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Biomedical subjects

R A Carleton

Publications and source records attributed to R A Carleton.

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

A simple, valid step test for estimating maximal oxygen uptake in epidemiologic studies.

The authors' modification of the Astrand-Rhyming Cycle Ergometer Test is of short duration, has low initial and peak work rates and was in an earlier study applied for population fitness testing (N = 587) at a survey center after other cardiovascular risk factor measures were obtained in the home. To add fitness testing in the home, the authors have designed a safe, brief 10 inch (25.4 cm) high step test for estimating maximal oxygen uptake (VO2max). Measured maximal oxygen uptake for step tests has been shown to be approximately 10% higher than that reported for cycle tests. All test instructions and stepping rates were included on a cassette tape; heart rates were monitored by a digital tachograph during the last 30 seconds of stepping. Maximal oxygen uptake was measured directly on a bicycle, estimated by the step test, and measured by the authors' bike test in 48 men and women aged 19-70 years who took part in a community fitness program in Pawtucket, Rhode Island in January-February 1983. No significant differences in maximal oxygen uptake were found between the bicycle protocols. The step test estimate of maximal oxygen uptake (VO2max) was significantly higher (12%) than directly measured VO2max, reflecting the expected difference between stepping and cycling. The correlation between direct and both estimates was 0.92. The cross-validation correlation between the estimates was 0.98. The authors' protocol provides accurate estimates of maximal oxygen uptake and is safe and suitable for in-the-home assessment of fitness of people aged 19-70 years for epidemiologic studies.

Adult↗
PubMed1985

Self-reported physical activity compared with maximal oxygen uptake.

Maximal oxygen uptake has been used as a measure of physical fitness. This measure increases by approximately 25% when sedentary individuals become more physically active. Oxygen uptake measurement in the laboratory or estimation in fieldwork is complex and costly with finite risk. For the present study, 36 men and 32 women completed the Paffenbarger Physical Activity Index Questionnaire, including a sweat-inducing physical activity frequency question, and had measurement of oxygen uptake during pedal ergometry. Using maximal oxygen uptake as the measure of fitness, the authors found that the Paffenbarger Physical Activity Index, although more detailed, may be less valid than the simpler sweat induction frequency question for estimating fitness. The correlations observed between the sweat question and oxygen uptake were 0.54 for males, 0.26 for females, and 0.46 for the total group. The correlations between the Physical Activity Index and oxygen uptake were 0.26 for males, 0.08 for females, and 0.29 for the total group. The regression relationship (oxygen uptake = 1.92 X (sweat days) + 23.76; standard error of estimate = 8.63 ml/kg/min) is significant for sweat versus oxygen uptake. While the confidence interval limits the practical ability to predict individual values, low cost, absence of risk, and population validity suggest that fitness can be assessed rapidly and simply for epidemiologic studies with a simple "sweat" question.

Adult↗
PubMed1985

Physical fitness and blood pressure: the role of age.

Most epidemiologic studies have shown an inverse relationship between resting blood pressure and usual levels of physical fitness or activity. The inference is that fitness lowers blood pressure. However, maximum oxygen uptake (VO2max--a widely accepted measure of fitness) and blood pressure are both correlated with age; young people usually have lower pressures and higher VO2max (ml X kg-1 X min-1). Systolic and diastolic pressures were measured and maximal oxygen uptake was estimated in 184 men and 227 women aged 18-65 years who were randomly selected as part of a cardiovascular risk factor survey conducted in two New England cities between April 1981 and March 1982. Initially, both measures of blood pressure were strongly and inversely correlated with estimated maximal oxygen uptake. However, when the effects of age were partialed out, the strength of the correlations decreased sharply for both males and females. The proportion of the variance in systolic pressure explained by maximal oxygen uptake decreased from 9.6 to 0.8% for males and 21.2 to 2.3% for females. Similar decreases were demonstrated for diastolic pressure in males (14.4 to 2.9%) and females (20.3 to 2.3%). These data indicate that the frequently observed relationship between fitness and blood pressure is strongly influenced by age. Future research to specifically examine the effects of physical activity and of physical fitness on blood pressure is needed.

Adolescent↗
PubMed1985

Applications of behavior modification to community health education: the case of heart disease prevention.

Principles of behavior modification increasingly have been applied to community health education and offer considerable promise for public health in general. Behavior modification procedures can be conceptualized in a 2 X 2 framework with desired goals being either to increase and strengthen or decrease and weaken behavior, and procedures producing essentially positive or negative consequences. Modifying specific behavioral risk factors for the prevention of heart disease may include the use of positive reinforcement, shaping, differential reinforcement, negative reinforcement, and "punishment." The use of an adequate "behavior analytic" history, highly acceptable interventions, observable effects, inexpensive materials and procedures, community-owned programs, and other practical guidelines can help optimize the effectiveness of behavior modification for health education in the community.

Behavior Therapy↗
PubMed1984

Circulatory effects of mental stress during exercise in coronary artery disease patients.

We examined the effects of mental stress during steady-state exercise on heart rate, blood pressure, pressure-rate product, and oxygen uptake in 10 coronary artery disease patients. Subjects walked at three mph with grade increases of 4% every two minutes until the target heart rate (60% peak heart rate from a previous symptom-limited exercise test) was reached. A computerized Stroop-Color-Word Test (mental stress) was added one minute after the subject reached steady-state exercise and lasted 11 +/- 4 minutes. When mental stress was added to steady-state exercise it significantly (p less than 0.01) increased the heart rate (101 +/- 15 to 108 +/- 19 beats per min), systolic (154 +/- 26 to 170 +/- 26 mmHg) and diastolic (86 +/- 10 to 92 +/- 13 mmHg) blood pressure, and pressure-rate product (158 +/- 42 to 179 +/- 48 x 10(-2)). This increase in the mean response during exercise and mental stress was not observed for oxygen uptake (17 +/- 6 to 18 +/- 5 ml/kg/min). The circulatory changes probably reflect increased sympathetic activity with both centrally mediated cardioacceleratory (and probably cardiac output) and vasoconstrictor effects during the combination of mental stress and steady-state exercise. The altered hemodynamics without concomitant changes in oxygen uptake has major implications concerning the safety of competitive exercise for people with coronary artery disease.

Adult↗
PubMed1983

Coronary heart disease and human behavior.

Coronary heart disease due to atherosclerosis is prevalent in people whose circulating cholesterol level is high, who smoke, who have elevated blood pressure, and, perhaps, whose fitness is low and/or body weight excessive. Whereas the epidemiologic evidence is relatively strong for each of these health factors (behavioral patterns and their physiological consequences), the evidence from clinical trial interventions is still ambiguous. Each of the health factors relates to personal and societal lifestyle. Each is influenced by individual choice and by the practices of health professionals. The relatively low risks of intervention, viewed in the light of its potentially high benefits, justify the attempt to engender a more healthful lifestyle on a public health scale. The present paper provides guidelines for health professionals and lists corollary recommendations for concerned individuals for each of the five relevant health factors. Application of these prescriptions by health professionals in concert with the individual holds promise for reduced coronary artery disease at the societal level.

Arteriosclerosis↗
PubMed1983

Aprindine therapy for refractory ventricular tachycardia.

Aprindine hydrochloride has been extensively used in Europe for the management of ventricular and supraventricular arrhythmias. Success has been achieved even in those cases that have proven refractory to standard antiarrhythmic agents. In this report, we describe our experience with aprindine therapy in seven patients with ventricular tachycardia in whom standard antiarrhythmic agents had proven either ineffective or had caused intolerable side effects. Aprindine was effective in five cases, and it failed in two. Neurologic side effects, although common, were easily controlled with adjustment of the dose. Agranulocytosis, a rare but serious side effect, was encountered in one of our patients. Relevant literature on aprindine is reviewed.

Agranulocytosis↗
PubMed1982

Incidence of death during jogging in Rhode Island from 1975 through 1980.

In the six years from 1975 through 1980, a total of 12 men died during jogging in the state of Rhode Island. The cause of death in 11 was coronary heart disease (CHD). One man died of an acute gastrointestinal hemorrhage. The prevalence of jogging in the Rhode Island population was determined using a random-digit telephone survey. Among men aged 30 through 64 years, 7.4% +/- 2.6% (mean +/- SEE) reported jogging at least twice a week. The incidence of death during jogging for men of this age group was one death per year for every 7,620 joggers, or approximately one death per 396,000 man-hours of jogging. This rate is seven times the estimated death rate from CHD during more sedentary activities in Rhode Island and suggests that exercise contributes to sudden death in susceptible persons. The occurrence of only one death per 7,620 joggers per year demonstrates that the risk of exercise is small and suggests that the routine exercise testing of healthy subjects before exercise training in not justified.

Adolescent↗
PubMed1982

Assessing VO2max in epidemiologic studies: modification of the Astrand-Rhyming test.

Direct measurement of maximum oxygen uptake (VO2max) is the standard index of cardiorespiratory fitness, but is practical only in a laboratory setting. Current cycle ergometer tests to estimate VO2max are difficult for inactive adults because most of these tests are lengthy and require a high initial exercise rate. We modified an existing test, the Astrand-Rhyming test, to avoid these problems. Maximum oxygen uptake was measured directly and estimated by means of our protocol in a test group of 50 men and women, ten for each decade between 20 and 70 yr, to develop multiple regression equations to correct for variations due to age. Equations for each sex were computed with directly measured VO2max as the dependent variable and with the estimated VO2max and age as independent variables. The validity of these equations was tested by deriving data from an additional 63 subjects (validity group). No significant differences were found between the directly measured VO2max and the VO2max estimated by our protocol and equations. For each group, the mean difference between the two values was less than 120 ml X min-1. Correlations between the measured and estimated VO2max ranged from 0.92-0.93 for the age groups. Our modification of the Astrand-Rhyming protocol accurately estimates VO2max and is safe and suitable for assessing cardiovascular fitness in epidemiologic studies of people between the ages of 20-70 yr.

Adult↗
PubMed1981

Effect of exercise training on the untrained limb exercise performance of men with angina pectoris.

This study examined the exercise capacity of trained and untrained limbs in men with angina pectoris before and after 8 weeks of arm ( n = 4) or leg (n = 7) physical training or a control (n = 4) period. Time to angina (mean +/- standard deviation) increased 3.6 +/- 2.7 minutes (p less than 0.01) during trained limb and 1.6 +/- 1.2 minutes (p less than 0.01) during untrained limb exercise. Myocardial oxygen demand at angina estimated by the product of heart rate and systolic blood pressure did not change with training. At a constant subanginal work load, rate-pressure product x 10(-2) was reduced by 35 +/- 22 (p less than 0.001) during trained limb and by 18 +/- 27 (p less than 0.05) during untrained limb exercise. The decrease in rate-pressure product with both trained and untrained limbs was greatest in subjects with the highest rate-pressure product at angina before training. Control subjects showed no change in any exercise measurement. Exercise training increases the exercise capacity of untrained limbs in patients with angina pectoris by a generalized training effect not dependent on adaptations in trained skeletal muscle. The improvement for both trained and untrained limbs results from a reduced rate-pressure product at subanginal work loads rather than from an increase in myocardial oxygen delivery. Subjects with the highest pretraining coronary arterial oxygen supply at the onset of angina benefit most from physical training.

Angina Pectoris↗
PubMed1980

Atrioventricular sequential pacemakers: indications, complications, and long-term follow-up.

Our experience with 32 patients with atrioventricular (AV) sequential pacemakers and an average follow-up of 22 months is presented. The pertinent literature and physiology are reviewed. The indications, advantages, and complications of AV sequential pacemakers are analyzed. Half of the patients required bifocal pacing for control of arrhythmia alone, while half required control of arrhythmia associated with congestive heart failure due primarily to a noncompliant left ventricle. It is anticipated that the hemodynamic improvement occurring as a results of AV sequential pacing will increase the use of this mode of cardiac pacing in selected patients.

Adult↗