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PubMed2004

Interval exercise versus continuous exercise in patients with moderate to severe chronic obstructive pulmonary disease--study protocol for a randomised controlled trial [ISRCTN11611768].

BACKGROUND: Physical exercise has become a cornerstone of management of chronic obstructive pulmonary disease (COPD) because it leads to clinically relevant improvements of exercise capacity and health-related quality of life (HRQL). Despite the scarcity of randomised trials directly comparing exercise protocols, current guidelines recommend high intensity continuous exercise for lower extremities as the probably most effective exercise modality. However, for patients admitted to inpatient respiratory rehabilitation programmes, it is often difficult to initiate such an exercise programme because they are severely limited by dyspnoea and leg fatigue and therefore unable to perform continuous exercise at higher intensities and for periods longer than 30 minutes. Interval exercise may be an attractive alternative for these COPD patients because it allows high intensity exercise with recovery periods. The aim of this study is to assess if interval exercise compared to high intensity continuous exercise is not of inferior effectiveness in terms of HRQL and exercise capacity improvements but associated with better exercise tolerance in patients with moderate to severe COPD at the beginning of a respiratory rehabilitation. METHODS/DESIGN: We will assign patients with moderately severe to severe COPD to either continuous exercise or interval exercise using a stratified randomisation. Patients will follow 12-15 exercise sessions during a comprehensive inpatient respiratory rehabilitation. Primary end point for effectiveness is HRQL as measured by the Chronic Respiratory Questionnaire (CRQ) two weeks after the end of rehabilitation and secondary endpoints include additional clinical outcomes such as functional exercise capacity, other HRQL measures, patients' experience of physical exercise as well as physiological measures of the effects of physical exercise such as cardiopulmonary exercise testing. Including expected drop-outs, we will need 52 patients per group to show differences corresponding to the minimal clinically important difference of the CRQ. Outcome assessors and investigators involved in data analysis will be blinded to group assignment until analyses have been carried out. DISCUSSION: Clinicians and the scientific community need evidence on the benefits and tolerance of exercise protocols available in clinical practice. The proposed trial will provide important and needed data on interval and continuous exercise for decision making in clinical practice.

Journal Article↗

PubMed2000

Nedocromil sodium for preventing exercise-induced bronchoconstriction.

BACKGROUND: Exercise-induced asthma causes cough, dyspnea, wheeze and chest tightness. Management of focuses on prevention through pharmaco-therapy and alternate strategies. Single use, pre-exercise beta2-agonists and non-steroidal anti-inflammatory agents such as the cromones are the most common treatments. OBJECTIVES: The objective of this review was to assess the effects of a single dose of nedocromil sodium to prevent exercise-induced bronchoconstriction. SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, the Cochrane Controlled Trials Register, Current Contents, review articles, textbooks and reference lists of articles. We also contacted the drug manufacturer and primary authors for additional citations. SELECTION CRITERIA: Randomised trials comparing a single dose of nedocromil sodium with placebo to prevent exercise-induced bronchoconstriction in people over six years of age. DATA COLLECTION AND ANALYSIS: Trial quality assessment and data extraction were conducted independently by two reviewers. Study authors were contacted for confirmation of data. MAIN RESULTS: Twenty randomised controlled trials involving 280 participants were identified. 15-60 min following inhalation of 4 mg nedocromil, the maximum fall in forced expiratory volume in one second due to exercise was improved by 15.6%, (95% CI:13.2 to 18.1) compared to the placebo response. The maximum percentage fall in peak expiratory flow rate was of the same magnitude (weighted mean difference 15.0%; 95% CI 8.3 to 21.6). Nedocromil shortened the time to recover lung normal function from more than 30 minutes with placebo to less than 10 minutes with the drug. The relative magnitude of its effect was greatest in patients with more severe exercise-induced bronchoconstriction (defined as an exercise-induced fall in lung function > 30% from baseline). There were no significant adverse effects reported. REVIEWER'S CONCLUSIONS: Nedocromil sodium used before exercise appears to reduce the severity and duration of exercise-induced bronchoconstriction. This effect appears to be more pronounced in people with severe exercise-induced bronchoconstriction.

Adolescent↗

PubMed1981

Value of exercise thallium-201 imaging in patients with diagnostic and nondiagnostic exercise electrocardiograms.

The role of exercise imaging with thallium-201 in the evaluation of patients suspected of having coronary artery disease was studied in 194 patients undergoing diagnostic coronary arteriography. Ninety-eight patients had 70 percent or more narrowing of one or more coronary vessels and 96 patients had either no or insignificant coronary artery disease. One hundren twenty-three of the 194 patients had conclusive treadmill exercise electrocardiograms (either positive or negative), and 71 had inconclusive exercise electrocardiograms. Fifty-four of the 98 patients with coronary artery disease were receiving propranolol at the time of testing. Forty-five (83 percent) of the 54 patients receiving propranolol and 33 (75 percent) of the 44 patients not receiving propranolol had abnormal exercise thallium images (difference not significant). In patients with conclusive exercise electrocardiograms the sensitivity of exercise imaging was not significantly different from that of exercise electrocardiograms (80 versus 74 percent), but the sensitivity of both tests combined (92 percent) was higher than that of either test alone (p less than 0.01). The specificity of exercise imaging (97 percent) electrocardiograms the sensitivity of exercise imaging was not significantly different from that of exercise electrocardiograms (80 versus 74 percent), but the sensitivity of both tests combined (92 percent) was higher than that of either test alone (p less than 0.01). The specificity of exercise imaging (97 percent) electrocardiograms the sensitivity of exercise imaging was not significantly different from that of exercise electrocardiograms (80 versus 74 percent), but the sensitivity of both tests combined (92 percent) was higher than that of either test alone (p less than 0.01). The specificity of exercise imaging (97 percent) was higher than that of exercise electrocardiograms (86 percent, p less than 0.02). The specificity of both tests combined was not significantly different from that of exercise electrocardiograms alone. The sensitivity (79 percent) and specificity (95 percent) of exercise imaging were not significantly different in patients with inconclusive exercise electrocardiograms when compared with those in patients whose exercise electrocardiograms were conclusive. These data indicate that exercise imaging is sensitive and specific in diagnosing coronary artery disease in the presence of diagnostic as well as nondiagnostic exercise electrocardiograms and that propranolol therapy does not affect the results.

Angina Pectoris↗

PubMed2003

Effect of exercise intensity, duration and mode on post-exercise oxygen consumption.

In the recovery period after exercise there is an increase in oxygen uptake termed the 'excess post-exercise oxygen consumption' (EPOC), consisting of a rapid and a prolonged component. While some studies have shown that EPOC may last for several hours after exercise, others have concluded that EPOC is transient and minimal. The conflicting results may be resolved if differences in exercise intensity and duration are considered, since this may affect the metabolic processes underlying EPOC. Accordingly, the absence of a sustained EPOC after exercise seems to be a consistent finding in studies with low exercise intensity and/or duration. The magnitude of EPOC after aerobic exercise clearly depends on both the duration and intensity of exercise. A curvilinear relationship between the magnitude of EPOC and the intensity of the exercise bout has been found, whereas the relationship between exercise duration and EPOC magnitude appears to be more linear, especially at higher intensities. Differences in exercise mode may potentially contribute to the discrepant findings of EPOC magnitude and duration. Studies with sufficient exercise challenges are needed to determine whether various aerobic exercise modes affect EPOC differently. The relationships between the intensity and duration of resistance exercise and the magnitude and duration of EPOC have not been determined, but a more prolonged and substantial EPOC has been found after hard- versus moderate-resistance exercise. Thus, the intensity of resistance exercise seems to be of importance for EPOC. Lastly, training status and sex may also potentially influence EPOC magnitude, but this may be problematic to determine. Still, it appears that trained individuals have a more rapid return of post-exercise metabolism to resting levels after exercising at either the same relative or absolute work rate; however, studies after more strenuous exercise bouts are needed. It is not determined if there is a sex effect on EPOC. Finally, while some of the mechanisms underlying the more rapid EPOC are well known (replenishment of oxygen stores, adenosine triphosphate/creatine phosphate resynthesis, lactate removal, and increased body temperature, circulation and ventilation), less is known about the mechanisms underlying the prolonged EPOC component. A sustained increased circulation, ventilation and body temperature may contribute, but the cost of this is low. An increased rate of triglyceride/fatty acid cycling and a shift from carbohydrate to fat as substrate source are of importance for the prolonged EPOC component after exhaustive aerobic exercise. Little is known about the mechanisms underlying EPOC after resistance exercise.

Adaptation, Physiological↗

PubMed2003

Accuracy of peak treadmill exercise echocardiography to detect multivessel coronary artery disease: comparison with post-exercise echocardiography.

AIMS: Although peak exercise echocardiography has been reported for both bicycle and treadmill exercise and has shown higher sensitivity than post-exercise imaging, little is known about its utility for identifying multivessel involvement. We sought to compare feasibility and accuracy of peak treadmill exercise echocardiography vs post-exercise echocardiography for identification of multivessel coronary artery disease and to assess its incremental value when combined with clinical and exercise test variables. METHODS AND RESULTS: The study group included 335 patients (228 men; mean (+/- SD) age 60 +/- 11 years). Two hundred and seventy-nine patients were included on the basis of having had an exercise echocardiography and a coronary angiography within 4 months of the exercise test. To avoid bias to coronary angiography, a subgroup of 56 consecutive non-diabetic patients referred for exercise echocardiography with pretest probability of coronary artery disease <10% and had atypical chest pain or were asymptomatic were also included and considered as having no coronary artery disease. Multivessel coronary artery disease (> or = 50% diameter stenosis in >1 vessel) was confirmed in 170 patients, whereas 165 patients were considered to have one-vessel coronary artery disease or no coronary lesions. Positive exercise echocardiography was defined as ischaemia or necrosis in at least two coronary territories. Post-exercise images were acquired within 125 s after exercise (49 +/- 15). Mean heart rate (bpm) was 139 +/- 19 at peak vs 117 +/- 22 at post-exercise imaging (P<0.001). Interpretable peak and post-exercise images were obtained for all patients. Sensitivity for predicting multivessel disease was higher with peak than with post-exercise imaging (79 vs 55%, P<0.001), with lower specificity (79 vs 88%, P<0.05). Predictive positive value was similar (80 vs 83%). Negative predictive value was again higher with peak imaging (78 vs 66%, P<0.01). Total accuracy was not different (79 vs 72%). A stepwise logistic regression analysis identified peak exercise echocardiography positivity for multivessel coronary artery disease as the strongest independent predictor of multivessel disease (odds ratio (OR): 7.36); also significant were male gender (OR: 4.22), diabetes mellitus (OR: 4.28), previous myocardial infarction (OR: 3.12) and increment of product heart rate x blood pressure (OR: 1.00). CONCLUSIONS: Peak treadmill exercise echocardiography is technically feasible and has higher sensitivity and negative predictive value for predicting multivessel disease than post-treadmill exercise echocardiography. This method adds independent and incremental values to clinical and exercise variables for the diagnosis of multivessel coronary artery disease. Therefore, in the clinical setting, peak exercise echocardiography should be performed to diagnose multivessel coronary artery disease.

Aged↗

PubMed1997

Post-exercise cutaneous hyperaemia resulting from local exercise of an extremity.

Large changes in skin blood flow occur after exercise. Most studies have concentrated on the systemic effects of vigorous exercise on skin blood flow. We were interested in the post-exercise response in the neighbourhood of focal exercise. We used a painless neuromuscular electronic stimulator to exercise the muscles of the forearm, producing flexion of the fingers. There was no change in blood pressure and only a small increase in heart rate during this exercise. We measured blood flow during a 5-min pre-exercise period and a 5-min post-exercise period at the forearm, at the dorsum of the index finger and on the pad of the index finger. We also measured values on the contralateral non-exercised extremity during exercise as well as during matched time periods in control experiments with no exercise. Exercise did elicit an increased blood flow in the post-exercise period at all three sites compared with the control experiments with no exercise and on the contralateral extremity. For example, the increase in blood flow at the finger dorsum was 2.1 +/- 0.1 ml (min 100 g)-1 after exercise compared with -0.08 +/- 0.09 ml min-1 100 g-1 during the control experiment and 0.1 +/- 0.1 ml (min 100 g)-1 on the contralateral arm (all P < 0.01). The local application of heat at the site of blood flow monitoring produced a substantial increase in the post-exercise response at the two finger locations [27.4 +/- 0.4 ml (min 100 g)-1 at the finger dorsum], but not at the arm. This is the first demonstration that highly focal exercise, unaccompanied by a systemic haemodynamic response, can elicit a post-exercise cutaneous hyperaemia. Local heating produced a large synergistic increase in the post-exercise hyperaemia at sites with arteriovenous microvascular perfusion but not at sites with primarily nutritive perfusion. These findings show that local vasoregulatory changes occur in response to exercise, even in the absence of whole-body haemodynamic and thermal change.

Arm↗

PubMed2007

Attenuated growth hormone response to resistance exercise with prior sprint exercise.

PURPOSE: This study examined effects of prior sprint exercise on hormonal responses to subsequent resistance exercise with different recovery periods between exercise bouts. METHODS: Nine men performed three types of exercise regimens: 1) resistance exercise only (R), 2) resistance exercise with prior sprint exercise and 60 min of rest (SR60), and 3) resistance exercise with prior sprint exercise and 180 min of rest (SR180). Sprint exercises consisted of maximal sprint cycling (eight sets of 5-s sprints with 30-s rest periods between sets) with prior 10-min warm-up. Resistance exercise consisted of five exercises, each with three sets at a 10-repetition maximum with 1-min rest periods. RESULTS: Prior sprint exercise significantly increased blood lactate, glycerol, epinephrine, norepinephrine, growth hormone (GH), and free testosterone concentrations (P < 0.05). Before the resistance exercise, free fatty acids concentration was higher in the SR180 trial than in the SR60 and R trials (P < 0.05), whereas GH concentration was significantly higher in the SR60 trial (P < 0.01). After the resistance exercise, no significant difference was found in responses of pH, epinephrine, norepinephrine, and free testosterone among trials. The SR180 trial showed a smaller GH response (peak value: 7.8 +/- 1.6 (SE) ng.mL(-1)) than in the R trial (12.8 +/- 3.7 ng.mL(-1)), with no significant difference between trials. In the SR60 trial, GH response to resistance exercise was attenuated (3.3 +/- 1.2 ng.mL(-1), P < 0.01). Maximal strength and power measured immediately before the resistance exercise showed no difference among trials. CONCLUSION: These results indicate that GH response to resistance exercise was attenuated strongly when the exercise was preceded by sprint exercise and a shorter (60 min) recovery period.

Exercise↗

PubMed2000

An office-based instrument for exercise counseling and prescription in primary care. The Step Test Exercise Prescription (STEP).

BACKGROUND: Available evidence suggests that despite physicians' positive attitudes toward exercise as an important part of promoting a healthy lifestyle, few physicians actually prescribe exercise for their patients. One barrier may be lack of a standard office instrument. OBJECTIVES: To determine the (1) exercise counseling habits among a large group of Canadian family physicians and (2) acceptance and utilization of an exercise counseling instrument geared to primary care practice. DESIGN: Randomized control trial. SETTING: Primary care practice. PARTICIPANTS: Family physicians (N = 400) from 3 regions of Canada, representing both rural and urban practice (ratio of 1:3). Patients (10 per practice) were healthy community dwellers older than 65 years obtained as a convenience sample in their family practice. INTERVENTIONS: In phase 1, 400 physicians listed as being in general or family practice by their provincial registries were randomly selected from a larger group listed by these registries and contacted by telephone. A total of 362 completed a 10-minute questionnaire that detailed practice demographics, preventive practice, and exercise counseling habits. In phase 2, 293 agreed to further participate in the administration of an exercise prescription randomly assigned to them by the study team. Two methods of exercise prescription were compared: counseling using the American College of Sports Medicine guidelines (control) and counseling using guidelines and an office-based step test (Step Test Exercise Prescription [STEP]) to determine fitness level and prescribe an exercise training heart rate. Physicians were asked to deliver their assigned exercise prescription to a convenience sample of the next 10 healthy patients older than 65 years who presented to the office. MAIN OUTCOME MEASURES: Primary outcome measures were physician exercise counseling confidence and knowledge before and after the study. Secondary outcomes included details of the exercise counseling sessions (e.g., time required). RESULTS: In phase 1, more than 90% of the 362 physicians claimed to practice preventive health counseling, and 70% claimed to include exercise counseling. Only 67.4% felt confident regarding their exercise prescribing, and most (93.8%) were interested in improving their exercise prescribing skills. The leading barriers to exercise prescription were described in order as inadequate time, lack of necessary skills and tools, and lack of reimbursement. In phase 2, no difference in physician profile, patient profile, or indications for exercise counseling were observed between control (n = 145) and STEP (n = 148) groups. STEP was significantly longer (16.4 vs 12.9 min; P = .001) to administer; however, improvement in physician confidence (P = .01) and knowledge (P = .009) were significantly greater compared with controls. CONCLUSIONS: Most family physicians practiced preventive exercise counseling but reported lack of time and skills as barriers to this practice. Physicians randomized to the STEP group took longer to deliver exercise advice but felt more confident and knowledgeable compared with controls.

Aged↗

PubMed2000

Exercise-based rehabilitation for coronary heart disease.

BACKGROUND: The burden of cardiovascular disease world-wide is one of great concern to patients and health care agencies alike. Circulatory diseases, including myocardial infarction (MI) and stroke, kill more people than any other disease. Cardiac rehabilitation aims to restore patients who have suffered myocardial infarction to optimal health through exercise only based rehabilitation or comprehensive cardiac rehabilitation (eg. smoking cessation advice, diet and counselling as well as exercise). Data from two published and widely cited meta-analyses (Oldridge 1988, O'Connor 1989) of over 4,000 patients each have demonstrated that patients randomised to exercise-based cardiac rehabilitation after MI have a statistically significant reduction in all-cause and cardiac mortality of about 20 to 25% compared to patients receiving conventional care. However, the trials included were small and often of poor methodological quality. Incomplete literature review methods may have resulted in publication bias thereby resulting in an over-estimate of the benefit of cardiac rehabilitation. The randomised controlled trials used in the reviews have focused almost exclusively on low-risk, middle-aged males post MI, thereby excluding women and the elderly. OBJECTIVES: To determine the effectiveness of exercise only rehabilitation and exercise in addition to other rehabilitation interventions (termed comprehensive cardiac rehabilitation) compared with usual care on the mortality, morbidity, health-related quality of life (HRQoL) and modifiable cardiac risk factors of patients with coronary heart disease. SEARCH STRATEGY: Electronic databases were searched for randomised controlled trials, using standardised trial filters, from the earliest date available to December 31st 1998. SELECTION CRITERIA: Men and women of all ages, in both hospital-based and community-based settings, who have had myocardial infarction, coronary artery bypass graft or percutaneous transluminal coronary angioplasty, or who have angina pectoris or coronary artery disease defined by angiography have been included. Studies involving participants following heart transplant, heart valve surgery or heart failure have been excluded. Follow up periods of less than 6 months were excluded. DATA COLLECTION AND ANALYSIS: Studies were selected independently by two reviewers, and data extracted independently. Authors were contacted where possible to obtain missing information. MAIN RESULTS: The current systematic review has allowed analysis of an increased number of patients from approximately 4500 in the earlier meta-analyses to 7683 (2582 in exercise only and 5101 in the comprehensive cardiac rehabilitation group). The quality of reporting overall was poor, with generally high losses to follow up. The pooled effect estimate for total mortality for the exercise only intervention shows a 27% reduction in all cause mortality (random effects model OR 0.73 (0.54, 0.98)). Similarly, comprehensive cardiac rehabilitation reduced all cause mortality compared to usual care, but to a lesser degree (OR 0.87 (0.71, 1.05)). Total cardiac mortality was reduced by 31% (random effects model OR 0.69 (0.51, 0.94)) and 26% (random effects model OR 0.74 (0.57, 0.96)) in the exercise only and comprehensive cardiac rehabilitation intervention groups respectively when compared to usual care. Neither intervention had any effect on the ocurrence of non-fatal myocardial infarction. There was a significant net reduction in total cholesterol in the comprehensive cardiac rehabilitation group (pooled WMD random effects model -0.57 mmol/l (-0.83, -0.31)), but not the exercise only rehabilitation group. Similarly, LDL was significantly reduced in the comprehensive cardiac rehabilitation group (pooled WMD random effects model -0.51 mmol/l (-0.82, -0.19). The effect of exercise only rehabilitation or comprehensive cardiac rehabilitation interventions on revascularisation rates, blood pressure or smoking behaviour could not be determined by this meta-analysis due to the small number of trials reporting these outcomes and heterogeneity between trials. It was not possible to combine the data from studies reporting HRQoL as an outcome. Eighteen different instruments were used to assess HRQoL in the 11 studies reporting it as an outcome. The data are presented qualitatively, only one trial reporting significant improvements with the intervention. REVIEWER'S CONCLUSIONS: Exercise-based cardiac rehabilitation appears to be effective in reducing cardiac deaths but the evidence base is weakened by poor quality trials. It is not clear from this review whether exercise only or a comprehensive cardiac rehabilitation intervention is more beneficial. The population studied in this review is still predominately male, middle aged and low risk. Identification of the ethnic origin of the participants was seldom reported. (ABSTRACT TRUNCATED)

Coronary Disease↗

PubMed1994

Cardiovascular responses to exercise. Effects of aging and exercise training in healthy men.

BACKGROUND: Cardiac aging alters many of the acute responses to exercise stress, but the extent to which chronic exercise (ie, training) can alter or improve the effects of aging in humans is largely unknown. METHODS AND RESULTS: Cardiovascular responses to graded supine exercise stress (beginning at 200 kpm and increasing by 200 kpm every 3 minutes till exhaustion) were assessed using radionuclide ventriculography in 13 older (age, 60 to 82 years) and 11 young (age, 24 to 32 years) rigorously screened healthy men before and after 6 months of endurance training. Repeated-measures ANOVA was used to test significance. During exercise, the old group had a lesser increase in heart rate (+105% old versus +166% young), a greater increase in mean blood pressure (+35% old versus +22% young), lesser increases in ejection fraction (+3 ejection fraction units old versus +11 units young) and peak ejection rate (+62% old versus +119% young), a greater increase in end-diastolic volume index (+8% old versus -10% young), a lesser fall in end-systolic volume index (-0% old versus -32% young), and a lesser increase in cardiac index (+135% old versus +189% young) (all P < .01 young/old versus exercise stage). Stroke volume index response to exercise was not different with aging (+14% old versus +6% young, P = NS). Exercise training increased maximal oxygen intake by 21% in the older group (28.9 +/- 4.6 to 35.1 +/- 3.8 mL.kg-1.min-1, P < .001) and by 17% in the young (44.5 +/- 5.1 to 52.1 +/- 6.3 mL.kg-1.min-1, P < .001) and increased peak workload by 24% in the old and 28% in the young. Exercise training had no differential effects on old versus young men. Among all subjects, training significantly reduced the resting heart rate by 12% (-8 beats per minute) and increased resting end-diastolic volume index by 13% (+9 mL/M2) and resting stroke volume index by 18% (+7 mL/M2) (all P < .01). At peak exercise, cardiac index increased by 16% (+1.07 L.M-2.min-1) compared with before training, which was the result of an increase in stroke volume of 18% (+7 mL/M2) (P < .001); peak heart rate was unchanged. The increase in stroke volume index at peak exercise was the result of both a 12% increase in end-diastolic volume index (+8 mL/M2) (P < .01) and an increase in ejection fraction (+3 ejection fraction units) (P < .05) at peak exercise. The increased ejection fraction at peak exercise occurred despite a 9% increase in systolic blood pressure (+18 mm Hg) (P < .01), suggesting an increase in contractility. Thus, both the young and old increased peak exercise cardiac output by use of the Frank-Starling mechanism (ie, cardiac dilatation) as well as an increase in ejection fraction. CONCLUSIONS: We conclude that there is an age-associated decline in heart rate, ejection fraction, and cardiac output responses to supine exercise in healthy men. Although the stroke volume responses of the young and old are similar, the old tend to augment stroke volume during exercise more through cardiac dilatation, with an increase in end-diastolic volume (+8%) but without much change in ejection fraction (+3 ejection fraction units), whereas the young rely more on an increase in the ejection fraction (+11 ejection fraction units) with no cardiac dilatation (-10%). Despite the significant cardiovascular changes that occur in the response to a single bout of exercise with aging, adaptations to chronic exercise training were not different with aging and included improvements in maximal workload and increases in ejection fraction, stroke volume index, and cardiac index at peak exercise.

Adult↗

PubMed2004

Residual effects of prior exercise and recovery on subsequent exercise-induced metabolic responses.

Data on the metabolic responses to repeated endurance exercise sessions are limited. Thus, the aims of this study were to examine (1) the impact of prior exercise on metabolic responses to a subsequent exercise session and (2) the effect of different recovery periods between two daily exercise sessions on metabolic responses to the second bout of exercise. Nine male elite athletes participated in four 25-h trials: one bout of exercise (ONE), two bouts of exercise separated by 3 h of rest and one meal (SHORT), two bouts of exercise separated by 6 h of rest and two meals (LONG), and a trial with no exercise (REST). All exercise bouts consisted of 10 min cycling at 50% followed by 65 min at 75% of maximal O2 uptake. Compared to no prior exercise (ONE), a previous bout of exercise (SHORT) was followed by higher mean O2 uptake, heart rate (HR), rectal temperature (TR), excess post-exercise oxygen consumption and lower respiratory exchange ratio (R) during and after a similar exercise session 3 h later. A longer rest interval between the two exercise bouts (6 h versus 3 h) and an additional meal resulted in a decrease in O2 uptake, HR, TR and an increase in R during the second bout of exercise, but no effects on post-exercise metabolism were found. Thus, augmented metabolic stress was observed when strenuous exercise was repeated after only 3 h of recovery, but this was attenuated when a longer recovery period including an additional meal was provided between the exercise sessions.

Adult↗

PubMed2001

Effects of prior exercise and recovery duration on oxygen uptake kinetics during heavy exercise in humans.

Prior heavy exercise (above the lactate threshold, LT) reduces the amplitude of the pulmonary oxygen uptake (VO2) slow component during heavy exercise, yet the precise effect of prior heavy exercise on the phase II VO2 response remains to be established. This study was designed to test the hypotheses that (1) prior heavy exercise increases the amplitude of the phase II VO2 response independently of changes in the baseline VO2 value and (2) the effect of prior exercise depends on the amount of external work done during prior exercise, irrespective of the intensity of the prior exercise. Nine subjects performed two 6 min bouts of heavy cycling exercise separated by 6 min baseline pedalling recovery (A), two 6 min heavy exercise bouts separated by 12 min recovery (6 min rest and 6 min baseline pedalling, B), and a bout of moderate exercise (below the LT) in which the same amount of external work was performed as during the prior heavy exercise, followed by 6 min heavy exercise (C). In both tests A and B, prior heavy exercise significantly increased the absolute VO2 amplitude at the end of phase II (by approximately 150 ml x min(-1)), and reduced the amplitude of the VO2 slow component by a similar amount. Following 12 min of recovery (B), baseline VO2, but not blood [lactate], had returned to pre-exercise levels, indicating that these effects occurred independently of changes in baseline VO2. Prior moderate exercise (C) had no effect on either the VO2 or blood [lactate] responses to subsequent heavy exercise. The VO2 response to heavy exercise was therefore dependent on the intensity of prior exercise, and the effects on the amplitudes of the phase II and slow VO2 components persisted for at least 12 min following prior heavy exercise.

Adult↗

PubMed1994

Supine exercise during lower body negative pressure effectively simulates upright exercise in normal gravity.

Exercise within a lower body negative pressure (LBNP) chamber in supine posture was compared with similar exercise against Earth's gravity (without LBNP) in upright posture in nine healthy male volunteers. We measured footward force with a force plate, pressure in soleus and tibialis anterior muscles of the leg with transducer-tipped catheters, calf volume by strain gauge plethysmography, heart rate, and systolic and diastolic blood pressures during two conditions: 1) exercise in supine posture within an LBNP chamber during 100-mmHg LBNP (exercise-LBNP) and 2) exercise in upright posture against Earth's gravity without LBNP (exercise-1 G). Subjects exercised their ankle joints (dorsi- and plantarflexions) for 5 min during exercise-LBNP and for 5 min during exercise-1 G. Mean footward force produced during exercise-LBNP (743 +/- 37 N) was similar to that produced during exercise-1 G (701 +/- 24 N). Peak contraction pressure in the antigravity soleus muscle during exercise-LBNP (115 +/- 10 mmHg) was also similar to that during exercise-1 G (103 +/- 13 mmHg). Calf volume increased significantly by 3.3 +/- 0.5% during exercise-LBNP compared with baseline values. Calf volume did not increase significantly during exercise-1 G. Heart rate was significantly higher during exercise-LBNP (99 +/- 5 beats/min) than during exercise-1 G (81 +/- 3 beats/min). These results indicate that exercise in supine posture within an LBNP chamber can produce similar musculoskeletal stress in the legs and greater systemic cardiovascular stress than exercise in the upright posture against Earth's gravity.

Adult↗

PubMed2003

Effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise.

The purpose of this study was to investigate the effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise. Pre-exhaustion exercise, a technique frequently used by weight trainers, involves combining a single-joint exercise immediately followed by a related multijoint exercise (e.g., a knee extension exercise followed by a leg press exercise). Seventeen healthy male subjects performed 1 set of a leg press exercise with and without pre-exhaustion exercise, which consisted of 1 set of a knee extension exercise. Both exercises were performed at a load of 10 repetitions maximum (10 RM). Electromyography (EMG) was recorded from the rectus femoris, vastus lateralis, and gluteus maximus muscles simultaneously during the leg press exercise. The number of repetitions of the leg press exercise performed by subjects with and without pre-exhaustion exercise was also documented. The activation of the rectus femoris and the vastus lateralis muscles during the leg press exercise was significantly less when subjects were pre-exhausted (p < 0.05). No significant EMG change was observed for the gluteus maximus muscle. When in a pre-exhausted state, subjects performed significantly (p < 0.001) less repetitions of the leg press exercise. Our findings do not support the popular belief of weight trainers that performing pre-exhaustion exercise is more effective in order to enhance muscle activity compared with regular weight training. Conversely, pre-exhaustion exercise may have disadvantageous effects on performance, such as decreased muscle activity and reduction in strength, during multijoint exercise.

Adult↗

PubMedDate not supplied

Predicting the adoption and maintenance of exercise participation using self-efficacy and previous exercise participation rates.

OBJECTIVES: To investigate the relationships among self-efficacy, changes in self-efficacy, past exercise participation, future exercise adherence, and exercise program format. METHODS: Two-year randomized trial involving subjects (n = 63) participating in an aerobic exercise program. Subjects were randomly assigned to one of three exercise conditions: higher-intensity home-based exercise, higher-intensity class-based exercise, or lower-intensity home-based exercise. RESULTS: Results indicated that baseline self-efficacy and exercise format had significant (p < .02), independent effects on adherence during the adoption and early maintenance phases of exercise behavior. In contrast, in predicting long-term exercise program maintenance, a significant (p < .05) self-efficacy x exercise format interaction indicated that self-efficacy predicted adherence only in the supervised home-based exercise conditions. Results also suggest that baseline self-efficacy, independent of the effect of past adherence, significantly (p < .03) predicted exercise adherence during the adoption phase, but not early maintenance phase, of exercise behavior. Finally, adherence change during the adoption phase of exercise behavior significantly (p < .04) predicted Year-one levels of self-efficacy even after adjusting for the effect of baseline self-efficacy. CONCLUSIONS: These results suggest that exercise program format as well as an individual's initial cognitive and behavioral experiences in an exercise program play significant roles in determining exercise adherence.

Exercise↗

PubMed1993

Endurance exercise training augments diastolic filling at rest and during exercise in healthy young and older men.

BACKGROUND: Diastolic filling at rest is altered markedly with advancing age. Whether exercise training can improve diastolic filling at rest or during exercise in either healthy older or healthy young men has not been determined. The purpose of this study was to determine if 6 months of aerobic exercise training improves diastolic filling. METHODS AND RESULTS: Radionuclide diastolic filling parameters were measured at rest and during exercise in 14 older (age, 60 to 82 years) and 17 young (age, 24 to 32 years) rigorously screened healthy males before exercise training and in 13 older and 11 young men after 6 months of endurance exercise training. Diastolic filling rates were expressed in two ways, as absolute milliliters of blood (mL.s-1.m-2) and normalized to the end-diastolic volume. At baseline, the peak early filling rates were lower in the older group compared with the young group as expressed in absolute milliliters of blood (older, 85 +/- 7 mL.s-1.m-2; young, 173 +/- 10 mL.s-1.m-2; P < or = .0001) and in end-diastolic volume per second (1.66 +/- 0.11 versus 2.55 +/- 0.08, P < .0001), whereas the peak atrial filling rates were greater in absolute milliliters of blood (85 +/- 5 versus 56 +/- 7 mL.s-1.m-2, P = .003) and in end-diastolic volume per second (1.70 +/- 0.12 versus 0.80 +/- 0.06, P < .0001). During exercise, at any given heart rate, the older group had a lower peak filling rate than the young group. Also, at peak exercise, the single peak filling rate was decreased in the older group in mL.s-1.m-2 (384 +/- 19 versus 565 +/- 36 mL.s-1.m-2, P = .0002) and in end-diastolic volume per second (6.01 +/- 0.25 versus 7.91 +/- 0.28 end-diastolic volume per second, P < .0001). Six months of intensive aerobic exercise training had similar effects in the old and young groups overall. Maximal oxygen consumption increased 19% (ANOVA training effect, P < or = .0001) and echocardiographic left ventricular mass increased 8% (ANOVA training effect, P = .002). Training increased the resting peak early filling rate in absolute milliliters of blood by +14% (ANOVA training effect, P = .02). During exercise, the peak early or single peak filling rate at any given heart rate was increased. At peak exercise, the single peak filling rate was increased by 14% in mL.s-1.m-2 (ANOVA training effect, P = .0004). The only age-related differential effect of training was on the peak atrial filling rate in end-diastolic volume per second, which decreased by 27% in the older group but was unchanged in the young (+5%) (ANOVA young versus older, P = .001). The independent predictors of a greater maximal oxygen consumption by multivariate analysis were a higher peak exercise heart rate, a greater resting peak early filling rate, the exercise trained state, and a younger age. CONCLUSIONS: Healthy older men have reduced early diastolic filling at rest and during exercise compared with young men. Endurance exercise training enhances early diastolic filling at rest and during exercise in both the old and the young. Training reduces the elevated resting atrial filling rate in the old, whereas the young were unchanged. The training-induced augmentation of early diastolic filling at rest and during exercise may be an important adaptation to allow an increase in stroke volume at rest and an increase in stroke volume, cardiac output, and maximal oxygen consumption during exercise.

Adult↗

PubMed2002

Partial normalization of the heart rate response to exercise after cardiac transplantation: frequency and relationship to exercise capacity.

OBJECTIVE: To determine the frequency of partial normalization of the heart rate response to graded exercise and its relationship to exercise capacity in cardiac transplant recipients. SUBJECTS AND METHODS: The study subjects were 95 adults (77 men, 18 women) who were available to perform a cardiopulmonary exercise test 1 year after orthotopic cardiac transplantation, which occurred between June 1988 and September 1998. All subjects received standard immunosuppressant medications. At the time of the exercise tests, the mean +/- SD age of the subjects was 49+/-14 years. The mean +/- SD resting left ventricular ejection fraction was 62%+/-8%. All subjects participated in a 6- to 8-week supervised exercise program, starting no later than 1 month after surgery. Subjects were given an exercise prescription for independent exercise training after finishing the supervised program. Self-reported weekly exercise training had a median value of 90 minutes (interquartile range, 0-210 minutes). Symptom-limited graded exercise was performed on a treadmill, with breath-by-breath analysis of expired air. RESULTS: For the entire cohort, peak exercise oxygen uptake was 19.9+/-4.8 mL x kg(-1) x min(-1) (61%+/-15% of age and sex predicted). Thirty-two subjects (34%) had a partially normalized heart rate response to graded exercise. The frequency was similar for men (25/77 [33%]) and for women (7/18 [39%]) and was independent of recipient or donor age. Peak exercise heart rate (147+/-18 vs 134+/-21 beats/min; P=.008) and heart rate reserve (46+/-15 vs 33+/-15 beats/min; P<.001) were greater for subjects with a partial normalization of heart rate response. Peak exercise oxygen uptake was similar for subjects with or without partial normalization of the heart rate response (20.9+/-5.8 vs 19.4+/-4.2 mL x kg(-1) x min(-1); P=.22). Submaximal exercise oxygen uptake during the first few minutes of exercise was also not affected by normalization of the heart rate response. CONCLUSION: At 1 year after cardiac transplantation, approximately one third of subjects had partial normalization of the heart rate response to graded exercise. However, a higher peak exercise heart rate and a larger heart rate reserve did not result in better aerobic exercise capacity.

Adult↗

PubMed1996

Post-exercise thermal homeostasis as a function of changes in pre-exercise core temperature.

We have previously reported that, following continuous exercise, a prolonged elevated plateau of esophageal temperature (Tes) was directly related to the Tes at the time of cutaneous vasodilation (Thdil) during exercise. In order to investigate the hypothesis that the factors which result in an increase of the post-exercise Thdil and define the post-exercise Tes elevation are related to pre-exercise Tes, nine healthy, young [24.0 (1.9) years], non-training males rested at 29 degrees C, 50% humidity for > 1 h (control). They then completed three successive cycles of 15 min treadmill running at 70% maximal oxygen consumption (VO2max) followed by 30 min rest. Esophageal, rectal (Tre) and skin (Tsk) temperatures and forearm cutaneous blood flow were recorded at 5-s intervals throughout. Laser-Doppler flowmetry of forearm skin blood flow was used to identify the Thdil during exercise. Pre-exercise Tes was 36.74 (0.25) degrees C and post-exercise Tes fell to stable and significant (P < 0.05) elevations above pre-exercise values at 37.22 (0.27) degrees C, 37.37 (0.27) degrees C and 37.48 (0.26) degrees C following each successive work bout respectively. Correspondingly, Thdil during each work bout rose in proportion to, and was not different than, the post-exercise Tes in the following recovery [37.20(0.23) degrees C, 37.41 (0.24) degrees C and 37.58 (0.24) degrees C]. Although the increases were less with each successive exercise bout, the differences between each exercise bout, in terms of post-exercise Tes and Thdil values, were significant (P < 0.05). These results reinforce our previous observations of elevations in Thdil and post-exercise Tes after a single exercise bout and lead to the tentative conclusions that (1) pre-exercise Tes has a direct influence on Thdil and post-exercise Tes, and (2) the exercise-induced increase of Thdil persists into recovery, influencing post-exercise thermal recovery.

Adult↗