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Type: Artigo de periódico
Title: Cardiorespiratory adaptations induced by aerobic training in middle-aged men: the importance of a decrease in sympathetic stimulation for the contribution of dynamic exercise tachycardia
Author: Chacon-Mikahil, MPT
Forti, VAM
Catai, AM
Szrajer, JS
Golfetti, R
Martins, LEB
Lima, EC
Wanderley, JS
Marin-Neto, JA
Maciel, BC
Gallo, L
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 parasympathetic 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, (V) over dot O-2 AT; peak O-2 uptake, (V) over dot O-2 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 (V) over dot O-2 AT (S = 1.06 and T = 1.33 l/min) and (V) over dot O-2 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.
Subject: sympathetic modulation of heart rate
dynamic exercise
aerobic training
autonomic nervous system
anaerobic threshold
middle-aged men
Country: Brasil
Editor: Assoc Bras Divulg Cientifica
Citation: Brazilian Journal Of Medical And Biological Research. Assoc Bras Divulg Cientifica, v. 31, n. 5, n. 705, n. 712, 1998.
Rights: aberto
Date Issue: 1998
Appears in Collections:Unicamp - Artigos e Outros Documentos

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