Cardiac Vagal Modulation of Heart Rate During Prolonged Submaximal Exercise in Animals with Healed Myocardial Infarctions: Effects of Training.
From: Dept. of Physiology, The Ohio State University, Columbus, OH 43210-1218, USA.
American journal of physiology. Heart and circulatory physiology
- Publish Date: Apr 2006
- ISSN: 0363-6135
- Volume: 290
- Issue: 4
- Pages: H1680-5
- Medium: Print
- Language: English
- Citation (JAMA): Kukielka Monica, Seals Douglas R, Billman George E, et al. Cardiac Vagal Modulation of Heart Rate During Prolonged Submaximal Exercise in Animals with Healed Myocardial Infarctions: Effects of Training.. Am. J. Physiol. Heart Circ. Physiol. Apr 2006;290:H1680-5
Abstract
The present study investigated the effects of long-duration exercise on heart rate variability [as a marker of cardiac vagal tone (VT)]. Heart rate variability (time series analysis) was measured in mongrel dogs (n = 24) with healed myocardial infarctions during 1 h of submaximal exercise (treadmill running at 6.4 km/h at 10% grade). Long-duration exercise provoked a significant (ANOVA, all P < 0.01, means +/- SD) increase in heart rate (1st min, 165.3 +/- 15.6 vs. last min, 197.5 +/- 21.5 beats/min) and significant reductions in high frequency (0.24 to 1.04 Hz) power (VT: 1st min, 3.7 +/- 1.5 vs. last min, 1.0 +/- 0.9 ln ms(2)), R-R interval range (1st min, 107.9 +/- 38.3 vs. last min, 28.8 +/- 13.2 ms), and R-R interval SD (1st min, 24.3 +/- 7.7 vs. last min 6.3 +/- 1.7 ms). Because endurance exercise training can increase cardiac vagal regulation, the studies were repeated after either a 10-wk exercise training (n = 9) or a 10-wk sedentary period (n = 7). After training was completed, long-duration exercise elicited smaller increases in heart rate (pretraining: 1st min, 156.0 +/- 13.8 vs. last min, 189.6 +/- 21.9 beats/min; and posttraining: 1st min, 149.8 +/- 14.6 vs. last min, 172.7 +/- 8.8 beats/min) and smaller reductions in heart rate variability (e.g., VT, pretraining: 1st min, 4.2 +/- 1.7 vs. last min, 0.9 +/- 1.1 ln ms(2); and posttraining: 1st min, 4.8 +/- 1.1 vs. last min, 2.0 +/- 0.6 ln ms(2)). The response to long-duration exercise did not change in the sedentary animals. Thus the heart rate increase that accompanies long-duration exercise results, at least in part, from reductions in cardiac vagal regulation. Furthermore, exercise training attenuated these exercise-induced reductions in heart rate variability, suggesting maintenance of a higher cardiac vagal activity during exercise in the trained state.
Mesh Headings (Keywords): Animals, Dogs, Exertion, Feedback, Heart, Heart Rate, Myocardial Infarction, Physical Conditioning, Animal, Physical Endurance, Recovery of Function, Vagus Nerve
Check for Full Text / PubMed Unique Identifier (PMID): 16339826
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