Cardiac vagal modulation of heart rate during prolonged submaximal exercise in animals with healed myocardial infarctions: effects of training

2006 ◽  
Vol 290 (4) ◽  
pp. H1680-H1685 ◽  
Author(s):  
Monica Kukielka ◽  
Douglas R. Seals ◽  
George E. Billman
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Exercise Training ◽  
Submaximal Exercise ◽  
Treadmill Running ◽  
Myocardial Infarctions ◽  
Vagal Activity ◽  
Long Duration ◽  
Exercise Treadmill ◽  
Exercise Induced

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 ms2), 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 ms2; and posttraining: 1st min, 4.8 ± 1.1 vs. last min, 2.0 ± 0.6 ln ms2). 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.

Effects of endurance exercise training on heart rate variability and susceptibility to sudden cardiac death: protection is not due to enhanced cardiac vagal regulation

2006 ◽  
Vol 100 (3) ◽  
pp. 896-906 ◽  
Author(s):  
George E. Billman ◽  
Monica Kukielka
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Exercise Training ◽  
Control Period ◽  
Exercise Program ◽  
Submaximal Exercise ◽  
Myocardial Infarctions ◽  
Vagal Activity ◽  
Similar Response ◽  
Before And After

Low heart rate variability (HRV) is associated with an increased susceptibility to ventricular fibrillation (VF). Exercise training can increase HRV (an index of cardiac vagal regulation) and could, thereby, decrease the risk for VF. To test this hypothesis, a 2-min coronary occlusion was made during the last min of a 18-min submaximal exercise test in dogs with healed myocardial infarctions; 20 had VF (susceptible), and 13 did not (resistant). The dogs then received either a 10-wk exercise program (susceptible, n = 9; resistant, n = 8) or an equivalent sedentary period (susceptible, n = 11; resistant, n = 5). HRV was evaluated at rest, during exercise, and during a 2-min occlusion at rest and before and after the 10-wk period. Pretraining, the occlusion provoked significantly ( P < 0.01) greater increases in HR (susceptible, 54.9 ± 8.3 vs. resistant, 25.0 ± 6.1 beats/min) and greater reductions in HRV (susceptible, −6.3 ± 0.3 vs. resistant, −2.8 ± 0.8 ln ms2) in the susceptible dogs compared with the resistant animals. Similar response differences between susceptible and resistant dogs were noted during submaximal exercise. Training significantly reduced the HR and HRV responses to the occlusion (HR, 17.9 ± 11.5 beats/min; HRV, −1.2 ± 0.8, ln ms2) in the susceptible dogs; similar response reductions were noted during exercise. In contrast, these variables were not altered in the sedentary susceptible dogs. Posttraining, VF could no longer be induced in the susceptible dogs, whereas four sedentary susceptible dogs died during the 10-wk control period, and the remaining seven animals still had VF when tested. Atropine decreased HRV but only induced VF in one of eight trained susceptible dogs. Thus exercise training increased cardiac vagal activity, which was not solely responsible for the training-induced VF protection.

Effect of endurance exercise training on heart rate onset and heart rate recovery responses to submaximal exercise in animals susceptible to ventricular fibrillation

2007 ◽  
Vol 102 (1) ◽  
pp. 231-240 ◽  
Author(s):  
George E. Billman ◽  
Monica Kukielka
Keyword(s):  
Heart Rate ◽  
Ventricular Fibrillation ◽  
Exercise Training ◽  
Endurance Exercise ◽  
Submaximal Exercise ◽  
Treadmill Running ◽  
Vagal Activity ◽  
Endurance Exercise Training ◽  
Increased Risk ◽  
Exercise Onset

Both a large heart rate (HR) increase at exercise onset and a slow heart rate (HR) recovery following the termination of exercise have been linked to an increased risk for ventricular fibrillation (VF) in patients with coronary artery disease. Endurance exercise training can alter cardiac autonomic regulation. Therefore, it is possible that this intervention could restore a more normal HR regulation in high-risk individuals. To test this hypothesis, HR and HR variability (HRV, 0.24- to 1.04-Hz frequency component; an index of cardiac vagal activity) responses to submaximal exercise were measured 30, 60, and 120 s after exercise onset and 30, 60, and 120 s following the termination of exercise in dogs with healed myocardial infarctions known to be susceptible ( n = 19) to VF (induced by a 2-min coronary occlusion during the last minute of a submaximal exercise test). These studies were then repeated after either a 10-wk exercise program (treadmill running, n = 10) or an equivalent sedentary period ( n = 9). After 10 wk, the response to exercise was not altered in the sedentary animals. In contrast, endurance exercise increased indexes of cardiac vagal activity such that HR at exercise onset was reduced (30 s after exercise onset: HR pretraining 179 ± 8.4 vs. posttraining 151.4 ± 6.6 beats/min; HRV pretraining 4.0 ± 0.4 vs. posttraining 5.8 ± 0.4 ln ms2), whereas HR recovery 30 s after the termination of exercise increased (HR pretraining 186 ± 7.8 vs. posttraining 159.4 ± 7.7 beats/min; HRV pretraining 2.4 ± 0.3 vs. posttraining 4.0 ± 0.6 ln ms2). Thus endurance exercise training restored a more normal HR regulation in dogs susceptible to VF.

Contractile function and myofibrillar ATPase activity in the exercise-trained dog heart

1977 ◽  
Vol 43 (6) ◽  
pp. 977-982 ◽  
Author(s):  
R. T. Dowell ◽  
H. L. Stone ◽  
L. A. Sordahl ◽  
G. K. Asimakis
Keyword(s):  
Heart Rate ◽  
Exercise Training ◽  
Atpase Activity ◽  
Contractile Function ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Submaximal Exercise ◽  
Treadmill Running ◽  
Myofibrillar Atpase ◽  
Myofibrillar Atpase Activity

Myocardial contractility and the enzymatic (ATPase) activity of cardiac contractile proteins were examined after exercise training using the chronically instrumented, unanesthetized dog as an experimental model. Before training, heart rate and the maximum rate of left ventricular pressure development (max dP/dt) were measured at rest and during submaximal exercise. Animals were then subjected to an 8- to 10-wk treadmill running program. Training was verified by the establishment of a 10- to 20-beat/min reduction in heart rate during submaximal exercise. After training max dP/dt was within normal limits at rest, but significantly elevated during submaximal exercise. When max dP/dt was plotted as a function of heart rate, either with the animal standing quietly on the treadmill or during submaximal exercise, a marked elevation in max dP/dt at any given heart rate was observed following training. Myofibrillar protein yield and ATPase activity values were nearly identical in left ventricles from exercise-trained and sedentary control dogs. Although exercise training by treadmill running improved contractile function in the unanesthetized dog myocardium, this response does not appear to involve alterations in myofibrillar ATPase activity.

Heart rate recovery after exercise: a predictor of ventricular fibrillation susceptibility after myocardial infarction

2005 ◽  
Vol 288 (4) ◽  
pp. H1763-H1769 ◽  
Author(s):  
Lauren L. Smith ◽  
Monica Kukielka ◽  
George E. Billman
Keyword(s):  
Myocardial Infarction ◽  
Heart Rate ◽  
Ventricular Fibrillation ◽  
Heart Rate Recovery ◽  
Treadmill Running ◽  
Vagal Activity ◽  
Circumflex Artery ◽  
Left Circumflex Artery ◽  
Exercise Treadmill ◽  
Parasympathetic Tone

Heart rate recovery after exercise, thought to be related to cardiac parasympathetic tone, has been shown to be a prognostic tool for all-cause mortality. However, the relationship between this variable and confirmed susceptibility to ventricular fibrillation (VF) has not been established. Therefore, myocardial ischemia was induced with a 2-min occlusion of the left circumflex artery during the last minute of exercise in mongrel dogs with myocardial infarction ( n = 105 dogs). VF was induced in 66 animals (susceptible), whereas the remaining 39 dogs had no arrhythmias (resistant). On a previous day, ECG was recorded and a time-series analysis of heart rate variability was measured 30, 60, and 120 s after submaximal exercise (treadmill running). The heart rate recovery was significantly greater in resistant dogs than in susceptible dogs at all three times, with the most dramatic difference at the 30-s mark (change from maximum: 48.1 ± 3.6 beats/min, resistant dogs; 31.0 ± 2.2 beats/min, susceptible dogs). Correspondingly, indexes of parasympathetic tone increased to a significantly greater extent in resistant dogs at 30 and 60 s after exercise. These differences were eliminated by atropine pretreatment. When considered together, these data suggest that resistant animals exhibit a more rapid recovery of vagal activity after exercise than those susceptible to VF. As such, postexercise heart rate recovery may help identify patients with a high risk for VF following myocardial infarction.

Heart rate adaptation to exercise training in cardiac-denervated dogs

1982 ◽  
Vol 52 (6) ◽  
pp. 1586-1590 ◽  
Author(s):  
G. A. Ordway ◽  
J. B. Charles ◽  
D. C. Randall ◽  
G. E. Billman ◽  
D. R. Wekstein
Keyword(s):  
Heart Rate ◽  
Exercise Training ◽  
Exercise Test ◽  
Citrate Synthase ◽  
Submaximal Exercise ◽  
Treadmill Running ◽  
Heart Rates ◽  
Cardiac Denervation ◽  
Submaximal Exercise Test ◽  
Test Intensity

To determine the effect of cardiac denervation on the development of a training-induced decrease in heart rate at rest and during submaximal exercise, six cardiac-denervated (CD) and six sham-operated (SO) dogs were exercise trained by means of a 6-wk treadmill running program. Gastrocnemius citrate synthase activity increased significantly to the same degree in CD and SO dogs indicating that both groups were equally trained. Resting heart rates (RHR) for SO dogs decreased significantly from 64 +/- 4.8 to 51 +/- 3.2 beats/min (mean +/- SE) from pre- to posttraining. CD dogs showed no changes in RHR (95 +/- 3.5 to 96 +/- 5.3 beats/min). Heart rate responses of SO dogs to a standardized, submaximal exercise test decreased significantly from pre- to posttraining. However, CD dogs displayed no decrease in heart rate responses to the standardized, submaximal exercise test. Additionally, at pre- and posttraining, as heart rates rose in response to exercise test intensity, they increased to a significantly greater degree in SO dogs compared with CD dogs. The results indicate that in dogs, cardiac denervation prevents the decreases in resting heart rate and heart rate during submaximal exercise normally associated with endurance exercise training.

scholarly journals Direct measurement of vagal tone in rats does not show correlation to HRV

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joseph T. Marmerstein ◽  
Grant A. McCallum ◽  
Dominique M. Durand
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Neural Activity ◽  
Vagal Tone ◽  
Neural Recording ◽  
The Body ◽  
Autonomic Nerve ◽  
Vagal Activity ◽  
Recording Technology

AbstractThe vagus nerve is the largest autonomic nerve, innervating nearly every organ in the body. “Vagal tone” is a clinical measure believed to indicate overall levels of vagal activity, but is measured indirectly through the heart rate variability (HRV). Abnormal HRV has been associated with many severe conditions such as diabetes, heart failure, and hypertension. However, vagal tone has never been directly measured, leading to disagreements in its interpretation and influencing the effectiveness of vagal therapies. Using custom carbon nanotube yarn electrodes, we were able to chronically record neural activity from the left cervical vagus in both anesthetized and non-anesthetized rats. Here we show that tonic vagal activity does not correlate with common HRV metrics with or without anesthesia. Although we found that average vagal activity is increased during inspiration compared to expiration, this respiratory-linked signal was not correlated with HRV either. These results represent a clear advance in neural recording technology but also point to the need for a re-interpretation of the link between HRV and “vagal tone”.

Effect of exercise training on heart rate variability in healthy older adults

1999 ◽  
Vol 138 (3) ◽  
pp. 567-576 ◽  
Author(s):  
Phyllis K. Stein ◽  
Ali A. Ehsani ◽  
Peter P. Domitrovich ◽  
Robert E. Kleiger ◽  
Jeffrey N. Rottman
Keyword(s):  
Older Adults ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Exercise Training ◽  
Healthy Older Adults

scholarly journals Heart Rate Variability, Time Estimation and Internet-Dependent Behaviour in 16–17-Year-Old Adolescents: A Study in Russian Arctic

Life ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 497
Author(s):  
Olga Krivonogova ◽  
Elena Krivonogova ◽  
Liliya Poskotinova
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Internet Addiction ◽  
Internet Use ◽  
Time Estimation ◽  
Vagal Activity ◽  
Russian Arctic ◽  
Severe Withdrawal ◽  
Dependent Behaviour ◽  
Nenets Autonomous

Internet-dependent behaviour in adolescents can contribute to a change in the function of the nervous system, which is reflected in the violation of time perception and autonomic regulation of the heart rate. The aim of the study was to determine groups of individuals with different risks of Internet addiction (IA) in relation to heart rate variability (HRV) parameters and the efficiency of time estimation in adolescents aged 16–17 years living in the Russian Arctic. Adolescents aged 16–17 years (n = 49–32 females, 17 males) living in Yamalo-Nenets Autonomous Okrug (Russia) were observed. Chen Scale Internet Addiction (CIAS) was used. The duration of an individual 1 min was determined. HRV parameters were determined using the "Varicard" equipment (Russia). In 16–17-year-old adolescents with different levels of risk of developing IA, including signs of IA, we revealed a high severity of symptoms of withdrawal from Internet use, difficulty in time estimation against the background of sympathicotonia and a decrease in vagal regulation of heart rate. In individuals with minimal symptoms of withdrawal from Internet use, the total HRV and vagal activity remain higher than in those with severe withdrawal symptoms, and their time estimation remains effective.

Reduced heart rate variability during sleep in long-duration spaceflight

2013 ◽  
Vol 305 (2) ◽  
pp. R164-R170 ◽  
Author(s):  
D. Xu ◽  
J. K. Shoemaker ◽  
A. P. Blaber ◽  
P. Arbeille ◽  
K. Fraser ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Substantial Reduction ◽  
Space Station ◽  
Power Spectral Analysis ◽  
Power Spectral ◽  
Long Duration ◽  
Fractal Properties ◽  
Wide Range ◽  
Simultaneous Movement

Limited data are available to describe the regulation of heart rate (HR) during sleep in spaceflight. Sleep provides a stable supine baseline during preflight Earth recordings for comparison of heart rate variability (HRV) over a wide range of frequencies using both linear, complexity, and fractal indicators. The current study investigated the effect of long-duration spaceflight on HR and HRV during sleep in seven astronauts aboard the International Space Station up to 6 mo. Measurements included electrocardiographic waveforms from Holter monitors and simultaneous movement records from accelerometers before, during, and after the flights. HR was unchanged inflight and elevated postflight [59.6 ± 8.9 beats per minute (bpm) compared with preflight 53.3 ± 7.3 bpm; P < 0.01]. Compared with preflight data, HRV indicators from both time domain and power spectral analysis methods were diminished inflight from ultralow to high frequencies and partially recovered to preflight levels after landing. During inflight and at postflight, complexity and fractal properties of HR were not different from preflight properties. Slow fluctuations (<0.04 Hz) in HR presented moderate correlations with movements during sleep, partially accounting for the reduction in HRV. In summary, substantial reduction in HRV was observed with linear, but not with complexity and fractal, methods of analysis. These results suggest that periodic elements that influence regulation of HR through reflex mechanisms are altered during sleep in spaceflight but that underlying system complexity and fractal dynamics were not altered.

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