beth Israel Hospital, Boston, Massachusetts, USA.

The tachycardia that accompanies isometric exercise decreases with age in humans; however, the mechanism of this decline is unknown. To determine whether less cardiac vagal withdrawal is associated with the age-related decrease in this response, we assessed high-frequency R-R interval variability (0.15-0.40 Hz), an index of cardiac vagal tone, before (control) and during isometric exercise to exhaustion in healthy young (21-29 yr; n = 12) and older (61-72 yr; n = 11) men. During control, the two groups did not differ in respiratory rate, mean arterial pressure, or heart rate, although the older subjects had a lower high-frequency amplitude (12.2 +/- 1.1 vs. 29.4 +/- 4.6 ms/Hz; P < 0.05). During isometric exercise, the respiratory rate and arterial pressure responses did not differ; however, the older men had a lower absolute heart rate and a smaller increase in heart rate, and only the young men demonstrated a significant decline in high-frequency amplitude. The heart rate responses to exercise were correlated with the declines in high-frequency amplitude (initial, r = -0.808; midpoint, r = -0.714; peak, r = -0.632; all P < 0.005), which were, in turn, correlated with the control high-frequency amplitude (initial, r = -0.727; midpoint, r = -0.643; peak, r = -0.610; all P < 0.01). Thus smaller declines in high-frequency amplitude, related to lower baseline amplitude, corresponded to smaller increases in heart rate throughout isometric exercise. Therefore, we conclude that the smaller tachycardiac response to isometric exercise in older humans is associated with an inability to decrease cardiac vagal tone below an already reduced baseline level.

This article has been cited by other articles:

				M. Takahashi, K. Matsukawa, T. Nakamoto, H. Tsuchimochi, A. Sakaguchi, K. Kawaguchi, and K. Onari Control of heart rate variability by cardiac parasympathetic nerve activity during voluntary static exercise in humans with tetraplegia J Appl Physiol, November 1, 2007; 103(5): 1669 - 1677. [Abstract] [Full Text] [PDF]

				R. Barbieri, E. C. Matten, A. A. Alabi, and E. N. Brown A point-process model of human heartbeat intervals: new definitions of heart rate and heart rate variability Am J Physiol Heart Circ Physiol, January 1, 2005; 288(1): H424 - H435. [Abstract] [Full Text] [PDF]

				D. D. Christou, P. Parker Jones, A. E. Pimentel, and D. R. Seals Increased abdominal-to-peripheral fat distribution contributes to altered autonomic-circulatory control with human aging Am J Physiol Heart Circ Physiol, October 1, 2004; 287(4): H1530 - H1537. [Abstract] [Full Text] [PDF]

				J. Hayano and F. Yasuma Hypothesis: respiratory sinus arrhythmia is an intrinsic resting function of cardiopulmonary system Cardiovasc Res, April 1, 2003; 58(1): 1 - 9. [Abstract] [Full Text] [PDF]

				P. P. Jones, L. F. Shapiro, G. A. Keisling, J. Jordan, J. R. Shannon, R. A. Quaife, and D. R. Seals Altered Autonomic Support of Arterial Blood Pressure With Age in Healthy Men Circulation, November 13, 2001; 104(20): 2424 - 2429. [Abstract] [Full Text] [PDF]

				K. Ishida, Y. Sato, K. Katayama, and M. Miyamura Initial ventilatory and circulatory responses to dynamic exercise are slowed in the elderly J Appl Physiol, November 1, 2000; 89(5): 1771 - 1777. [Abstract] [Full Text] [PDF]

				H. Olsen, E. Vernersson, and T. Lanne Cardiovascular response to acute hypovolemia in relation to age. Implications for orthostasis and hemorrhage Am J Physiol Heart Circ Physiol, January 1, 2000; 278(1): H222 - H232. [Abstract] [Full Text] [PDF]

				F. Iellamo, P. Pizzinelli, M. Massaro, G. Raimondi, G. Peruzzi, and J. M. Legramante Muscle Metaboreflex Contribution to Sinus Node Regulation During Static Exercise : Insights From Spectral Analysis of Heart Rate Variability Circulation, July 6, 1999; 100(1): 27 - 32. [Abstract] [Full Text] [PDF]

				S. Sakata, J. Hayano, S. Mukai, A. Okada, and T. Fujinami Aging and spectral characteristics of the nonharmonic component of 24-h heart rate variability Am J Physiol Regulatory Integrative Comp Physiol, June 1, 1999; 276(6): R1724 - R1731. [Abstract] [Full Text] [PDF]