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Biomedical subjects

M L Pollock

Publications and source records attributed to M L Pollock.

At least 91 records · Page 5Linked to original sources
PubMed1985

Reduced training intensities and loss of aerobic power, endurance, and cardiac growth.

Twelve subjects participated in an exercise program of cycling and running 40 min/day, 6 days/wk. After 10 wk, they continued to train with either a one-third or two-thirds reduction in work rates for an additional 15 wk. Frequency and duration for the additional training remained the same as during the 10 wk of training. The average increases in maximum O2 uptake (VO2 max) were between 11 and 20% when measured during cycling and treadmill running after 10 wk of training. VO2 max was not maintained at the 6-day/wk training levels with a one-third reduction in training intensity but was still higher than pretraining levels. With a two-thirds reduction in intensity, VO2 max declined to an even greater extent than with the one-third reduction. Short-term endurance (approximately 5 min) was maintained in the one-third reduced group but was markedly reduced in the two-thirds reduced group. Long-term endurance was decreased significantly from training by 21% in the one-third reduced group (184-145 min) and by 30% in the two-thirds reduced group (202-141 min). Calculated left ventricular mass, obtained from echocardiographic measurements, increased approximately 15% after training but returned to control levels after reduced training in both groups. These results demonstrate that training intensity is an essential requirement for maintaining the increased aerobic power and cardiac enlargement with reduced training.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1985

Exercise regimens after myocardial revascularization surgery: rationale and results.

Although the exercise prescription for the patient after myocardial revascularization surgery has unique differences from the regimen for the patient after infarction, there are many similarities. Most differences between the two patient groups apply during the initial weeks of rehabilitation (approximately 6 to 8 weeks). In the inpatient program the patient after CABG surgery usually begins ROM exercise and ambulation earlier. Upper extremity ROM exercises are emphasized more with the surgery patient, and the rate of progression of the intensity and duration of training is faster. Most data concerning morbidity, mortality, physiologic and psychologic factors, and return to work show similar results for patients after coronary bypass surgery and after MI.

Ambulatory Care↗
PubMed1984

Work capacity and left ventricular function during rehabilitation after myocardial revascularization surgery.

A prospective randomized trial was conducted to evaluate the effects of exercise-based cardiac rehabilitation after myocardial revascularization surgery (MRS) on work capacity (measured in mets) and left ventricular function as determined from ejection fraction (LVEF). Twenty-eight patients undergoing MRS were randomly assigned to experimental (aerobic exercise, n = 19) or control (muscle relaxation and low-level exercise, n = 9) groups. Patients were studied before surgery (T1) and 2 (T2), 8 (T3), and 24 (T4) weeks after surgery with first-pass radionuclide angiography both while they were at rest and during maximal upright cycle ergometric exercise. Subsets of patients were also studied at T2, T3, and T4 at a standard workload of 75 W, and during maximal exercise 1 year after surgery (T5). Work capacity improved in both groups although significantly more so in the experimental group (3.9, 3.8, 6.0, and 7.3 mets and 3.7, 3.7, 4.9, and 5.7 mets at T1, T2, T3, and T4 in the experimental and control groups, respectively). The differences between groups were significant by T3. Peak exercise LVEF increased significantly in both groups from T1 to T2 then decreased at T3 and remained unchanged through T5. Peak exercise LVEF at T3 to T5 remained significantly above that observed at T1. LVEF responses were not related to the exercise program. During a standard workload, heart rate decreased, blood pressure increased, and LVEF did not change in either group. After conclusion of the formal protocol (T4), work capacity and LVEF did not change for either group throughout an additional 6 months (T5).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗
PubMed1984

Exercise prescription for the cardiac patient: an update.

Exercise prescription for patients after myocardial infarction and for those after coronary artery bypass grafting is contrasted with prescription for healthy adults. Calculation of target training heart rate and the rating of perceived exertion scale for the cardiac patient are examined. The authors discuss in detail exercise prescription for the cardiac patient during in-patient, outpatient, and community-based programs. A well-rounded approach including flexibility, strength, and aerobic components is emphasized.

Adrenergic beta-Antagonists↗
PubMed1984

Research progress in validation of clinical methods of assessing body composition.

Anthropometry is the method of choice for estimating body composition in the clinical setting. The method can be accurate, and requires little time, space, equipment, or financial outlay. Although used extensively in epidemiological research, height/weight indices are not as accurate as skinfold and circumference measures for estimating body composition. The validity of estimating body density is enhanced by using a combination of skin-fold and circumference measures in a multiple-regression model. Some recently developed generalized equations may have a broader application for use in varied populations than several population-specific equations. The newer equations take into account the potential change in ratio of internal to external fat and bone density with age, and the nonlinear relationship between skinfold fat and body density. The validity of using skinfolds for estimating body density can be significantly affected by caliper selection and measurement procedures. Inter-observer errors appear to be the most problematic, with improper skinfold site selection causing the greatest variation among observers. To improve the validity of the anthropometric technique for use in the clinical setting, more precise standards and description of methods need to be developed.

Adult↗
PubMed1984

Methodological factors and the prediction of body fat in female athletes.

The effect of skinfold caliper, investigator technique, and various skinfold prediction equations on estimates of body fatness was investigated using college-age female basketball players. Four skinfold calipers, four investigators, and five prediction equations from the literature were selected for study. Skinfolds were obtained on 16 athletes for each of five sites by all four investigators using each caliper. Triceps and subscapular skinfolds showed less variation among investigators (mean differences of 1-4 mm) as compared to suprailiac, abdomen, and thigh skinfolds (mean differences of up to 5-6 mm). Differences among investigators were less using the Harpenden and Holtain than for the Lange and Adipometer calipers. All three sources of variation--caliper, investigator, and prediction equation--contributed significantly to the variability in estimates of mean fat content of this sample, which ranged from 14.1-28.1% depending on which of the 80 caliper-investigator-prediction equation combinations (four calipers, four investigators, and five equations) was used. Using any one prediction equation, the range in mean percent fat due to the 16 caliper-investigator combinations was 7%. The results illustrate the need for standardization of skinfold sites, caliper, and prediction equations for reliable estimation of body composition in a specific population.

Adipose Tissue↗
PubMed1983

Effect of exercise protocol on the left ventricular response to exercise.

The purpose of this study was to determine whether the left ventricular response during exercise radionuclide angiography would be influenced by exercise protocol. One hundred twenty healthy volunteers (aged 18 to 40 years) performed upright bicycle exercise using 1 of 5 protocols. Ejection fraction was measured using first-pass radionuclide angiography. Exercise protocols were as follows: (1) graded exercise (25 W increase every 2 minutes) to fatigue, heart rate greater than 85% of age-predicted maximum, n = 53; (2) graded exercise to 85% of age-predicted maximal heart rate or to fatigue with heart rate less than 85% of age-predicted maximum, n = 26; (3) graded exercise to fatigue, with "exercise" imaging performed immediately after exercise, n = 15; (4) abrupt presentation of a supermaximal work load (400 W), n = 10; (5) graded exercise to a work load of 75 W preceding the abrupt presentation of a supermaximal work load (300 to 400 W), n = 16. Protocols 2 and 3, representing less than maximal stress, yield higher ejection fractions than Protocol 1 and may reduce the sensitivity of exercise radionuclide angiography. Protocols 4 and 5, representing supermaximal stress, yield lower ejection fractions than Protocol 1 and may reduce the specificity of exercise radionuclide angiography. Thus, exercise protocol has a significant influence on the left ventricular response during exercise radionuclide angiography.

Adolescent↗
PubMed1983

Evaluation of functional capacity during exercise radionuclide angiography.

This study compared functional capacity during treadmill exercise testing and during bicycle exercise radionuclide angiography. 262 patients performed maximal upright bicycle exercise and also performed maximal graded exercise testing using either the Bruce (n = 158) or Naughton (n = 104) treadmill protocols. The functional capacity was well correlated between bicycle and treadmill for Bruce (r = 0.89), Naughton (r = 0.93), or combined treadmill (r = 0.90) protocols. However, the functional capacity was significantly lower during bicycle than during treadmill testing for Bruce (8.3 vs. 10.5 METs), Naughton (7.8 vs. 8.7 METs), or combined treadmill (8.1 vs. 9.8 METs) protocols. Treadmill functional capacity could be predicted from bicycle functional capacity using the following equations: Bruce METs = 1.00 X (bike METs) + 2.23, Naughton METs = 0.94 X (bike METs) + 1.40, and combined treadmill METs = 0.98 X (bike METs) + 1.85.

Adult↗
PubMed1983

Dysrhythmia detection in myocardial revascularization surgery patients.

Dysrhythmia detection in myocardial revascularization surgery patients. Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 281-286, 1983. In order to document the type and prevalence of significant dysrhythmias in myocardial revascularization surgery patients, cardiac electrical activity was recorded during graded exercise testing, 24-h ambulatory electrocardiography, and electrocardiographic-monitored exercise training. Patients participated in a cardiac rehabilitation program that began approximately 2 wk post-surgery, and attended three monitored exercise sessions per week for 12 consecutive weeks. Graded exercise testing and 24-h ambulatory electrocardiography were administered in the second and eighth weeks of the study (weeks 1 and 6 of the exercise program) post-surgery. Eighty-eight percent of the patients exhibited significant dysrhythmias. A greater number of significant dysrhythmias were found during the second 6 wk of the study in comparison with the first 6 wk. Graded exercise testing was not as effective as ambulatory electrocardiography and monitored exercise training in dysrhythmia detection. Not all dysrhythmias were detected by any one technique, thus a combination of methods may be best for optimal surveillance and detection.

Anti-Arrhythmia Agents↗
PubMed1982

Comparative analysis of physiologic responses to three different maximal graded exercise test protocols in healthy women.

The purpose of this study was to compare the three most commonly used maximal graded exercise test (GXT) protocols in healthy women. Submaximal and maximal metabolic and hemodynamic responses were determined from two treadmill protocols, Bruce and Balke, and a bicycle protocol, in 49 women. Maximum oxygen uptake (VO2 max) was significantly different among protocols (Bruce=40.3, Balke=38.4, and Bike=36.6 ml/kg . min -1). Maximum heart rate (HR max) was significantly lower during Bike (178 beats/min) than during Bruce (182) and Balke (183) protocols. No differences in rate of increase in HR or systolic blood pressure (BP) per increase in multiples of the rest metabolic (METs) were found between Bruce and Balke protocols. The rate of recovery of HR and systolic BP was not different among tests. Comparisons of active and sedentary groups showed differences in VO2 max and submaximal HR and recovery HR at common minutes; however, the rate of increase in HR and systolic BP during exercise and the rate of decrease during recovery were not significantly different. Prediction of VO2 max with Bruce and Balke protocols from treadmill time was r=0.91 (SEE +/- 2.7 ml/kg . min -1) and r=0.94 (SEE 2.2 ml/kg . min -1), respectively. These data suggest a difference between men and women in increased HR and systolic BP per METs increase in exertion.

Adipose Tissue↗
PubMed1982

Effect of habitual exercise on left ventricular response to exercise.

To evaluate the effects of chronic physical exercise on left ventricular ejection fraction (LVEF) and ejection rate (LVER), radionuclide angiography was performed at rest and during upright-bicycle exercise in 45 healthy men. The subjects varied widely in exercise habits and working capacity. They were divided into three subgroups on the basis of habitual physical activity. Aerobic training was done more than 7, 2-4, and less than 1 h/wk by subgroups of athletes, trained, and untrained men, respectively. The results indicate marked differences in work capacity (298, 233, and 181 W in the athletes, trained, and untrained groups, respectively). Resting LVEF (72, 69, and 68%) and LVER (4.1, 3.4, and 3.6 s-1) were not significantly different among the groups. With maximal exercise, however, small but statistically significant differences in LVEF (75, 69, and 68%; P less than 0.05 athletes vs. trained and athletes vs. untrained) and in LVER (7.5, 6.3, and 5.2 s-1; P less than 0.05 among all groups) were observed. Work capacity was, however, poorly correlated with exercise LVEF (r = 0.18) and LVER (r = 0.47). The results of this study indicate that the enhanced working capacity observed secondary to increases in habitual physical activity can be attributed to differences in LVEF and LVER only in the most general terms. Accordingly the results agree with previous suggestions based primarily on echocardiographic data that the primary cardiac adaptation to exercise is dimensional rather than functional in character.

Adult↗
PubMed1982

Left ventricular function at rest, peak exercise and postexercise.

To determine whether the temporal sequence of imaging could influence the results of exercise radionuclide angiography, 15 healthy volunteers were studied at rest, during peak bicycle exercise and immediately postexercise using first pass radionuclide angiography. Responses at rest, peak and postexercise included: heart rate (67 to 174 to 170 bpm), double product (7.4 to 31.5 to 27.5 mm Hg X bpm X 10(3)), left ventricular ejection fraction (68 to 69 to 80%) and mean normalized left ventricular ejection rate (3.63 to 6.56 to 8.56 s-1). The results indicate that left ventricular ejection fraction and mean normalized ejection rate were different during exercise and immediately postexercise although heart rate and double product were not. The results indicate that the temporal sequence of imaging is a significant procedural variable in the conduct of exercise radionuclide angiography.

Adult↗
PubMed1982

Diagnostic capabilities of exercise testing soon after myocardial revascularization surgery.

The purpose of this investigation was to compare data on early exercise testing for variables known to be of diagnostic/prognostic value following myocardial infarction in post-myocardial revascularization surgery patients. 70 patients were evaluated soon after surgery, by cardiac catheterization, moderate-intensity treadmill exercise testing, and rest and exercise radionuclide angiography. The results indicated no significant differences among groups with satisfactory and unsatisfactory results by catheterization compared for METs, peak heart rate, double product, ST-segment change, angina pectoris, and dysrhythmias. Significant differences were found among groups when rest and exercise ejection fraction and exercise-induced regional wall motion abnormality were taken into account. It was concluded that the moderate-intensity treadmill exercise test was ineffective in differentiating current cardiac function and arterial/graft status among postmyocardial revascularization surgery patients. Exercise radionuclide angiographic studies were able to identify groups of patients with adequate or inadequate postoperative cardiac catheterization results.

Cardiac Catheterization↗
PubMed1982

Effects of propranolol on perceived exertion soon after myocardial revascularization surgery.

Effect of propranolol on perceived exertion soon after myocardial revascularization surgery. Med. Sci. Sports Exercise. Vol. 14, No. 4, pp. 276-280, 1982. This study evaluated the effects of propranolol on ratings of perceived exertion (RPE), heart rate (HR), and systolic blood pressure (SBP) during graded exercise testing of myocardial revascularization surgery patients before hospital discharge. Eighty-six men performed a symptom-limited, graded exercise test on a treadmill an average of 11 d after surgery. Patients were assigned to three groups: those not taking propranolol (no-propranolol group, N = 54), those taking propranolol (propranolol group, N = 22), and those exhibiting exertional hypotension during testing (hypotensive group, N = 10). Test results showed that estimated METs during peak exercise were similar for the three groups. The propranolol group demonstrated a lower HR for submaximal and peak exercise when compared with the no-propranolol group, but RPE was the same for matched exercise intensities. The hypotensive group failed to increase SBP during exercise, but perceived the matched exercise intensities to be the same as the other two groups. The HR response of the hypotensive group was similar to that of the no-propranolol group. Thus, an abnormal SBP response during exercise was not reflected in a changed RPE when compared with patients who increased SBP appropriately. It was concluded that propranolol does not affect RPE during graded exercise testing soon after cardiac surgery.

Adult↗