Ralph S. Paffenbarger

Compendium of physical activities: classification of energy costs of human physical activities.

A coding scheme is presented for classifying physical activity by rate of energy expenditure, i.e., by intensity. Energy cost was established by a review of published and unpublished data. This coding scheme employs five digits that classify activity by purpose (i.e., sports, occupation, self-care), the specific type of activity, and its intensity as the ratio of work metabolic rate to resting metabolic rate (METs). Energy expenditure in kilocalories or kilocalories per kilogram body weight can be estimated for all activities, specific activities, or activity types. General use of this coding system would enhance the comparability of results across studies using self reports of physical activity.

Physical Activity and Reduced Occurrence of Non-Insulin-Dependent Diabetes Mellitus

BACKGROUND Physical activity is recommended by physicians to patients with non-insulin-dependent diabetes mellitus (NIDDM), because it increases sensitivity to insulin. Whether physical activity is effective in preventing this disease is not known. METHODS We used questionnaires to examine patterns of physical activity and other personal characteristics in relation to the subsequent development of NIDDM in 5990 male alumni of the University of Pennsylvania. The disease developed in a total of 202 men during 98,524 man-years of follow-up from 1962 to 1976. RESULTS Leisure-time physical activity, expressed in kilocalories expended per week in walking, stair climbing, and sports, was inversely related to the development of NIDDM: The incidence rates declined as energy expenditure increased from less than 500 kcal to 3500 kcal. For each 500-kcal increment in energy expenditure, the age-adjusted risk of NIDDM was reduced by 6 percent (relative risk, 0.94; 95 percent confidence interval, 0.90 to 0.98). This association remained the same when the data were adjusted for obesity, hypertension, and a parental history of diabetes. The association was weaker when we considered weight gain between the time of college attendance and 1962 (relative risk, 0.95; 95 percent confidence interval, 0.90 to 1.00). The protective effect of physical activity was strongest in persons at highest risk for NIDDM, defined as those with a high body-mass index, a history of hypertension, or a parental history of diabetes. These factors, in addition to weight gain since college, were also independent predictors of the disease. CONCLUSIONS Increased physical activity is effective in preventing NIDDM, and the protective benefit is especially pronounced in persons at the highest risk for the disease.

Physical Activity, All-Cause Mortality, and Longevity of College Alumni

We examined the physical activity and other life-style characteristics of 16,936 Harvard alumni, aged 35 to 74, for relations to rates of mortality from all causes and for influences on length of life. A total of 1413 alumni died during 12 to 16 years of follow-up (1962 to 1978). Exercise reported as walking, stair climbing, and sports play related inversely to total mortality, primarily to death due to cardiovascular or respiratory causes. Death rates declined steadily as energy expended on such activity increased from less than 500 to 3500 kcal per week, beyond which rates increased slightly. Rates were one quarter to one third lower among alumni expending 2000 or more kcal during exercise per week than among less active men. With or without consideration of hypertension, cigarette smoking, extremes or gains in body weight, or early parental death, alumni mortality rates were significantly lower among the physically active. Relative risks of death for individuals were highest among cigarette smokers and men with hypertension, and attributable risks in the community were highest among smokers and sedentary men. By the age of 80, the amount of additional life attributable to adequate exercise, as compared with sedentariness, was one to more than two years.

The Association of Changes in Physical-Activity Level and Other Lifestyle Characteristics with Mortality among Men

BACKGROUND Recent trends toward increasing physical exercise, stopping cigarette smoking, and avoiding obesity may increase longevity. We analyzed changes in the lifestyles of Harvard College alumni and the associations of these changes with mortality. METHODS Men who were 45 to 84 years of age in 1977 and who had reported no life-threatening disease on questionnaires completed in 1962 or 1966 and again in 1977 were classified according to changes in lifestyle characteristics between the first and second questionnaires. We analyzed changes in their level of physical activity, cigarette smoking, blood pressure, and body weight, and the relation of these factors to mortality between 1977 and 1985. RESULTS Of the 10,269 men, 476 died during this period (which totaled 90,650 man-years of observation). Beginning moderately vigorous sports activity (at an intensity of 4.5 or more metabolic equivalents) was associated with a 23 percent lower risk of death (95 percent confidence interval, 4 to 42 percent; P = 0.015) than not taking up moderately vigorous sports. Quitting cigarette smoking was associated with a 41 percent lower risk (95 percent confidence interval, 20 to 57 percent; P = 0.001) than continuing smoking, but with a 23 percent higher risk than constant nonsmoking. Men with recently diagnosed hypertension had a lower risk of death than those with long-term hypertension (relative risk, 0.75; 95 percent confidence interval, 0.55 to 1.02; P = 0.057), as did men with consistently normal blood pressure (relative risk, 0.52; 95 percent confidence interval, 0.40 to 0.68; P < 0.001). Maintenance of lean body mass was associated with a lower mortality rate than long-term, recent, or previous obesity. The associations between changes in lifestyle and mortality were independent and were largely undiminished by age. Our findings on death from coronary heart disease mirrored those on death from all causes. CONCLUSIONS Beginning moderately vigorous sports activity, quitting cigarette smoking, maintaining normal blood pressure, and avoiding obesity were separately associated with lower rates of death from all causes and from coronary heart disease among middle-aged and older men.

Influences of cardiorespiratory fitness and other precursors on cardiovascular disease and all-cause mortality in men and women

OBJECTIVE To quantify the relation of cardiorespiratory fitness to cardiovascular disease (CVD) mortality and to all-cause mortality within strata of other personal characteristics that predispose to early mortality. DESIGN--Observational cohort study. We calculated CVD and all-cause death rates for low (least fit 20%), moderate (next 40%), and high (most fit 40%) fitness categories by strata of smoking habit, cholesterol level, blood pressure, and health status. SETTING Preventive medicine clinic. STUDY PARTICIPANTS Participants were 25341 men and 7080 women who completed preventive medical examinations, including a maximal exercise test. MAIN OUTCOME MEASURES Cardiovascular disease and all-cause mortality. RESULTS There were 601 deaths during 211996 man-years of follow-up, and 89 deaths during 52982 woman-years of follow-up. Independent predictors of mortality among men, with adjusted relative risks (RRs) and 95% confidence intervals (CIs), were low fitness (RR, 1.52;95% CI, 1.28-1.82), smoking (RR, 1.65; 95% CI, 1.39-1.97), abnormal electrocardiogram (RR, 1.64;95% CI, 1.34-2.01), chronic illness (RR, 1.63;95% CI, 1.37-1.95), increased cholesterol level (RR, 1.34; 95% CI, 1.13-1.59), and elevated systolic blood pressure (RR, 1.34; 95% CI, 1.13-1.59). The only statistically significant independent predictors of mortality in women were low fitness (RR, 2.10; 95% Cl, 1.36-3.21) and smoking (RR, 1.99; 95% Cl, 1.25-3.17). Inverse gradients were seen for mortality across fitness categories within strata of other mortality predictors for both sexes. Fit persons with any combination of smoking, elevated blood pressure, or elevated cholesterol level had lower adjusted death rates than low-fit persons with none of these characteristics. CONCLUSIONS Low fitness is an important precursor of mortality. The protective effect of fitness held for smokers and nonsmokers, those with and without elevated cholesterol levels or elevated blood pressure, and unhealthy and healthy persons. Moderate fitness seems to protect against the influence of these other predictors on mortality. Physicians should encourage sedentary patients to become physically active and thereby reduce the risk of premature mortality.

Physical Activity and Coronary Heart Disease in Men The Harvard Alumni Health Study

BackgroundThe quantity and intensity of physical activity required for the primary prevention of coronary heart disease (CHD) remain unclear. Therefore, we examined the association of the quantity and intensity of physical activity with CHD risk and the impact of other coronary risk factors. Methods and ResultsWe followed 12 516 middle-aged and older men (mean age 57.7 years, range 39 to 88 years) from 1977 through 1993. Physical activity was assessed at baseline in kilojoules per week (4.2 kJ=1 kcal) from blocks walked, flights climbed, and participation in sports or recreational activities. During follow-up, 2135 cases of incident CHD, including myocardial infarction, angina pectoris, revascularization, and coronary death, occurred. Compared with men expending <2100 kJ/wk, men expending 2100 to 4199, 4200 to 8399, 8400 to 12 599, and ≥12 600 kJ/wk had multivariate relative risks of 0.90, 0.81, 0.80, and 0.81, respectively (P for trend=0.003). When we considered the independent effects of specific physical activity components, only total sports or recreational activities (P for trend=0.042) and vigorous activities (P for trend=0.02) were inversely associated with the risk of CHD. These associations did not differ within subgroups of men defined by coronary risk factors. Finally, among men with multiple coronary risk factors, those expending ≥4200 kJ/wk had reduced CHD risk compared with men expending <4200 kJ/wk. ConclusionsTotal physical activity and vigorous activities showed the strongest reductions in CHD risk. Moderate and light activities, which may be less precisely measured, showed nonsignificant inverse associations. The association between physical activity and a reduced risk of CHD also extends to men with multiple coronary risk factors.

Measurement of physical activity to assess health effects in free-living populations.

For physical activity surveys that would identify relations to chronic diseases, quality of life, and longevity, the method of choice remains the questionnaire, especially if it can be standardized and administered in uniform fashion to large populations. A sample questionnaire derived largely from epidemiological experience with the Harvard Alumni Health Study is presented that requests anthropometric estimates; physician-diagnosed diseases by year of onset; contemporary physical activities including walking, stair-climbing, and recreational pursuits; food-frequency data that estimate nutrient values and caloric intakes; and social habits affecting health. The questionnaire presents opportunities for cross-sectional, retrospective, and prospective studies. Personal characteristics, physical activities, and other elements of lifestyle may be used as predictor or outcome variables in testing specific hypotheses. Representative surveys are described that have validated and used questionnaires of various complexities, some complemented by measures of physiological fitness. The epidemiological survey questionnaire, when properly designed and administered, can measure effectively energy intake, energy retention, energy expenditure, physiological fitness, quality of life, and health maintenance.

Relative Intensity of Physical Activity and Risk of Coronary Heart Disease

Background—Current recommendations prescribe at least moderate-intensity physical activity, requiring ≥3 METs (metabolic equivalents) for ≥30 minutes almost daily, generating ≈1000 kcal/wk. Defining intensity using an absolute scale in METs may be limited because it neglects variations in physical fitness: an activity requiring a particular MET value commands greater physical effort among less fit than more fit persons. It is unknown whether moderate-intensity exercise, relative to an individual’s capacity, is associated with reduced coronary heart disease (CHD) rates. Methods and Results—We followed 7337 men (mean age, 66 years) from 1988 to 1995. At baseline, men reported their actual activities and, using the Borg Scale, the perceived level of exertion when exercising (relative intensity). During follow-up, 551 men developed CHD. After multivariate adjustment, the relative risks of CHD among men who perceived their exercise exertion as “moderate,” “somewhat strong,” and “strong” or more intense were 0.86 (95% confidence interval, 0.66 to 1.13), 0.69 (0.51 to 0.94), and 0.72 (0.52 to 1.00), respectively (Ptrend=0.02), compared with “weak” or less intense. This inverse association extended to men not fulfilling current recommendations, ie, expending <1000 kcal/wk in physical activity or not engaging in activities of ≥3 METs (Ptrend=0.03 and 0.007, respectively). Conclusions—There is an inverse association between relative intensity of physical activity (an individual’s perceived level of exertion) and risk of CHD, even among men not satisfying current activity recommendations. Recommendations for “moderate”-intensity physical activity may need to consider individual fitness levels instead of globally prescribing activities of ≥3 METs.

Accuracy of the college alumnus physical activity questionnaire

The validity and reproducibility of the Physical Activity Index from the College Alumnus Questionnaire (PAI-CAQ) were determined in 78 men and women (21-59 yr) with a broad range of physical activity habits. The PAI-CAQ was computed as the sum of energy expended in stair climbing, walking, and sports and recreational physical activity recalled from the past week. Data were validated against measures of cardiorespiratory fitness, body fatness, motion detection, and physical activity records. All physical activity was recorded by participants for six 48-hour periods. Each day of the week, including weekends, were represented at least twice in the physical activity records. Age-adjusted correlation coefficients between like activities on the College Alumnus Questionnaire and physical activity records ranged from 0.25 to 0.65 in men and 0.28 to 0.86 in women. Correlations between the PAI-CAQ and validation criteria that reflected total and heavy-intensity physical activities were higher (r = 0.34-0.69, p < 0.05) than for lighter-intensity physical activities and motion detection expressed in MET-min.d-1 and kcal.d-1 (r < 0.35, p > 0.05). Test-retest reproducibility was higher over 1 month (r = 0.72) than over 8 and 9 months (r = 0.34 and 0.43) (p < 0.05). Energy expended in walking and stair climbing was underestimated on the College Alumnus Questionnaire, resulting in lower PAI-CAQ scores, as compared to the physical activity records.

Physical Activity and Coronary Heart Disease Risk in Men Does the Duration of Exercise Episodes Predict Risk

BackgroundPhysical activity is associated with a decreased risk of coronary heart disease (CHD). However, it is unclear whether the duration of exercise episodes is important: Are accumulated shorter sessions as predictive of decreased risk as longer sessions if the same amount of energy is expended? Methods and ResultsIn the Harvard Alumni Health Study, we prospectively followed 7307 Harvard University alumni (mean age 66.1 years) from 1988 through 1993. At baseline, men reported their walking, stair climbing, and participation in sports or recreational activities. For each of the latter activities, they also reported the frequency and average duration per episode. During follow-up, 482 men developed CHD. In age-adjusted analysis, a longer duration of exercise episodes predicted lower CHD risk (P trend=0.04). However, after total energy expended on physical activity and potential confounders was accounted for, duration no longer had an independent effect on CHD risk (P trend=0.25); that is, longer sessions of exercise did not have a different effect on risk compared with shorter sessions, as long as the total energy expended was similar. In contrast, higher levels of total energy expenditure significantly predicted decreased CHD risk in both age-adjusted (P trend=0.009) and multivariate (P trend=0.046) analyses. ConclusionsThese data clearly indicate that physical activity is associated with decreased CHD risk. Furthermore, they lend some support to recent recommendations that allow for the accumulation of shorter sessions of physical activity, as opposed to requiring 1 longer, continuous session of exercise. This may provide some impetus for those sedentary to become more active.