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PubMed2006

Cardiopulmonary exercise testing in children and adolescents with asthma who report symptoms of exercise-induced bronchoconstriction.

Patients with asthma often report symptoms of exercise-induced bronchoconstriction. We performed cardiopulmonary exercise testing to establish the cause of exercise limitation in patients with asthma, under treatment, who reported symptoms of exercise-induced bronchoconstriction. Ten of the 42 patients meeting criteria for inclusion in our study (24%) developed exercise-induced bronchoconstriction. Exercise limitation without exercise-induced bronchoconstriction was found in both obese and non-obese patients, suggesting that poor fitness is a problem independent of body habitus. Including cardiopulmonary exercise testing in the management of children with suspected exercise-induced bronchoconstriction would provide a better understanding of the etiology of their symptoms and facilitate more appropriate treatment.

Adolescent↗

PubMed1996

A comparison of the effects of strength and aerobic exercise training on exercise capacity and lipids after coronary artery bypass surgery.

BACKGROUND: Coronary artery surgery improves symptoms and prognosis in patients with angina. Aerobic exercise rehabilitation improves exercise capacity and prognosis in cardiac patients. Strength exercise training has not been extensively studied. DESIGN: We studied the effects of 6 months aerobic and strength exercise training after coronary artery surgery in 81 men, mean age 57 years. RESULTS: Treadmill time(s) increased by 130.3 (95% confidence interval 46.4 to 214.2) in the aerobic group; by 83.1 (0.9 to 165.3) in the strength group, and by 34.3 (-1 to 69.6) in the control group (P = 0.04, control versus aerobic) after 3 months; and by 196.4 (112.2 to 280.7) in the aerobic group, by 122.7 (37.7 to 207.6) in the strength group and by 27 (-40.4 to 94.4) in the control group (P = 0.002, control versus aerobic, and P = 0.03 control versus strength) after 6 months. The level of fitness improved more in the strength-trained group, and there was a minor reduction in body weight and degree of fatness. There were no changes in lipoprotein levels. Aerobic exercise training causes early and sustained benefit in treadmill exercise capacity, while the effects of strength exercise training are later in onset. Exercise training alone did not influence lipid levels. CONCLUSION: Cardiac rehabilitation programmes should be comprehensive, including advice on diet and other risk factor modifications in addition to exercise sessions involving aerobic and strength training elements.

Aged↗

PubMed1996

Physical responses to different modes of interval exercise in patients with chronic heart failure--application to exercise training.

METHOD: In exercise training with chronic heart failure patients, working muscles should be stressed with high intensity stimuli without causing cardiac overstraining. This is possible using interval method exercise. In this study, three interval exercise modes with different ratios of work/ recovery phases (30/60 s, 15/60 s and 10/60 s) and different work rates were compared during cycle ergometer exercise in heart failure patients. Work rate for the three interval modes was 50% (30/60 s), 70% (15/60 s) and 80% (10/60 s) of the maximum achieved during a steep ramp test (increments of 25 w/10 s) corresponding to 71, 98 and 111 watts on average. Metabolic and cardiac responses to the three interval exercises were then examined including catecholamine levels and perceived exertion. Parameters measured during interval exercise were compared with an intensity level of 75% peak VO2, determined during an ordinary ramp exercise test (increments of 12.5 W.min-1). RESULTS: (mean +/- SEM) (1) In all three interval modes, VO2, ventilation and lactate did not increase significantly during the course of exercise. Mean values during the last work phase were between 754 +/- 30 and 803 +/- 46 ml.min-1 for VO2, between 26 +/- 3 and 28 +/- 1 l.min-1 for ventilation and between 1.24 +/- 0.14 and 1.29 +/- 0.10 mmol.l-1 for lactate. (2) In mode 10/60 s, heart rate and systolic blood pressure increased significantly (82 +/- 4 --> 85 +/- 4 beats.min-1; 124 +/- 5 --> 134 +/- 5 mmHg; P < 0.05 each), while in mode 15/60 s catecholamines increased significantly (norepinephrine 0.804 +/- 0.089 --> 1.135 +/- 0.094 nmol.l-1; P < 0.008; epinephrine 0.136 +/- 0.012 --> 0.193 +/- 0.019 nmol.l-1; P < 0.005). (3) In all three modes, rating of leg fatigue and dyspnoea increased significantly during exercise but remained within the range of values considered 'very light to fairly light' on the Borg scale. (4) Compared to an intensity level of 75% peak VO2, work rate during interval work phases was between 143 and 221%, while cardiac stress (rate-pressure product) was significantly lower (83-88%). CONCLUSION: All three interval modes resulted in physical response in an acceptable range of values, and thus can be recommended.

Chronic Disease↗

PubMed2001

Exercise in chronic pulmonary disease: aerobic exercise prescription.

Endurance exercise training (EXT) is singly the most important aspect of rehabilitation for patients with chronic pulmonary disease. When effective, this modality of physical reconditioning leads to improved functional exercise capacity and reduced breathlessness. Early implementation is desirable to obtain more meaningful responses (e.g., when FEV1 falls below 50% of the predicted value in patients with chronic obstructive disease). Preparation for effective EXT requires optimization of respiratory system mechanics (e.g., using bronchodilator therapy), prevention of gas exchange failure (i.e., using supplemental oxygen), nutritional guidance, and psychological support (e.g., to overcome stigmata of disability, fear, and inclination to panic). EXT should be applied using a rigorous, scientifically based aerobic exercise prescription (AXRx) that recognizes basic principles of the human response to exercise prescription while considering individual pathophysiological limitations and identifying safety thresholds for exercise participation. The mode of aerobic exercise should use large muscle groups of the legs (e.g., treadmill or cycle ergometer). The recommended duration is an accumulation of 30 min of exercise per session at the target intensity, achieved by continuous or interval training. EXT should be supervised with a recommended frequency of at least three times per week for 6--8 wk. Target exercise intensity can be monitored by oxygen uptake, work rate, heart rate, or perceived exertion. Target intensity can be determined initially on the basis of 40% of a reference value for maximum oxygen uptake and linked to other variables through predictable interrelationships. All aspects of the AXRx must be reviewed with regard to progression during training. Pulmonary rehabilitation must recognize the importance of achieving clinically meaningful responses (e.g., increased 6-min walking distance of 54 m) as well as the need for maintenance exercise program to sustain the benefits.

Exercise↗

PubMed1997

Intense exercise increases the post-exercise threshold for sweating.

We demonstrated previously that esophageal temperature (T(es)) remains elevated by approximately 0.5 degrees C for at least 65 min after intense exercise. Following exercise, average skin temperature (T(avg)) and skin blood flow returned rapidly to pre-exercise values even though T(es) remained elevated, indicating that the T(es) threshold for vasodilation is elevated during this period. The present study evaluates the hypothesis that the threshold for sweating is also increased following intense exercise. Four males and three females were immersed in water (water temperature, T(w) = 42 degrees C) until onset of sweating (Immersion 1), followed by recovery in air (air temperature, T(a) = 24 degrees C). At a T(a) of 24 degrees C, 15 min of cycle ergometry (70% VO2max) (Exercise) was then followed by 30 min of recovery. Subjects were then immersed again (T(w) = 42 degrees C) until onset of sweating (Immersion 2). Baseline T(es) and T(skavg) were 37.0 (0.1) degrees C and 32.3 (0.3) degrees C, respectively. Because the T(skavg) at the onset of sweating was different during Exercise [30.9 (0.3) degrees C] than during Immersion 1 and Immersion 2 [36.8 (0.2) degrees C and 36.4 (0.2) degrees C, respectively] a corrected core temperature, T((es) (calculated)), was calculated at a single designated skin temperature, T((sk)(designated)), as follows: T((es)(calculated)) = T(es) + [beta/(1-beta)][T(skavg)-T((sk)(designated))]. The T((sk)(designated)) was set at 36.5 degrees C (mean of Immersion 1 and Immersion 2 conditions) and beta represents the fractional contribution of T(skavg) to the sweating response (beta for sweating = 0.1). While T((es)(calculated)) at the onset of sweating was significantly lower during exercise [36.7 (0.2) degrees C] than during Immersion 1 [37.1 (0.1) degrees C], the threshold of sweating during Immersion 2 [37.3 (0.1) degrees C] was greater than during both Exercise and Immersion 1 (P < 0.05). We conclude that intense exercise decreases the sweating threshold during exercise itself, but elicits a subsequent short-term increase in the resting sweating threshold.

Adult↗

PubMed1998

State anxiety following resistance exercise: the role of gender and exercise intensity.

Two experiments were conducted to investigate the effect of resistance exercise on state anxiety. In experiment 1, participants engaged in three 20-min bouts of resistance exercise, with intensity set as a function of perceived exertion. Results indicated that the relationship between resistance exercise and anxiety was moderated by both exercise intensity and gender. Although females reported no change in anxiety, males reported an increase in anxiety following moderate- and high-intensity exercise, and a decrease in anxiety following low intensity exercise. Experiment 2 was designed to replicate these findings utilizing a more precise manipulation of exercise intensity. Results indicated that the change in anxiety was again moderated by exercise intensity but was unaffected by gender. Both males and females reported increases in anxiety following 20 min of high-intensity exercise (75-85% of 1 RM), as well as significant decreases in anxiety following low-intensity exercise (40-50% of 1 RM).

Adult↗

PubMed2006

Colitis-induced oxidative damage of the colon and skeletal muscle is ameliorated by regular exercise in rats: the anxiolytic role of exercise.

Epidemiological studies have shown that exercise protects the gastrointestinal tract, reducing the risk of diverticulosis, gastrointestinal haemorrhage and inflammatory bowel disease, while many digestive complaints occurring during exercise are attributed to the adverse effects of exercise on the colon. In order to assess the effects of regular exercise on the pathogenesis of colitis, Sprague-Dawley rats of both sexes were either kept sedentary or given exercise on a running wheel (0.4 km h(-1), 30 min for 3 days week(-1)). At the end of 6 weeks, under anaesthesia, either saline or acetic acid (4%, 1 ml) was given intracolonically. Holeboard tests were performed for the evaluation of anxiety at 24 h before and 48 h after induction of colitis. Increased 'freezing time' in the colitis-induced sedentary group, representing increased anxiety, was reduced in the exercised colitis group (P < 0.05). On the third day following the colonic instillation, the rats were decapitated under brief ether anesthesia and the distal 8 cm of the colons were removed. In the sedentary colitis group, macroscopic and microscopic damage scores, malondialdehyde level and myeloperoxidase activity were increased when compared to the control group (P < 0.01-0.001), while exercise prior to colitis reduced all the measurements with respect to sedentary colitis group (P < 0.05-0.001). The results demonstrate that low-intensity, repetitive exercise protects against oxidative colonic injury, and that this appears to involve the anxiolytic effect of exercise, suggesting that exercise may have a therapeutic value in reducing stress-related exacerbation of colitis.

Animals↗

PubMed1985

Thermic effect of food at rest, during exercise, and after exercise in lean and obese men of similar body weight.

The thermic effect of food at rest, during 30 min of cycle ergometer exercise, and after exercise was studied in eight lean (mean +/- SEM, 10 +/- 1% body fat, hydrostatically-determined) and eight obese men (30 +/- 2% body fat). The lean and obese mean were matched with respect to age, height, weight, and body mass index (BMI) to determine the relationship between thermogenesis and body composition, independent of body weight. All men were overweight, defined as a BMI between 26-34, but the obese had three times more body fat and significantly less lean body mass than the lean men. Metabolic rate was measured by indirect calorimetry under four conditions on separate mornings, in randomized order, after an overnight fast: 3 h of rest in the postabsorptive state; 3 h of rest after a 750-kcal mixed meal (14% protein, 31.5% fat, and 54.5% carbohydrate); during 30 min of cycling and for 3 h post exercise in the postabsorptive state; and during 30 min of cycling performed 30 min after the test meal and for 3 h post exercise. The thermic effect of food, which is the difference between postabsorptive and postprandial energy expenditure, was significantly higher for the lean than the obese men under the rest, post exercise, and exercise conditions: the increments in metabolic rate for the lean and obese men, respectively, were 48 +/- 7 vs. 28 +/- 4 kcal over 3 h rest (P less than 0.05); 44 +/- 7 vs. 16 +/- 5 kcal over 3 h post exercise (P less than 0.05); and 19 +/- 3 vs. 6 +/- 3 kcal over 30 min of exercise (P less than 0.05). The thermic effect of food was significantly negatively related to body fat content under the rest (r = -0.55), post exercise (r = -0.66), and exercise (r = -0.58) conditions. The results of this study indicate that for men of similar total body weight and BMI, body composition is a significant determinant of postprandial thermogenesis; the responses of obese are significantly blunted compared with those of lean men.

Adipose Tissue↗

PubMed1992

Gas exchange, metabolite status and excess post-exercise oxygen consumption after repetitive bouts of exhaustive exercise in juvenile rainbow trout.

Juvenile rainbow trout (approximately 6 g) were exercised to exhaustion in two 5 min bouts given 6 h apart. Resting levels of whole-body lactate and glycogen were restored prior to the second bout. The rate of O2 consumption increased about threefold 5 min after each bout of exercise, while recovery time decreased from 4 h after the first bout to 2-3 h after the second. The excess post-exercise oxygen consumption, i.e. 'oxygen debt', was significantly reduced by 40% after the second exercise bout, despite almost identical rates of lactate clearance and glycogen resynthesis. The rates of CO2 and ammonia excretion increased sixfold and threefold, and recovery times decreased from 4-6 h to 3 h and from 3 h to 1.5 h, respectively. After the first bout, whole-body lactate levels peaked at 5 min post-exercise at about 8.5 times pre-exercise levels. After the second bout, lactate levels peaked at 0 min post-exercise and fell more rapidly during recovery. Whole-body glycogen levels decreased by 70% and 80% and ATP levels decreased by 75% and 65% after the first and second bouts, respectively, while glucose levels increased about 1.5-fold immediately after both bouts. Creatine phosphate levels decreased by 70% and 80% after the first and second bouts, respectively. After 6 h of recovery, creatine phosphate levels were higher after the second bout than after the first. These findings suggest that exhaustive exercise may cause a 'non-specific' increase in metabolic rate not directly related to the processing of metabolites, which is reduced upon a subsequent exercise bout. This is in contrast with the classical 'oxygen debt hypothesis', which states that the oxygen debt and lactate clearance are linked. Furthermore, it appears that two sequential exercise bouts are sufficient to induce a 'training effect', i.e. improved rates of metabolic recovery.

Adenosine Triphosphate↗

PubMed1988

Effect of 6 d of exercise training on responses to maximal and sub-maximal exercise in middle-aged men.

Nine sedentary men (53 +/- 3 yr) were studied before and after 6 d of endurance exercise training to determine the effects on maximal oxygen uptake (VO2max), and on the heart rate, blood pressure, and metabolic responses to a standard bout of steady-state sub-maximal exercise. The subjects exercised approximately 1 h.d-1 at about 68% of VO2max. The 6-d protocol elicited no improvement in VO2max (2.50 +/- 0.14 before vs 2.58 +/- 0.15 l.min-1 after training). Heart rates were significantly lower by 5 to 8 b.min-1, systolic blood pressures were reduced by 16 to 19 mm Hg, and blood lactate concentrations were 25 to 35% less at the same exercise intensities (60, 70, and 80% of VO2max) after 6 d of exercise. Rate pressure product was about 15% lower at the same exercise intensity after 6 d of training (P less than 0.05). The respiratory exchange ratio during submaximal exercise was 0.02 to 0.04 units lower (P less than 0.05; P less than 0.01) after 6 d of exercise, indicating a shift in substrate utilization favoring fat oxidation. These findings suggest that short-term endurance training can induce heart rate, blood pressure, and metabolic adaptations to sub-maximal exercise before there is a significant increase in VO2max in sedentary, middle-aged men who are capable of vigorous exercise.

Blood Pressure↗

PubMed1986

Estimation of exercise capacity from oxygen consumption in the recovery phase of submaximal exercise.

We analyzed the transient response of oxygen consumption (VO2) after the sudden termination of exercise. The study population consisted of 20 male athletes (age 13 to 15.9 years) and 87 male patients, 59 of whom (age 4.8 to 17.8 years) were considered to be normal subjects, and 28 of whom (age 6 to 14.8 years) had restricted physical activity because of underlying heart diseases (restricted group). The exercise tests were performed according to Bruce's protocol and terminated at signs of exhaustion. As soon as exercise ceased, the examinee sat on a chair and took rested completely. VO2 was measured every 30 seconds throughout the test. We characterized the rate of the initial decay of the VO2 transient as the ratio of the 30 second VO2 right after the exercise to that at the end of the exercise (Irv). This index did not differ significantly among the groups. On the other hand, Exc, the Irv normalized by the end-exercise VO2, was a sensitive index for separating the restricted group from the control and athlete groups. Should the Exc remain sensitive enough to quantify exercise capacity regardless of the intensity of the exercise imposed, even the submaximal exercise test should enable us to safely evaluate the exercise capacity of patients with impaired cardiac function.

Adolescent↗

PubMed2000

Role of exercise stress testing and safety monitoring for older persons starting an exercise program.

While the benefits of physical activity and exercise among older persons are becoming increasingly clear, the role of exercise stress testing and safety monitoring for older persons who want to start an exercise program is unclear. Current guidelines regarding exercise stress testing likely are not applicable to the majority of persons aged 75 years or older who are interested in restoring or enhancing their physical function through a program of physical activity and exercise. In addition to being expensive and of unproven benefit, the current policy of routine exercise stress testing potentially could deter many older persons from participating in an exercise program. Research is needed to investigate current physician practices, evaluate the risk of adverse cardiac events, determine the role of pharmacological stress testing, and measure and compare absolute and relative exercise intensities. To assist clinicians, we offer a set of recommendations regarding precautions that can be taken to minimize the risk of adverse cardiac events among previously sedentary older persons who do not have symptomatic cardiovascular disease and are interested in starting an exercise program. JAMA. 2000;284:342-349

Aged↗

PubMed2004

Impact of left ventricular diastolic function on exercise capacity in patients with chronic mitral regurgitation: an exercise echocardiography study.

BACKGROUND: Mitral regurgitation (MR) is known as one of the most frequent causes of heart failure and sudden death. In spite of increasing prevalence of MR, there have been no available data on cardiac determinants of exercise capacity in patients with chronic MR. HYPOTHESIS: This study aimed to investigate cardiac determinants of exercise capacity in patients with chronic MR. METHODS: We consecutively enrolled 32 patients (11 men, mean age: 44 +/- 14 years) who had greater than moderate MR with normal left ventricular (LV) systolic function (LV ejection fraction >50%). Conventional echocardiographic indices and parameters measured by Doppler tissue imaging at septal side of mitral annulus were obtained before exercise. Mitral regurgitation fraction, forward stroke volume, pulmonary venous flow velocities, and systolic pulmonary artery pressure (sPAP) were also obtained with standard methods. RESULTS: Left ventricular ejection fraction was 61 +/- 6% and MR fraction was 48 +/- 13%. All patients finished a symptom-limited treadmill exercise test with a peak heart rate of >85% of predicted maximum heart rate. Mean exercise time was 9.95 +/- 2.17 min, corresponding to 11 +/- 2 metabolic equivalents. Among pre-exercise echocardiographic variables, only early diastolic mitral annulus velocity (E') and pulmonary venous reversal flow velocity (PVa) showed a significant correlation with exercise time (r = 0.44, p = 0.011, and r = -0.40, p = 0.040, respectively), which persisted after multivariate analysis (p = 0.011 and 0.038, respectively). Other parameters such as systolic mitral annulus velocity, resting and postexercise sPAP, forward stroke volume, LV size, LV ejection fraction, left atrial size, and regurgitant fraction showed no significant correlation. CONCLUSIONS: Left ventricular diastolic function is an important determinant of exercise capacity in patients with chronic MR. Both E' and PVa, accepted surrogate estimates for LV diastolic function, may be useful for identifying patients with chronic MR and with poor exercise capacity.

Adult↗

PubMed2006

Effects of graded levels of exercise on ipsilateral and contralateral post-exercise resting rectus femoris mechanomyography.

Mechanomyography has shown that "resting" muscle is mechanically active, with greater activity after vigorous exercise. This experiment studied the post-exercise resting mechanomyography activity that results from different levels of exercise; the effects of exercise levels on the contralateral non-exercised limb; and the effects of resting muscle length on post-exercise resting mechanomyographic activity. Ten healthy volunteers had mechanomyography recordings over both mid-rectus femoris, at rest, before and after sets (1, 5, 10, 20, and 30 repetitions) of right leg extensions on an isokinetic dynamometer at 60 s(-1). Sets were performed a week apart, after only sedentary activity during the previous two hours. No definite threshold effect was shown. There was a linear correlation between mechanomyography and work done (R = 0.61, P < 0.01). There was a positive correlation of change of activity between the two thighs (R = 0.62, P < 0.01), with the non-exercised thigh demonstrating about half the activity of the exercised thigh. Finally, we observed that mechanomyographic activity was greater when rectus femoris muscle length was shorter (i.e. when the leg was extended versus flexed). We conclude that resting mechanomyography increases with increasing work and that there is a cross-over for increase in mechanomyography in the non-exercised leg, suggesting a neural mechanism. The greater mechanomyographic activity at shorter muscle lengths suggests that muscle that is less stretched could more freely oscillate, producing higher MMG amplitudes. Altered activity of the muscle spindle gamma loop or Golgi tendon apparatus may also play a role in altered activity with different muscle length.

Adult↗

PubMed2006

Long-term versus intermediate-term supervised exercise training in advanced heart failure: effects on exercise tolerance and mortality.

AIM: To date there have been no studies exploring the effects of long-term versus intermediate-term and short-term supervised exercise training program in patients with severe chronic heart failure (CHF) on optimal medical therapy. We assessed exercise tolerance and mortality in CHF patients undergoing long- versus intermediate-term exercise training (ET). METHODS: Forty-two consecutive severe CHF patients (New York Heart Association functional class III) were referred for a supervised exercise and cardiac rehabilitation program and were followed-up for 3 years: 20/42 (48%) patients discontinued ET after intermediate-term period of 1.6+/-0.8 years (Group A, intermediate-term ET), and 22/42 (52%) remained on the ET program for 3.0+/-0.3 years (Group B, long-term ET). Exercise duration, 6-min walked distance and metabolic equivalents (METs) assessed by modified Bruce protocol were recorded before, 4.5 months after, and 3 years after initiation of ET. RESULTS: Both groups were comparable regarding age, gender, prevalence of ischemic etiology, mean ejection fraction and medications. Risk factors for ischemic heart disease were similar, except for the prevalence of diabetes, which was higher in Group A compared to Group B (11/20 versus 5/22, p=0.03). Significantly more Group A patients died after ET discontinuation (4/20 versus 0/22, p=0.01). At the end of follow-up a significant improvement could be seen in Group B patients compared to A in exercise duration, 6-min walked distance and metabolic equivalents (p<0.01 for all). CONCLUSIONS: Higher survival rate was observed in severe CHF patients undergoing long-term versus intermediate-term exercise training. Long-term supervised exercise training is safe and improves exercise tolerance in these patients.

Exercise Therapy↗

PubMed2006

Prior heavy exercise increases oxygen cost during moderate exercise without associated change in surface EMG.

The aim of this study was to test the hypothesis that prior heavy exercise results in a higher oxygen cost during a subsequent bout of moderate exercise due to changes in muscle activity. Eight male subjects (25+/-2 yr, +/-SE) performed moderate-moderate and moderate-heavy-moderate transitions in work rate (cycling intensity, moderate=90% LT, heavy=80% VO(2) peak). The second bout of moderate exercise was performed after 6 min (C) or 30s (D) of recovery. Pulmonary gas exchange was measured breath-by-breath and surface electromyography was obtained from the vastus lateralis and medialis muscles. Root mean square (RMS) and median power frequency (MDPF) were computed. Prior heavy exercise increased DeltaVO(2)/DeltaWR (C: +2.0+/-0.8 ml min(-1)W(-1), D: +3.4+/-0.8 ml min(-1)W(-1); P<0.05) and decreased exercise efficiency (C: -13.3+/-5.6%, D: -22.2 +/-4.9%; P<0.05) during the second bout of moderate exercise in the absence of changes in RMS. MDPF was slightly elevated ( approximately 2%) during the second bout of moderate exercise, but MDPF was not correlated with V O(2) (r=0.17). These findings suggest that the increased oxygen cost during moderate exercise following heavy exercise is not due to increased muscle activity as assessed by surface electromyography.

Adult↗

PubMed2000

Effects of oral L-arginine supplementation on exercise-induced QT dispersion and exercise tolerance in stable angina pectoris.

We assessed the effects of L-arginine (an endogenous precursor of nitric oxide) on the magnitude of exercise-induced QT dispersion in patients with coronary artery disease. The study had a randomized double-blind cross-over design. Twenty-five patients with stable coronary artery disease underwent two separate exercise tests: after oral administration of L-arginine (6 g/24 h for 3 days) or placebo. Indications for cessation of exercise included: pulse limit, exhaustion, chest pain, ST segment depression >2 mm. We found that arginine significantly increased exercise duration from 604+/-146 to 647+/-159 s (P<0.03). However, it had no effect on the sum of exercise-induced ST segment depressions (1.9+/-2.3 and 2.4+/-3.3 on and off arginine, respectively, NS). Exercise shortened QT interval to a similar extent in patients treated with placebo or arginine. QT dispersion changed during exercise from 55+/-21 to 60+/-19 ms (NS) and from 60+/-21 to 53+/-17 ms (NS), respectively. We conclude that, in patients with coronary artery disease, oral supplementation of L-arginine does not affect exercise-induced changes in QT interval duration, QT dispersion or the magnitude of ST segment depression. However, it significantly increases exercise tolerance, most likely due to improved peripheral vasomotion. These results may be of clinical and therapeutic importance.

Aged↗

PubMed2003

Walking trials in postmenopausal women: effect of low doses of exercise and exercise fractionization on coronary risk factors.

We studied the fractionization of walking training and searched for the minimum dose to affect coronary risk factors in two randomized controlled trials. Altogether 134 (Study I) and 121 (Study II) healthy, sedentary postmenopausal women started the trials, and 130 (Study I) and 116 (Study II) completed them. In Study I the exercise intensity was 65% of the maximal aerobic power (VO2max) and a total of 300 kcal was expended in one (Group W1) or two (Group W2) daily walking bouts. In Study II the exercise was continuous, and the exercise intensity (% of VO2max) and energy expenditure (kcal session(-1)) were 55% and 300 kcal (Group W3), 45% and 300 kcal (Group W4), 55% and 200 kcal (Group W5) and 45% and 200 kcal (Group W6). All the subjects walked 5 days a week. The outcome measures were blood pressure, serum lipoproteins and blood glucose and plasma insulin in fasting state and also during 2-h oral glucose tolerance test in Study I. There was no change in diastolic pressure in the original study groups, but in the combined exercise group (W1+W2) in Study I, the mean diastolic pressure declined by -3.0 mmHg (95% con-fidence interval (CI) -5.5 to -0.4) (P=0.025) in comparison with that of the controls. The mean blood glucose declined by -0.21 mmol L(-1) (CI -0.33 to -0.09) in Group W1 and -0.13 mmol L(-1) (CI -0.25 to -0.01) in Group W2 compared to controls (P=0.03). Also the 2-h glucose concentration decreased in Groups W1 and W2 compared to controls. Systolic blood pressure, serum lipoproteins and insulin levels did not change in Study I or Study II. We conclude that our training program with the greatest exercise dose, exercise intensity 65% of VO2max and weekly expenditure of 1500 kcal had a minimal, positive effect on diastolic pressure and blood glucose, and the effect was similar in one or two daily exercise session groups. This exercise dose is probably close to the minimum to affect coronary risk factors in healthy postmenopausal women. To get a more pronounced and clinically relevant effect, a greater exercise dose is needed.

Adaptation, Physiological↗