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beta-Adrenoceptor blockers are widely used clinically and can be classified as nonselective (beta 1 and beta 2) or selective (beta 1). Impairment of exercise performance is a well-known side effect of this group of drugs. This paper reviews mechanisms that could potentially be responsible for this impairment. In addition to cardiovascular and metabolic effects, beta-blockade inhibits Na(+)-K+ ATPase pumps controlling ion movement between muscle and plasma and thus may contribute to muscle fatigue through this mechanism. To investigate the relationship between the change in plasma [K+] and exercise performance, we studied healthy male subjects taking propranolol. Eight subjects performed maximal incremental cycle ergometer exercise tests during control (no drug), low dose (LD) (40 mg daily), and high dose (HD) (265 +/- 4.3 (SE) mg daily) of propranolol. The control plasma [K+] (5.8 +/- 0.12 mequiv./L) during exercise was significantly lower than either the LD (6.4 +/- 0.05 mequiv./L) or HD (6.1 +/- 0.16 mequiv./L) values. There was no significant difference between plasma [K+] for the LD and HD of propranolol. However, maximum oxygen uptake was reduced only while taking the HD of propranolol. Six of the subjects also performed three 30-s bouts of high intensity exercise on an isokinetic cycle ergometer while taking the LD and HD of propranolol. There was no significant difference between doses for the increase in plasma [K+] (LD, 7.8 +/- 0.35 mequiv./L vs. HD, 7.6 +/- 0.36 mequiv./L) during exercise. However, exercise performance was significantly reduced during HD compared with LD. These results suggest that the increases in plasma [K+] with propranolol did not play a direct significant role in the reduced performance observed during the HD.

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.

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.

This paper attempts to provide evidence that the heart rate variability power spectrum (HRVPS) reflects the presence of neural control of cardiac regulation. A normal individual is seen to have a characteristic HRVPS (comprising a 0.1-Hz peak and a respiratory peak at 0.25-0.34 Hz), which is altered in a predictable manner in response to orthostatic stress and exercise, while in two patients with autonomic neuropathy, the HRVPS failed to demonstrate such a characteristic alteration in response to orthostatic stress. Postinfarct HRVPS signatures were studied in two patients with anterior and inferior infarcts so as to lend insight using non-invasive means into both the healing process and the dominant deliterious sympathetic or protective vagal tone due to the infarct. When subjects with transplanted hearts were studied, their HRVPS did not exhibit the characteristic pattern of a normal individual; rather, the HRVPS energy was spread over a wider and higher frequency range. However, one of the transplanted patients surprisingly but consistently revealed the characteristic HRVPS; the post-transplant time at the time of the study was 33 months and the patient had the typically high resting heart rate of a transplant recipient but a wide standard deviation like that of a normal individual. This could be the first noninvasively demonstrated evidence in humans of reinnervation of a transplanted heart. Thus, the HRVPS constitutes a simple non-invasive method to assess cardiac neuroregulatory response and disorders and it is proposed that it be referred to as the heart rate variability cardiogram (HRVC).

Cardiopulmonary exercise testing is an objective method of assessing the functional capacity of a patient. In contrast to clinical assessment and resting investigations, exercise testing is useful in detecting early changes in patients with cardiac or respiratory disease. Although a number of different types of ergometers can be used for testing, the ones used commonly are the cycle and treadmill. Comparison of these two modes of exercise shows no significant clinical difference between them; therefore, either can be used for routine cardiopulmonary exercise testing. There are various types of exercise protocols, but generally the protocol should involve large muscle groups and should be tolerated by the population being tested. The main goal when selecting an exercise protocol is to strike a balance between workload increments that do not prematurely fatigue the subject and at the same time allow the subject to reach a maximum power output within 8 to 15 minutes. Whatever the exercise test protocol used, the intensity should be increased to a symptom-limited maximum. This procedure is safe as long as contraindications for starting a test and indications for terminating a test are adhered to strictly. The assessment of cardiorespiratory responses during exercise ranges from simple and noninvasive techniques to those that are invasive and complex. In the majority of cases all the information needed for proper assessment of the patient can be acquired with simple noninvasive techniques.

Reactive hyperemia responses (RHR) of various magnitudes were obtained after release of a brief occlusion in six of 10 coronary bypass grafts. All of the vein grafts responded to an injection of sodium nitroprusside (50 microgram) directly into the open graft with an increase in blood flow that was always greater than the flow recorded after release of the occlusion. This response indicates that there were no flow-limiting stenoses and that the distal vascular beds were responsive to vasodilator stimuli. RHR's, expressed as percent repayment of calculated flow debt, were correlated significantly (r = 0.96, p less than 0.01) with the magnitude of the decrease in vein graft pressure measured during occlusion of the graft. It is suggested that the decrease in pressure is related to the amount of blood flow from alternate sources to the vascular bed during occlusion of the graft, and that this collateral flow is an important determinant of the magnitude of RHR in bypass grafts.

The ability to determine cardiac output (Q) noninvasively during a nonsteady state (NSS) incremental exercise test was assessed. Seven healthy subjects performed two maximal incremental cycle ergometer exercise tests (100 kpm/min increments every minute), and also steady state exercise (SS) at 25, 50, and 75 percent of their maximum power output. The Q was determined by the indirect CO2 Fick method; mixed venous PCO2 was calculated using the exponential CO2 rebreathing method. No significant differences were observed for the cardiac output/oxygen uptake relationship (Q/VO2) obtained between the two incremental exercise tests. During NSS, the Q/VO2 was linear (r = .89; intercept = 5.69 L/min; slope = 5.39). During the SS, Q/VO2 was linear (r = .90; intercept = 5.47 L/min; slope = 4.87). No significant difference was observed between the SS and NSS Q/VO2 relationships (p greater than 0.05), and the NSS relationship was similar to Q/VO2 values previously reported in the literature. Accurate and reproducible measurements of Q can be obtained noninvasively in healthy subjects using the exponential CO2 rebreathing method during incremental progressive exercise tests, with similar values at comparable VO2 to those obtained in the steady state.