Time-course of endothelial adaptation following acute and regular exercise.

BACKGROUND: Regular exercise training has emerged as a powerful tool to improve endothelium-dependent vasorelaxation. However, little is known about the magnitude of change and the permanence of exercise-induced adaptations in endothelial function. DESIGN: Rats were randomized to either 6 weeks of regular exercise or one bout of exercise. Rats were then sacrificed 0, 6, 12, 24, 48, 96 or 192 h post-exercise, and vascular responsiveness to acetylcholine was determined. METHODS: Endothelium-dependent dilation was assessed by exposure to accumulating doses of acetylcholine in ring segments of the abdominal aorta from female Sprague-Dawley rats that either exercised regularly for 6 weeks or performed a single bout of exercise. RESULTS: A single exercise session improved endothelium-dependent vasodilatation for about 48 h. Six weeks of regular exercise induced a significantly larger improvement that lasted for about 192 h. Sensitivity to acetylcholine was twofold higher in chronically trained animals than in those exposed to a single bout of exercise. The decay after a single bout of exercise was about eightfold faster than that after 6 weeks of training. CONCLUSION: The present data extend our concept of exercise-induced adaptation of endothelium-dependent vasodilatation in two regards: (1) a single bout of exercise improves endothelium-dependent dilation for about 2 days, with peak effect after 12-24 h; (2) regular exercise further improves adaptation and increases the sensitivity to acetylcholine approximately fourfold, which slowly returns to sedentary levels within a week of detraining.     

Acute effects of endurance exercise on human adipose tissue metabolism

In order to study the acute effects of exercise on adipose tissue metabolism, 27 sedentary male subjects, 18 to 27 years of age, performed a prolonged aerobic exercise test. Biopsies of adipose tissue were obtained from the suprailiac fat depot before and immediately after a 90-minute period of exercise on ergocycle at an average intensity of 88% of maximal heart rate. Fat cells, isolated by collagenase digestion, were measured for their glucose conversion into triglycerides and for lipolytic activity. Adipose tissue lipoprotein lipase activity released by heparin was also determined. Mean basal and insulin-stimulated glucose conversion into triglycerides decreased significantly with exercise (P less than .05) while adipose tissue lipoprotein lipase activity increased (P less than .01). Fat cell lipolysis increased during exercise only for its epinephrine-stimulated values (P less than .05). The total amount of work performed during the test was correlated only with changes in lipoprotein lipase activity (r = .42, P less than .05). Finally, the changes induced by exercise in lipoprotein lipase activity (r = .37, P less than .05) and insulin-stimulated glucose conversion into triglycerides (r = .61, P less than .01) were positively correlated with fat cell weight. These results indicate that adipose tissue metabolic activities are selectively influenced by endurance exercise. They also suggest that these metabolic changes are not closely coupled with the amount of work performed in a prolonged exercise bout.     

Effect of antihypertensive medication on endurance exercise capacity in hypertensive sportsmen.

Beta-adrenoceptor blockade can influence exercise capacity negatively, but data on the effect of converting enzyme inhibition and of calcium entry blockade on exercise capacity in hypertensive sportsmen are scarce. This report deals with the effect of the various types of antihypertensive medication on endurance exercise capacity in 14 hypertensive sportsmen, aged 39 +/- 3 years and weighing 73 +/- 2 kg (mean +/- s.e.m.). The patients were treated for 3 weeks with either placebo, atenolol (50 mg/day) enalapril (10 mg/day) or verapamil (240 mg/day) following a double-blind randomized cross-over design. At the end of each treatment period, they performed an endurance exercise test on the bicycle until exhaustion at 70% of their previously determined exercise capacity. Venous blood was sampled before and after exercise. In comparison with placebo, total exercise duration was not affected by enalapril (-3 +/- 7%) or verapamil (-7 +/- 11%). During treatment with atenolol, two patients had to interrupt their intake of the beta-blocker because of side effects. In the 12 remaining subjects, exercise duration was significantly decreased by 38 +/- 12% (P less than 0.01). Atenolol also induced decreases in plasma-free fatty acid concentration before and after exercise and an increase in potassium concentration after exercise, whereas enalapril and verapamil did not induce metabolic changes. During exercise, systolic blood pressure was decreased by atenolol (P less than 0.001) and enalapril (P less than 0.01) and diastolic blood pressure by enalapril (P less than 0.001), verapamil (P less than 0.05) and atenolol(P = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)     

Time-course effects of endurance training on fat oxidation in sedentary elderly people.

OBJECTIVE: To investigate alterations in whole body fat oxidation after 7 and 14 weeks of progressive endurance training in sedentary elderly subjects. DESIGN: Longitudinal, 14 weeks of progressive endurance training on a cycle ergometer (3 training sessions per week). Full sets of measurements were performed before, and after 7 and 14 weeks of training. SUBJECTS: 13 healthy sedentary subjects (5 men, 8 women) (age 62.8 +/- 2.3 y). MEASUREMENTS: 24 h indirect calorimetric measurements under standardised conditions: light-activity programme, fixed food composition, neutral daily energy balance. Body composition (by isotope dilution and skinfold thicknesses). Maximal oxygen consumption. RESULTS: Loss of 0.7 kg fat mass in the first 7 weeks of training and a further 2.4 kg of fat in the second 7 weeks. There was a transient increase in sleeping fat oxidation after 7 weeks of training (+26.1%), associated with transient increase in daily fat oxidation (+/- 11.9%), but fat oxidation then returned to baseline values in the second 7 weeks. There was a correlation between within-subject changes in sleeping fat oxidation after 7 weeks of training and variations in FFM (r = 0.62, P = 0.02) and maximal oxygen consumption (r = -0.56, P < 0.05). CONCLUSION: In sedentary elderly subjects, progressive endurance training was associated with a transient increase in sleeping fat oxidation and daily fat oxidation. In free-living conditions, possible changes in daily fat oxidation may have induced a negative fat balance, as judged by fat mass loss.     

Effects of extreme endurance running on cardiac autonomic nervous modulation in healthy trained subjects

This study examined spectral components of heart rate variability (HRV) during endurance mountain running in 8 healthy trained subjects. The data showed that during this type of mountain running, all spectral components of HRV may severely decrease, particularly very-low-frequency and low-frequency (LF) power, suggesting extreme activation of the sympathetic nervous system. The physiologic response of the heart in this situation was the downregulation of the beta-adrenergic receptors to protect myocardial function, with a subsequent increase in parasympathetic tone, reflected by an increase in high-frequency (HF) power and a decrease in the LF/HF ratio.     

Cardiac autonomic modulation during recovery from acute endurance versus resistance exercise.

BACKGROUND: The kinetics of parasympathetic reactivation after dynamic endurance exercise have been well elucidated. However, autonomic recovery of cardiac function after resistance exercise is not known. PURPOSE: The purpose of this study was to assess cardiac autonomic modulations during recovery from acute resistance exercise versus acute endurance exercise. METHODS: Electrocardiogram readings were collected before and 30 min after a single bout of endurance or resistance exercise in 14 male participants (aged 25.3+/-2.5 years). Heart rate (HR) variability was spectrally decomposed using an autoregressive approach. High frequency (HF) power was considered representative of vagal modulation. All values were expressed in both absolute and normalized units (normalized for change in total power). RESULTS: A mode-by-time interaction (P<0.05) was detected for HR, which remained elevated to a greater extent after resistance exercise. Total power was significantly reduced after resistance exercise (P<0.05) but not endurance exercise. An interaction (P<0.05) was also detected for both a change in absolute natural log function HF power and natural log function low frequency (LF) power (P<0.05), as both variables decreased more after resistance exercise. When normalized for changes in total power, interactions in LF and HF power were lost. The LF/HF ratio was significantly increased after both resistance and endurance exercise (P<0.05). CONCLUSION: Greater elevations in HR after acute resistance exercise versus acute endurance exercise may be related to greater reductions in cardiac parasympathetic tone.     

Relationship between exercise endurance capacity and cardiovascular risk factors in seventh decade subjects

Evidence suggests that physical activity is related to lower coronary risk factors in middle-aged subjects, but to date data are lacking for older persons. A total of 32 healthy male subjects in their seventh decade (64 +/- 3 years) were divided into 2 groups based on maximal exercise tests (Bruce protocol). Group I consisted of 14 individuals who showed "excellent" work capacity (exercise duration of greater than or equal to 10 min, 11 +/- 1 min), and Group II 18 individuals with "fair" work capacity (7.5 +/- 1 min). None of them showed ECG evidence of ischemia in these tests. As compared with Group II, Group I showed lower casual and 24 hour ambulatory blood pressure (136 +/- 21 vs 114 +/- 11 mmHg for the average daily systolic pressure respectively), higher apo A-I levels (116 +/- 36 vs 139 +/- 20 mg/dl) and lower apo B/A-I ratios. There was no significant difference in triglycerides, total and HDL cholesterol or apo-B levels between these two groups. Body mass index and smoking habits were similar in Groups I and II. These results suggest that even in older persons, excellent physical fitness is related to lower cardiovascular risk factors.     

Effects and adverse effects of autonomic blockade in physical exercise

Training bradycardia during autonomic blockade has been studied in rats and humans. The heart rate after autonomic blockade (intrinsic heart rate) is also lowered as a part of the adaptation to training. However, this nonautonomic component of the cardiac adaptation requires a long duration of intense endurance training to appear. This is in contrast to the autonomic component of the training bradycardia. From animal studies we have concluded that even if the training bradycardia is due to an adaptation within the heart itself, the adrenergic nerves are important for the development of a slow intrinsic heart rate. Neither the beta-receptor stimulation nor the degree of the heart rate increase during exercise is the main stimulus for the development of a training-induced bradycardia. Well-trained bicyclists had an intrinsic heart rate 20 beats lower than untrained normal control subjects. The heart rate at rest and the maximal heart rate were also on an average 20 beats lower for the bicyclists. There was no significant difference between propranolol and the beta 1 selective metoprolol in this study regarding their effects on heart rate and on deterioration of the maximal oxygen consumption after blockade. This deterioration was more marked in the well-trained than in the sedentary group. Based upon studies both in normal subjects and patients a careful rating of symptoms including physical exertion, fatigue or pain in the legs, dyspnea and chest pain using a Borg scale is recommended during exercise testing with beta blockade.(ABSTRACT TRUNCATED AT 250 WORDS)     

Caffeine slows heart rate autonomic recovery following strength exercise in healthy subjects

Introduction and objectivesStudies assessing the effects of caffeine (CAF) on the cardiovascular system have demonstrated that CAF can delay cardiac recovery following exercise. This study intended to assess the impact of CAF intake before physical exercise on heart rate variability (HRV) and cardiovascular parameters.MethodsThis is a prospective, crossover, controlled clinical trial conducted at the University of Pernambuco, Petrolina, PE, Brazil. The experimental protocol was split into three stages with a minimum of 48 hours between them. Exercises intensity was standardized based on the one repetition maximum test (1RM), obtaining the load of each volunteer for the intensity of 75% of 1RM. In the second and third phases, the control protocols were applied and 300 mg caffeine was given 45 minutes before training. HRV indices were determined at the subsequent times: 0 to 5 minutes of rest (before) and during 30 minutes of recovery (Rec) (after exercise), divided into six intervals, each of 5 minutes.ResultsThe final sample involved 30 volunteers. CAF delayed HRV recovery after resistance exercise. In general, CAF impaired recovery of HRV after resistance exercise. Significant changes were observed in the RMSSD, SDNN, TINN, SD1, low frequency and high frequency indices between the control and CAF group.ConclusionCAF protocol delayed parasympathetic regulation of heart rhythm following exercise, slowing recovery of HR, blood pressure and HRV indices after exercise.     

Cardiac adverse effects and acute exercise in elderly subjects

Cardiac arrhythmias, ST segment depressions and other cardiac adverse effects are occasionally seen in relation to physical exercise in elderly people. However, the magnitude, quality, and time-dependence of these events need to be clarified. During voluntary maximal cycle ergometer exercise (CEE), immediate cardiac disturbances as a reason for exercise termination were registered in a sample of 75-year-old men and women (N=203) (population group, PG). Any referrals to hospital following cardiac incidents within 24 hours post-CEE were obtained from patient records. Ambulatory ECG was recorded 24 hours before and after CEE in 23 elderly subjects (12 men, 11 women) capable of maximal effort (Holter group, HG). In the PG, 23.4% of the men and 6.4% of the women had to terminate CEE because of cardiac disturbances. One subject was referred to hospital because of exercise-induced atrial fibrillation. In the HG, no long-lasting effect of exercise on the occurrence of cardiac disturbances was found in elderly subjects capable of maximal effort.     

Hemodynamic effects of isometric exercise in normotensive and hypertensive subjects

Isometric exercise increases arterial pressure and heart rate in normotensive individuals and also in patients with labile and fixed essential hypertension. The hypertensinogenic effect of isometric exercise is mediated through an increase in cardiac output because the peripheral vascular resistance is usually not affected. The cardioaccelerating effects of isometric exercise are mediated through an initial vagal withdrawal and a later stimulation of the sympathetic system. However hypertensive patients with defective sympathetic adjustments are not immune to the hypertensinogenic and cardioaccelerating effects of isometric exercise. Since isometric exercises are performed several times during daily activities, they may result in dangerous elevations in arterial pressure in patients with already increased arterial pressure, and this may eventually lead to cerebrovascular accidents and/or cardiac decompensation. It is therefore recommended that patients with elevated arterial pressure, or persons prone to hypertension, should refrain from such activities.     

Lung growth in newborn guinea pigs: effects of endurance exercise.

Newborn Hartley albino guinea pigs were exercised daily on a rodent treadmill at 25 m/min, 0 degree grade for a maximum of 1 1/2 h. Groups were exercised for 1, 2 and 3 weeks. Controls were age-matched sedentary animals. A separate group of animals was sacrificed after 12 h of life to establish baseline lung growth data. A morphological and biochemical comparison was made between the lungs of exercised and sedentary animals. No effect of exercise on lung growth was observed. After 2 weeks of exercise animals had diminished somatic growth compared to the controls. The data was pooled from exercised and control guinea pigs at 1 and 3 weeks, at which time there were no differences, in order to obtain normal growth data. The only change between 0 week and 1 week was a slight increase in femur length. Between 1 week (and also 0 week) and 3 weeks there were significant increases in lung volume, lung weight, protein content, inter-alveolar wall distance, mean chord length of alveoli and ducts, and gas exchanging surface area. The guinea pig lung is well alveolated at birth and there was no evidence of subsequent alveolar multiplication. Enlargement of airspaces suggested that lung growth was primarily brought about by dilation. The lack of alveolar multiplication following exercise may be due to the fact the alveoli are fully developed at birth.     

The beneficial effect of regular endurance exercise training on blood pressure and quality of life in patients with hypertension

Regular aerobic exercise can reduce blood pressure and is recommended as part of the lifestyle modification to reduce high blood pressure and cardiovascular risk. Hypertension itself, or/and pharmacological treatment for hypertension is associated with adverse effects on some aspects of quality of life. This study was performed to evaluate the effects of regular endurance exercise training on quality of life and blood pressure. Patients with mild to moderate hypertension (systolic blood pressure 140-180 or diastolic blood pressure 90-110 mm Hg) were randomized to a moderate-intensity aerobic exercise group training for 3 sessions/week over 10 weeks or to a non-exercising control group. Health-related quality of life was assessed with the Short Form 36-item Health Survey (SF-36) at baseline and after 6 and 10 weeks. In the 102 subjects (47 male, mean age 47 years) who completed the study, reductions in blood pressure in the exercise group at 10 weeks (-13.1/-6.3 mm Hg) were significant (P < 0.001) compared to baseline and to the control group (-1.5/+6.0 mm Hg). Unlike the control group, the exercise group showed an increase in exercise capacity from 8.2 +/- 1.6 to 10.8 +/- 2.2 METS (P < 0.01) and showed higher scores on 7 out of 8 subscales (P < 0.05) of the SF-36. Improvement in bodily pain and general health sub-scores correlated with reduction in systolic blood pressure. Regular endurance training improves both blood pressure and quality of life in hypertensive patients and should be encouraged more widely.     

Low frequency regular exercise improves flow-mediated dilatation of subjects with mild hypertension.

Although exercise is recommended for the primary prevention of hypertension, and although it is generally known to have a beneficial effect on endothelial function, working individuals often find it difficult to maintain a consistent exercise regimen. In the present study, therefore, we examined the effects of infrequently performed exercise on flow-mediated dilatation (FMD), which is an index of endothelial function, in 15 subjects with hypertension (mild hypertensives) and 10 normotensive subjects (normotensives). All subjects performed mild bicycle exercise twice a week for 12 weeks. To assess the FMD, the diameter of the brachial artery was measured using ultrasound at baseline, during reactive hyperemia, and following sublingual administration of nitroglycerin. Measurement of these parameters was performed twice, at the beginning and the end of the exercise program. At the baseline, FMD was significantly lower in the mild hypertensives than in the normotensives. Nitroglycerin-mediated dilatation (NTG-D) was similar in the two groups. The exercise decreased blood pressure in the mild hypertensives, and increased high-density lipoprotein (HDL) cholesterol in both groups. The exercise improved FMD without altering NTG-D in the mild hypertensives, but did not result in any change in the normotensives. Multiple regression analysis revealed that the elevation in FMD was positively associated with changes in HDL cholesterol, and negatively associated with changes in plasma norepinephrine and systolic blood pressure. These findings suggest that regular exercise at a low frequency improves FMD, and thereby endothelial function, and lowers blood pressure in mild hypertensives.     

The limits of endurance exercise

A skeletal design which favours running and walking, including the greatest ratio of leg length to body weight of any mammal; the ability to sweat and so to exercise vigorously in the heat; and greater endurance than all land mammals other than the Alaskan Husky, indicates that humans evolved as endurance animals. The development of tools to accurately measure time and distance in the nineteenth century inspired some humans to define the limits of this special capacity. Beginning with Six-Day Professional Pedestrian Races in London and New York in the 1880s, followed a decade later by Six-Day Professional Cycling Races – the immediate precursor of the first six-day Tour de France Cycliste race in 1903, which itself inspired the 1928 and 1929 4,960 km “Bunion Derbies” between Los Angeles and New York across the breadth of the United States of America – established those unique sporting events that continue to challenge the modern limits of human endurance. But an analysis of the total energy expenditure achieved by athletes competing in those events establishes that none approaches those reached by another group – the explorers of the heroic age of polar exploration in the early twentieth century. Thus the greatest recorded human endurance performances occurred during the Antarctic sledding expeditions led by Robert Scott in 1911/12 and Ernest Shackleton in 1914/16.By man-hauling sleds for 10 hours daily for approximately 159 and 160 consecutive days respectively, members of those expeditions would have expended close to a total of 1,000,000 kcal. By comparison completing a Six-Day Pedestrian event (55,000 kcal) or the Tour de France (168,000 kcal), or cycling (180,000 kcal) or running (340,000 kcal) across America, requires a considerably smaller total energy expenditure. Thus the limits of human endurance were set at the start of the twentieth century and have not recently been approached. Given good health and an adequate food supply to prevent starvation and scurvy, these limits are set by the mind, not by the body. For it is the mind that determines who chooses to start and who best stays the distance. Based on a paper presented as the pre-dinner speech at the Cardiology at the Limits Conference, Cape Town, April 1, 2006     

Acute effects of exercise on neuropsychological function in elderly subjects

Fit elderly score higher on tests of fluid intelligence than aged-matched sedentary controls. Elderly patients who have taken part in exercise programs have shown improvement in mental function. We compared the effects of 45 minutes of exercise on memory, mood, and cognitive function in elderly subjects to a control intervention using a randomized control study design. Neuropsychological tests employed where the color slide test, digit symbol test, digit span test, logical memory test, word fluency test, and the Mini-Mental State Examination. We measured mood using a mood test and geriatric depression scale. Each subject was tested before, and immediately after, control and exercise sessions. Fifteen elderly subjects [ten men and five women; mean age, 66 years, (range, 60 to 85 years)] completed the study. There was a greater improvement in six of the eight scores of cognitive function following exercise, compared to control. These differences were significantly greater following exercise for the logical memory test score (P less than or equal to 0.02) and Mini-Mental State Examination (P less than or equal to 0.025) compared with the control intervention.     

Ventriculoarterial coupling during exercise in normal human subjects.

To examine the relative roles of ventricular contractility and loading conditions for cardiovascular adjustment during exercise, 10 normal human subjects were studied using a framework of ventriculoarterial coupling. Anaerobic threshold was evaluated to determine the work rates of aerobic and anaerobic exercise. Ventricular contractile properties were quantified by the slope of the end-systolic pressure-volume relationship (ventricular elastance) and arterial system properties were expressed by the end-systolic pressure-stroke volume relationship (arterial elastance). During aerobic exercise, left ventricular end-diastolic volume and stroke volume were increased by 14 and 33%, with plasma norepinephrine levels being doubled. Arterial elastance was reduced by 30%, but ventricular elastance did not change significantly. During anaerobic exercise, ventricular end-diastolic volume returned to the resting value, while stroke volume remained increased by 31%. In contrast to aerobic exercise, ventricular elastance rose substantially by 89% in association with about a 10 times increase in plasma norepinephrine. Arterial elastance remained the same as in aerobic exercise. Thus, the increase in stroke volume was primarily mediated by changes in loading conditions during aerobic exercise and by enhanced contractility during anaerobic exercise.     

A comparison of the effects of salbutamol and ipratropium bromide on exercise endurance in patients with COPD

STUDY OBJECTIVE: Inhaled bronchodilators are the first-line pharmacotherapy against COPD. The purpose of the present study was to investigate the effects of beta(2)-agonists and anticholinergic agents on the exercise capacity of patients with COPD. METHODS: A total of 67 stable patients with COPD were recruited at the Kyoto University Hospital. After inhaling 400 micro g salbutamol, 80 micro g ipratropium bromide, or an identical placebo in a randomized, double-blind, crossover fashion, the patients performed cycle endurance tests at a constant workload of 80% of the maximum work rate reached on progressive cycle ergometry, and the endurance time was recorded. RESULTS: Both salbutamol and ipratropium bromide significantly improved the endurance time by 29 s (15%; p < 0.001) and 27 s (14%; p < 0.001), respectively, in comparison with the placebo. However, there was no statistically significant difference between them (p = 0.71). The dyspnea ratios were also similarly reduced by both bronchodilators. The difference in the endurance time between therapy with salbutamol and placebo was significantly, but moderately, related to the difference between therapy with ipratropium bromide and placebo. In addition, there were no relationships, or only weakly significant relationships, between the change in FEV(1) and the change in the endurance time, the highest oxygen uptake, and the highest minute ventilation for both salbutamol and ipratropium bromide. CONCLUSIONS: Therapy with both salbutamol and ipratropium bromide improved exercise capacity, as evaluated by the endurance time, and reduced dyspnea similarly in patients with COPD. In addition, the effects of the different bronchodilators on exercise capacity varied within individuals, and a complex mechanism may be responsible for the different effects of these two bronchodilators on exercise capacity vs airflow limitation. These results support the conclusion that both types of inhaled bronchodilators can be used as first-line drugs for the treatment of stable patients with COPD.     

Aerobic capacity estimated by exercise vs cold-exposure: endurance training effects in rats

Two widely used measures of aerobic capacity, the maximal rate of oxygen consumption elicited by exercise (VO2max(ex)) and that induced by cold-exposure (VO2max(cold)), were compared before and after a six-week endurance training period in rats. A laddermill was used to elicit by running VO2max(ex) in a few attempts without training. Endurance training was incremented to achieve 85% of the weekly measured VO2max(ex) during the 25 min/day, 5 days/week sessions. Additional rats were left untrained either as controls or for weekly VO2max(ex) measurement. Mean VO2max(ex) was significantly greater by 34% and 20% (VO2max(ex)Mb, 29% and 9%) in the trained and weekly run groups, respectively, but no differences were found in either VO2max(cold) or body mass. Both training and the measurement of VO2max by exercise were sufficient to elevate VO2max(ex) but the enhancement of cold-exposure VO2 reported by others after endurance training was not apparent in VO2max(cold). Thus, the thermogenically-based VO2max(cold) did not reflect the adaptation to endurance training shown by exercise-elicited VO2max. We conclude that VO2max(ex) and VO2max(cold) cannot be used interchangeably as measures of aerobic capacity.