Physiologic basis for the age-related decline in aerobic work capacity

Enhancement of bicycle exercise capacity in patients with chronotropic incompetence through closed-loop stimulation: a randomized crossover trial

AIMS

This study aimed to investigate the effectiveness of closed-loop stimulation (CLS) pacing compared with the traditional DDD mode in patients with chronotropic incompetence (CI) using bicycle-based cardiopulmonary exercise testing (CPET).

METHODS AND RESULTS

This single-centre, randomized crossover trial involved 40 patients with CI. Patients were randomized to receive either DDD-CLS or DDD mode pacing for 2 months, followed by a crossover to the alternative mode for an additional 2 months. Bicycling-based CPET was conducted at the 3- and 5-month follow-up visits to assess exercise capacity. Other cardiopulmonary exercise outcome measures and health-related quality of life (QoL) were also assessed. DDD-CLS mode pacing significantly improved exercise capacity, resulting in a peak oxygen uptake (14.8 ± 4.0 vs. 12.0 ± 3.6 mL/kg/min, P < 0.001) and oxygen uptake at the ventilatory threshold (10.0 ± 2.2 vs. 8.7 ± 1.8 mL/kg/min, P < 0.001) higher than those of the DDD mode. However, there were no significant differences in other cardiopulmonary exercise outcome measures such as ventilatory efficiency of carbon dioxide production slope, oxygen uptake efficiency slope, and end-tidal carbon dioxide between the two modes. Patients in the DDD-CLS group reported a better QoL, and 97.5% expressed a preference for the DDD-CLS mode.

CONCLUSION

DDD-CLS mode pacing demonstrated improved exercise capacity and QoL in patients with CI, highlighting its potential as an effective pacing strategy for this patient population.

Sex differences in heart failure patients assessed by combined echocardiographic and cardiopulmonary exercise testing

Background

We aimed to test the differences in peak VO₂ between males and females in patients diagnosed with heart failure (HF), using combined stress echocardiography (SE) and cardiopulmonary exercise testing (CPET).

Methods

Patients who underwent CPET and SE for evaluation of dyspnea or exertional intolerance at our institution, between January 2013 and December 2017, were included and retrospectively assessed. Patients were divided into three groups: HF with preserved ejection fraction (HFpEF), HF with mildly reduced or reduced ejection fraction (HFmrEF/HFrEF), and patients without HF (control). These groups were further stratified by sex.

Results

One hundred seventy-eight patients underwent CPET-SE testing, of which 40% were females. Females diagnosed with HFpEF showed attenuated increases in end diastolic volume index (P = 0.040 for sex × time interaction), significantly elevated E/e' (P < 0.001), significantly decreased left ventricle (LV) end diastolic volume:E/e ratio (P = 0.040 for sex × time interaction), and lesser increases in A-VO₂ difference (P = 0.003 for sex × time interaction), comparing to males with HFpEF. Females diagnosed with HFmrEF/HFrEF showed diminished increases in end diastolic volume index (P = 0.050 for sex × time interaction), mostly after anaerobic threshold was met, comparing to males with HFmrEF/HFrEF. This resulted in reduced increases in peak stroke volume index (P = 0.010 for sex × time interaction) and cardiac output (P = 0.050 for sex × time interaction).

Conclusions

Combined CPET-SE testing allows for individualized non-invasive evaluation of exercise physiology stratified by sex. Female patients with HF have lower exercise capacity compared to men with HF. For females diagnosed with HFpEF, this was due to poorer LV compliance and attenuated peripheral oxygen extraction, while for females diagnosed with HFmrEF/HFrEF, this was due to attenuated increase in peak stroke volume and cardiac output. As past studies have shown differences in clinical outcomes between females and males, this study provides an essential understanding of the differences in exercise physiology in HF patients, which may improve patient selection for targeted therapeutics.

Extreme duration exercise affects old and younger men differently

Aim & Methods

Extreme endurance exercise provides a valuable research model for understanding the adaptive metabolic response of older and younger individuals to intense physical activity. Here, we compare a wide range of metabolic and physiologic parameters in two cohorts of seven trained men, age 30 ± 5 years or age 65 ± 6 years, before and after the participants travelled ≈3000 km by bicycle over 15 days.

Results

Over the 15‐day exercise intervention, participants lost 2–3 kg fat mass with no significant change in body weight. V̇O₂max did not change in younger cyclists, but decreased (p = 0.06) in the older cohort. The resting plasma FFA concentration decreased markedly in both groups, and plasma glucose increased in the younger group. In the older cohort, plasma LDL‐cholesterol and plasma triglyceride decreased. In skeletal muscle, fat transporters CD36 and FABPm remained unchanged. The glucose handling proteins GLUT4 and SNAP23 increased in both groups. Mitochondrial ROS production decreased in both groups, and ADP sensitivity increased in skeletal muscle in the older but not in the younger cohort.

Conclusion

In summary, these data suggest that older but not younger individuals experience a negative adaptive response affecting cardiovascular function in response to extreme endurance exercise, while a positive response to the same exercise intervention is observed in peripheral tissues in younger and older men. The results also suggest that the adaptive thresholds differ in younger and old men, and this difference primarily affects central cardiovascular functions in older men after extreme endurance exercise.

Cardiac rehabilitation and improvement of chronotropic incompetence: Is it the exercise or just the beta blockers?

INTRODUCTION

Clinical use of chronotropic response has been limited due to lack of consensus on the appropriate formula for chronotropic index (Ci) calculation and the definition of chronotropic incompetence.

OBJECTIVES

To assess the effects of cardiac rehabilitation programs (CRP) on Ci, irrespective of betablockers (BB) use and dosage. Assess the relative contribution of change in Ci on improvement in functional capacity.

METHODS

Retrospective analysis of a sample of patients admitted to a CRP after acute coronary syndrome, with at least 12 months of follow-up. Ci was calculated using the conventional (CCi) and the Brawner formula (BCi) for age-predicted maximum heart rate. Ci and functional capacity were estimated at three time points: T1 and T2, before and at the end of the CRP, and T3, at 12 months. The sample was categorized according to BB dosage modification between T1 and T3: G1 - reduced; G2 - no change; G3 - increased.

RESULTS

In G1, CCi increased from 63.5% in T1 to 77.9% in T3; in G2, from 67.3% to 77.9%; in G3, from 71.2% to 75.4%. In G1, BCi increased from 110.4% to 140.0%; in G2, from 122.8% to 140.1%; in G3, from 133.3% to 139.2%. An average increase in 1.0% in CCi was associated with an average increase in functional capacity of 0.37 METS.

CONCLUSIONS

Chronotropic index significantly improves with CRP, irrespective of BB dose changes. CCi is more closely related with improvement in functional capacity than BCi. Improvement of Ci is an important predictor of functional capacity and prognosis in cardiovascular disease patients.

An individually adjusted endurance test reveals differences in physical fitness between young and old Beagles

OBJECTIVE

Aim was to establish an individually adapted endurance test for dogs on a treadmill, which takes the individual's physical condition into account. To check the applicability of the test, two age groups of clinically healthy beagles were examined.

METHODS

A total of 10 clinically healthy Beagles were enrolled and divided in a younger (1-3 years, n = 5) and older group (> 8 years, n = 5). The individual comfort gait speed of each dog was determined on a treadmill with integrated force plates. A maximal time of 20 minutes at trot was set for the endurance test. The test was terminated prematurely if the dog showed signs of fatigue (massive panting, unwillingness to move further). Blood samples were taken at general examination (G), prior to (B) and post exercise (P) for determination of lactate level (LL), oxygen and carbon dioxide partial pressure (pO2, pCO₂), bicarbonate (HCO₃ ^-), base excess (BE) and pH. On each occasion (G, B, P) heart rate (HR) and respiratory rate (RR) were recorded. Additionally, vertical ground reaction forces (Fz) were analysed.

RESULTS

The older dogs (age: 10.4 ± 0.89 years) completed the test with less speed and duration compared to the younger dogs (age: 2.4 ± 0.89 years), which managed to complete the maximum time. Lactate levels in the older dogs were higher than in the younger dogs at all timepoints of examination. Contrary to the younger dogs, there was no significant increase in the heart rate of the older dogs. Ground reaction forces were not significantly different between the groups.

CONCLUSION AND CLINICAL RELEVANCE

Whereas standardised endurance tests allow for the comparison of fitness levels between dogs, an individually adjusted endurance test aims at objectively determining the physical fitness of the single dog taking into account its individual performance. Such a test allows to examine the individual performance development over time and to evaluate medicinal therapies or dietary measures, e. g. in aging dogs. HR, RR, LL, blood gases (pCO₂, pO₂) and acid-base metabolism (HCO₃ ^-, BE, pH) were found to be appropriate parameters for determining the physical capacity of the dogs during endurance tests as these parameters change under physical stress and are indicative for the onset of fatigue.

Prognostic impact of peak oxygen uptake and heart rate reserve in patients after off-pump coronary artery bypass grafting

BACKGROUND

Peak oxygen uptake (peak VO₂ ) and heart rate reserve (HRR) are independent prognostic markers of cardiovascular disease. However, the impact of peak VO₂ and HRR on long-term prognosis after off-pump coronary artery bypass grafting (OP-CABG) remains unclear.

HYPOTHESIS

To determine the prognostic impact of peak VO₂ and HRR in patients after OP-CABG.

RESULTS

We enrolled 327 patients (mean age, 65.1 ± 9.3 years; male, 80%) who underwent OP-CABG and participated in early phase II cardiac rehabilitation. All participants underwent cardiopulmonary exercise testing (CPET) at the beginning of such rehabilitation. Overall, 48 (14.6%) patients died during the median follow-up period of 103 months. The non-survivor had significantly lower levels of peak VO₂ (10.6 ± 0.5 vs. 13.7 ± 0.2 ml/kg/min, p < .01) and HRR (24.2 ± 1.8 vs. 32.7 ± 0.8 beats/min, p < .01) than the survivor. In both groups, peak VO₂ significantly correlated with HRR (p < .01). Moreover, patients were divided into four groups according to the peak VO₂ and HRR levels for predicting total mortality. The low-peak VO₂ /low-HRR group had a significantly higher mortality risk than the other groups (hazards ratio, 5.61; 95% confidence interval, 2.59-12.16; p < .01). After adjusted the confounding factors, peak VO₂ and HRR were independently associated with total mortality (both p < .05).

CONCLUSIONS

HRR is a simple parameter of CPET and an important prognostic marker for the risk stratification of total mortality even in patients with low-peak VO₂ after OP-CABG.

Reduced exercise capacity and clinical outcomes following acute myocardial infarction

Reduced exercise capacity is known to be an important predictor of poor prognosis and disability in patients with cardiovascular diseases and chronic heart failure, and even members of the general population. However, data about exercise capacity assessed by cardiopulmonary exercise testing (CPX) in acute myocardial infarction (AMI) patients who underwent primary percutaneous coronary intervention (PCI) is scarce. Among 594 consecutive AMI patients who underwent primary PCI, we examined 136 patients (85.3% men, 64.9 ± 11.9 years) who underwent CPX during hospitalization for AMI. CPX was usually performed 5 days after the onset of AMI. Reduced exercise capacity was defined as peak VO₂ ≤ 12. Clinical outcomes including all-cause death, myocardial infarction, and hospitalization due to heart failure were followed. Among 136 patients, reduced exercise capacity (peak VO₂ ≤ 12) was seen in 38 patients (28%). Patients with reduced exercise capacity were older, more likely to have hypertension, and had lower renal function. In echocardiography, patients with reduced exercise capacity had higher E/e' and larger left atrial dimension. Multivariate logistic analysis showed that E/e' (OR 1.19, 95% CI 1.09-1.31, p < 0.001) was an independent predictor of reduced exercise capacity (peak VO₂ ≤ 12). Median follow-up term was 12 months (IQR 9-22). The occurrence of composite endpoints of all-cause death, myocardial infarction, and hospitalization due to heart failure was significantly higher in patients with peak VO₂ ≤ 12 than those with peak VO₂ > 12 (p < 0.001). Reduced exercise capacity following primary PCI in AMI patients is associated with diastolic dysfunction and may lead to poorer clinical outcomes.

Heart rate reserve during dipyridamole stress test applied to potential heart donors in brain death

BACKGROUND

A blunted heart rate reserve (HRR) during dipyridamole stress echocardiography (DSE) is a prognostically unfavorable sign of cardiac autonomic dysfunction. Short-term adjustments of heart rate (HR) are thought to rise from changes in neural input to the heart. DSE is applied in potential heart donors to rule out underlying coronary artery disease and left ventricular dysfunction. The aim of this study is to assess HRR during DSE in brain death.

METHODS

We enrolled two groups: group 1 (N.=49, 22 men, 54.6±8.8 years) with patients in brain death enrolled in the nationwide marginal donor heart recruiting program; group 2 (N.=49, 18 men, 66.4±12.0 years) referred to DSE for suspected or known coronary artery disease. All underwent DSE (0.84 mg/kg in 6') by quality-controlled readers certified via web-based training (1487/CE Lazio-1). We assessed left ventricular contractile reserve (LVCR) as stress/rest ratio of force (systolic blood pressure/end-systolic volume). HRR was calculated as the peak/rest HR ratio from 12-lead EKG.

RESULTS

The two study groups were similar for prevalence of inducible ischemia (4/49 vs. 9/49, P=NS). Group 1 showed higher resting HR (group 1: 88.1±15.5 bpm vs. group 2: 66.5±11.5 bpm, P<0.01) and similar peak HR (group 1: 94.7±15.3 bpm vs. group 2: 89.5±19.3 bpm, P=0.144), with blunted HRR (group 1: 1.08±0.10 bpm vs. group 2: 1.36±0.31 bpm, P<0.01). HRR was unrelated to LVCR.

CONCLUSIONS

HRR is almost abolished and unrelated to LVCR in brain-dead patients during DSE. The modulation of neural input to the heart is essential to determine HRR, and plays no significant role in determining the inotropic response during DSE.

Comparing the Aerobic Fitness of Professional Male Soccer Players and Soccer Referees

We looked to compare the aerobic performance between professional soccer referees and players. Fifty male soccer referees and 61 male soccer players were tested on a treadmill. The referees and players possessed 15 ± 7 years and 7 ± 3 years of experience in soccer, respectively. Significant differences were observed between the referees and players with regards to: age (34.8 ± 4.6 years vs 20.8 ± 2.7 years; P < 0.001, maximum oxygen uptake (54.7 ± 5.4 mL·kg·min vs 58.8 ± 4.4 mL·kg·min; P < 0.001), and maximal heart rate in peak exercise (184 ± 11 bpm vs 192 ± 9 bpm, P < 0.001). Less significant differences also were observed and included; running speed at the maximum oxygen uptake (16.6 ± 1 km·h vs 16.4 ± 1.1 km·h), running speed at the ventilatory threshold (213.5 ± 1.1 km·h vs 13.2 ± 0.9 km·h), and percentage of maximal oxygen uptake at the ventilatory threshold (285.1% ± 3.2% vs 84.1% ± 6.2%). The effect size of most comparative variables between the two groups was small (<0.6). Older elite-level soccer referees are able to reach and maintain aerobic physical fitness levels similar to professional soccer players. Aerobic physical fitness may be a measurable factor for maintaining elite-level soccer licensure rather than age alone.

Acclimation to a thermoneutral environment abolishes age-associated alterations in heart rate and heart rate variability in conscious, unrestrained mice

Mice are among the most widely used translational models of cardiovascular aging and offer a method to quickly assess lifespan changes in a controlled environment. The standard laboratory temperature (20-22 °C), however, imposes a cold stress on mice that causes an increase in sympathetic nervous system-mediated activation of brown adipose tissue (BAT) to maintain a core body temperature of 36-37 °C. Thus, while physiologic data obtained recapitulate human physiology to a certain degree, interpretations of previous research in mice may have been contaminated by a cold stress, due to housing mice below their thermoneutral zone (30 °C). The purpose of this investigation was to examine how chronic sympathetic stimulation evoked by acclimation to 20 °C might obscure interpretation of changes in autonomic modulation of heart rate (HR) and heart rate variability (HRV) that accompany advancing age. HR and HRV before and after administration of a dual-autonomic blockade were measured via in-vivo ECG in young (3 months) and aged (30 months) male C57BL/6 telemetry-implanted mice following temperature acclimation for 3 days at 30 °C or 20 °C. Mean basal and intrinsic HR of both young and aged mice became markedly reduced at 30 °C compared to 20 °C. In both age groups, HRV parameters in time, frequency, and non-linear domains displayed increased variability at 30 °C compared to 20 °C under basal conditions. Importantly, age-associated declines in HRV observed at 20 °C were ameliorated when mice were studied at their thermoneutral ambient temperature of 30 °C. Thus, an accurate understanding of autonomic modulation of cardiovascular functions in mice of advanced age requires that they are housed in a metabolically neutral environment.

Healthy Aging and Cardiovascular Function: Invasive Hemodynamics During Rest and Exercise in 104 Healthy Volunteers

OBJECTIVES

The aim of this study was to evaluate the association between age and invasive cardiovascular hemodynamics during upright exercise among healthy adults.

BACKGROUND

The marked age-related decline in maximal exercise oxygen uptake (peak VO₂) may contribute to the high burden of heart failure among older individuals and their greater severity of exertional symptoms. However, the mechanisms underlying this decline are not well understood.

METHODS

A total of 104 healthy community-dwelling volunteers age 20 to 76 years well screened for cardiovascular disease underwent exhaustive upright exercise with brachial and pulmonary artery catheters; radionuclide ventriculography; and expired gas analysis for the measurement of peak VO₂, cardiac output, left ventricular stroke volume, end-diastolic volume, end-systolic volume, ejection fraction, pulmonary capillary wedge pressure, and arteriovenous oxygen difference.

RESULTS

Over a 5.5-decade age range, there was a 40% decline in peak VO₂ due primarily to reduced peak exercise cardiac output; peak arteriovenous oxygen difference was unaffected by age. The lower age-related exercise cardiac output was related to lower peak exercise heart rate and stroke volume. Aging was also associated with lower peak exercise ejection fraction, indicating reduced inotropic reserve. Peak exercise end-diastolic volume was lower with aging despite similar left ventricular filling pressure, suggesting age-related reduced diastolic compliance limiting the use of the Frank-Starling mechanism to compensate for reduced chronotropic and inotropic reserves. These age relationships were unaffected by sex.

CONCLUSIONS

The age-related decline in exercise capacity among healthy persons is due predominantly to cardiac mechanisms, including reduced chronotropic and inotropic reserve and possibly reduced Frank-Starling reserve. Peak exercise left ventricular filling pressure and arteriovenous oxygen difference are unchanged with healthy aging.

Heart Rate Response During Treadmill Exercise Test in Children and Adolescents With Congenital Heart Disease

Background: Impaired exercise capacity is a common feature of congenital heart disease (CHD). In adults with CHD, it has been shown that impaired heart rate response during exercise may contribute to exercise limitation. Systematic data in children and adolescents on this topic is limited. We therefore purposed to assess heart rate response during treadmill exercise testing in children and adolescents with CHD compared to healthy controls. Methods: One hundred and sixty three children and adolescents (103 with CHD, median age 15 years and 60 age-matched controls) performed cardiopulmonary exercise testing and were included in this study. Beyond peak oxygen consumption, increase in heart rate from resting level to peak exercise (heart rate reserve) and decrease of heart rate after peak exercise (heart rate recovery) were measured. Chronotropic index was defined as percentage of age predicted maximal heart rate reserve. According to data from adults on bicycle exercise, chronotropic incompetence was assumed for chronotropic index below 0.8. Results: While resting heart rate was similar between both groups, peak heart rate, heart rate reserve as well as chronotropic index were lower in the CHD group than in controls. Chronotropic index was lowest in patients with single ventricle hemodynamics and correlated with peak oxygen consumption. Heart rate recovery was impaired in the CHD group 1 and 2 min after peak exercise compared to controls and correlated with peak oxygen consumption. Chronotropic index below 0.8 was a relatively frequent finding even in the control group suggesting that the threshold of 0.8 appears inadequate for the identification of chronotropic incompetence using treadmill exercise testing in children. After normalizing to the 2.5th chronotropic index percentile of the control group we obtained a chronotropic incompetence threshold of 0.69. Conclusion: As an adjunct to measurement of peak oxygen consumption, heart rate response to exercise appears to be a physiologically important diagnostic parameter in children and adolescents with CHD. However, interpretation of heart rate response needs to consider specific age characteristics and the mode of exercise test. Our data may help future studies on chronotropic incompetence using treadmill ergometer protocols in children and adolescents.

Cardiorespiratory responses and myocardial function within incremental exercise in healthy unmedicated older vs. young men and women

BACKGROUND

Age-related differences concerning cardiorespiratory responses and myocardial function during exercise have not been extensively investigated in healthy populations.

AIMS

To compare cardiorespiratory performance and myocardial function during maximal exercise in healthy/unmedicated men (older, n = 24, 63-75 years; young, n = 22, 19-25 years) and women (older, n = 18, age = 63-74 years; young, n = 23, 19-25 years).

METHODS

Oxygen uptake (VO₂), ventilation minute (V _E), heart rate (HR), stroke volume (SV), cardiac output (Q), O₂ pulse (O₂p), preejection period (PEP), and left ventricular ejection time (LVET) were assessed during cycle incremental exercise.

RESULTS

HR and SV remained equivalent between age groups until 75 and 50% peak workload, respectively. Q increased by 2.5 and 4.5 times in older and young groups, respectively. However, Q/VO₂ ratio was always similar across age and sex groups (∼0.50). The energetic efficiency ratio (W/VO₂) was also alike in older and young men, but slightly lower in women. At maximal exercise, cardiorespiratory responses were lower in older than young men and women: VO₂ (-40 to 50%), V _E (-35 to 37%), HR (-23%), SV (-26 to 29%), Q (-43 to 45%), and O₂p (-15 to 20%). Cardiac and SV indices were lower in older than young groups by approximately 42 and 25%, respectively. LVET was longer in the older individuals, while PEP was similar across age groups. Hence, PEP/LVET was lowered among older vs. young men and women.

CONCLUSION

Submaximal work capacity was preserved in healthy and unmedicated older individuals. Age-related lessening of maximal performance in both sexes was due to poor chronotropic and, particularly, inotropic properties of the heart.

With age a lower individual breathing reserve is associated with a higher maximal heart rate

INTRODUCTION

Maximal heart rate (HRmax) is linearly declining with increasing age. Regular exercise training is supposed to partly prevent this decline, whereas sex and habitual physical activity do not. High exercise capacity is associated with a high cardiac output (HR x stroke volume) and high ventilatory requirements. Due to the close cardiorespiratory coupling, we hypothesized that the individual ventilatory response to maximal exercise might be associated with the age-related HRmax.

METHODS

Retrospective analyses have been conducted on the results of 129 consecutively performed routine cardiopulmonary exercise tests. The study sample comprised healthy subjects of both sexes of a broad range of age (20-86 years). Maximal values of power output, minute ventilation, oxygen uptake and heart rate were assessed by the use of incremental cycle spiroergometry.

RESULTS

Linear multivariate regression analysis revealed that in addition to age the individual breathing reserve at maximal exercise was independently predictive for HRmax. A lower breathing reserve due to a high ventilatory demand and/or a low ventilatory capacity, which is more pronounced at a higher age, was associated with higher HRmax. Age explained the observed variance in HRmax by 72% and was improved to 83% when the variable "breathing reserve" was entered.

DISCUSSION

The presented findings indicate an independent association between the breathing reserve at maximal exercise and maximal heart rate, i.e. a low individual breathing reserve is associated with a higher age-related HRmax. A deeper understanding of this association has to be investigated in a more physiological scenario.

Age-related differences in skeletal muscle microvascular response to exercise as detected by contrast-enhanced ultrasound (CEUS)

Background

Aging involves reductions in exercise total limb blood flow and exercise capacity. We hypothesized that this may involve early age-related impairments of skeletal muscle microvascular responsiveness as previously reported for insulin but not for exercise stimuli in humans.

Methods

Using an isometric exercise model, we studied the effect of age on contrast-enhanced ultrasound (CEUS) parameters, i.e. microvascular blood volume (MBV), flow velocity (MFV) and blood flow (MBF) calculated from replenishment of Sonovue contrast-agent microbubbles after their destruction. CEUS was applied to the vastus lateralis (VLat) and intermedius (VInt) muscle in 15 middle-aged (MA, 43.6±1.5 years) and 11 young (YG, 24.1±0.6 years) healthy males before, during, and after 2 min of isometric knee extension at 15% of peak torque (PT). In addition, total leg blood flow as recorded by femoral artery Doppler-flow. Moreover, fiber-type-specific and overall capillarisation as well as fiber composition were additionally assessed in Vlat biopsies obtained from CEUS site. MA and YG had similar quadriceps muscle MRT-volume or PT and maximal oxygen uptake as well as a normal cardiovascular risk factors and intima-media-thickness.

Results

During isometric exercise MA compared to YG reached significantly lower levels in MFV (0.123±0.016 vs. 0.208±0.036 a.u.) and MBF (0.007±0.001 vs. 0.012±0.002 a.u.). In the VInt the (post-occlusive hyperemia) post-exercise peaks in MBV and MBF were significantly lower in MA vs. YG. Capillary density, capillary fiber contacts and femoral artery Doppler were similar between MA and YG.

Conclusions

In the absence of significant age-related reductions in capillarisation, total leg blood flow or muscle mass, healthy middle-aged males reveal impaired skeletal muscle microcirculatory responses to isometric exercise. Whether this limits isometric muscle performance remains to be assessed.

Cyclic AMP reverses the effects of aging on pacemaker activity and If in sinoatrial node myocytes

Aging reduces pacemaker activity and shifts the voltage dependence of activation of the funny current, I_f, in sinoatrial node myocytes. Sharpe et al. find that these effects of aging can be reversed by application of exogenous cAMP but not by stimulation of endogenous cAMP.

Aerobic capacity decreases with age, in part because of an age-dependent decline in maximum heart rate (mHR) and a reduction in the intrinsic pacemaker activity of the sinoatrial node of the heart. Isolated sinoatrial node myocytes (SAMs) from aged mice have slower spontaneous action potential (AP) firing rates and a hyperpolarizing shift in the voltage dependence of activation of the “funny current,” I_f. Cyclic AMP (cAMP) is a critical modulator of both AP firing rate and I_f in SAMs. Here, we test the ability of endogenous and exogenous cAMP to overcome age-dependent changes in acutely isolated murine SAMs. We found that maximal stimulation of endogenous cAMP with 3-isobutyl-1-methylxanthine (IBMX) and forskolin significantly increased AP firing rate and depolarized the voltage dependence of activation of I_f in SAMs from both young and aged mice. However, these changes were insufficient to overcome the deficits in aged SAMs, and significant age-dependent differences in AP firing rate and I_f persisted in the presence of IBMX and forskolin. In contrast, the effects of aging on SAMs were completely abolished by a high concentration of exogenous cAMP, which restored AP firing rate and I_f activation to youthful levels in cells from aged animals. Interestingly, the age-dependent differences in AP firing rates and I_f were similar in whole-cell and perforated-patch recordings, and the hyperpolarizing shift in I_f persisted in excised inside-out patches, suggesting a limited role for cAMP in causing these changes. Collectively, the data indicate that aging does not impose an absolute limit on pacemaker activity and that it does not act by simply reducing the concentration of freely diffusible cAMP in SAMs.

The Influence of Age on Hemodynamic Parameters During Rest and Exercise in Healthy Individuals

OBJECTIVES

In this study, the authors sought to obtain hemodynamic estimates across a wide age span and in both sexes for future reference and compare these estimates with current guideline diagnostic hemodynamic thresholds for abnormal filling pressure and pulmonary hypertension.

BACKGROUND

At present, the influence of age on hemodynamic function is largely unknown. Because many diseases with proposed cardiac impact are more prevalent in the older population, it is pivotal to know how hemodynamic parameters are affected by age itself to discern the influence of disease from that of physiological aging.

METHODS

Sixty-two healthy participants, evenly distributed with respect to age (20 to 80 years) and sex (32 women/30 men), were prospectively enrolled in the study. Participants were all deemed healthy by medical history, echocardiography, exercise test, spirometry, blood tests, and electrocardiogram. Participants had hemodynamic parameters measured using right heart catheterization during rest, passive leg raise, and incremental exercise.

RESULTS

During rest, all hemodynamic parameters were similar between age groups, apart from blood pressure. During leg raise and incremental exercise, there was augmented filling pressure (p < 0.0001) and diminished cardiac output (p = 0.001) and hence a higher pressure:flow ratio (pulmonary artery pressure/capillary wedge pressure to cardiac output) with progressive age, evident from the earliest ages. All indexed hemodynamic measures were similar between sexes. The diagnostic threshold (pulmonary capillary wedge pressure ≥25 mm Hg) currently used during exercise testing to diagnose abnormal left ventricular filling pressure was measured in 30% of our healthy elderly participants.

CONCLUSIONS

Cardiac aging was progressive without sex differences in healthy participants. The hemodynamic reference values obtained suggest that the diagnostic threshold for abnormal filling pressure should be individually determined according to age of the patient.

The Role of Exercise in Cardiac Aging: From Physiology to Molecular Mechanisms

Aging induces structural and functional changes in the heart that are associated with increased risk of cardiovascular disease and impaired functional capacity in the elderly. Exercise is a diagnostic and therapeutic tool, with the potential to provide insights into clinical diagnosis and prognosis, as well as the molecular mechanisms by which aging influences cardiac physiology and function. In this review, we first provide an overview of how aging impacts the cardiac response to exercise, and the implications this has for functional capacity in older adults. We then review the underlying molecular mechanisms by which cardiac aging contributes to exercise intolerance, and conversely how exercise training can potentially modulate aging phenotypes in the heart. Finally, we highlight the potential use of these exercise models to complement models of disease in efforts to uncover new therapeutic targets to prevent or treat heart disease in the aging population.

Post aortic dissection: Gap between activity recommendation and real life patients aerobic capacities

BACK GROUND

Regular exercise at a safe level, i.e. 3-5 metabolic equivalents, is recommended to improve blood pressure control and quality of life even after aortic dissection, although aerobic exercise capacities in these patients are unexplored yet.

METHODS

We prospectively collected data from 105 patients with a history of post aortic dissection referred for a cardiopulmonary exercise testing (CPX) aiming to guide exercise rehabilitation.

RESULTS

The population was composed of 76% of male, with a mean age of 57.9±12.4years. There were an equal distribution between the two type of dissection (47% of type A and 53% of type B aortic dissection). No cardiac event occurred during or after CPX. One third of patients have normal aerobic exercise capacity defined as peak oxygen uptake upper than 85% of their predicted capacity. Mean oxygen uptake peak was quite low 19.2±5.2ml/kg/min (5.5±1.5 metabolic equivalents). Aerobic capacity was limited by cardiac chronotropic incompetence in 42% or peripheral deconditioning in 45%. Blood pressure remained in an acceptable range during the exercise. Systolic and diastolic blood pressures were respectively 151±20 and 77±13mmHg at first ventilatory threshold.

CONCLUSIONS

CPX is a safe exploration in patients with post aortic dissection syndrome. Given the fact that most of these patients are faced with significant alteration of aerobic capacities, the recommended daily practice of moderate exercise at 3-5 METS should be adapted and personalized to each patient thanks to CPX.

Aging alters muscle reflex control of autonomic cardiovascular responses to rhythmic contractions in humans

We investigated the influence of aging on the group III/IV muscle afferents in the exercise pressor reflex-mediated cardiovascular response to rhythmic exercise. Nine old (OLD; 68 ± 2 yr) and nine young (YNG; 24 ± 2 yr) males performed single-leg knee extensor exercise (15 W, 30 W, 80% max) under control conditions and with lumbar intrathecal fentanyl impairing feedback from group III/IV leg muscle afferents. Mean arterial pressure (MAP), cardiac output, leg blood flow (QL), systemic (SVC) and leg vascular conductance (LVC) were continuously determined. With no hemodynamic effect at rest, fentanyl blockade during exercise attenuated both cardiac output and QL ∼17% in YNG, while the decrease in cardiac output in OLD (∼5%) was significantly smaller with no impact on QL (P = 0.8). Therefore, in the face of similar significant ∼7% reduction in MAP during exercise with fentanyl blockade in both groups, LVC significantly increased ∼11% in OLD, but decreased ∼8% in YNG. The opposing direction of change was reflected in SVC with a significant ∼5% increase in OLD and a ∼12% decrease in YNG. Thus while cardiac output seems to account for the majority of group III/IV-mediated MAP responses in YNG, the impact of neural feedback on the heart may decrease with age and alterations in SVC become more prominent in mediating the similar exercise pressor reflex in OLD. Interestingly, in terms of peripheral hemodynamics, while group III/IV-mediated feedback plays a clear role in increasing LVC during exercise in the YNG, these afferents seem to actually reduce LVC in OLD. These peripheral findings may help explain the limited exercise-induced peripheral vasodilation often associated with aging.

Do 12-week yoga program influence respiratory function of elderly women?

Aging produces several respiratory limitations and reduces tolerance to physical efforts, sometimes leading to pulmonary diseases in the elderly. The literature draws attention to the possible benefits of Yoga practice among the elderly, presenting evidence for significant improvements in quality of life. It was hypothesized that yoga practice can improve respiratory function in the elderly. The effects of a yoga program on pulmonary volumes and respiratory muscle strength were verified in 36 elderly women divided into a yoga group [YG] (63.1 ± 13.3 years of age) and a control group (61.0 ± 6.9 years of age). Maximal inspiratory and expiratory pressure (MIP and MEP) were assessed by a manovacuometer and tidal volume (VT), vital capacity (VC) and minute ventilation (VE) were measured by a ventilometer. The program comprised 65 min sessions, 3 times/week during 12 weeks. The heart rate and respiratory rate decreased significantly in the YG (76-39 ± 8-03 vs. 74-61±10.26 bpm and 18.61 ± 3.15 vs. 16.72 ± 3.12 resp/min, respectively). In the YG, VT and VE increased significantly (0.55 ± 0.22 vs. 0.64 ± 0.2 ml and 9.19 ± 2.39 vs. 10.05 ± 2.11 ml, respectively), as well as VC (1.48 ± 0.45 vs. 2.03 ± 0.72 ml). Improvements were also found in MIP and MEP in the YG (62.17 ± 14.77 vs. 73.06 ± 20.16 cmH2O and 80.56 ± 23.94 vs. 86.39 ± 20.16 cmH2O, respectively). It was concluded that a 12-week yoga program significantly improves pulmonary function of aged women.

A study of the 200-metre fast walk test as a possible new assessment tool to predict maximal heart rate and define target heart rate for exercise training of coronary heart disease patients

Objective:

To develop a new predictive model of maximal heart rate based on two walking tests at different speeds (comfortable and brisk walking) as an alternative to a cardiopulmonary exercise test during cardiac rehabilitation.

Design:

Evaluation of a clinical assessment tool.

Setting:

A Cardiac Rehabilitation Department in France.

Subjects:

A total of 148 patients (133 men), mean age of 59 ±9 years, at the end of an outpatient cardiac rehabilitation programme.

Main measures:

Patients successively performed a 6-minute walk test, a 200 m fast-walk test (200mFWT), and a cardiopulmonary exercise test, with measure of heart rate at the end of each test. An all-possible regression procedure was used to determine the best predictive regression models of maximal heart rate. The best model was compared with the Fox equation in term of predictive error of maximal heart rate using the paired t-test.

Results:

Results of the two walking tests correlated significantly with maximal heart rate determined during the cardiopulmonary exercise test, whereas anthropometric parameters and resting heart rate did not. The simplified predictive model with the most acceptable mean error was: maximal heart rate = 130 − 0.6 × age + 0.3 × HR200mFWT (R2 = 0.24). This model was superior to the Fox formula (R2 = 0.138). The relationship between training target heart rate calculated from measured reserve heart rate and that established using this predictive model was statistically significant ( r = 0.528, p < 10−6).

Conclusions:

A formula combining heart rate measured during a safe simple fast walk test and age is more efficient than an equation only including age to predict maximal heart rate and training target heart rate.

The effect of lifelong exercise dose on cardiovascular function during exercise

An increased "dose" of endurance exercise training is associated with a greater maximal oxygen uptake (Vo2max), a larger left ventricular (LV) mass, and improved heart rate and blood pressure control. However, the effect of lifelong exercise dose on metabolic and hemodynamic response during exercise has not been previously examined. We performed a cross-sectional study on 101 (69 men) seniors (60 yr and older) focusing on lifelong exercise frequency as an index of exercise dose. These included 27 who had performed ≤ 2 exercise sessions/wk (sedentary), 25 who performed 2-3 sessions/wk (casual), 24 who performed 4-5 sessions/wk (committed) and 25 who performed ≥ 6 sessions/wk plus regular competitions (Masters athletes) over at least the last 25 yr. Oxygen uptake and hemodynamics [cardiac output, stroke volume (SV)] were collected at rest, two levels of steady-state submaximal exercise, and maximal exercise. Doppler ultrasound measures of LV diastolic filling were assessed at rest and during LV loading (saline infusion) to simulate increased LV filling. Body composition, total blood volume, and heart rate recovery after maximal exercise were also examined. Vo2max increased in a dose-dependent manner (P < 0.05). At maximal exercise, cardiac output and SV were largest in committed exercisers and Masters athletes (P < 0.05), while arteriovenous oxygen difference was greater in all trained groups (P < 0.05). At maximal exercise, effective arterial elastance, an index of ventricular-arterial coupling, was lower in committed exercisers and Masters athletes (P < 0.05). Doppler measures of LV filling were not enhanced at any condition, irrespective of lifelong exercise frequency. These data suggest that performing four or more weekly endurance exercise sessions over a lifetime results in significant gains in Vo2max, SV, and heart rate regulation during exercise; however, improved SV regulation during exercise is not coupled with favorable effects on LV filling, even when the heart is fully loaded.

Depressed pacemaker activity of sinoatrial node myocytes contributes to the age-dependent decline in maximum heart rate

An inexorable decline in maximum heart rate (mHR) progressively limits human aerobic capacity with advancing age. This decrease in mHR results from an age-dependent reduction in "intrinsic heart rate" (iHR), which is measured during autonomic blockade. The reduced iHR indicates, by definition, that pacemaker function of the sinoatrial node is compromised during aging. However, little is known about the properties of pacemaker myocytes in the aged sinoatrial node. Here, we show that depressed excitability of individual sinoatrial node myocytes (SAMs) contributes to reductions in heart rate with advancing age. We found that age-dependent declines in mHR and iHR in ECG recordings from mice were paralleled by declines in spontaneous action potential (AP) firing rates (FRs) in patch-clamp recordings from acutely isolated SAMs. The slower FR of aged SAMs resulted from changes in the AP waveform that were limited to hyperpolarization of the maximum diastolic potential and slowing of the early part of the diastolic depolarization. These AP waveform changes were associated with cellular hypertrophy, reduced current densities for L- and T-type Ca(2+) currents and the "funny current" (If), and a hyperpolarizing shift in the voltage dependence of If. The age-dependent reduction in sinoatrial node function was not associated with changes in β-adrenergic responsiveness, which was preserved during aging for heart rate, SAM FR, L- and T-type Ca(2+) currents, and If. Our results indicate that depressed excitability of individual SAMs due to altered ion channel activity contributes to the decline in mHR, and thus aerobic capacity, during normal aging.

The effect of age-related differences in body size and composition on cardiovascular determinants of VO2max

BACKGROUND

A reduction in maximal stroke volume (SVmax) and total blood volume (TBV) has been hypothesized to contribute to the decline in maximal oxygen uptake (VO2max) with healthy aging. However, these variables have rarely been collected simultaneously in a board age range to support or refute this hypothesis. It is also unclear to what extent scaling size-related cardiovascular determinants of VO2max affects the interpretation of age-related differences.

METHODS

A retrospective analysis of VO2max, maximal cardiac output (QCmax), TBV, and body composition including fat-free mass (FFM) in 95 (51% M) healthy adults ranging from 19-86 years.

RESULTS

Absolute and indexed VO2max, QCmax, and maximal heart rate decreased in both sexes with age (p ≤ .031). SVmax declined with age when scaled to total body mass or body surface area (p ≤ .047) but not when expressed in absolute levels (p = .120) or relative to FFM (p = .464). Absolute and indexed TBVs (mL/kg; mL/m(2)) were not significantly affected by age but increased with age in both sexes when scaled to FFM (p ≤ .013). A lower arteriovenous oxygen difference (a-vO2diff) contributed to the reduction in VO2max with age in treadmill exercisers (p = .004) but not in the entire cohort (p = .128).

CONCLUSION

These results suggest (a) a reduction in absolute SVmax, and TBV do not contribute substantially to the age-related reduction in VO2max, which instead results from a smaller QCmax due to a lower maximal heart rate, and (b) body composition scaling methods should be used to accurately describe the effect of aging on physical function and cardiovascular variables.

Cardiovascular abnormalities in Klinefelter syndrome

BACKGROUND

Several epidemiological studies have demonstrated an increased mortality from cardiovascular causes in patients with Klinefelter Syndrome (KS). Little information is available about the nature of the underlying cardiovascular abnormalities. Aim of the study was to investigate exercise performance, left ventricular architecture and function, vascular reactivity, and carotid intima-media thickness in a group of patients with KS.

MATERIALS AND METHODS

Sixty-nine patients with KS and 48 age-matched controls participated in our population-controlled study. Forty-eight Klinefelter subjects were on testosterone treatment at the time of the investigation while 21 were naive and underwent a complete Doppler echocardiographic examination, a cardiopulmonary exercise test as well as a vascular study including measures of carotid intima-media thickness and endothelial function with flow-mediated dilation of the brachial artery. Patients with KS on testosterone therapy (n=48) were also matched against a population of men with treated secondary hypogonadism (n=21).

RESULTS

Patients with KS exhibited a wide array of cardiovascular abnormalities including left ventricular diastolic dysfunction, reduced maximal oxygen consumption (p<0.01), increased intima-media thickness (p<0.05) (-34% and +42% vs. controls, respectively) and a high prevalence of chronotropic incompetence (55% of patients, p<0.01). No significant difference was found between treated and untreated KS in variance with men treated for secondary hypogonadism.

CONCLUSION

Left ventricular diastolic dysfunction, impaired cardiopulmonary performance, chronotropic incompetence, and increased intima-media thickness suggest that cardiovascular abnormalities are a common finding in KS that is not reversed by testosterone replacement therapy and may represent the pathophysiological underpinnings of the increased risk of dying from heart disease.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Left ventricular diastolic function and exercise capacity in community-dwelling adults ≥65 years of age without heart failure

Left ventricular diastolic dysfunction (LVDD) has been reported to have strong correlation with exercise capacity. However, this relationship has not been studied extensively in community-dwelling older adults. Data on pulse and tissue Doppler echocardiographic estimates of resting early (E) and atrial (A) transmitral peak inflow and early (Em) mitral annular velocities, and six-minute walk test were obtained from 89 community-dwelling older adults (mean age, 74; range, 65-93 years; 54% women), without a history of heart failure. Overall, 47% had cardiovascular morbidity and 60% had normal diastolic function (E/A 0.75-1.5 and E:Em <10). Among the 36 individuals with LVDD, 83%, 14% and 3% had grade I (E/A <0.75, regardless of E/E(m)), II (E/A 0.75-1.5 and E/E(m) ≥10) and III (E/A>1.5 and E/E(m) ≥10) LVDD, respectively. Those with LVDD were older (77 versus 73 years; p = 0.001) and had a trend for higher prevalence of cardiovascular morbidity (58% versus 40%; p = 0.083). LVDD negatively correlated with six-minute walk distance (1013 versus 1128 feet; R = -0.25; p = 0.017). This association remained significant despite adjustment for cardiovascular morbidity (R = -0.35; p = 0.048), but lost significance when adjusted for age (R = -0.32; p = 0.105), age and cardiovascular morbidity (R = -0.38; p = 0.161), and additional adjustment for sex, race, body mass index, and systolic blood pressure (R = -0.44; p = 0.365). In conclusion, most community-dwelling older adults without heart failure had normal left ventricular diastolic function or grade-I LVDD. Although LVDD was associated with decreased performance on a six-minute walk test, that association was no longer evident after adjustment for age, body mass index and cardiovascular morbidity.

Relationship of age and exercise performance in patients with heart failure: the HF-ACTION study

BACKGROUND

More than three fourths of patients with heart failure (HF) are 65 years and older, and older age is associated with worse symptoms and prognoses than is younger age. Reduced exercise capacity is a chief HF complaint and indicates poorer prognosis, especially among elderly persons, but the mechanisms underlying functional decline in older patients with HF are largely unknown.

METHODS

Baseline cardiopulmonary exercise testing data from the HF-ACTION trial were assessed to clarify age effects on peak oxygen consumption (VO(2)) and ventilation-carbon dioxide production (VE/VCO(2)) slope.

RESULTS

Among 2,331 New York Heart Association class II-IV patients with HF, increased age corresponded to decreased peak VO(2) (-0.14 mL kg(-1) min(-1) per year >40 years; P < .0001) and increased VE/VCO(2) slope (0.30 U/y >70 years; P < .0001). In a multivariable model with 34 other potential determinants, age was the strongest independent predictor of peak VO(2) (partial R(2) 0.130, total R(2) 0.392; P < .001) and a significant but relatively weaker predictor of VE/VCO(2) slope (partial R(2) 0.037, total R(2) 0.199; P < .001). Blunted peak heart rate was also a strong predictor of peak VO(2). Although peak heart rate and age were strongly correlated, both were significant independent predictors of peak VO(2) when analyzed simultaneously in a model. Aggregate comorbidity increased significantly with age but did not account for age effects on peak VO(2).

CONCLUSIONS

Age is the strongest predictor of peak VO(2) and a significant predictor of VE/VCO(2) slope in the HF-ACTION population. Age-dependent comorbidities do not explain changes in peak VO(2). Age-related changes in cardiovascular physiology, potentially magnified by the HF disease state, should be considered a contributor to the pathophysiology and a target for more effective therapy in older patients with HF.

Variables influencing heart rate

In both physiologic and pathological conditions, instantaneous heart rate value is the result of a rather complex interplay. It constantly varies under the influence of a number of factors: nonmodifiable and modifiable ones. Pharmacologic blockade with beta-adrenergic antagonists and/or with parasympathetic antagonists such as atropine have permitted the identification of the mechanisms of autonomic nervous regulation of heart rate in a variety of physiologic and pathological conditions. The analysis of heart rate and blood pressure variability has yielded additional information on the autonomic control of the circulation, which has proven to have diagnostic and prognostic implications in a number of clinically relevant conditions such as hypertension, acute myocardial infarction, heart failure, and predisposition to sudden cardiac death. This article will summarize, based on available epidemiologic and clinical studies, the key variables influencing heart rate and heart rate variability in view of the known association between heart rate and cardiovascular disease.

Left ventricular function and exercise capacity

CONTEXT

Limited information exists regarding the role of left ventricular function in predicting exercise capacity and impact on age- and sex-related differences.

OBJECTIVES

To determine the impact of measures of cardiac function assessed by echocardiography on exercise capacity and to determine if these associations are modified by sex or advancing age.

DESIGN

Cross-sectional study of patients undergoing exercise echocardiography with routine measurements of left ventricular systolic and diastolic function by 2-dimensional and Doppler techniques. Analyses were conducted to determine the strongest correlates of exercise capacity and the age and sex interactions of these variables with exercise capacity.

SETTING

Large tertiary referral center in Rochester, Minnesota, in 2006.

PARTICIPANTS

Patients undergoing exercise echocardiography using the Bruce protocol (N = 2867). Patients with echocardiographic evidence of exercise-induced ischemia, ejection fractions lower than 50%, or significant valvular heart disease were excluded.

MAIN OUTCOME MEASURE

Exercise capacity in metabolic equivalents (METs).

RESULTS

Diastolic dysfunction was strongly and inversely associated with exercise capacity. Compared with normal function, after multivariate adjustment, those with moderate/severe resting diastolic dysfunction (-1.30 METs; 95% confidence interval [CI], -1.52 to -0.99; P < .001) and mild resting diastolic dysfunction (-0.70 METs; 95% CI, -0.88 to -0.46; P < .001) had substantially lower exercise capacity. Variation of left ventricular systolic function within the normal range was not associated with exercise capacity. Left ventricular filling pressures measured by resting E/e' of 15 or greater (-0.41 METs; 95% CI, -0.70 to -0.11; P = .007) or postexercise E/e' of 15 or greater (-0.41 METs; 95% CI, -0.71 to -0.11; P = .007) were similarly associated with a reduction in exercise capacity, each in separate multivariate analyses. Individuals with impaired relaxation (mild dysfunction) or resting E/e' of 15 or greater had a progressive increase in the magnitude of reduction in exercise capacity with advancing age (P < .001 and P = .02, respectively). Other independent correlates of exercise capacity were age (unstandardized beta coefficient, -0.85 METs; 95% CI, -0.92 to -0.77, per 10-year increment; P < .001), female sex (-1.98 METs; 95% CI, -2.15 to -1.84; P < .001), and body mass index greater than 30 (-1.24 METs; 95% CI, -1.41 to -1.10; P < .001).

CONCLUSION

In this large cross-sectional study of those referred for exercise echocardiography and not limited by ischemia, abnormalities of left ventricular diastolic function were independently associated with exercise capacity.

Effects of short-term treadmill exercise training or growth hormone supplementation on diastolic function and exercise tolerance in old rats

Whether the lusitropic potential of short-term exercise in aged rats is linked to an augmentation in the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and an alteration in the cardiac renin angiotensin system (RAS) is unknown. Old (28-month-old) male, Fischer 344xBrown Norway rats were randomized to 4 weeks of GH supplementation (300 microg subcutaneous, twice daily) or 4 weeks of treadmill running, or were used as sedentary controls. Six-month-old rats, sedentary or exercised, were used as young controls. Training improved exercise capacity in old animals. Exercise and GH attenuated age-related declines in myocardial relaxation despite an exercise-induced suppression of IGF-1. The regulatory protein, sarcoplasmic Ca2+ adenosine triphosphatase (SERCA2), increased with exercise but not GH. Among aged rats, the cardiac RAS was not altered by training or GH. Thus, the signaling pathway underlying the lusitropic benefit of short-term habitual exercise in the aged rat may be distinct from GH-mediated benefits and independent of the cardiac RAS.

Há correlação entre o nível de atividade auto-referido e desempenho físico observado em mulheres idosas?

Este estudo visou verificar se havia associação entre o nível de atividade físico-funcional auto-referido e o desempenho físico de idosas em centro de reabilitação. Foram selecionadas 37 mulheres idosas (com em média 72,7±5,9 anos) pelas fichas de admissão em serviço de atividade física de um centro de referência em reabilitação. Para a avaliação do nível de atividade física auto-referido empregou-se o Perfil de Atividade Humana (PAH); na observação direta de desempenho físico aplicaram-se os testes de caminhada em 6 minutos (TC6') e levantar da cadeira em 30 segundos (TSL30"). Foi encontrada correlação positiva fraca (r=0,41) e estatisticamente significante (p=0,01) entre os valores do PAH e o TC6'; e uma tendência de associação entre a classificação do nível de atividade e a variável categórica TC6' (p=0,08). Também foi encontrada correlação positiva fraca (r=0,36) e estatisticamente significante (p=0,02) entre o PAH e o TSL30". Pode-se afirmar que o auto-relato de nível de atividade física das idosas estudadas correlaciona-se, porém fracamente, ao desempenho físico observado. Sugerem-se novas pesquisas com amostras representativas da população idosa em uma comunidade, não apenas de pacientes de centro de reabilitação, para averiguar possíveis tendências à subestimação ou superestimação do nível de atividade física em avaliações auto-referidas.

Decreased maximal heart rate with aging is related to reduced {beta}-adrenergic responsiveness but is largely explained by a reduction in intrinsic heart rate

A decrease in maximal exercise heart rate (HR(max)) is a key contributor to reductions in aerobic exercise capacity with aging. However, the mechanisms involved are incompletely understood. We sought to gain insight into the respective roles of intrinsic heart rate (HR(int)) and chronotropic beta-adrenergic responsiveness in the reductions in HR(max) with aging in healthy adults. HR(max) (Balke treadmill protocol to exhaustion), HR(int) (HR during acute ganglionic blockade with intravenous trimethaphan), and chronotropic beta-adrenergic responsiveness (increase in HR with incremental intravenous infusion of isoproterenol during ganglionic blockade) were determined in 15 older (65 +/- 5 yr) and 15 young (25 +/- 4 yr) healthy men. In the older men, HR(max) was lower (162 +/- 9 vs. 191 +/- 11 beats/min, P < 0.0001) and was associated with a lower HR(int) (58 +/- 7 vs. 83 +/- 9 beats/min, P < 0.0001) and chronotropic beta-adrenergic responsiveness (0.094 +/- 0.036 vs. 0.154 +/- 0.045 DeltaHR/[isoproterenol]: P < 0.0001). Both HR(int) (r = 0.87, P < 0.0001) and chronotropic beta-adrenergic responsiveness (r = 0.61, P < 0.0001) were positively related to HR(max). Accounting for the effects of HR(int) and chronotropic beta-adrenergic responsiveness reduced the age-related difference in HR(max) by 83%, rendering it statistically nonsignificant (P = 0.2). Maximal oxygen consumption was lower in the older men (34.9 +/- 8.1 vs. 48.6 +/- 6.7 ml x kg(-1) x min(-1), P < 0.0001) and was positively related to HR(max) (r = 0.62, P < 0.0001), HR(int) (r = 0.51, P = 0.002), and chronotropic beta-adrenergic responsiveness (r = 0.47, P = 0.005). Our findings indicate that, together, reductions in HR(int) and chronotropic responsiveness to beta-adrenergic stimulation largely explain decreases in HR(max) with aging, with the reduction in HR(int) playing by far the greatest role.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Aerobic fitness and field test performance in elite Spanish soccer referees of different ages

The major aim of this study was to examine the physical fitness of elite Spanish soccer referees in relation to their age. A secondary aim was to assess the population criterion validity of the 12 min running test (12 MRT) against aerobic-fitness laboratory tests. Participants were 45 soccer referees (age 35.5+/-4.4 years, height 178.3+/-5.0 cm, body mass 75.1+/-6.6 kg, body fat 11.3+/-2.15%, VO2(max), 54.9+/-3.9 ml kg(-1) min(-1)) who were enrolled in the Referees Technical Committee of the Royal Spanish Soccer Federation. They were divided into three age groups: young (Y, 27-32 years, n=15), average (A, 33-38 years, n=17) and old (O, 39-45 years, n=13). No age-related effects were observed for VO2(max), 12 MRT or 200 m sprint performance in either the pooled or grouped data. However, age-related performance decrements were observed for 50 m sprint performance and the ventilatory threshold (VT) running speed. Twelve MRT performance was moderately related to VO2(max), (r=0.46, P=0.002), VT (km h(-1)) (r=0.49, P<0.001), and peak treadmill velocity (PTV) (r=0.60, P<0.001). The results showed that older elite-level referees may be able to limit the expected age-related performance decrements in both aerobic and anaerobic performance usually reported for sedentary people. Additionally, these results show that older referees are able to reach physical fitness levels that have been suggested to be appropriate for coping with match demands.

Gender differences in the decline in aerobic capacity and its physiological determinants during the later decades of life

We investigated the hemodynamic determinants of the age-associated decline in maximal oxygen uptake (V(O2 max)) and the influence of gender on the decline in V(O2 max) and its determinants in old and very old men and women. Sedentary, 60- to 92-yr-old women (n = 71) and men (n = 29), with no evidence of cardiovascular disease, underwent maximal treadmill exercise tests during which V(O2 max) and maximal cardiac output (Q(max)) were determined. V(O2 max) and age were inversely related in both women (-23 +/- 2 ml.min(-1).yr(-1); P < 0.0001) and men (-57 +/- 5 ml.min(-1).yr(-1); P < 0.0001). The absolute slope of the V(O2 max) vs. age relationship was twofold steeper in men than in women (P < 0.0001). Q(max) was also inversely related to age in a gender-specific manner (women = -87 +/- 25 ml.min(-1).yr(-1), P = 0.0009; men = -215 +/- 50 ml.min(-1).yr(-1), P = 0.0002; P = 0.01 women vs. men). Age-related changes in maximal exercise arteriovenous oxygen content difference (a-vD(O2)) were marginally different (P = 0.08) between women (-0.12 +/- 0.03 ml.dl(-1).yr(-1), P = 0.0003) and men (-0.22 +/- 0.04 ml.dl(-1).yr(-1), P < 0.0001). Age-associated decreases in Q(max) and a-vD(O2) contributed equally to the declines in V(O2 max) in both men and women. In the later stages of life, V(O2 max), Q(max), and a-vD(O2) decrease with age more rapidly in older men than they do in older women. As a result, the gender differences dissipate in the later decades of life. Declines in Q(max) and a-vD(O2) contribute equally to the age-related decrease in V(O2 max) in men and women.

Transcriptional basis for exercise limitation in male eNOS-knockout mice with age: heart failure and the fetal phenotype

Endothelium-derived nitric oxide (NO) is pivotal in regulating mitochondrial O(2) consumption (Vo(2)) and glucose uptake in mice. The aim of this study was to investigate the mechanism of age- and genotype-related exercise limitation in male endothelial NO synthase (eNOS)-knockout (KO, n = 16) and wild-type (WT, n = 19) mice. Treadmill testing was performed at 12, 14, 16, 18, and 21 mo of age. Vo(2), CO(2) production, respiratory exchange ratio, and maximal running distance were determined during treadmill running. There were good linear correlations for increase of speed with increase of Vo(2). The difference between KO and WT mice was not significant at 12 mo but was significant at 18 mo. Linear regression showed that KO mice consumed more O(2) at the same absolute and relative workloads, suggesting that Vo(2) was not inhibited by NO in KO mice. KO mice performed 30-50% less work than WT mice at each age (work = vertical distance x weight). In contrast to WT mice, the work performed by KO mice significantly decreased from 17 +/- 1.4 m.kg at 12 mo to 9.4 +/- 1.7 m.kg at 21 mo. Running distance was significantly decreased from 334 +/- 27 m at 12 mo to 178 +/- 38 m at 21 mo, and maximal Vo(2), CO(2) production, and respiratory exchange ratio per work unit were significantly higher in KO than in WT mice. Gene arrays showed evidence of a fetal phenotype in KO mice at 21 mo. In conclusion, age- and genotype-related exercise limitations in maximal work performed and maximal running distance in male eNOS-KO mice indicated that fetal phenotype and age were related to onset of heart failure.

Prediction of mortality in chronic heart failure from peak oxygen consumption adjusted for either body weight or lean tissue

BACKGROUND

Peak oxygen consumption (pVO2) reflects oxygen extraction from the skeletal muscles, but is routinely corrected for body weight. We hypothesized that correcting pVO2 for lean tissue rather than total body weight would improve the prediction of prognosis in patients with chronic heart failure (CHF).

METHODS AND RESULTS

A total of 272 CHF outpatients (mean age 61 +/- 12 years, New York Heart Association [NYHA] class 2.3 +/- 0.8) underwent a cardiopulmonary exercise testing and body composition assessment by dual-energy X-ray absorptiometry. During a median follow-up of 608 days (range 8-3656), 75 patients died. Univariate survival analysis showed strong survival prediction from pVO2 adjusted for total weight or lean tissue (chi2 17.7, P < .001; chi2 27.5, P < .0001, respectively). Both predicted survival significantly in bivariate analysis, (chi2 4.6, P = .032; chi2 16.6, P < .0001). The predictive effects were independent of exercise protocol (treadmill versus cycle ergometer) (both P < .001). Multivariate analysis showed that pVO2 adjusted for lean tissue had prognostic importance independently of NYHA class, ejection fraction, and ventilation and carbon dioxide production slope (P < .05 for each). In patients with NYHA class I and II (n = 160), pVO2 adjusted for lean tissue predicted outcome (P = .03).

CONCLUSION

Adjustment for lean tissue instead for body weight increases the prognostic power of pVO2, particularly in patients with mild heart failure.

Stair climbing test as a predictor of cardiopulmonary complications after pulmonary lobectomy in the elderly

BACKGROUND

The objective of this study was to assess the role of a symptom-limited stair climbing test in predicting postoperative cardiopulmonary complications in elderly candidates for lung resection.

METHODS

A consecutive series of 109 patients more than 70 years of age who underwent pulmonary lobectomy for lung carcinoma from January 2000 through May 2003 formed the prospective database of this study. All patients in the analysis performed a preoperative symptom-limited stair climbing test. Univariate and multivariate analyses were performed to identify predictors of postoperative cardiopulmonary complications.

RESULTS

At univariate analysis, the patients with complications had a lower forced expiratory capacity percentage of predicted (p = 0.048), predicted postoperative forced expiratory volume in 1 second percentage of predicted (p = 0.049), climbed a lower height at preoperative stair climbing test (p = 0.0004), and presented a greater proportion of cardiac comorbiditiy with respect to the patients without complications (p = 0.02). After logistic regression analysis, significant predictors of postoperative complications resulted in the presence of a concomitant cardiac disease (p = 0.04) and a low height climbed preoperatively (p = 0.0015).

CONCLUSIONS

A symptom-limited stair climbing test was a safe and simple instrument capable of predicting cardiopulmonary complications in the elderly after lung resection.