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ABSTRACT: Reduced baroreceptor sensitivity (BRS) results in changes in autonomic modulation. Patients with chronic obstructive pulmonary disease (COPD) may have altered BRS. Therefore, we compared BRS between COPD patients and normal controls.
We compared 14 COPD patients [mean (±SD) age, 62 ± 8 years] to 14 healthy controls [mean (±SD) age, 59 ± 6 years] for the loss of BRS. All patients received β(2)-agonist therapy but were free from any other type of medication that would interfere with autonomic responses, all controls were free from cardiopulmonary disease, and none was taking medications. All participants were female, post-menopausal, had no known cardiac disease and were ex-smokers. Reduced baroreceptor sensitivity was determined using the slope of the magnitude of R-R widening over the increase in systolic blood pressure following Valsalva maneuver.
The mean BRS in controls versus COPD patients showed a mean value of 6.15 ± 2.26 versus 1.91 ± 2.92 ms/mmHg (p < 0.001).
These findings are consistent with other abnormalities of autonomic disruption as previously reported, and demonstrate a severe blunting of the baroreceptor response in individuals with COPD. The cause of this altered BRS response in COPD is not fully clear, we postulate that air trapping with persistent elevation of intrathoracic pressure may lead to a subsequent blunting of the sensitivity of the baroreceptors.
Clinical Autonomic Research 04/2012; 22(4):185-9. · 1.30 Impact Factor
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ABSTRACT: Aerobic exercise is a powerful mechanism by which cardiovascular and autonomic parameters may be improved. We sought to quantify the extent of benefit that could be achieved by a short-term monitored exercise regimen on several autonomic parameters during recognized mental and physical stressors in young normotensive African-American men matched for a family history of hypertension, a group at high risk for the development of hypertension. Autonomic modulations were derived using spectral decomposition of the electrocardiogram and beat-to-beat blood pressures (BPs). Arterial compliance was obtained using contour analysis of the radial artery pulse wave. The analysis of variance revealed that compared with a matched sedentary control group, aerobic capacity of the trained group significantly increased by 16%. Autonomic modulations, arterial compliance and BP responses significantly improved during some of the stressors, whereas no such improvements were seen in the control group. Attenuated responses, mediated through a favourable shift in sympathovagal balance and enhanced arterial compliance, provide mechanistic evidence of how certain variables may be improved due to aerobic conditioning in a population at high risk for the development of hypertension.
Journal of human hypertension 11/2008; 23(4):267-73. · 2.80 Impact Factor
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ABSTRACT: The application of principal component analysis and cluster analysis (PCA-CA) using heart rate variability (HRV) parameters to identify the most severe chronic obstructive pulmonary disease (COPD) subjects in a mixture of normal and COPD population is discussed. These parameters were obtained from real physiological data and cross-spectral analysis (i.e. the coherence and partial coherence between heart rate, blood pressure and respiration signals). Results demonstrated that these two groups could be differentiated with greater than 99.0% accuracy. Furthermore, differences on the same HRV parameters between all four severity levels of COPD subjects were also investigated. These groups were differentiated with over 88.0% accuracy. In analyzing the studied data of the COPD population, the technique correctly characterized 8.5% of COPD group as severe COPD. It was concluded that the PCA-CA technique identified the combination of parameters that can classify disease severity (COPD) as well as differences between normal and COPD subjects in a mixed population. The PCA-CA technique could perhaps also be used to classify other diseases non-invasively.
Bioengineering Conference, 2003 IEEE 29th Annual, Proceedings of; 04/2003
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ABSTRACT: The purpose of this study was to determine how heart rate and
blood pressure variabilities (HRV and BPV) change with steady-state
exercise up to the ventilatory threshold (VT). The VT was determined
using the V-slope method of computer regression analysis of the plot of
carbon dioxide production versus oxygen consumption (VO2max). Twelve
healthy subjects performed 1) cycle ergometry (exercise protocol) at
50%, 75% and 100% of previously determined VT and 2) sitting at rest and
breathing at matched respiratory rates and volume (controlled breathing,
CB) as during the exercise protocol. Throughout the CB protocol carbon
dioxide was added to maintain normal gas homeostasis. Heart rate and
blood pressure spectra for both protocols were derived from 3-minute
epochs of stationary data using frequency domain analyses. These data
were analyzed by repeated measures ANOVA and coherence analyses between
heart rate and respiration as well as blood pressure and respiration.
The ANOVA revealed significant changes in heart rate and blood pressure
spectra for both low frequency (LF, 0.04-0.15 Hz) and high frequency
(HF, 0.15-0.4 Hz) modulations between all stages of the exercise
protocol (p<0.05) but no significant changes for any of the CB
protocol. Coherence analyses showed significant decrease in heart rate
and blood pressure coherences during exercise than during control
breathing
Bioengineering Conference, 2002. Proceedings of the IEEE 28th Annual Northeast; 02/2002
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ABSTRACT: The effects of autonomic dysfunction and regular activity on the cardiovascular system were investigated. The 48 participants included 12 subjects with tetraplegia, 12 subjects with paraplegia, 12 sedentary subjects, and 12 endurance-trained able-bodied controls. Central and peripheral autonomic data were obtained at rest to estimate efferent cardiac vagal output and sympathetic vasomotor control, and plasma norepinephrine concentration was determined as a marker of peripheral sympathetic activity. Cardiovascular parameters were obtained using a noninvasive cardiac output maneuver. The group with paraplegia did not differ from the sedentary group for efferent cardiac vagal output, but all other group comparisons were different (p <0.05). Sympathetic vasomotor control and stroke index were also similar between the paraplegia and sedentary groups, whereas both were increased in the endurance-trained group and were significantly reduced in the tetraplegia group. A strong relation between efferent cardiac vagal output and stroke index was established for the total group (r = 0.78, p <0.01), and analysis of covariance determined that the slope of this relation was similar among the groups. Sympathetic vasomotor control correlated significantly with plasma norepinephrine (r = 0.57, p <0.01), and a relation between sympathetic vasomotor control and stroke index was identified for the total group (r = 0.40, p <0.01). These results suggest that vagal control of resting central cardiac function is maintained despite autonomic dysfunction. The comparable findings in the paraplegia and sedentary groups suggest that regardless of peripheral autonomic dysfunction, the absence of regular physical activity has a similar effect on the resting vagal modulation and stroke index.
Clinical Autonomic Research 02/2001; 11(1):29-34. · 1.30 Impact Factor
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ABSTRACT: Loss of autonomic balance characterized by increased sympathetic activity and decreased vagal activity has been implicated as a major cardiovascular risk factor. Aspirin's cardioprotective abilities involve a multitude of physiologic processes. However, the effects of aspirin on cardiac autonomic activity are unknown. In a double-blind crossover study, 22 subjects randomly received either aspirin or placebo in the amounts of 325 mg with each meal (three times per day) over a 2.5-day period. The total amount of aspirin ingested was 2,275 mg, which resulted in plasma levels of 3.3 mg/dl. At the conclusion of each treatment, subjects were evaluated for autonomic physiology activity using standard autonomic tests. Power spectral analyses of the electrocardiograms were used to delineate autonomic function. A 2 x 4 repeated measures analysis of variance revealed significant and favorable changes in autonomic activity after the use of aspirin. Specifically, at rest high-frequency (HF) power was significantly higher (mean, 1,090 + 1,463.5 msec2) compared with the placebo (mean, 692 742 msec2) (p <0.05). Low-frequency (LF) power was significantly reduced (mean, 963 745 msec2) after aspirin compared with placebo (mean, 1,100 906 msec2). After the aspirin treatment, a significantly lower LF-to-HF power ratio (mean, 1.7 2 msec2) was noted at rest when compared with the placebo (mean, 2.5 2.7 msec2) (p <0.05). Similar significant trends were seen during the sustained isometric contraction after aspirin therapy for HF power (mean 210 2.15 msec2) compared with placebo (mean, 213 184 msec2) (p <0.05). Accordingly, the LF-to-HF power ratio was lower as well when compared to placebo treatment (mean, 2.3 3.5 msec2) (mean, 5.3 8.4 msec2) (p <0.05). No differences were found in breathing rates for hemodynamic variables between any of the protocols. The significant reduction of LF-to-HF ratio, a marker of sympathovagal balance, for both protocols appeared to be largely due to a withdrawal of LF modulation and concomitant but lesser increase in HF modulation. Favorable alterations in autonomic outflow through prostaglandin inhibition may be one of the mechanisms by which low therapeutic amounts of aspirin provide prophylactic cardioprotection.
Clinical Autonomic Research 09/2000; 10(4):197-201. · 1.30 Impact Factor
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ABSTRACT: Patients with COPD have an increased sympathetic modulation and reduced baroreflex sensitivity (BRS). Therefore, we studied the effects of breathing 31% supplemental oxygen (SuppO(2)) on autonomic modulation in a group of COPD patients.
We measured autonomic modulation before and during the administration of SuppO(2) on 51 patients with COPD using time-frequency analysis of R-R intervals and BP before and after intervention. This was done via a counterbalanced crossover design. The BRS index was determined using the sequence method.
Significant differences were seen in oxygen saturation levels following breathing with SuppO(2) ([mean +/- SD] 96.4+/-1.5%) when compared to those seen after breathing with compressed air (CA) (92.8+/-2.9%; p<0.0001). Significant increases were seen in the natural log-transformed high-frequency modulation (HFln) (SuppO(2), 10.8+/-1.3 natural logarithm [ln] ms(2)/Hz; CA, 10.6+/-1.3 ln ms(2)/Hz; p<0.028) and BRS (SuppO(2), 3.3+/-2.2 ms/mm Hg; CA, 2.8+/-1.8 ms/mm Hg) following the supplemental oxygen treatment (p<0.015). The low-frequency/high-frequency ratio of heart rate variability revealed significant differences between the two treatments (SuppO(2), 2.7 +/-1.2; CA, 3.1+/-1.3; p<0.008). The analysis of BP variability data revealed significant decreases in the HFln (CA, 6.9+/-1.0 mm Hg(2)/Hz; SuppO(2), 6.5+/-1.2 mm Hg(2)/Hz; p<0.0001). Hemodynamic data also revealed a decrease in mean heart rate after breathing SuppO(2) compared with that after breathing CA (CA, 87.3+/-13.3 beats/min; SuppO(2), 85.0+/-12.4 beats/min; p<0.0004). The arterial pulse pressure significantly decreased when breathing SuppO(2) compared with that when breathing CA (CA, 57.2+/-13.5 mm Hg; SuppO(2), 53.3+/-13.0 mm Hg; p<0.0023).
Oxygen supplementation in COPD patients significantly and favorably alters autonomic modulation.
Chest 09/2000; 118(3):691-6. · 5.25 Impact Factor
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ABSTRACT: Twenty-six healthy subjects with a diagnosis of Präder-Willi syndrome were compared with 26 age-, gender-, and body mass index-matched controls for autonomic modulation and baroreflex sensitivity. Electrocardiograms, beat-to-beat finger blood pressures, and respiration were recorded for several minutes in the following sequence: (1) supine, (2) after transition from supine to standing, (3) sitting, (4) during a Valsalva maneuver, (5) while performing moderate exercise, and (6) during recovery from exercise while seated. All recordings were channeled and stored in a computer; analyses were carried out at a later date. Power spectral analysis (fast-Fourier transform) of heart period variability was used to assess cardiac autonomic modulation. The slope of the regression equation between heart period and blood pressure rise after the Valsalva maneuver was used as an index of baroreflex sensitivity. Analysis of variance failed to reveal significant differences in any of the autonomic and baroreflex sensitivity variables between the two groups. Because breathing patterns entrain autonomic modulation, we verified respiration and found no differences between the two groups. Therefore, findings in the current investigation indicate that cardiac autonomic modulation in patients with Präder-Willi syndrome does not differ from age and body mass index-matched subjects.
Clinical Autonomic Research 09/2000; 10(4):203-6. · 1.30 Impact Factor
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ABSTRACT: The effects of autonomic disruption and inactivity were studied on the venous vascular system. Forty-eight subjects, 24 with spinal cord injury (SCI) and 12 sedentary and 12 active able-bodied controls, participated in this study. Peripheral autonomic data were obtained to estimate sympathetic vasomotor control [low-frequency component of systolic blood pressure (LF(SBP))]. Vascular parameters were determined using strain-gauge venous occlusion plethysmography: venous capacitance (VC), venous emptying rate (VER), and total venous outflow (VO(t)). An additional vascular parameter was calculated: venous compliance [(VC/occlusion pressure) x 100]. VC and VO(t) were significantly different (SCI < sedentary < active). VER adjusted for VC was not different for any group comparison, whereas venous compliance was significantly lower in the SCI group than in the able-bodied groups and in the sedentary group compared with the active group. Regression analysis for the total group revealed a significant relationship between LF(SBP) and venous compliance (r = 0.64, P < 0.0001). After controlling for LF(SBP) through analysis of covariance, we found that mean differences for all venous vascular parameters did not change from unadjusted mean values. Our findings suggest that in subjects with SCI, the loss of sympathetic vasomotor tone contributes more than inactivity to reductions in venous vascular function. Heightened VC, VO(t), vasomotor tone, and venous compliance in the active group compared with the sedentary group imply that regular endurance training contributes to optimal venous vascular function and peripheral autonomic integrity.
AJP Heart and Circulatory Physiology 02/2000; 278(2):H515-20. · 3.71 Impact Factor
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ABSTRACT: Mechanoreceptor contribution to efferent autonomic outflow is incompletely understood. To determine the effects of mechanoreceptor stimulation on autonomic reflexes, we compared autonomic responses in 34 subjects using a cross-over, counter-balanced design, in which hemodynamic, electromyographic, metabolic, and autonomic data were gathered during rest, passive, and active movement protocols. Because metaboreceptors and ventilatory responses influence autonomic outflow we verified and controlled for these influences during all protocols through comparisons of breath-by-breath gas exchange measurements. Verification of active and passive movements was made via electromyographic recordings of the moving legs. Spectral analysis of R-R variability was used to assess autonomic activity, and low to high frequency ratios were considered representative of sympathovagal balance. A repeated measures analysis of variance revealed significant modulating effects of mechanoreceptor stimulation on sympathovagal balance during passive movement upon efferent autonomic outflow (p < 0.01) independent of central command, chemoreceptor, and metaboreceptor stimulation. Furthermore, breathing frequency and volume were identical for both movement protocols. Therefore, findings in this investigation suggest that modulating influences are being exerted by mechanoreceptor stimulation on autonomic outflow to the heart.
Clinical Autonomic Research 09/1998; 8(4):201-5. · 1.30 Impact Factor
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ABSTRACT: The pathogenesis of blood pressure (BP) rise in aging women remains unexplained, and one of the many incriminating factors may include abnormalities in arteriolar resistance vessels. The aim of this study was to determine the effects of unopposed estrogen on arteriolar distensibility, baroreceptor sensitivity (BRS), BP changes, and rate-pressure product (RPP). We tested the hypotheses that estrogen replacement therapy (ERT) enhances arteriolar distensibility and ameliorates BRS, which leads to decreases in BP and RPP. Postmenopausal women participated in a single-blind crossover study; the participants of this study, after baseline measurements, were randomly assigned to receive estrogen (ERT) or a drug-free treatment with a 6-wk washout period between treatments. The single-blind design was instituted because subjects become unblinded due to physiological changes (i.e., fluid shifts, weight gain, and secretory changes) associated with estrogen intake. However, investigators and technicians involved in data collection and analyses remained blind. After each treatment, subjects performed identical autonomic tests, during which electrocardiograms, beat-by-beat BPs, and respiration were recorded. The area under the dicrotic notch of the BP wave was used as an index of arteriolar distensibility. The magnitude of the reflex bradycardia after a precipitous rise in BP was used to determine BRS. Power spectral analysis of heart rate variability was used to assess autonomic activity. BPs were recorded from resistance vessels in the finger using a beat-by-beat photoplethysmographic device. RPP, a noninvasive marker of myocardial oxygen consumption, was calculated. Repeated-measures analyses of variance revealed a significantly enhanced arteriolar distensibility and BRS after ERT (P < 0.05). A trend of a lower sympathovagal balance at rest was observed after ERT, however, this trend did not reach statistical significance (P = 0.061) compared with the other treatments. The above autonomic changes produced significantly lower systolic and diastolic BP changes and RPPs (P < 0.05) at rest and during isometric exercise. We conclude that short-term unopposed ERT favorably enhances arteriolar distensibility, BRS, and hemodynamic parameters in postmenopausal women. These findings have clinical implications in the goals for treating cardiovascular risk factors in aging women.
The American journal of physiology 06/1998; 274(5 Pt 2):H1539-44.
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ABSTRACT: This study tested the hypothesis that skeletal muscle mass is reduced in elderly women and men after adjustment first for stature and body weight. The hypothesis was evaluated by estimating appendicular skeletal muscle mass with dual-energy X-ray absorptiometry in a healthy adult cohort. A second purpose was to test the hypothesis that whole body 40K counting-derived total body potassium (TBK) is a reliable indirect measure of skeletal muscle mass. The independent effects on both appendicular skeletal muscle and TBK of gender (n = 148 women and 136 men) and ethnicity (n = 152 African-Americans and 132 Caucasians) were also explored. Main findings were 1) for both appendicular skeletal muscle mass (total, leg, and arm) and TBK, age was an independent determinant after adjustment first by stepwise multiple regression for stature and weight (multiple regression model r2 = approximately 0.60); absolute decrease with greater age in men was almost double that in women; significantly larger absolute amounts were observed in men and African-Americans after adjustment first for stature, weight, and age; and >80% of within-gender or -ethnic group between-individual component variation was explained by stature, weight, age, gender, and ethnicity differences; and 2) most of between-individual TBK variation could be explained by total appendicular skeletal muscle (r2 = 0.865), whereas age, gender, and ethnicity were small but significant additional covariates (total r2 = 0.903). Our study supports the hypotheses that skeletal muscle is reduced in the elderly and that TBK provides a reasonable indirect assessment of skeletal muscle mass. These findings provide a foundation for investigating skeletal muscle mass in a wide range of health-related conditions.
Journal of Applied Physiology 08/1997; 83(1):229-39. · 3.75 Impact Factor
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ABSTRACT: This study investigated the effect of abnormal autonomic cardiovascular function on heart rate variability (HRV) in individuals classified into four groups: complete quadriplegia, incomplete quadriplegia, low paraplegia, and non-spinal cord injury (SCI) controls. Measurements were collected at baseline and during provocative maneuvers. Spectral analysis using a fast-Fourier transform algorithm revealed two spectral components of HRV, termed low frequency (LF) and high frequency (HF); the LF-to-HF ratio (estimate of sympathovagal balance) was also calculated. Each group of subjects with quadriplegia exhibited significantly lower spectral components for both baseline and composite provocative measures compared with the non-SCI controls (P < 0.05). In addition, the group with paraplegia demonstrated significantly lower HF baseline and LF composite levels than controls (P < 0.05). No differences were observed among all groups for the LF-to-HF ratio. This consistency in the LF-to-HF ratio suggests that the two autonomic divisions that regulate the cardiovascular system maintain homeostasis even when one component is severely compromised. This is supported by the additional findings of decreased parasympathetic activity in the two groups with quadriplegia and the absence of significant differences among any of the four groups at rest in either heart rate or blood pressure.
The American journal of physiology 02/1997; 272(2 Pt 2):H835-42.
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ABSTRACT: Investigations of autonomic nervous system activity using spectral analysis of heart rate (HR) and blood pressure (BP) variability is very popular in many scientific disciplines, and yet only half of all studies involving spectral analysis control for respiration. Because respiration modulates HR and BP variability, knowledge of the respiratory rate is necessary for the proper interpretation of HR and BP power spectra. We devised and validated a new signal-processing technique to derive respiration from the blood pressure wave. This technique is based on the relationship between oscillations in the area under the dicrotic notch of the pulse wave and respiration. The results of our view signal-processing technique yielded significant correlations between protocols of the actual number of respiratory cycles and our blood pressure-derived respiratory cycles and their respective spectra for a number of standard autonomic tests (P < 0.05). Our method will allow retrospective extraction of the respiratory wave and as such afford a more precise interpretation of HR and BP spectra.
The American journal of physiology 06/1996; 270(5 Pt 2):H1672-5.
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ABSTRACT: Because respiration modulates autonomic activity, we determined the magnitude of perturbation of changing breathing frequency and tidal volume on metabolic, hemodynamic, psychometric, and R-R interval power spectral parameters. Seated subjects breathed at three different rates and five different volumes with each of the different rates. Breathing rates and volumes were percentages of the subject's resting breathing pattern and, therefore, identical across all subjects. Increases in rate and volume resulted in significant perturbations in end-tidal CO2 production, CO2 production, ventilatory equivalent for O2, comfort levels, and R-R interval power spectra (P < 0.05). The magnitude of the perturbations in the above parameters indicated a substantial upset in all subjects' metabolic, hemodynamic, and comfort homeostasis, precipitating a significant loss of vagal tone. The implications of our findings are that imposed breathing patterns used to modulate autonomic outflow should be tailored to the individual's resting breathing pattern. These data further support the urgent need for concomitant metabolic and respiratory measurements when analyzing and interpreting heart rate variability data.
The American journal of physiology 10/1995; 269(4 Pt 2):H1437-40.
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ABSTRACT: To assess environmental control on autonomic parameters between race and sex, we studied cross-sectionally, 119 West Point cadets of both sexes and of African-American and Caucasian descent. Specifically, heart period variability (HPV) and baroreceptor sensitivity index (BRSI) were assessed non-invasively. All participants had lived at the Academy for at least 1 year, had similar diets, ages, fitness status, access to medical care and educational backgrounds. Familial aggregation of hypertension was 46% for African-American and 30% for Caucasian, respectively. Autonomic outflow was assessed using the magnitude of the respiratory sinus arrhythmia (RSA) during sitting, standing and augmented breathing. Autocorrelations on 64 successive heart periods provided low frequency (LF) or high frequency (HF) distributions. The ratio of LF over HF was considered representative of sympathovagal balance. Baroreceptor sensitivity (BRSI) was assessed by recording cardiac deceleration in response to a Valsalva-induced increase in BP. Analysis of variance failed to reveal significant differences in any of these BP regulatory mechanisms between any of the groups. Prior investigations failed to control for the many environmental factors mentioned above and have therefore indicated significant epidemiological differences in the occurrence of hypertension between different races. Our results strongly suggest that environmental control seems to be an important modulator in the pathogenic mosaic of autonomic derangement, and should be strongly considered in future research.
Journal of Human Hypertension 03/1995; 9(2):107-11. · 2.80 Impact Factor
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R E De Meersman
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ABSTRACT: Aging is associated with an accentuated shift toward sympathetic outflow. Evidence suggests that sympathetic and vagal-cardiac activity change reciprocally. If this hypothesis is correct, then aging would result in an attenuation of vagal-cardiac activity. The current cross-sectional investigation assessed the relationship between aging, vagal-cardiac activity, and arteriolar compliance (AC). Respiratory sinus arrhythmia (RSA) and finger plethysmography, noninvasive measures of vagal-cardiac activity and arteriolar compliance, respectively, were made on 70 normotensive male subjects (age range 15-81 years). Both RSA and AC decreased with age (r = .71 and .89, respectively, p < .001). Analysis of variance revealed significant differences between the six decade groups for RSA and AC (p < .05). These findings support the notion that there is an age-related loss of vagal-cardiac activity that could be partly explained by the loss of arteriolar compliance. These findings are consistent with the hypothesis that there is autonomic nervous system compensation of cardiovascular function in response to an age-related decrease in arteriolar compliance in a normotensive population.
Journal of Gerontology 03/1993; 48(2):B74-8.
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R E De Meersman
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ABSTRACT: Heart rate variability, a noninvasive marker of parasympathetic activity, diminishes with aging and is augmented after exercise training. Whether habitual exercise over time can attenuate this loss is unknown. This cross-sectional investigation compared 72 male runners, aged 15 to 83 to 72 age- and weight-matched sedentary control subjects for the amplitude of their heart rate variability. Heart rate variability was assessed during rest while subjects were breathing at a rate of 6 breaths per minute and at an augmented tidal volume (tidal volume = 30% of vital capacity). Fitness levels were assessed with on-line, open-circuit spirometry while subjects were performing an incremental stress test. Overall results between the two groups showed that the physically active group had significantly higher fitness levels (p < 0.001), which were associated with significantly higher levels of heart rate variability, when compared with their sedentary counterparts (p < 0.001). These findings provide suggestive evidence for habitual aerobic exercise as a beneficial modulator of heart rate variability in an aging population.
American Heart Journal 03/1993; 125(3):726-31. · 4.65 Impact Factor
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R E De Meersman
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ABSTRACT: Significant increases in maximum oxygen consumption (VO2max) were noted in nine young track athletes following an 8-week high-intensity running period (P less than 0.05). VO2max was measured, prior to and following the training program, using an on-line, open-circuit spirometry system. Parasympathetic activity was assessed using heart period variation (R-R interval in milliseconds) during carefully controlled breathing activity (R sinus arrhythmia). Following the training program, a 7.3% increase in aerobic capacity was associated with a 23.1% augmentation of efferent parasympathetic activity (P less than 0.01). These data suggest that enhanced aerobic capacity increases efferent parasympathetic tone.
European Journal of Applied Physiology and Occupational Physiology 02/1992; 64(5):434-6.
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R E De Meersman
Sports Medicine 03/1990; 9(2):71-5. · 5.16 Impact Factor
