William G. Herbert

A nomogram to predict exercise capacity from a specific activity questionnaire and clinical data

Recent investigations suggested that clinical exercise testing can be optimized by individualizing the protocol, depending on the purpose of the test and the subject tested. This requires some knowledge of a patients exercise capacity before beginning the test. The accuracy of a simple physical activity questionnaire and readily available clinical data in predicting subsequent treadmill performance was examined. A brief, self-administered questionnaire (VSAQ) was developed for veterans who were referred to exercise testing for clinical reasons. The VSAQ was designed to determine which specific daily activities were associated with symptoms of cardiovascular disease (fatigue, chest pain and shortness of breath). Two hundred twelve consecutive patients (mean age 62 +/- 8 years) referred for maximal exercise testing were studied. Clinical and demographic variables were added to VSAQ responses in a stepwise regression model to determine their ability to predict treadmill performance. Only metabolic equivalents by VSAQ, and age were significant predictors of treadmill performance; these 2 variables yielded R = 0.82 (SEE 1.43; p < 0.001), and explained 67% of the variance in exercise capacity. The regression equation reflecting the relation between age, VSAQ and exercise capacity was: achieved metabolic equivalents = 4.7 + 0.97 (VSAQ) - 0.06 (age). Using this equation, a nomogram was developed. Incorporating the VSAQ with the nomogram requires only a few minutes, and yields a reasonably accurate estimate of a patients exercise capacity. Although the present equation is population-specific, a similar approach in different populations may be useful for individualizing protocols for clinical exercise testing.

Effects of combined aerobic and resistance training versus aerobic training alone in cardiac rehabilitation.

PURPOSE This study examined the effects of performing combined resistance and aerobic training, versus aerobic training alone, in patients with coronary artery disease. METHODS Thirty-six patients with coronary artery disease were randomized to either an aerobic-only training group (AE) or a combined aerobic and resistance training group (AE + R). Both groups performed 30 minutes of aerobic exercise 3 days/week for 6 months. In addition, AE + R group performed two sets of resistance exercise on seven different Nautilus machines after completion of aerobic training each day. Twenty patients (AE: n = 10; AE + R: n = 10) completed the training protocol with > 70% attendance. RESULTS Strength gains for AE + R group were greater than for AE group on six of seven resistance machines (P < 0.05). VO2peak increased after training for both AE and AE + R (P < 0.01) with no difference in improvement between the groups. Resting and submaximal exercise heart rates and rate-pressure product were lower after training in the AE + R group (P < 0.01), but not in the AE group. AE + R increased lean mass in arm, trunk, and total body regions (P < 0.01), while AE increased lean mass in trunk region only (P < 0.01). Percent body fat was reduced for AE + R after training (P < 0.05) with a between group trend toward reduced body fat (P = 0.09). Lean mass gain significantly correlated with strength increase in five of seven resistance exercises for AE + R. CONCLUSIONS Resistance training adds to the effects of aerobic training in cardiac rehabilitation patients by improving muscular strength, increasing lean body mass, and reducing body fat.

Clinical effectiveness and safety of powered exoskeleton-assisted walking in patients with spinal cord injury: systematic review with meta-analysis

Background Powered exoskeletons are designed to safely facilitate ambulation in patients with spinal cord injury (SCI). We conducted the first meta-analysis of the available published research on the clinical effectiveness and safety of powered exoskeletons in SCI patients. Methods MEDLINE and EMBASE databases were searched for studies of powered exoskeleton-assisted walking in patients with SCI. Main outcomes were analyzed using fixed and random effects meta-analysis models. Results A total of 14 studies (eight ReWalk™, three Ekso™, two Indego®, and one unspecified exoskeleton) representing 111 patients were included in the analysis. Training programs were typically conducted three times per week, 60–120 minutes per session, for 1–24 weeks. Ten studies utilized flat indoor surfaces for training and four studies incorporated complex training, including walking outdoors, navigating obstacles, climbing and descending stairs, and performing activities of daily living. Following the exoskeleton training program, 76% of patients were able to ambulate with no physical assistance. The weighted mean distance for the 6-minute walk test was 98 m. The physiologic demand of powered exoskeleton-assisted walking was 3.3 metabolic equivalents and rating of perceived exertion was 10 on the Borg 6–20 scale, comparable to self-reported exertion of an able-bodied person walking at 3 miles per hour. Improvements in spasticity and bowel movement regularity were reported in 38% and 61% of patients, respectively. No serious adverse events occurred. The incidence of fall at any time during training was 4.4%, all occurring while tethered using a first-generation exoskeleton and none resulting in injury. The incidence of bone fracture during training was 3.4%. These risks have since been mitigated with newer generation exoskeletons and refinements to patient eligibility criteria. Conclusion Powered exoskeletons allow patients with SCI to safely ambulate in real-world settings at a physical activity intensity conducive to prolonged use and known to yield health benefits.

Knee Extensor and Flexor Torque Development With Concentric and Eccentric Isokinetic Training

This study assessed muscular torque and rate of torque development following concentric (CON) or eccentric (ECC) isokinetic training. Thirty-eight women were randomly assigned to either CON or ECC training groups. Training consisted of knee extension and flexion of the nondominant leg three times per week for 20 weeks (SD = 1). Eccentric training increased ECC knee extension and flexion peak torque more than CON training. The ECC group improved acceleration time and time to peak torque with ECC movements versus the CON group. Slow-velocity ECC isokinetic training yielded greater ECC and similar CON torque development gains versus CON training over the course of 20 weeks in young women.

Supervision of Exercise Testing by Nonphysicians: A Scientific Statement From the American Heart Association

The standard exercise test is a well-established procedure that has been widely used in cardiovascular medicine for many decades, with staffing issues that have changed over time. The test is frequently considered the “gatekeeper” to more expensive and/or invasive procedures since it is often the first diagnostic evaluation when coronary artery disease (CAD) is suspected. Thus, it is used to help guide decisions regarding diagnosis and/or medical and interventional management. Moreover, the prognostic value of aerobic capacity and other variables obtained during exercise is firmly established in those who are apparently healthy and in virtually all patient populations.1,2 Generally, peak or symptom-limited exercise testing is used to detect signs or symptoms of myocardial ischemia and to discern fundamental information on exercise capacity, exercise hemodynamics, dysrhythmias, oxygenation, neuroautonomic health, symptoms, and other physiological responses. In most instances, peak effort entails at least brief periods of high-intensity exercise, and evidence suggests that such vigorous physical exertion may cause a transient increase in the risk of cardiovascular events in high-risk individuals.3,4 Because the exercise test is typically performed in patients with known or suspected cardiovascular disease, guidelines and scientific statements on exercise testing have historically recommended physician presence for supervision as a means both to optimize functional and diagnostic testing decisions and safety and to administer emergency treatment should complications occur. However, systematic surveys of multiple centers and reports from individual clinical exercise laboratories have shown that contemporary exercise tests are often conducted and supervised by nonphysicians (eg, exercise physiologists, nurses, physical therapists [PTs], physician assistants [PAs]). These reports and empirical evidence suggest that testing efficacy and safety are similar in laboratories where tests are directly supervised by physicians and those where nonphysicians administer testing under the egis of a physician supervisor.5–11 This issue …

Relationships Among Bone Mineral Density, Body Composition, and Isokinetic Strength in Young Women

The purpose of this study was to examine the relationships among bone mineral density (BMD), body composition, and isokinetic strength in young women. Subjects were 76 women (age: 20 ± 2 yr, height: 164 ± 6 cm, weight: 57 ± 6 kg, body fat: 27 ± 4%) with a normal body mass index (18–25 kg/m2). Total body, nondominant proximal femur, and nondominant distal forearm BMD were measured with dual-energy x-ray absorptiometry. Isokinetic concentric (CON) and eccentric (ECC) strength of the nondominant thigh and upper arm were measured at 60 deg/sec. Fat-free mass (FFM) correlated (P < 0.001) with BMD of the total body (r = 0.56) and femoral neck (r = 0.52), whereas fat mass (FM) did not relate to BMD at any site. Leg FFM, but not FM, correlated with BMD in all regions of interest at the proximal femur. Weak associations were observed between arm FFM and forearm BMD. Isokinetic strength did not relate to BMD at any site after correcting for regional FFM. In conclusion, strong, independent associations exist between BMD and FFM, but not FM or isokinetic strength, in young women.

Effect of β-blockade on the interpretation of the exercise ECG: ST level versus Δ STHR index

The diagnostic value of exercise-induced ST segment depression is considered to be decreased in patients receiving β-blockers. One approach to improving predictive accuracy has been to use the ratio of maximal change in exercise-induced ST segment depression to the corresponding maximal change in heart rate (Δ STHR index). The present study compared these two ECG methods. The records of exercise tests performed on 3047 male veterans were screened to exclude patients with prior revascularization procedures or myocardial infarction, those receiving digoxin, and those with certain resting ECG abnormalities; the use of β-blocker drugs at the time of testing was also noted. All exercise tests were sign/symptom limited. Significant angiographic coronary disease was defined as ≥75% reduction in luminal diameter of at least one coronary artery. Disease severity was evaluated in an expanded study group that included patients with prior myocardial infarction. Mean maximal heart rate was 21 beats · min−1 lower for those receiving β-blockers (p < 0.05), but there was no difference in mean metabolic equivalent (MET) level achieved. The diagnostic accuracy of an abnormal test result for determination of the presence or absence of coronary artery disease was not significantly different in the subgroup taking β-blockers versus the subgroup not taking β-blockers (N = 200), and use of the Δ STHR index did not improve test performance. For discrimination of severe disease, test accuracy was also unaffected by β-blockers and was not improved by the Δ STHR index (N = 454). Exercise testing is a useful predictor of the presence and/or severity of coronary artery disease in patients taking β-blockers. Withholding these medications before testing does not appear to alter interpretation of the exercise ECG.

Comparison of computer ST criteria for diagnosis of severe coronary artery disease

To determine which computer ST criteria are superior for predicting patterns and severity of coronary artery disease during exercise testing, 230 male veterans were studied who had both coronary angiography and a treadmill exercise test. Significant (p < or = 0.05) differences in computer-scored ST criteria were observed among patients with progressively increasing disease severity. Three-vessel/left main disease produced responses significantly different from 1- and 2-vessel disease or those with < 70% occlusion. Discriminant function analysis revealed that horizontal or downsloping ST depression measured at the J junction during exercise or recovery, or both, was the most powerful predictor of severe disease. With use of a cut point of 0.075 mV ST depression, horizontal or downsloping ST depression alone yielded a sensitivity of 50% (95% confidence interval = 35 to 65%) and specificity of 71% for prediction of severe disease; the only additional variable that added significantly to the prediction was exercise capacity, which improved sensitivity to 57% (95% confidence interval = 41 to 72%) with no change in specificity. Measurements of ST amplitude at the J junction and at 60 ms after the J point without slope considered and other scores, including the Treadmill Exercise Score, ST Integral, and ST/heart rate index, had a lower but comparable predictive accuracy when compared with horizontal or downsloping ST depression. Prediction of coronary artery disease severity can be achieved using computerized electrocardiographic measurements obtained during exercise testing. The most powerful marker for severe coronary artery disease is the amount of horizontal or downsloping ST-segment depression during exercise or recovery, or both, a measurement that stimulates the traditional visual approach.

Post-myocardial infarction exercise testing. Non-Q wave versus Q wave correlation with coronary angiography and long-term prognosis.

BackgroundThe presence or absence of baseline diagnostic Q waves has been believed to compromise the accuracy of standard exercise electrocardiography in identifying severe coronary artery disease (three-vessel and/or left main disease); therefore, a retrospective analysis was performed using a personal computer data base of exercise test responses and cardiac catheterization results to evaluate this premise, and follow-up was performed to observe how Q waves and/or severe coronary disease impacted on survival. Methods and ResultsTwo hundred fifty-three male patients who had survived a myocardial infarction were studied. Patients on digitalis, those with left bundle branch block or left ventricular hypertrophy on their baseline electrocardiogram, those with previous revascularization procedures, and those with significant valvular or congenital heart disease were excluded. All patients performed either a low-level predischarge or a sign/symptom limited exercise test and underwent diagnostic coronary angiography within 32 days of each test (range, 0–90 days). Long-term follow-up on patients was performed for an average of 45 months (± 17 months). Group NQMI comprised 103 post-myocardial infarction patients lacking Q waves at the time of exercise testing and group QMI comprised 150 patients who developed Q waves with their myocardial infarction. The cut points of .1 mm (χ2 = 14.39, p < 0.001) and .2 mm (V2 = 26.11, p < 0.001) of exerciseinduced ST segment depression were reliable markers of severe coronary disease in Q wave infarct survivors. This was also true for non-Q wave infarct survivors as .1 mm (χ2 = 6.02, p = 0.01) and > 2 mm (χ2 = 4.37, p = 0.04) of ST segment depression were reliable markers of severe coronary disease. Receiver operating characteristic curve analysis revealed that exercise-induced ST segment depression had discriminating power for the identification of severe coronary artery disease in both the Q wave myocardial infarction patients (area = 0.735, z = 4.47, p < 0.001) and the non-Q wave infarct patients (area = 0.700, z = 3.20, p < 0.001). After 4.4 years of cumulative follow-up, patients with severe coronary disease had an infarct-free survival rate of 72% (95% CI, 50.0–86.0O), whereas those without severe disease had an 86% (95% CI, 76.5–91.5%) infarct-free survival rate (Cox χ2 = 4.00, p = 0.045). Non-Q wave patients had an infarct-free survival rate of 81% (95% CI, 66.0–89.5%), whereas those with Q waves had an infarct-free survival rate of 85% (95% CI, 73.9–91.3%) (Cox χ2 = 0.0005, p = NS). ConclusionsThe presence or absence of diagnostic Q waves has no significant effect on the ability of the exercise electrocardiogram to identify severe coronary artery disease in survivors of myocardial infarction. Long-term infarct-free survival of patients with myocardial infarction is more related to the presence of severe coronary disease rather than if they suffered a non-Q wave or Q wave infarction.

Effects of short-term PAP treatment on endurance exercise performance in obstructive sleep apnea patients

Objective: To measure the effects of 4 weeks of nasal positive airway pressure therapy (PAP) on exercise performance in obstructive sleep apnea patients (OSA).Background: Little published research is available which describes the effects of OSA on exercise tolerance or upon the potential of exercise testing to evaluate the outcomes of PAP therapy.Methods: Exercise testing was performed on an electronic cycle ergometer with continuous ramping to allow collection of numerous data points for each subject, up to a vigorous terminal intensity. Linear regression established each subjects pre-treatment scores for the dependent variables at 60% of estimated peak power (W(60%)). Responses at the pre-treatment W(60%) test were used to quantify and compare to responses at the same power output after treatment.Results: OSA by nocturnal polysomnography was moderately severe in this group; the respiratory distress index was 48+/-22 (mean+/-SD; n=9). Exercise heart rates after PAP therapy averaged 10.2 bt/min less at W(60%) (P<0.05). Other variables were lower but non-significantly so, further suggesting a lower cardiorespiratory exercise demand after treatment, i.e. oxygen consumption ( downward arrow7.6%), and Rating of Perceived Exertion ( downward arrow8.8%).Conclusion: Brief treatment with PAP therapy improves objective markers of aerobic exercise performance.