Comparison of hemodynamic responses to cycling and resistance exercise in congestive heart failure secondary to ischemic cardiomyopathy.
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Cardiomyopathies↗
Biomedical subjects
N McCartney
Publications and source records attributed to N McCartney.
Neural regulation of heart rate variability in endurance athletes and sedentary controls.
OBJECTIVE: The aim was to examine the cardiac autonomic responses to orthostatic stress and recovery from steady state exercise in endurance trained athletes and sedentary subjects. METHODS: The power spectrum of heart rate variability was measured before and after exercise in 10 male long distance runners and 14 male sedentary control subjects. Both groups were comparable in sex, age, and body mass index. Continuous ECG recordings were obtained during the following physiological manoeuvres: 45 min supine rest state; 10 min standing; 15 min steady state exercise at 50% maximum workload, and 15 min while supine during post-exercise recovery. The resting heart rate of athletes was lower than controls, at 52(SD 4.9) v 67(8.7) beats.min-1, p < 0.001. Power spectrum analysis was performed using autoregressive modelling. RESULTS: The resting high frequency (HF) vagal component was higher in athletes than controls, at 62 (10.7) v 44(22.4) beats.min-1.Hz-1, p < 0.05. The resting low frequency (LF) peak power was significantly reduced in athletes, at 54(9.9) v 70(19.5) in control, p < 0.05. Although no group differences were observed during upright posture or exercise, the LF:HF area ratio had already returned to pre-exercise levels within 5 min of recovery in athletes. Conversely, it required up to 15 min of recovery before a noticeable decrease in the LF:HF area ratio was seen in controls. CONCLUSIONS: These data support the hypothesis that endurance training modifies heart rate control in whole or in part through neurocardiac mechanisms.
Adult↗
Randomised controlled trial of weightlifting exercise in patients with chronic airflow limitation.
UNLABELLED: BACKGROUND PATIENTS: with chronic airflow obstruction are often limited by muscle fatigue and weakness. As exercise rehabilitation programmes have produced modest improvements at best a study was designed to determine whether specific muscle training techniques are helpful. METHODS: Thirty four patients with chronic airflow limitation (forced expiratory volume in one second (FEV1) 38% of predicted values) were stratified for FEV1 to vital capacity (VC) ratio less than 40% and arterial oxygen desaturation during exercise and randomised to a control or weightlifting training group. In the experimental group training was prescribed for upper and lower limb muscles as a percentage of the maximum weight that could be lifted once only. It was carried out three times a week for eight weeks. RESULTS: Three subjects dropped out of each group; results in the remaining 14 patients in each group were analysed. Adherence in the training group was 90%. In the trained subjects muscle strength and endurance time during cycling at 80% of maximum power output increased by 73% from 518 (SE69) to 898 (95) s, with control subjects showing no change (506 (86) s before training and 479 (89) s after training). No significant changes in maximum cycle ergometer exercise capacity or distance walked in six minutes were found in either group. Responses to a chronic respiratory questionnaire showed significant improvements in dyspnoea and mastery of daily living activities in the trained group. CONCLUSIONS: Weightlifting training may be successfully used in patients with chronic airflow limitation, with benefits in muscle strength, exercise endurance, and subjective responses to some of the demands of daily living.
Aged↗
Factors affecting blood pressure during heavy weight lifting and static contractions.
Brachial arterial pressure was directly recorded in 31 healthy male volunteers through protocols examining the effects of the Valsalva maneuver, muscle size and strength, contraction force, contraction type (concentric, isometric, eccentric), changes in joint angle, and muscle fatigue on the blood pressure response to resistance exercise. Weight lifting at the same relative intensity produced similar increases in blood pressure, regardless of individual differences in muscle size or strength. Concentric, isometric, or eccentric exercise at the same relative intensity caused similar increases despite differences in force production. In weight lifting, the greatest increase in blood pressure occurred at the joint angle corresponding to the weakest point in the strength curve and the least at the angle corresponding to the strongest point. Isometric contractions of the same relative intensity at different joint angles produced identical blood pressures despite differences in absolute force production. When subjects attempted to maintain a maximum isometric contraction for 45 s, the blood pressure increase remained the same despite a marked diminution in force. Thus the magnitude of the blood pressure response depends on the degree of effort or central command and not actual force production. A brief Valsalva maneuver, which exaggerates the increase in blood pressure, is unavoidable when desired force production exceeds approximately 80% maximum voluntary contraction.
Adult↗
Usefulness of weightlifting training in improving strength and maximal power output in coronary artery disease.
The effects of 10 weeks (20 sessions) of combined weightlifting and aerobic training (n = 10) were compared with the effects of aerobic training alone (n = 8) on indexes of strength and aerobic exercise capacity in 18 men with coronary artery disease (CAD). Initial test performance was similar between groups. After aerobic training, the maximal load that could be lifted once only (1-repetition maximum) in single-arm curl, single-leg press and single-knee extension exercises increased by 13% (11.8 to 13.3 kg; p less than 0.01), 4% (97.0 to 101.0 kg; difference not significant) and 5% (28.2 to 29.7 kg; difference not significant), respectively; corresponding gains with combined weightlifting and aerobic training were 43% (12.2 to 17.4 kg; p less than 0.01), 21% (99.0 to 120.0 kg; p less than 0.01) and 24% (29.0 to 36.0 kg; p less than 0.01). After aerobic training, the initial 1-repetition maximum could be lifted an average of 4 times, compared with 14 times after combined training. Maximal progressive incremental cycle ergometer power output increased by 2% in the aerobic control group (1,088 to 1,113 kpm/min; difference not significant) and by 15% (1,030 to 1,180 kpm/min; p less than 0.05) in the experimental group. Cycling time at 80% of initial maximal power before attaining a Borg (0 to 10) rating of perceived exertion of 7 (very severe) increased by 11% (604 to 672 seconds; difference not significant) and by 109% (541 to 1,128 seconds; p less than 0.05) in the control and weight-trained patients, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Coronary Disease↗
Comparison of direct and indirect measures of systemic arterial pressure during weightlifting in coronary artery disease.
Based on auscultation measurements after exercise, circuit weight training in cardiac patients has been reported to provoke minimal increases in systolic pressure. Direct (brachial artery catheter) and indirect (sphygmomanometry) measures of blood pressure were compared at rest, during lifting with the legs (approximately the fourth, ninth and fourteenth repetition) and during 2 minutes of recovery after lifting with the arms and legs. Subjects performed 15 repetitions of single-arm curl, single-arm military press and single- and double-leg press exercises at 40 and 60% of the maximum load that could be lifted once on a multistation weightlifting apparatus. Indirect measures of systolic pressure at rest were 13% less than those recorded directly (130 +/- 7 vs 149 +/- 8 torr; p less than 0.01); diastolic pressures were similar using either method. This pattern was maintained during lifting with the legs at both intensities, and after exercise with both the legs and the arms. The mean systolic pressure recorded indirectly immediately after exercise was 63 torr (31%) and 76 torr (34%) less than the average peak intraarterial value recorded during leg and arm exercises, respectively. The highest intraarterial pressures were generated during the final repetitions of the set; immediately after the last repetition, both systolic and diastolic pressures rapidly decreased. It is concluded that indirect estimates of systolic pressure are significantly less than true arterial values at rest, and during and after lifting. Moreover, indirect measurements after lifting do not allow accurate conclusions to be drawn about the arterial pressures generated during lifting because of the rapid decrease in pressure that occurs after exercise.
Blood Pressure↗
Measuring quality of life in cardiac spouses.
The purpose of this study was to develop an objective instrument to measure changes in quality of life of spouses of post-myocardial infarction (MI) patients, and to determine its responsiveness and validity. A 70-item list of potential areas of concern was compiled; the 25 most frequent and important concerns comprised the framework of the final questionnaire. The questions on the Quality of Life Questionnaire for Cardiac Spouses (QL-SP) were categorized into the Emotional Function Dimension (EFD), and the Physical and Social Function Dimension (PSFD). Subjects (n = 39) completed the QL-SP and a battery of established questionnaires at home, 1-2 weeks post-hospital discharge for the patient, and 8 weeks later. Scores on the QL-SP between visits were improved for both the EFD (t = 5.56, p less than 0.001), and the PSFD (t = 6.11, p less than 0.001). The agreement between predicted and observed relationships between the dimension changes and other index changes, as measured statistically by a kappa with Cicchetti weights, was significant (kappa w = 0.43, p = 0.0012). The QL-SP appears to be responsive and valid, and may be useful in evaluating clinical and research intervention strategies.
Activities of Daily Living↗
Positive adaptations to weight-lifting training in the elderly.
Maximal weight-lifting performance, isometric strength, isokinetic torque, whole muscle and individual fiber cross-sectional areas, and muscle evoked contractile properties were assessed in 14 elderly males before and after 12 wk of weight-lifting training. Dynamic elbow flexion training of one arm resulted in a significant 48% mean increase in the maximal load that could be lifted once (1 RM) and a smaller improvement in isokinetic torque (8.8%) but no change in isometric strength. In the contralateral control arm, 1 RM and isokinetic torque increased by 12.7 and 6.5%, respectively, but isometric strength did not change. The interpolated twitch technique confirmed complete motor unit activation during a maximal isometric contraction of the elbow flexors before and after the training. Bilateral leg press training effected mean increases of 17 and 23% in isokinetic torque and dynamic lifting capacity, respectively. The mean maximal cross-sectional area of the elbow flexors (biceps brachii and brachialis) increased by 17.4% in the trained arm but did not change the control arm. The increase in the mean area of type II fibers in the biceps brachii muscle in the trained arm (30.2%) was greater than the corresponding change in the control arm (10.7%, P less than 0.05). The most significant change in the evoked contractile properties of the trained elbow flexors was the increase in twitch half-relaxation time. It is concluded that older individuals retain the potential for significant increases in strength performance and upper limb muscle hypertrophy in response to overload training.
Adaptation, Physiological↗
Weightlifting training in cardiac patients. Considerations.
Cardiovascular disease is the leading cause of morbidity and mortality in most of the industrialised nations in the world. Many treatment strategies are used for patients with coronary artery disease. One of these strategies is the use of cardiac exercise rehabilitation. The traditional approach to cardiac exercise rehabilitation has been the training of large muscle groups using aerobic activities such as cycling or walking. These types of activities have been demonstrated to improve maximal exercise performance and endurance. However, although aerobic performance is improved it does not address another very important component of exercise rehabilitation--namely muscular strength. Weightlifting training has been demonstrated to improve muscular strength in healthy individuals. Until recently this form of exercise training of patients with cardiac disease has been avoided due to the haemodynamic response observed during isometric (static) exercise. Weightlifting has recently been demonstrated not to be a pure isometric exercise and a different haemodynamic response has been found even in patients with cardiac disease. For this reason studies of weightlifting training have been performed in selected groups of patients with coronary artery disease. The results of these studies in this limited group of patients have demonstrated the activity is safe and beneficial in terms of improving the patient's functional capacity. Weightlifting training may also favourably affect the risk factors for coronary artery disease. Based on studies reviewed in this paper, recommendations can be made for the weightlifting training of patients with coronary artery disease. These include restriction to patients who are asymptomatic or only mildly symptomatic; initiation of training only after a period of aerobic training; the use of single limb activities; a maximum intensity no greater than 60% of 1 repetition maximum; patients train at their own rate; initially performed in a medically supervised programme; periodic reassessment of the exercise prescription; and patients should record their heart rate and response to exercise.
Coronary Disease↗
Maximal isokinetic cycle ergometry in patients with coronary artery disease.
We assessed the utility of short-term (30 s) maximal isokinetic cycle ergometry as an additional method of investigating the limitations to exercise in 33 carefully selected patients with documented coronary artery disease. The technique proved safe and reproducible in these patients. In relation to normal standards, performance was better in the maximal isokinetic cycle ergometer test (peak power = 819 +/- 116 W; average power = 532 +/- 72 W; total work = 13.1 +/- 2.1 kJ; 95-101% of predicted) than in the progressive incremental exercise test (VO2 = 1.80 +/- 0.37 l.min-1; power output = 919 +/- 165 kpm.min-1; 70-80% of predicted). Beta blockade did not affect maximal performance during either isokinetic or progressive incremental cycling, although maximal heart rate was significantly lower during both tests in patients on beta blockade. Power output in the progressive exercise was not as strongly related to the indices measured during the 30 s isokinetic test (r = 0.59-0.63) as it was in previous studies of healthy individuals (r = 0.89). The ability to detect individual variations in short-term exercise capacity measured with maximal isokinetic cycle ergometry may have significant potential value 1) as an additional method of determining the limitations to exercise and 2) when executing an exercise prescription in patients with coronary artery disease.
Adrenergic beta-Antagonists↗
Improvement in maximal isokinetic cycle ergometry with cardiac rehabilitation.
It is unclear whether improvements in short-term (30 s) exercise capacity are associated with the increased aerobic exercise tolerance frequently observed in cardiac patients following training. Carefully selected patients with documented coronary artery disease were randomly allocated either to a control group (N = 10) or to 12 wk of endurance exercise training (N = 12); both progressive incremental cycle ergometer testing (maximal power output and peak VO2) and 30 s maximal isokinetic cycle ergometry (peak power, total work, and fatigue index) were measured on entry into the study and 12 wk later. Initial maximum performance measures in progressive incremental exercise and in maximal short-term isokinetic cycling were similar in both groups. Following the training program, maximum power output measured during progressive incremental exercise increased by 21% (P less than 0.005) and peak VO2 increased by 18% (P less than 0.005) in the exercise group, but they were unchanged in the control group. Isokinetic peak power and total work improved by 14% (P less than 0.001) and 11%, respectively, in the exercise group, whereas there were corresponding reductions of 6 and 8% in the control subjects, with little change in fatigue index in either group. The similar relative increases in isokinetic peak power and peak VO2 suggest that improvement in short-term exercise capacity may be an important contributor to the improvement in aerobic exercise tolerance frequently observed in cardiac patients undergoing an endurance exercise program.
Coronary Disease↗
The effects of strength training in patients with selected neuromuscular disorders.
Five subjects with spinal muscular atrophy, limb-girdle or facioscapulohumeral muscular dystrophy, were studied. Measurements pre- and post-training included: maximum isometric, dynamic and isokinetic strength, in single-arm curl and double-leg press exercises; contractile properties of the elbow flexors; computerized tomography of the upper arms and thighs; muscle biopsies from the biceps brachii muscle of each arm in three subjects. Dynamic weight training was performed 3 times per week for 9 wk; exercises comprised unilateral arm curls (the contralateral arm acted as a control), and bilateral leg press. Strength increases in the trained arm were between 19 and 34%, and from -14 to +25% in the control arm; leg strength increased from 11 to 50%. Moreover, the pretraining maximum load could be lifted from 3 to 48 times in the trained limbs, and from 1 to 13 times in an untrained limb before fatigue. Contractile properties of the elbow flexors were unchanged with training, but pre-intervention, three subjects demonstrated incomplete motor unit activation. Most of the gains in strength were apparently due to a neural adaptation, rather than muscle hypertrophy. The tomograms and biopsy samples were inadequate to determine muscle, or muscle fiber areas with confidence; they did indicate however, no additional overt muscle structural damage. Strength training may be a potentially useful therapeutic option in the management of selected neuromuscular disorders.
Adult↗
Influence of muscle power on aerobic performance and the effects of training.
This paper reviews briefly the authors' experience with a short (30 s) maximal isokinetic cycling test in which peak and average power, the decline in power during the test (fatigue index, FI), and the total work accomplished are measured by a computer assisted technique. In an untrained population, the power variables and total work were linearly related to height and lean thigh volume and decline with age; the FI was less in subjects who took part in regular leisure activity. A close linear relationship was found between the total work in 30 s and maximal oxygen intake (VO2 max). The method was applied to studies of the effects of endurance exercise in sedentary young and old men and in patients with coronary artery disease. In the young and old men training increased VO2 max by 28% and 38% respectively, with no change in isokinetic power measurements in the young, but increases of 12% in total work in 30 s in the old. In cardiac patients, reductions in initial VO2 max were greater than in the isokinetic test variables. Control subjects showed reductions in maximal 30 s performance after the study period (12 wk) with no change in VO2 max. Exercised subjects increased VO2 max by 18.5% with variable changes in 30 s performance. There is a close link between maximal short-term muscle capacity and VO2 max in healthy subjects. VO2 max may be increased by training, but this may or may not be accompanied by increases in maximal short-term capacity, presumably depending on the mechanisms that are limiting in any given case.
Adult↗
Muscle power and metabolism in maximal intermittent exercise.
Muscle power and the associated metabolic changes in muscle were investigated in eight male human subjects who performed four 30-s bouts of maximal isokinetic cycling at 100 rpm, with 4-min recovery intervals. In the first bout peak power and total work were (mean +/- SE) 1,626 +/- 102 W and 20.83 +/- 1.18 kJ, respectively; muscle glycogen decreased by 18.2 mmol/kg wet wt, lactate increased to 28.9 +/- 2.7 mmol/kg, and there were up to 10-fold increases in glycolytic intermediates. External power and work decreased by 20% in both the second and third exercise periods, but no further change occurred in the fourth bout. Muscle glycogen decreased by an additional 14.8 mmol/kg after the second exercise and thereafter remained constant. Muscle adenosine triphosphate (ATP) was reduced by 40% from resting after each exercise period; creatine phosphate (CP) decreased successively to less than 5% of resting; in the recovery periods ATP and CP increased to 76 and 95% of initial resting levels, respectively. Venous plasma glycerol increased linearly to 485% of resting; free fatty acids did not change. Changes in muscle glycogen, lactate, and glycolytic intermediates suggested rate limitation at phosphofructokinase during the first and second exercise periods, and phosphorylase in the third and fourth exercise periods. Despite minimal glycolytic flux in the third and fourth exercise periods, subjects generated 1,000 W peak power and sustained 400 W for 30 s, 60% of the values recorded in the first exercise period.(ABSTRACT TRUNCATED AT 250 WORDS)
Acid-Base Equilibrium↗
Maximal short term exercise capacity in healthy subjects aged 15-70 years.
Fifty males and 50 females, 15-71 years of age, exercised maximally for 30 s on an isokinetic ergometer at a pedalling frequency of 60 rev./min. Results were compared with maximal oxygen uptake (VO2 max.) obtained in a progressive incremental exercise test. Total work in 30 s was higher in males than females, declined linearly by about 6% per decade of age (r = -0.65), and was related closely to height (r = 0.75) and to lean thigh volume estimated anthropometrically (r = 0.84). A close association with vital capacity (r = 0.86) was also found that accounted statistically for the combined effects of age and height. The percentage decline in power during 30 s (fatigue index) was lower in subjects reporting greater leisure activity. A close relationship was found between total work in 30 s and VO2max. (r = 0.86), with vital capacity and leisure activity exerting additional influences on VO2max. (P less than 0.001; multiple r = 0.93). The well-established reduction with age in VO2max. is associated with an apparent parallel reduction in the power output capacity of large muscle groups recruited in heavy dynamic leg exercise.
Adolescent↗
Torque-velocity relationship in isokinetic cycling exercise.
Seven healthy female subjects performed brief (less than 10 s) periods of maximal exercise on a constant-velocity cycle ergometer, over the functional range of pedaling velocities, and an isometric contraction with each leg. There was an inverse relationship between peak torque and pedal crank velocity in all subjects; isometric torque was (mean +/- SE) 19.8 +/- 8.3% greater than the torque recorded at the slowest velocity of 11 rpm. The torque-velocity relationship was described best by a single exponential equation: y = 189.6 X e-0.0834x, where y is peak torque in Newton . meters and x is crank velocity in revolutions per minute. Peak power was a parabolic function of crank velocity; the data were fitted suitably by a second-order polynomial equation: y = -0.0589x2 + 14.504x + 47.092, where y is peak power in watts and x is crank velocity in revolutions per minute. Maximal peak power occurred at crank velocities ranging from 120 to 160 rpm, when the torque was 0.36 +/- 0.06 of the maximal isometric tension. These results demonstrate the importance of recording velocity in measurements of dynamic maximal power.
Adult↗
Muscle performance and metabolism in maximal isokinetic cycling at slow and fast speeds.
To provide a description of the metabolic changes in muscle during maximal dynamic exercise, muscle biopsies were obtained in five healthy subjects before and after 30 s of isokinetic exercise at two pedaling frequencies (60 and 140 rpm) associated with contrasting fatigue characteristics. Higher peak power was attained at 140 rpm (1,473 + 185 W) (mean +/- SE) than at 60 rpm (1,122 +/- 70 W), but the decline in power during 30 s (fatigue index) was greater at 140 rpm (61.6 +/- 3.2 vs. 21.5 +/- 2.4%), total work in 30 s being similar (18.1 +/- 1.10 vs. 20.1 +/- 1.10 kJ). Changes in the concentration of muscle metabolites were similar; creatine phosphate concentration fell to approximately 50% of resting values, and the glycolytic intermediates glucose 6-phosphate, fructose 6-phosphate, and fructose 1,6-biphosphate increased up to 30-fold. Muscle lactate concentration ([La-]) was 29.0 +/- 3.98 and 31.0 +/- 4.31 mmol/kg wet wt immediately postexercise at 140 and 60 rpm, respectively. Even after only 10 s exercise (n = 2), large increases were measured in glycolytic intermediates and [La-]. In the two subjects, muscle [La-] increased to 17.2 and 15.1 mmol/kg at 140 rpm and to 14.3 and 14.2 mmol/kg at 60 rpm. In this type of exercise, glycogenolysis is activated very rapidly at both pedal speeds; the changes in glycolytic intermediates were consistent with rate-limiting steps at the phosphofructokinase and pyruvate dehydrogenase reactions. The greater fatigue at the higher speed is not accompanied by different biochemical changes than at 60 rpm.
Adenosine Triphosphate↗
Normal standards for an incremental progressive cycle ergometer test.
One hundred healthy subjects (50 male and 50 female), selected to provide an even distribution of age (15 to 71 yr) and height (165 to 194 cm in males and 152 to 176 cm in females), underwent a progressively incremental (100 kpm/min each min) exercise test to a symptom-limited maximum. Measurements were made of O2 intake and CO2 output, ventilation and breathing pattern, heart rate and blood pressure, and rating of perceived exertion. The ventilatory anaerobic threshold was identified. Predictive data were derived for measurements at maximal and submaximal exercise. Maximal power output (Wmax) and oxygen intake (VO2max) varied with sex (0, male; 1, female), age (yr), and height (Ht, cm): Wmax = 20.4 (Ht) - 8.74 (Age) - 288 (Sex) - 1,909 kpm/min (SEE, 216; r, 0.858); VO2max = 0.046 (Ht) - 0.021 (Age) - 0.62 (Sex) - 4.31 L/min (SEE, 0.458; r, 0.869). The extent of leisure time activity exerted a positive influence on VO2max (r, 0.47; p less than 0.001); VO2max was also related to lean thigh volume (r, 0.79). Maximal heart rate (HR) declined as a function of age: HRmax = 202 - 0.72 (Age) beats/min (SEE, 10.3; r, 0.72). Maximal O2 pulse (O2Pmax) was related to height and was systematically higher in males than in females: O2Pmax = 0.28 (Ht) - 3.3 (Sex) - 26.7 ml/beat (SEE, 2.8; r, 0.86). Ventilation was closely related to CO2 output, and the maximal tidal volume was related to vital capacity. The VO2 increased linearly with power throughout the test; in an individual subject, the intercept of this relationship was positively influenced by weight and height.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗