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Results for “Exercise training”

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PubMed1992

Exercise training and the prevention of restenosis after percutaneous transluminal coronary angioplasty (PTCA).

To evaluate whether exercise training prevents the restenosis after percutaneous transluminal coronary angioplasty (PTCA), treadmill exercise with thallium-201 myocardial scintigraphy was performed at first and thirteenth week after PTCA in 18 patients with training and in 20 patients without training. Total treadmill exercise duration and maximal pressure rate product 13 weeks after PTCA increased significantly in the trained group, whereas there was no significant change in the untrained group. ST segment depression from the baseline did not change significantly in both groups. Myocardial perfusion obtained by Tl-201 scintigraphy improved significantly in the trained group, whereas there was no significant change in the untrained group. The restenosis rates at the third month after PTCA was 17% (3/18) in the trained group and 40% (8/20) in the untrained group. It is concluded that in patients with coronary artery disease, exercise training improves myocardial perfusion by preventing the progression of coronary artery stenosis after PTCA.

Angioplasty, Balloon, Coronary↗

PubMed2006

Response of high-sensitivity C-reactive protein to exercise training in an at-risk population.

BACKGROUND: High-sensitivity C-reactive protein (hsCRP) is promoted as an independent predictor of atherosclerotic risk. In addition, cardiorespiratory fitness is inversely related to hsCRP in single-sex cross-sectional analyses. Our objective was to determine if modulating fitness with exercise training imposes changes in high-sensitivity C-reactive protein in a mixed-sex population at risk for cardiovascular disease. METHODS: We studied baseline and postintervention plasma hsCRP in 193 sedentary, overweight to mildly obese, dyslipidemic men and women who were randomized to 6 months of inactivity or 1 of 3 aerobic exercise groups: low amount-moderate intensity (energy equivalent of approximately 19.3 km/wk at 40%-55% peak VO2), low amount-high intensity (energy equivalent of approximately 19.3 km/wk at 65%-80% peak VO2), or high amount-high intensity (energy equivalent of approximately 32.2 km/wk at 65%-80% peak VO2). RESULTS: At baseline, the study population was at intermediate to high cardiovascular risk as defined by hsCRP. Cardiorespiratory fitness was inversely related to hsCRP (P < .001) even after adjusting for significant and expected sex differences. Fitness, hormone replacement therapy use, and high-density lipoprotein cholesterol accounted for the sex difference in baseline hsCRP. Fitness, high-density lipoprotein cholesterol, fasting insulin, hormone replacement therapy, and visceral adiposity were all independent predictors for baseline hsCRP (r2 = 0.34 for the entire model, P < .0001). However, despite significant improvements in fitness, visceral adiposity, subcutaneous adiposity, and insulin sensitivity, hsCRP did not change in response to exercise training (P > .20). CONCLUSIONS: Cardiorespiratory fitness is inversely related to hsCRP independent of sex and accounts for most of the large sex disparity in hsCRP. Nonetheless, in the absence of a significant change in diet, 6 months of aerobic exercise training does not produce a significant change in hsCRP in an at-risk population.

Adult↗

PubMed2003

Randomized controlled trial of exercise training in postmenopausal breast cancer survivors: cardiopulmonary and quality of life outcomes.

PURPOSE: To determine the effects of exercise training on cardiopulmonary function and quality of life (QOL) in postmenopausal breast cancer survivors who had completed surgery, radiotherapy, and/or chemotherapy with or without current hormone therapy use. METHODS: Fifty-three postmenopausal breast cancer survivors were randomly assigned to an exercise (n = 25) or control (n = 28) group. The exercise group trained on cycle ergometers three times per week for 15 weeks at a power output that elicited the ventilatory equivalent for carbon dioxide. The control group did not train. The primary outcomes were changes in peak oxygen consumption and overall QOL from baseline to postintervention. Peak oxygen consumption was assessed by a graded exercise test using gas exchange analysis. Overall QOL was assessed by the Functional Assessment of Cancer Therapy-Breast scale. RESULTS: Fifty-two participants completed the trial. The exercise group completed 98.4% of the exercise sessions. Baseline values for peak oxygen consumption (P =.254) and overall QOL (P =.286) did not differ between groups. Peak oxygen consumption increased by 0.24 L/min in the exercise group, whereas it decreased by 0.05 L/min in the control group (mean difference, 0.29 L/min; 95% confidence interval [CI], 0.18 to 0.40; P <.001). Overall QOL increased by 9.1 points in the exercise group compared with 0.3 points in the control group (mean difference, 8.8 points; 95% CI, 3.6 to 14.0; P =.001). Pearson correlations indicated that change in peak oxygen consumption correlated with change in overall QOL (r = 0.45; P <.01). CONCLUSION: Exercise training had beneficial effects on cardiopulmonary function and QOL in postmenopausal breast cancer survivors.

Breast Neoplasms↗

PubMed1991

Effects of exercise training at an intensity relative to lactate threshold in mildly obese women.

To determine the effects of exercise training on the anthropometric and physiologic characteristics, twenty-eight mildly obese women were studied prior to and following a 14-week exercise training program. The present data demonstrated that regular aerobic training at an intensity corresponding to lactate threshold (LT) led to significant improvements in VO2max (12%) and VO2LT (16%) and significant reductions in systolic (5%) and diastolic blood pressure (9%). Weight (5%) and percent body fat (11%) decreased significantly, while LBM remained essentially unchanged. Although the change in HDLC and HDLC/TC did not reach statistical significance, the TC (8%) and LDLC (7%) decreased significantly. These alterations in cardiorespiratory, anthropometric, and metabolic characteristics clearly demonstrate that training intensity relative to LT may be appropriate for obese individuals to improve the aerobic capacity, lipid-lipoprotein metabolism, and anthropometric profile.

Adult↗

PubMed1999

Moderate and high intensity exercise training in HIV-1 seropositive individuals: a randomized trial.

HIV-infected individuals are frequently active, but guidelines for exercise in this population lack scientific support, since studies on the effects of exercise training on immunologic variables of HIV-1 positive individuals have shown conflicting results. Exercise capacity, immunologic markers (CD4, CD8 and CD4:CD8 ratio), anthropometric measurements, and depression scores were evaluated to compare the effects of two intensities of aerobic exercise on HIV-1 seropositive individuals. Twenty-one healthy subjects (14 men, 7 women), carriers of the HIV-1 virus (CD4>200 cells x mm(-3)), and inactive for at least 6 months, completed a 12 week exercise training program (36 sessions of 1 h, 3 times per week), in a moderate intensity group (60+/-4% of maximal heart rate) or a high intensity group (84+/-4% of maximal heart rate). Exercise capacity estimated by treadmill time was increased significantly in both moderate intensity (680+/-81 s before; 750+/-151 s after) and high intensity (651+/-122 s before; 841+/-158 s after) groups, but the high intensity group presented a significantly larger increment (p<0.01). There were no significant changes in the immunologic variables, anthropometric measurements or depression scores. Thus, HIV-seropositive individuals that participate in moderate and high intensity exercise programs are able to increase their functional capacity without any detectable changes in immunologic variables, anthropometric measurements or depression scores.

Adult↗

PubMed2002

A randomized trial of exercise training after renal transplantation.

BACKGROUND: Significant health benefits result from regular physical activity, many which are important for transplant recipients. Although exercise capacity improves initially after transplant, it is not normalized, and only two studies have reported the effects of exercise training in this population. We report a randomized clinical trial of exercise after renal transplantation (RTX). METHODS: One hundred sixty-seven patients were randomized at 1 month after RTX into two groups: exercise intervention (EX) and usual care (UC), with repeat testing at 6 and 12 months. Ninety-five patients completed the following testing at both testing times: symptom-limited treadmill testing with measurement of peak oxygen uptake (peak Vo2); isokinetic muscle testing for muscle strength; and dual-energy X-ray absorptiometry scans for body composition. The SF-36 Health Status Questionnaire assessed self-reported functioning. The exercise intervention consisted of individually prescribed programs to be conducted at home with regular phone follow-up to enhance adherence. Repeated measures analysis of variance was performed to determine differences between the groups for the three testing times. RESULTS: At 1 year 67% of the EX group were exercising regularly compared with 36% of the UC group (P=0.01). Compared with the UC group, the EX group had significantly greater gains in peak Vo2 (P=0.016), percent age-predicted Vo2 (P=0.03), and muscle strength (P=0.05), and a trend toward higher self-reported physical functioning (P=0.06). There were no differences between the groups in changes in body composition. At 1 year, peak Vo2 was significantly correlated with age, percent fat, muscle strength, hematocrit, and self-reported physical functioning. CONCLUSIONS: Exercise training after RTX results in higher levels of measured and self-reported physical functioning; however, exercise alone does not affect body composition.

Adult↗

PubMedDate not supplied

Exercise training frequency in early post-infarction cardiac rehabilitation. Influence on aerobic conditioning.

PURPOSE: The convalescent period after myocardial infarction (MI) has been associated with a "spontaneous" improvement in functional aerobic capacity that may be because of normal recovery processes unrelated to formal exercise training. The purpose of this study was to determine whether the frequency of formal training sessions is an important variable affecting the magnitude of improvement in cardiorespiratory fitness during phase II cardiac rehabilitation. METHODS: The effect of exercise training frequency on cardiorespiratory fitness was evaluated during a 5-week early (phase II) cardiac rehabilitation program in 50 low-risk, male patients recovering from acute MI. Baseline graded treadmill tests to fatigue endpoints, with direct measurement of maximal oxygen uptake (VO2max), were administered 4 weeks after MI. The subjects were then randomly assigned to either a control group (n = 12) and restricted to "very light" physical activity (requiring < 50% of VO2max) at home, or to one of three training groups which, in addition to very light home activity, performed moderately intense (approximately 70% of VO2max) aerobic exercise for 30 to 35 minutes either once per week (n = 13), twice per week (n = 13), or three times per week (n = 12) in the hospital-based phase II program. The four groups were similar in age, clinical status, and use of beta- and calcium channel blockers. RESULTS: Submaximal and maximal cardiorespiratory responses were initially similar in all four groups. Each of the four groups demonstrated significant (P < .05) increases in maximal treadmill duration at follow-up. However, VO2max increased significantly only in the three training groups. The spontaneous improvement in treadmill duration in the control group, in the absence of formal exercise training, may simply reflect recovery from the acute cardiac event. Those training two and three sessions per week also showed significant, comparable decreases in submaximal exercise heart rate and rate-pressure product and similar increases in maximal treadmill duration and VO2max. CONCLUSIONS: Results suggest that two exercise sessions per week is as effective as three per week for cardiorespiratory conditioning in the early weeks of phase II cardiac rehabilitation.

Exercise Test↗

PubMed2000

Exercise training enhances relaxation of the isolated guinea-pig saphenous artery in response to acetylcholine.

The effects of exercise training were investigated on the vascular responses in the isolated guinea-pig saphenous artery. Exercising animals swam 5 days week-1 for 6 weeks (60 min day-1 for weeks 1 and 2; 75 min day-1 for weeks 3 and 4; 90 min day-1 for weeks 5 and 6), while control animals were placed into shallow water for the same duration. Trained animals had significantly higher ventricular:body weight ratios, increased citrate synthase activity in the latissimus dorsi, and enhanced Na+ pump concentrations in the latissimus dorsi and gastrocnemius muscles (P < 0.05). In vitro isometric techniques were used to measure constriction and relaxation responses of saphenous artery rings from trained and control animals. There were no significant differences in the constriction responses to KCl (50 mm) and phenylephrine (0.3-100 microM) in arterial rings from control versus trained animals. Relaxation responses to acetylcholine (10 microM; ACh-relaxation), following preconstriction with phenylephrine (10 microM), were significantly enhanced in rings from trained animals (P < 0.05). Acetylcholine relaxed the vessels to 47 +/- 6% (control) and 18 +/- 3% (trained) of the preconstriction responses to phenylephrine. The nitric oxide synthase inhibitor N G-nitro-L-arginine (L-NA; 50 microM) significantly attenuated the ACh-relaxation in control and trained animals (P < 0.05). The effect of L-NA on the ACh-relaxation was significantly larger in trained (change in ACh-relaxation with L-NA = 29 +/- 9%) than control (14 +/- 3%) animals (P < 0.05). In conclusion, exercise training enhanced the ACh-relaxation of the isolated guinea-pig saphenous artery. Inhibition of nitric oxide synthase attenuated the ACh-relaxation of rings from control and trained animals, but this effect was significantly larger in the vessels from trained animals. These results are consistent with the idea that nitric oxide could contribute to the enhanced ACh-relaxation of the saphenous artery with exercise training.

Acetylcholine↗

PubMed1996

Serum leptin levels are reduced in response to exercise training, but not hormone replacement therapy, in older women.

The aim of this study was to evaluate the effects of exercise training and hormone replacement therapy (HRT) on serum leptin levels in older women. Previously sedentary, healthy women, aged 60-72 yr, were assigned to control (n = 16), exercise (n = 17), HRT (n = 15), or exercise + HRT (n = 13) groups. Exercise training consisted of a 2-month flexibility-exercise program followed by a 9-month exercise program that included walking, jogging, and stair climbing. HRT consisted of 11 months of continuous conjugated estrogens (0.625 mg/day) and medroxyprogesterone acetate (5 mg/day) for 13 days every third month. Body composition was assessed by dual-energy x-ray absorptiometry, and serum insulin levels were measured in the fasted state and in response to a glucose challenge. Leptin levels were reduced by 23 +/- 25% and 22 +/- 27% (both P < 0.01) in response to exercise and exercise + HRT, respectively. There was no effect of HRT on leptin. Fat mass was the strongest predictor of serum leptin concentration, both before (r = 0.81; P < 0.001) and after (r = 0.85; P < 0.001) the study period, and the change in fat mass in the exercisers was significantly correlated with the change in leptin (r = 0.55; P < 0.01). There did not seem to be an effect of exercise, independent of the reduction in fat mass, on leptin. Insulin levels were significantly correlated with leptin levels, but this was not independent of the association with adiposity. The curvilinear relationship between leptin level and fat mass and the finding that the ratio of leptin mass to fat mass decreased after weight loss suggest that fat cell size is an important determinant of circulating leptin levels.

Adipose Tissue↗

PubMed2006

Reduced skeletal muscle inhibitor of kappaB beta content is associated with insulin resistance in subjects with type 2 diabetes: reversal by exercise training.

Skeletal muscle insulin resistance plays a key role in the pathogenesis of type 2 diabetes. It recently has been hypothesized that excessive activity of the inhibitor of kappaB (IkappaB)/nuclear factor kappaB (NFkappaB) inflammatory pathway is a mechanism underlying skeletal muscle insulin resistance. However, it is not known whether IkappaB/NFkappaB signaling in muscle from subjects with type 2 diabetes is abnormal. We studied IkappaB/NFkappaB signaling in vastus lateralis muscle from six subjects with type 2 diabetes and eight matched control subjects. Muscle from type 2 diabetic subjects was characterized by a 60% decrease in IkappaB beta protein abundance, an indicator of increased activation of the IkappaB/NFkappaB pathway. IkappaB beta abundance directly correlated with insulin-mediated glucose disposal (Rd) during a hyperinsulinemic (40 mU x m(-2) x min(-1))-euglycemic clamp (r = 0.63, P = 0.01), indicating that increased IkappaB/NFkappaB pathway activity is associated with muscle insulin resistance. We also investigated whether reversal of this abnormality could be a mechanism by which training improves insulin sensitivity. In control subjects, 8 weeks of aerobic exercise training caused a 50% increase in both IkappaB alpha and IkappaB beta protein. In subjects with type 2 diabetes, training increased IkappaB alpha and IkappaB beta protein to levels comparable with that of control subjects, and these increments were accompanied by a 40% decrease in tumor necrosis factor alpha muscle content and a 37% increase in insulin-stimulated glucose disposal. In summary, subjects with type 2 diabetes have reduced IkappaB protein abundance in muscle, suggesting excessive activity of the IkappaB/NFkappaB pathway. Moreover, this abnormality is reversed by exercise training.

Adult↗

PubMed2003

Effects of exercise training on coronary heart disease risk factors in renal transplant recipients.

BACKGROUND: Multiple risk-factor interventions that include lifestyle changes have been proved to be effective in reducing risk profile in persons at high risk for developing coronary heart disease (CHD). There have not been similar studies involving transplant recipients. The purpose of this study is to examine effects of exercise training on cardiovascular risk profile during the first year after renal transplantation. We used traditional CHD risk factors and the Framingham CHD prediction methods. METHODS: Ninety-six transplant recipients were randomly assigned to 2 groups at 1 month posttransplantation: the exercise training (EX group; n = 51) and usual care groups (UC group; n = 45). Testing was performed at baseline and 12 months posttransplantation and included maximal exercise testing and evaluation of CHD risk factors and risk-factor categories, determined by means of the Framingham equations. RESULTS: Overall 10-year CHD risk score did not change in either group. All patients showed increases in total cholesterol (TC) level, high-density lipoprotein fraction of cholesterol (HDL-C), and body mass index over time. No differences were observed between groups, except for a trend toward greater improvement in HDL cholesterol levels in the EX group (P = 0.07). Significantly more patients in the EX group moved out of the high-risk category in TC-HDL ratio. All patients remained in the high-risk category for physical fitness. There was a significant negative correlation of CHD risk and maximal exercise capacity (r = -0.406; P < 0.001). CONCLUSION: Exercise training alone does not reduce CHD risk during the first year after transplantation. Research to determine the effects of multiple risk interventions during a longer period in transplant recipients is warranted.

Adult↗

PubMed1996

Exercise training improves functional status in patients with peripheral arterial disease.

PURPOSE: In patients with intermittent claudication (IC) a structured walking exercise program improves exercise performance. However, few studies have evaluated the effects of exercise training on functional status during daily activities. We hypothesized that a supervised exercise training program would improve functional status in patients with IC, with 24 weeks of training more beneficial than 12 weeks. A secondary aim was to evaluate the effects of strength training and combinations of strength and treadmill training on functional status. METHODS: Twenty-nine men with disabling IC were randomized to 12 weeks of either supervised treadmill training (3 hr/wk at a work intensity sufficient to produce claudication), strength training (3 hr/wk of resistive training of six muscle groups of each leg), or to a nonexercising control group. Functional status was assessed by questionnaires characterizing walking ability (Walking Impairment Questionnaire, WIQ), habitual physical activity level (Physical Activity Recall, PAR), and physical, social, and role functioning, well-being, and overall health (Medical Outcomes Study SF-20, MOS). Patients alos had their activity levels monitored with an activity monitor (Vitalog). RESULTS: After 12 weeks of treadmill training PAR scores increased by 48 metabolic equivalent hr/wk, the MOS physical functioning score by 24 percentage points, and the number of bouts of walking activity measured by the Vitalog by 4.5 bouts/hr (all p < 0.05). No changes were seen in WIQ scores. After 12 additional weeks of treadmill training improvements initially observed in the PAR, MOS, and Vitalog scores were maintained, and in addition the ability to walk distances (WIQ) improved by 31 percentage points, and the IC severity score had improved by 29 percentage points (both p < 0.05). After 12 weeks of strength training patients improved their WIQ walking speed, stair climbing scores, and MOS well-being scores with no other changes in functional status. Subjects in the control group did not improve functional status by any measure. Twelve weeks of treadmill training after the strength training program maintained WIQ walking speed scores, and activity level defined by Vitalog improved. Twelve weeks of combined treadmill and strength training after the control period had no effect on functional status. CONCLUSIONS: A supervised treadmill training program improved functional status during daily activities, with 24 weeks more effective than 12. In addition, treadmill training alone was more effective in improving functional status in patients with IC than strength training or combinations of the training modalities.

Aged↗

PubMed2001

Determinants of oxygen uptake kinetics in older humans following single-limb endurance exercise training.

We hypothesised that the observed acceleration in the kinetics of exercise on-transient oxygen uptake (VO2) of five older humans (77 +/- 7 years (mean +/- S.D.) following 9 weeks of single-leg endurance exercise training was due to adaptations at the level of the muscle cell. Prior to, and following training, subjects performed constant-load single-limb knee extension exercise. Following training VO2 kinetics (phase 2, tau) were accelerated in the trained leg (week 0, 92 +/- 44 s; week 9, 48 +/- 22 s) and unchanged in the untrained leg (week 0, 104 +/- 43 s; week 9, 126 +/- 35 s). The kinetics of mean blood velocity in the femoral artery were faster than the kinetics of VO2, but were unchanged in both the trained (week 0, 19 +/- 10 s; week 9, 26 +/- 11 s) and untrained leg (week 0, 20 +/- 18 s; week 9, 18 +/- 10 s). Maximal citrate synthase activity, measured from biopsies of the vastus lateralis muscle, increased (P < 0.05) in the trained leg (week 0, 6.7 +/- 2.0 micromol x (g wet wt)(-1) x min(-1); week 9, 11.4 +/- 3.6 micromol x (g wet wt)(-1) x min(-1)) but was unchanged in the untrained leg (week 0, 5.9 +/- 0.5 micromol x (g wet wt)(-1) x min(-1); week 9, 7.9 +/- 1.9 micromol x (g wet wt)(-1) x min(-1)). These data suggest that the acceleration of VO2 kinetics was due to an improved rate of O2 utilisation by the muscle, but was not a result of increased O2 delivery.

Aged↗

PubMed1993

The influence of high-intensity exercise training on the Wlim-Tlim relationship.

When exercise to exhaustion is performed using at least two different intensities, work to fatigue (Wlim) can be expressed as a linear function of time to fatigue (Tlim). Whereas the slope of this function is related to endurance ability, the y-intercept is associated with the potential to perform high intensity interval exercise. The purpose of the present investigation was to determine the influence of 8-wk intermittent high-intensity exercise training on the y-intercept derived from the Wlim-Tlim relationship. Eight healthy, untrained male students (19.1 +/- 0.6 yr) completed five 60-s bouts of maximal exercise on the cycle ergometer, three times a week, for 8 wk. Seven controls avoided regular activity for the same period. Prior to and immediately following the training period, the Wlim-Tlim relationship, VO2max, and total work completed in five 60-s exercise bouts on the cycle ergometer were determined. Correlational analysis established relationships between the y-intercept and total work accomplished in the interval test pre- (r = 0.90; P < 0.01; N = 15) and post-training (r = 0.92; P < 0.01; N = 15), confirming that the y-intercept is related to the ability to perform exercise of this nature. Moreover, the "anaerobic" energy yield, calculated from total work and oxygen consumed during the interval exercise, was also related to the y-intercept (r = 0.78; P < 0.01). Interval training significantly increased both the y-intercept (P = 0.0015) and total work accomplished in the interval test (P = 0.001), while the slope of the Wlim-Tlim relationship (critical power) remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed2001

The effect of combined aerobic and resistance exercise training on vascular function in type 2 diabetes.

OBJECTIVES: The purpose of this study was to examine whether exercise training stimulates a generalized improvement in vascular function in patients with type 2 diabetes mellitus. BACKGROUND: Exercise is often recommended for patients with type 2 diabetes to improve physical conditioning and glycemic control. This study examined the effect of eight weeks of exercise training on conduit and resistance vessel function in patients with type 2 diabetes, using a randomized crossover design. METHODS: Both resistance vessel endothelium-dependent and -independent functions were determined by forearm plethysmography and intrabrachial infusions of acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, in 16 patients with type 2 diabetes. Conduit vessel endothelial function was assessed in 15 of these patients using high-resolution ultrasound and flow-mediated dilation of the brachial artery; glyceryl trinitrate (GTN) was used as an endothelium-independent dilator. RESULTS: Flow-mediated dilation increased from 1.7 +/- 0.5% to 5.0 +/- 0.4% following training (p < 0.001). The forearm blood flow ratio to ACh was significantly improved (analysis of variance, p < 0.05). Responses to SNP and GTN were unchanged. Endothelium-dependent vasodilation was enhanced in both conduit and resistance vessels. CONCLUSIONS: If endothelial dysfunction is an integral component of the pathogenesis of vascular disease, as currently believed, this study supports the value of an exercise program in the management of type 2 diabetes.

Diabetes Mellitus, Type 2↗

PubMed1992

Adrenergic responsiveness and intrinsic sinoatrial automaticity of exercise-trained rats.

The purpose of this study was to test the hypothesis that bradycardia in exercise-trained rats results from decreased intrinsic automaticity of the sinoatrial (SA) node and/or alterations in the responsiveness of the beta-receptors of atrial pacemaker cells. Male Sprague-Dawley rats were divided into exercise trained (ET) and sedentary (SED) groups. ET rats underwent a 12-16 wk program of progressive treadmill training, during which time the SED rats were cage confined. In vivo, resting heart rates were significantly less (P less than 0.05) in ET rats (301 +/- 8 bpm) compared with the SED group (320 +/- 6 bpm). In vitro experiments were conducted on atria isolated from ET and SED rats, and the beta-adrenoceptor agonist isoproterenol was used to investigate cardiac adrenergic control of chronotropic mechanisms in spontaneously beating right atria and inotropic mechanisms in electrically paced (1 Hz) left atria. There were no significant differences between ET and SED cardiac preparations in either the efficacy (maximal response) or potency (EC50) of isoproterenol dose-response relationships for chronotropic or inotropic responses. Intrinsic right atrial beating frequency, measured in the presence of beta-adrenoceptor block by propranolol and cholinergic muscarinic block by atropine, was lower in ET rats. We conclude that training-induced bradycardia in rats is related, at least in part, to alterations in intrinsic automaticity of SA nodal pacemaker tissue, but does not appear to be associated with changes in the properties of the beta 1-adrenoceptors or their affiliated signal transduction mechanisms in either SA pacemaker cells or atrial myocytes.

Animals↗

PubMed2000

Influence of upper- and lower-limb exercise training on cardiovascular function and walking distances in patients with intermittent claudication.

PURPOSE: The effects of upper-limb (arm cranking) and lower-limb (leg cranking) exercise training on walking distances in patients with intermittent claudication was assessed. METHODS: Sixty-seven patients (33 to 82 years old) with moderate to severe intermittent claudication were recruited, and the maximum power generated during incremental upper- and lower-limb ergometry tests was determined, as were pain-free and maximum walking distances (by using a shuttle walk test). Patients were randomly assigned to an upper-limb training group (n = 26) or a lower-limb training group (n = 26). An additional untrained group (n = 15) was recruited on an ad hoc basis in parallel with the main trial by using identical inclusion criteria. This group was subsequently shown to possess a similar demographic distribution to the two exercise groups. Supervised training sessions were held twice weekly for 6 weeks. RESULTS: Both training programs significantly improved the maximum power generated during the incremental upper- and lower-limb ergometry tests (P <. 001), which may reflect an increase in central cardiovascular function that was independent of the training mode. More importantly, pain-free and maximum walking distances also improved in both training groups (P <.001). The improvements in the training groups were similar; there were no changes in the untrained control group. These findings suggest that the symptomatic improvement after upper-limb exercise training may result, in part, from systemic cardiovascular effects rather than localized metabolic or hemodynamic changes. CONCLUSION: Carefully prescribed upper-limb exercise training can evoke a rapid symptomatic improvement in patients with claudication, while avoiding the physical discomfort experienced when performing lower-limb weight-bearing exercise.

Adult↗

PubMed1982

Heart rate adaptation to exercise training in cardiac-denervated dogs.

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

Adaptation, Physiological↗