Abstract |
We investigated the effects of aerobic training on the efferent autonomic control of heart rate (HR) during dynamic exercise in middle-aged men, eight of whom underwent exercise training (T) while the other seven continued their sedentary (S) life style. The training was conducted over 10 months (three 1-h/sessions/week on a field track at 70-85% of the peak HR). The contribution of sympathetic and para-sympathetic exercise tachycardia was determined in terms of differences in the time constant effects on the HR response obtained using a discontinuous protocol (4-min tests at 25, 50, 100 and 125 watts on a cycle ergometer), and a continuous protocol (25 watts/min until exhaustion) allowed the quantification of the parameters (anaerobic threshold, VO2 AT; peak O2 uptake, VO2 peak; power peak) that reflect oxygen transport. The results obtained for the S and the T groups were: 1) a smaller resting HR in T (66 beats/min) when compared to S (84 beats/min); 2) during exercise, a small increase in the fast tachycardia (delta 0-10 s) related to vagal withdrawal (P < 0.05, only at 25 watts) was observed in T at all powers; at middle and higher powers a significant decrease (P < 0.05 at 50, 100 and 125 watts) in the slow tachycardia (delta 1-4 min) related to a sympathetic-dependent mechanism was observed in T; 3) the VO2 AT (S = 1.06 and T = 1.33 l/min) and VO2 peak (S = 1.97 and T = 2.47 l/min) were higher in T (P < 0.05). These results demonstrate that aerobic training can induce significant physiological adaptations in middle-aged men, mainly expressed as a decrease in the sympathetic effects on heart rate associated with an increase in oxygen transport during dynamic exercise.
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Authors | M P Chacon-Mikahil, V A Forti, A M Catai, J S Szrajer, R Golfetti, L E Martins, E C Lima-Filho, J S Wanderley, J A Marin Neto, B C Maciel, L Gallo-Júnior |
Journal | Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
(Braz J Med Biol Res)
Vol. 31
Issue 5
Pg. 705-12
(May 1998)
ISSN: 0100-879X [Print] Brazil |
PMID | 9698778
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Topics |
- Adaptation, Physiological
- Exercise
- Heart Rate
(physiology)
- Humans
- Male
- Middle Aged
- Parasympathetic Nervous System
- Physical Exertion
- Sympathetic Nervous System
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