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PubMed2006

Muscular performance after concentric and eccentric exercise in trained men.

PURPOSE: We studied previously resistance-trained men and compared the effects of concentric and eccentric training on performance and structural muscle parameters. METHODS: Seventeen trained individuals (age 26.9 +/- 3.4 yr) participated in 12 wk of either maximum concentric (N = 8) or eccentric (N = 9) resistance training of the elbow flexors. The functional performance was measured as the maximum concentric and eccentric strength and angular velocity at standard loads. Muscle cross-sectional area and cross-sectional area of single cells were used as measures of muscular hypertrophy. Fiber-type proportions were assessed by staining cells for myofibrillar ATPase. RESULTS: Both eccentric and concentric training increased concentric strength to a similar extent (14 vs 18%), whereas eccentric training led to greater increases in eccentric strength than concentric training did (26 vs 9%). The maximum angular velocity at all loads was enhanced equally in both training groups. The cross-sectional area of both the elbow flexors (+11%) and of the type I and type IIA fibers increased only after the eccentric training. In addition, the relative cross-sectional area occupied by the type II fibers increased from 64 to 73% after the eccentric training. There were only minor changes in the fiber-type proportions. CONCLUSION: The present data suggest that for resistance-trained men, increases in concentric strength and velocity performance after eccentric training are largely mediated by changes in fiber and muscle cross-sectional area. However, hypertrophy alone could not explain the increase in eccentric strength. Because the increases in strength and velocity performance after concentric training could not be ascribed to muscular adaptations alone, we suggest that they may be attributable to additional neural factors.

Adult↗

PubMed2005

Exercise tolerance, exercise hyperpnea and central chemosensitivity to carbon dioxide in sleep apnea syndrome in heart failure patients.

BACKGROUND: Sleep apnea syndrome (SAS) and exercise hyperpnea are common in patients with chronic heart failure (CHF), and although it is not known whether they are both regulated by the same mechanisms, the hypothesis of the present study was that they are related to augmented central chemosensitivity. METHODS AND RESULTS: The oxygen desaturation index (ODI) was evaluated in 29 patients and those with ODI > 5 times/h underwent polysomnography. Patients with an apnea-hypopnea index (AHI) > 15 /h without evidence of obstructive apnea were defined as central SAS (CSAS). Cardiopulmonary exercise testing was performed to determine peak oxygen uptake and the VE-VCO2 slope. A hypercapnic gas mixture (7% CO2/93% O2) was used to activate the central chemoreflex. Nine patients had central SAS (CHF-CSAS) and 20 did not have apnea (CHF-nonSAS). Patients with CHF-CSAS had a lower peak oxygen uptake than the CHF-nonSAS group (13.0+/-2.4 vs 16.9+/-4.3 ml x kg(-1) x min(-1), p < 0.05). There was a significant correlation between central chemosensitivity and the AHI (r = 0.63, p < 0.05), between central chemosensitivity and the VE - VCO2 slope (r = 0.50, p < 0.01), whereas the VE-VCO2 slope showed an insignificant tendency to correlate with AHI (r = 0.44, p = 0.07). Conclusion CHF-CSAS is associated with impaired exercise tolerance and elevated central chemosensitivity is the responsible mechanism for CSAS and exercise hyperpnea.

Aged↗

PubMed2003

Approximation equation for oxygen uptake kinetics in decrement-load exercise starting from low exercise intensity.

The purpose of the present study was to determine the degree of fitting an approximation equation for oxygen uptake (Vo(2)) in decrement-load exercise (DLE). Work rate was started from 120 watts and was decreased by a rate of 15 watts per min. The initial work rate of DLE corresponded to 72+/-10% of the work rate at anaerobic threshold determined in incremental-load exercise (ILE). Vo(2) in DLE increased rapidly, reached a peak, and decreased linearly until the end of the exercise. Vo(2) in DLE was higher than that in ILE at the same work rate except in the early periods in ILE and DLE. This difference ranged from 300 to 400 ml/min. This difference is a result of repayment of oxygen debt in DLE and from the oxygen deficit induced by the delay of response of Vo(2) in ILE. As work rate in DLE can be obtained by the difference between work rates in constant-load exercise (CLE) and ILE, we postulated that the approximation equation for Vo(2) kinetics in DLE could be expressed by a combination of approximation equations in CLE and in ILE. When time delay was taken into consideration in this equation, the fitting of data obtained by using the equation was better than that of data obtained by using the equation without a parameter of time delay. The degree of fitting ranged from 94 to 98% (r(2)). Thus, it seems that Vo(2) including oxygen debt in DLE can be approximated by the equation used in this study.

Adult↗

PubMed2000

Ramp exercise protocols for clinical and cardiopulmonary exercise testing.

Historically, the protocol used for exercise testing has been based on tradition, convenience or both. In the 1990s, a considerable amount of research has focused on the effect of the exercise protocol on test performance, including exercise tolerance, diagnostic accuracy, gas exchange patterns and the accuracy with which oxygen uptake (VO2) is predicted from the work rate. Studies have suggested that protocols which contain large and/or unequal increments in work cause a disruption in the normal linear relation between VO2 and work rate, leading to an overprediction of metabolic equivalents. Other studies have demonstrated that such protocols can mask the salutary effects of an intervention, and some have suggested that the protocol design can influence the diagnostic performance of the test. Guidelines published by major organisations have therefore suggested that the protocol be individualised based on the patient being tested and the purpose of the test. The ramp approach to exercise testing has recently been advocated because it facilitates recommendations made in these guidelines. This article reviews these issues and discusses the evolution of ramp testing which has occurred in the 1990s.

Energy Metabolism↗

PubMed1994

Cardiorespiratory responses to intermittent exercise and relaxation as compared with continuous exercise.

Cardiorespiratory responses to intermittent exercise and relaxation were comparable to cardiorespiratory responses to continuous exercise. The time of workout and work loads were kept constant in both protocols. Even though in the intermittent exercise and relaxation protocol the 10 subjects rested nearly two-thirds of the duration of the workout, cardiorespiratory responses were similar to those which the same subjects attained while exercising continuously throughout the entire steady state workout at approximately 64% maximal heart rate.

Adolescent↗

PubMed2000

[Acute effects of oxygen on dyspnea and exercise tolerance in patients with pulmonary emphysema with only mild exercise-induced oxyhemoglobin desaturation].

The effects of oxygen on dyspnea and exercise tolerance during a 6-mimute walk test were examined in 10 patients with chronic pulmonary emphysema (CPE) who had only mild hypoxemia at rest (PaO2 > 60 Torr) and mild exercise-induced oxyhemoglobin desaturation (lowest SpO2 > 88%) on compressed air. As a whole, oxygen supplementation (2 l/min) resulted in a 7% increase in the distance walked in 6 min (6 MD), a 3% increase in the lowest SpO2, and an 8% decrease in the dyspnea score. In 6 of 7 patients with severe airflow limitation (one-second forced expiratory volume (FEV1) < 40% of predicted value), 6 MD (7-15%) increased significantly on oxygen, an improvement that correlated significantly with FEV1 (r = -0.65, p < 0.05). These results suggest that supplementary oxygen improves dyspnea and exercise tolerance in CPE patients with only mild exercise-induced hypoxemia despite severe airflow limitation. The long-term efficacy of oxygen in such patients needs further study.

Aged↗

PubMed1979

The magnitude of exercise-induced ST segment depression and the predictive value of exercise testing.

The assess whether the magnitude of exercise induced ST segment depression improves the predictive values of symptom limited exercise tests, and helps in the recognition of patients with more severe coronary heart disease, 90 consecutive patients with positive treadmill tests who also underwent selective coronary arteriography were reviewed. The predictive value improved progressively with the increasing ST depression and was most reliable in a select group of patients with normal electrocardiographic baseline who were not receiving digitalis (73% with ST depression greater than or equal to 1 mm to 100% with ST depression greater than or equal to 4 mm). The incidence of 2 and 3 vessel disease increased from 61% with ST depression greater than or equal to 1 mm in the overall population to 100% with ST depression greater than or equal to 4 mm in the select group, and the incidence of left main trunk lesions increased, respectively from 6 to 30%. The prediction of 2 and 3 vessels disease was found to be significantly greater when patients were dichotomized into those with ST depression greater than or equal to 4 mm compared to less than 4 mm. It is concluded that the magnitude of ST segment depression definitely improves the predictive values of exercise tests as well as the ability to recognize the patients with more severe disease. However, the markedly positive exercise tests cannot be utilized to accurately predict the presence of 2 or 3 vessel disease in individual cases unless ST depression attains 4 mm or more in patients with normal electrocardiographic baseline who are not taking digitalis. In this group, the ability to predict left main trunk lesion is approximately 30%.

Coronary Angiography↗

PubMed1986

Studies on ergometer exercise testing. II. Effect of previous myocardial infarction, digoxin, and beta-blockade on exercise electrocardiography.

The results of exercise electrocardiography were studied in a random sample of 317 subjects with clinical suspicion of coronary artery disease. In 278 patients with coronary artery disease the rate of false negative tests was 18% with and 12% without previous myocardial infarction. If ST elevation was considered a negative response, the corresponding values were 25% and 13%, respectively, p less than 0.01. The greatest prevalence of negative tests was seen after anterior myocardial infarction: 27% or 42% when ST elevation was not included into positive responses. The sensitivity of exercise-induced ST depression for the presence of multivessel disease was lower after anterior infarction (67%) than in other patients with previous infarction (86%), p less than 0.01. The corresponding specificities were 71% and 22%, respectively, p less than 0.005. If ST elevation was included into positive responses these differences were abolished. In subjects without myocardial infarction the sensitivity was 89% and specificity 43%. Digitalized patients had somewhat higher sensitivity in the exercise electrocardiogram than those without digoxin, 90% vs. 81% (p less than 0.05), but the difference was not seen with exclusion of ST elevation. The specificity was not influenced by digitalis. beta-blockade had no effect on the sensitivity or specificity, but the prevalence of postexercise ST evolution was lower with (11%) than without (30%) beta-blockade. The prevalence of slowly ascending ST depression was reduced by three factors: the presence of digitalis in patients without previous myocardial infarction, infarction itself, and the extent of coronary artery disease. We conclude that exercise electrocardiography has only a limited value in prediction of multivessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗

PubMed1994

Effect of eccentric exercise on plasma enzyme activities previously elevated by eccentric exercise.

The purpose of this study was to investigate whether plasma activities of creatine kinase (CK) and glutamic-oxaloacetic transaminase (GOT), elevated by eccentric exercise, would be affected by a second bout of eccentric exercise. A group of 26 male students [20.3 (SD 1.9) years] were placed in one of three groups. Group A (n = 8) performed one bout of 24 maximal eccentric actions (ECC) of the forearm flexors (ECC1), and groups B (n = 10) and C (n = 8) performed two bouts of ECC (ECC1, ECC2). The ECC2 was performed by the opposite arm 3 days (group B) or 5 days (group C) after ECC1. None of the subjects had performed this eccentric exercise prior to this study. Maximal isometric force (MIF), range of motion (ROM), upperarm circumference (CIR), muscle soreness level (SOR), and plasma CK and GOT activities were measured before and for 8 days (group B) or 10 days (groups A, C) postexercise. The MIF, ROM, CIR, and SOR changed significantly after exercise (P < 0.01), and no significant differences in changes were found between ECC1 and ECC2, or among the groups. This suggested that ECC1 and ECC2 produced a similar stress to the forearm flexor muscles. Therefore, it was expected that CK and GOT activities would show similar increases after ECC1 and ECC2. However, increases in CK and GOT activities after ECC2 were significantly smaller (P < 0.01) than after ECC1 in both groups B and C. The results of this study confirmed that CK and GOT responses were diminished when initial blood enzyme activities were elevated.

Adult↗

PubMed1986

Beneficial effects of exercising at moderate altitude on red cell oxygen transport and on exercise performance.

The effect of a ascent to moderate altitude (2,300 m) and altitude training on the O2-transport properties of Hb and their possible consequences on tissue oxygenation during exercise were studied on six control and six training subjects. A rapid increase in P-50 values (+2.4 mm Hg, 0.32 kPa) was measured within one day after ascent. At the end of the stay at altitude (13th day) P-50 values were higher in subjects performing training than in controls. At altitude a slow but constant increase in 2,3-DPG, pyruvate kinase activity and reticulocyte count was found, which was more pronounced in training subjects as compared to controls. Ascent to altitude resulted in a decreased maximal performance capacity (-9%), but both groups recovered during the stay. In training subjects maximal exercise performance was increased after descent. Exercise at altitude was performed at a lower heart rate (controls: -10/min; training: -18/min) and at a lower lactate concentration (-4 mmol/l). These data indicate a positive effect of adaptation to altitude on exercise performance. Training itself shifts the ODC to the right and adds this effect to the effects of passive altitude adaptation on the O2-binding properties of hemoglobin.

Acclimatization↗

PubMed2002

Influence of glucose ingestion by humans during recovery from exercise on substrate utilisation during subsequent exercise in a warm environment.

Carbohydrate (CHO) ingestion during short-term recovery from prolonged running has been shown to increase the capacity for subsequent exercise in a warm environment. The aim of this study was to examine the effects of the amount of glucose given during recovery on substrate storage and utilisation during recovery and subsequent exercise in a warm environment. A group of 11 healthy male volunteers took part in two experiments in a controlled warm environment (35 degrees C, 40% relative humidity), 1 week apart. On each occasion the subjects completed two treadmill runs (T1 and T2) at a speed equivalent to 60% of maximal oxygen uptake, for 90 min, until they were fatigued, or until aural temperature (T(aur)) reached 39 degrees C. The two runs were separated by a 4 h recovery period (REC), during which subjects consumed 55 g of naturally enriched [U-(13)C]-glucose in the form of a 7.5% carbohydrate-electrolyte solution (CES, mass of solution 667 g) immediately after T1. The subjects then consumed either: the same quantity of CES, or an equivalent volume of an electrolyte placebo, at 60, 120 and 180 min during REC, providing a total of 220 g (C220) or 55 g (C55) of [U-(13)C]-glucose, respectively. Expired gases were collected at 15 min intervals during exercise and 60 min intervals during REC, for determination of total CHO and fat oxidation by indirect respiratory calorimetry, and orally ingested [U-(13)C]-glucose oxidation, estimated from the (13)C:(12)C ratio of expired CO(2). Substrate metabolism did not differ between conditions during T1. Despite the fact that total CHO (P < 0.05) and ingested glucose oxidation (P < 0.01) were greater during REC of the C220 condition, glycogen synthesis was estimated to be approximately fivefold greater (P < 0.01) than in the C55 condition. During T2 the rate of total CHO oxidation was higher (P < 0.01) and total fat oxidation lower (P < 0.01) at all times during the C220 compared to the C55 condition. The greater CHO oxidation during C220 appeared to be met from ingested sources, as the rate of [U-(13)C]-glucose oxidation was greater (P < 0.01) at all times during T2, compared to C55. Whilst more of the ingested substrate remained unoxidised on completion of T2 during C220, exercise duration was similar in the two experimental conditions, and was limited by thermoregulatory incapacity (T(aur) > 39 degrees C) rather than substrate availability per se.

Administration, Oral↗

PubMed2002

Resistance exercise training attenuates exercise-induced lipid peroxidation in the elderly.

This study examined the effects of 6 months of resistance exercise (RX) on basal and post-aerobic exercise lipid peroxidation (LIPOX). Men and women [n = 62, mean (SD) age 68.4 (6) years] were divided randomly into either a control (n = 16, CON), low-intensity training [LEX n = 24; 50% one-repetition maximum (1RM), 13 repetitions/exercise], or high-intensity training (HEX n = 22, 80% 1RM, 8 repetitions/exercise) group. Pre- and post-training, subjects performed a graded aerobic exercise test (GXT). Blood samples were collected prior to and 10 min following each GXT. Subjects trained 3 times per week for 6 months using 12 RX machines. LIPOX was determined by measuring levels of thiobarbituric reactive acid substances (TBARS) and lipid hydroperoxides (PEROX). RX had no effect on resting LIPOX. Post-training, post-GXT TBARS were lower in the LEX and HEX groups by 14% and 18%, respectively, compared to CON (P < 0.05). Post-GXT PEROX levels were lower (P < 0.05) in LEX and HEX compared to CON [CON 3.51 (0.56) nmol/ml, LEX 2.89 (0.80) nmol/ml, HEX 2.99 (0.63) nmol/ml]. Serum total and non-protein (glutathione) thiols were higher in the LEX and HEX groups following training compared to CON (P < 0.05). These data suggest that RX can (1) reduce serum LIPOX, (2) provide protection against oxidizing agents in vitro, and (3) provide a "cross-protection" against the oxidative stress generated by aerobic exercise, perhaps mediated by improvements in the thiol portion of the antioxidant defense.

Aged↗

PubMed2004

Perceived speech difficulty during exercise and its relation to exercise intensity and physiological responses.

The aim of this study was to establish how ratings of perceived speech production difficulty (PSPD) during exercise of varying intensities are correlated with various physiological responses, in order to determine whether the PSPD is suitable for prescribing exercise training intensity. An incremental running test was performed to establish the subjects' maximal oxygen consumption (VO(2max)) and ventilatory anaerobic threshold (VAT). During the test, the subjects were asked to read a written text. The subjects graded their PSPD at each stage of the test using a 13-level PSPD scale. Throughout the test, various cardiopulmonary parameters were measured breath-by-breath. Regressions of VO(2), heart rate (HR), and pulmonary ventilation (V(E)), all as percentages of their respective measured maximal values, plotted as a function of PSPD showed that the overall associations among those variables are strong and statistically significant ( P<0.05). However, the individual variability within each relative VO(2), V(E) or HR was found to be rather large. The subjects' distribution in relation to their PSPD at the VAT scattered widely across the PSPD scale. These results indicate that estimating exercise intensity by measuring speech difficulty is not valid. Thus it may be assumed that the "talk test", in its present non-standardized form, is a questionable substitute for the anaerobic threshold, HR, or for any other objective physiological measure for prescribing individual training exercise intensity.

Adult↗

PubMed2005

The effects of exercise-induced muscle damage on maximal intensity intermittent exercise performance.

Exercise-induced muscle damage (EIMD) is a common occurrence following activities with a high eccentric component. Alterations to the torque-velocity relationship following EIMD would appear to have serious implications for athletic performance, particularly as they relate to impairment of maximal intensity exercise. However, this has been studied infrequently. The purpose of this study was to assess the effects of EIMD on maximal intermittent sprint performance. Ten male participants (age 22.4 +/- 3.2 years, height 178.6 +/- 5.2 cm, mass 80.6 +/- 10.7 kg) performed 10 x 6 s cycle ergometer sprints, interspersed with 24 s recovery against a load corresponding to 0.10 kp/kg and 10 x 10 m sprints from a standing start, each with 12 s active (walking) recovery. All variables were measured immediately before and at 30 min, 24, 48 and 72 h following a plyometric exercise protocol comprising of 10 x 10 maximal counter movement jumps. Repeated measures ANOVA showed significant changes over time (all P<0.05) for perceived soreness, plasma creatine kinase activity (CK), peak power output (PPO), sprint time and rate of fatigue. Soreness was significantly higher (P<0.01) than baseline values at all time intervals (3.1, 4.9, 5.5 and 3.2 at 30 min, 24, 48 and 72 h, respectively). CK was significantly elevated (P<0.05) at 24 h (239 IU/l) and 48 h (245 IU/l) compared to baseline (151 IU/l). PPO was significantly lower (P<0.05) than baseline (1,054 W) at all time intervals (888, 946, 852 and 895 W, at 30 min, 24, 48 and 72 h, respectively). The rate of fatigue over the ten cycling sprints was reduced compared to baseline, with the greatest reduction of 48% occurring at 48 h (P<0.01). This was largely attributed to the lower PPO in the initial repetitions, resulting in a lower starting point for the rate of fatigue. Values returned to normal at 72 h. Sprint times over 10 m were higher (P<0.05) at 30 min, 24 h and 48 h compared to baseline (1.96 s) with values corresponding to 2.01, 2.02 and 2.01 at 30 min, 24 h and 48 h, respectively. Values returned to baseline by 72 h. The results provide further evidence that, following a plyometric, muscle-damaging exercise protocol, the ability of the muscle to generate power is reduced for at least 3 days. This is also manifested by a small, but statistically significant reduction in very short-term (approximately 2 s) intermittent sprint running performance. These findings have implications for appropriate training strategies in multiple sprint sports.

Adaptation, Physiological↗

PubMed2005

Influence of exercise duration on post-exercise steroid hormone responses in trained males.

The purpose of this study was to systematically evaluate the effect of endurance exercise duration on hormone concentrations in male subjects while controlling for exercise intensity and training status. Eight endurance-trained males (19-49 years) completed a resting control session and three treadmill runs of 40, 80, and 120 min at 55% of VO2max . Blood samples were drawn before the session and then 1, 2, 3 and 4 h after the start of the run. Plasma was analyzed for luteinizing hormone (LH), dehydroepiandrosterone sulfate (DHEAS), cortisol, and free and total testosterone. LH was significantly greater at rest compared to the running sessions. Both free and total testosterone generally increased in the first hour of the 80 and 120 min runs and then showed a trend for a steady decline for the next 3 h of recovery. Dehydroepiandrosterone sulfate increased in a dose-response manner with the greatest increases observed during the 120-min run, followed by the 80-min run. Cortisol only increased in response to the 120-min run and showed a decline across time in all other sessions. The ratios of anabolic hormones (testosterone and DHEAS) to cortisol were greater during the resting session and the 40-min run compared to the longer runs. The results indicate that exercise duration has independent effects on the hormonal response to endurance exercise. At a low intensity, longer duration runs are necessary to stimulate increased levels of testosterone, DHEAS and cortisol and beyond 80 min of running there is a shift to a more catabolic hormonal environment.

Adaptation, Physiological↗

PubMed2005

Use of atropine in patients with recent myocardial infarction during exercise myocardial perfusion study. Use of atropine during exercise myocardial perfusion SPECT.

BACKGROUND: Patients with recent myocardial infarction frequently require a myocardial perfusion study for risk stratification. However a conclusive study cannot be accomplished in many due to non-attainment of target heart rate. AIM OF THE STUDY: To evaluate the effect of pre-stress administration of atropine in exercise performance of patients with recent myocardial infarction. MATERIAL AND METHODS: Study included 43 test and 43 control patients and were matched for their age, sex, status of pretest exercise tolerance, area of infarction and for interval between infarction and stress thallium test. Atropine (0.01 mg/kg) was administered intravenously 3 min prior to treadmill stress in all the 43 test patients and no atropine was administered to control patients. RESULTS: Target heart rate was attained in 95.3% patients receiving atropine compared to in 67.4% of control patients. There was no significant difference between mean ages (p>0.33), basal BP (p>0.47), peak BP (p>0.18) of both groups. There was significant difference between the increment in exercise-induced heart rate (p<0.004), peak heart rate (p<0.001) and double product (p<0.001) attained between both groups. No significant adverse effect was noted in patients who received atropine. CONCLUSION: Pre-stress administration of atropine in patients with recent myocardial infarction is safe and results in a significantly better exercise performance, which might be useful in decreasing the number of equivocal myocardial perfusion studies.

Adult↗

PubMed1983

Computer-derived treadmill exercise score quantifies the degree of revascularization and improved exercise performance after coronary artery bypass surgery.

A computer-derived treadmill exercise score (TES) that quantifies the severity of the ischemic ST response to exercise was used to detect noninvasively graft occlusion or the progression of new lesions after coronary artery bypass surgery. Three months after surgery TES completely normalized in 68% of patients and improved by more than 70% in another 18% of patients, thus reflecting excellent improvement in exercise-induced ischemia in 87% of patients. Surgical results correlated well with completeness of revascularization as shown by repeat coronary angiography. When TES, done serially up to 4 years after surgery, remained unchanged, grafts were patent and no new critical lesions had occurred. Deterioration in TES always predicted either late graft occlusion or appearance of new, high-grade lesions in the native vessels. Thus TES provides a new, accurate method that quantifies the ischemic response to exercise and detects graft occlusion or new obstructive lesions in the native coronary arteries.

Arterial Occlusive Diseases↗

PubMed1989

Evaluation of coronary artery disease in the patient unable to exercise: alternatives to exercise stress testing.

Exercise stress testing is a well-established method for the diagnostic, prognostic, and functional assessment of patients with known or suspected CAD. A variety of alternative tests have been described in patients unable to perform leg exercise. Atrial pacing and dipyridamole imaging have been evaluated most extensively, and results compare favorably with those of exercise testing for diagnosing the presence of CAD. Both tests may be used to assess prognosis after myocardial infarction, and dipyridamole imaging may be useful in patients undergoing preoperative evaluation. The use of the cold pressor test and isometric handgrip exercise have also been described. However, the value of both tests is limited by a relatively low sensitivity for detecting the presence of CAD. Other testing modalities--arm ergometry, intravenous infusion of beta-adrenergic agonists, and transthoracic pacing--show promise but require further assessment to confirm their value.

Adrenergic beta-Agonists↗