Peter A. Rechnitzer

Age-related changes in speed of walking

Self-paced walking was used as a measure of the neuromuscular slowing observed with aging. The effects of age on the choice of speed of walking, stride length, and step frequency were described for 289 males and 149 females aged 19 to 102 yr. These subjects were asked to walk at three self-selected paces (slow, normal, and fast) over an 80-m indoor course. Sixty-two years coincided with an accelerated decline in speed of walking. Before 62 yr, there was a 1 to 2% per decade decline in normal walking speed. After 63 yr, females showed a 12.4% per decade decrease and males showed a 16.1% per decade decrease. The eldest group (63 yr and older) had a significantly slower speed of walking and smaller step length than the younger groups (19 to 39 and 40 to 62 yr) for all paces. Heart rate at the three paces was not changed across age. In a multiple regression analysis, the only significant independent variable for walking speed at all three paces was (age), which accounted for 19 to 38% of the variance. When the population was divided into two age ranges (19 to 62 and 63 to 102 yr), walking speed was associated with height before 62 yr and with height and age after 62 yr.

Energy cost of treadmill and floor walking at self-selected paces

SummaryOxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19–29 years (n=20) and 55–66 years (n=22), walk at four self-selected paces, from “rather slowly” to “as fast as possible”. A two-variable quadratric model relating VO2 (ml·kg−1·min−1) to velocity (m·s−1) was adopted for prediction purposes. However, age and fatness significantly (p<0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m·s−1, the energy cost for the treadmill (age 55–66 years) was 10.58 ml·kg−1·min−1 and for the floor, 11.04 ml·kg−1·min−1 (p<0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations.

Reasons for dropout from exercise programs in post-coronary patients.

The dropout rate in the 7-yr Ontario Exercise Heart Collaborative Study of post-coronary men engaged in exercise programs was examined in order to determine possible contributing factors. A questionnaire pertaining to psychosocial and program-related variables was distributed to 728 subjects who were previously assigned randomly on the basis of four prognostic risk factors (occupation, personality, hypertension, and angina) into exercise groups: low intensity exercise (LIE), and high intensity exercise (HIE). Comparisons of answers by the 639 respondents (266 dropouts; 373 compliers) were made initially by chi-square analysis to determine significant categories of questions and, subsequently, by a logistic transform to determine the specific questions which related significantly to the dropout rate. It was found that three main categories were associated with a high dropout rate: convenience aspects of the exercise center, perceptions of the exercise program, and family/lifestyle factors. These three main categories should be carefully considered when designing and implementing potential compliance-improving strategies for secondary prevention exercise programs entailing long-term adherence.

Work Patterns Associated with Type A Behavior: A Managerial Population

Managers (236) from 12 different companies were examined for the prevalence of Type A behavior. In addition, a number of work habits and job related variables (work hours per week, travel habits, job satisfaction, job tension factors, salary) were obtained on each respondent. Overall, 61% of the managers were classified as Type As, and between companies the percentage varied between 50 and 76%. Type A behavior was also found to be related to recent company growth rates. On work habits, it was found that that extreme Type A s tend to work more hours per week and travel more days per year. It was also found that the Type A s tend to be less satisfied with their jobs. Using factor analysis, fivejobfactors were isolated and these were entitled Ambiguity, Locked-In, Stagnation, Isolation, and Contentment. Type As were found to be different from Type Bs on the factors Locked-In and Contentment. The Locked-In factor is interpreted as reflecting greater self-confidence among the Type As. The Contentment factor reflected job conditions most likely responsible for eliciting Type A behavior. These included: supervisory responsibility for people, a feeling of competition in work, heavy work loads, and conflicting demands. It was also found that Type As earned higher salaries than Type Bs. The results are combined with those of a previous study on the same group of managers, which measured a number of health variables related to Type A behavior and coronary heart disease. A conceptual model is proposed showing the pathways by which susceptible individuals encounter job conditions which elicit Type A behavior and, consequently, higher coronary risk.

Health patterns associated with type A behavior: a managerial population.

Type A Behavior is a behavioral syndrome found to be related to coronary heart disease and characterized by excessive drive, ambition, and competitiveness. Managers from 12 different companies were examined for this syndrome and for a number of the known risk factors in coronary heart disease (blood pressure, cholesterol, triglycerides, uric acid, smoking, and fitness). Those individuals exhibiting extreme Type A Behavior (Type A) showed significantly higher blood pressure (systolic and diastolic) and higher cholesterol and triglyceride levels. A greater percentage of these individuals were cigarette smokers. On serum uric acid there were no differences. In each age group, Type As were less interested in exercise, although differences in cardio-respiratory fitness were found only in the oldest age group. Type A Behavior also was related to age, education, company growth rates, and stress symptoms. Overall, the Type A1s were found to be higher on a number of risk factors known to be associated with coronary heart disease. With regard to the Type A2s (individuals with less developed Type A Behavior), the findings were not conclusive.

Relation of exercise to the recurrence rate of myocardial infarction in men: Ontario exercise-heart collaborative study

The Ontario Exercise-Heart Collaborative Study was a multicenter randomized clinical trial of high Intensity exercise for the prevention of recurrent myocardial infarction in men. The 4-year recurrence rate among 379 patients on a program of high intensity exercise did not differ significantly from that among 354 control patients on a program of light exercise, despite the greater reduction in heart rate in the former group. The relative odds of recurrence in the high intensity group were 1.09, with 95% confidence limits of 0.61 and 1.96.

Exercise and human collateralization: an angiographic and scintigraphic assessment.

The effect of exercise on the development of intercoronary collaterals and on left ventricular function is controversial. Twenty male patients (mean age 48 years, range 36-54 years) who had suffered an acute myocardial infarction were randomly allocated to an exercise group (10 patients) and a control group (10 patients). Both groups underwent coronary angiography, left ventricular function studies and myocardial perfusion studies with labeled microspheres, before and after the 7-month experimental period. Both groups had similar extent of disease as measured angiographically and both had mild progression of disease. Neither group showed changes in extent of collateralization, myocardial perfusion or left ventricular function. The exercise group had a significant increase in anginal threshold and a significant (p <0.01) decrease in heart rate at a given work load. Exercise, therefore, does not appear to affect progression of disease, myocardial perfusion, extent of collateralization, or left ventricular function in patients with coronary artery disease.

Predictors of dropout from cardiac exercise rehabilitation: Ontario exercise-heart collaborative study*

The Ontario Exercise-Heart Collaborative Study was a multicenter randomized clinical trial of high intensity exercise for the prevention of recurrent myocardial infarction in 733 men. Of the 678 subjects who could have participated for at least 3 years, 315 (46.5%) dropped out. Stepwise multiple linear logistic regression analysis was carried out to examine the relation between subject characteristics and the probability of dropping out during the study. Analysis was performed on the entry group as a whole by considering those subjects who had reinfarction while complying with the program and also by excluding all subjects with reinfarctions. The consistent and statistically significant predictors of dropout in both analyses were smoking and a blue collar occupation. Angina was significantly associated with dropout only when reinfarctions were excluded. It may be important to consider these factors when investigating the potential for compliance-improving strategies in reducing dropout from exercise rehabilitation programs.

Effect of Exercise on Coronary Tree Size in the Rat

Using the vinyl acetate corrosion cast technique devised by Tepperman and Pearlman, it has been demonstrated that, in the rat, forced physical exercise (treadmill or swimming) causes an increase in apparent coronary tree size provided the exercise is not too strenuous or frequent.

Determinants of the training response in elderly men

As part of a prospective randomized trial of the effect of regular exercise in older men, factors determining the magnitude of VO2max increase observed with endurance training were examined in 88 elderly [age 62.9 +/- 3.0 (SD) yr] males. VO2max before and after training was recorded as the highest VO2 observed during two incremental treadmill tests. One year of thrice weekly training sessions increased VO2max (12%, P less than 0.05) in the training group relative to baseline and to a control group (n = 100). The association between the post-training VO2max (VO2max, T2) and the following explanatory variables was assessed using multiple regression analysis: the initial VO2max (VO2max, T1); the reason for stopping the initial treadmill test: leisure time activity during the year previous to the study: the training intensity (speed of walking or running, pulse rate during training, and percentage of heart rate reserve); pulmonary function (forced expiratory volume in 1 s); adiposity (skinfold thickness at 8 sites) and frequency of training. VO2max T1, speed of walking or running during training, reason for stopping the treadmill test, and skinfold thickness were significantly related to post-training VO2max. The intensity and frequency of the training stimulus explained over 10% of the variance in the training effect. Subjects whose test was halted because of fatigue increased VO2max more than those whose test was discontinued for medical or other reasons, even when speed of running was held constant. Previous activity had only a weak effect on training response. The total variance explained by these independent variables was 62%.