Habitual physical activity and glucose tolerance. Males age 16-64 in a total community.

The data being reported are part of an epidemiologic study of health and disease in an entire community, Tecumseh, Michigan. Approximately 1,300 males age 16-65 were classified into three groups on the basis of their habitual leisure and occupational physical activity. A blood sample was drawn one hour after a glucose challenge and analyzed for glucose concentration. A measure of body fatness (sun of four skinfolds) was also available on the men. Glucose concentration of the three physical activity groups was compared by analyses of variance within narrow age group. There was no significant relationship between glucose tolerance and habitual physical activity. There was a slight, but in some age groups significant, relationship between glucose tolerance and body fatness. The population was then divided within each age group into subgroups (thirds) by sum of skinfolds. The analysis was repeated in each age-fatness group. Glucose tolerance was better in the active men but only among the leanest subgroup of subjects.

Variability of some objective measures of physical activity.

The purpose of this study was to determine how many days subjects should be monitored to provide an estimate of habitual physical activity in employed men engaged in a wide range of occupations. Caloric intake, movement recorders (accelerometers and pedometers), and heart rate were the measurements studied in 30 subjects who were monitored during their waking hours for 7 continuous days. A repeated measures ANOVA showed no significant difference between days (P > 0.05) for any of the measures when only weekdays were compared. However, when weekend days were included a majority of the measures showed a significant F-ratio (P < 0.05). An estimate was made of the number of days required to measure a 7-d period with less than 5% error. The average for all the different measures was 4.9 d. It appears that at least 5 or 6 d are needed to minimize the intra-individual variance a reasonable degree. Weekdays as well as weekend days need to be included.

Smoking habits, alcohol consumption and maximal oxygen uptake.

Maximal oxygen uptake (Vo2max) was measured or estimated in 597 males, aged 16-69. Smoking and drinking habits were also determined in this population. After the influences of age, weight, skinfold thickness, and drinking habits were removed, smokers clearly had decreased Vo2max. Similarly, when the relationships were corrected for age, weight, skinfolds and smoking habits, the heaviest drinkers and the non-drinkers had the lowest, Vo2max and the moderate drinkers had the highest Vo2max, at least in the younger age groups. The same results were found when only those subjects in whom Vo2max was measured (essentially subjects under age 40) were included. Levels of habitual physical activity could not account for these differences.

The oxygen requirement for horizontal and grade walking on a motor-driven treadmill.

Oxygen uptake (VO2) was measured in males age 10-59 while they walked at 3 mph at various grades on a motor-driven treadmill. The number of subjects in each age group was as follows: age 10-11, N = 24; age 12-13, N = 46; age 14-15, N = 55; age 16-17, N = 53; age 18-19, N = 30; age 20-24, N = 56; age 25-29, N = 35; age 30-34, N = 32; age 35-39, N = 99; age 40-44, N = 106; age 45-49, N = 78; age 50-54, N = 42; and age 55-59, N = 11. Subjects walked at 3 mph at 0% grade for 3 min; thereafter, the treadmill was raised 3% every third minute with speed maintained. Oxygen uptake was measured continuously but only the values during the last minute at each grade were used in the present analysis. The subjects were in a "steady state," insofar as VO2 was concerned, by the second minute. These data were used to validate formulas for estimating VO2 in horizontal and grade walking published in Guidelines for Graded Exercise Testing and Exercise Prescription (1). The formulas are accurate for estimating the mean oxygen requirement in grade walking from 6-18% in adult males. In horizontal walking and walking at 3% grade, the formulas underestimate VO2 in all age groups. In boys under age 18, the formulas underestimate the energy requirement in walking at all grade levels.

Estimation of energy expenditure by a portable accelerometer.

A small portable accelerometer was developed to estimate the energy expenditure of daily activities. The accelerometer is reported to be an improvement over movement counters currently on the market. The oxygen requirement of 14 different activities was measured in 21 subjects while each wore the accelerometer on the waist. A movement counter (mercury switch), which is available commercially, was also worn on the waist and another was worn on the left wrist. The reproducibility of the accelerometer readings was high (4 subjects, 14 activities; r = 0.94) and was superior to either the waist movement counter (r = 0.63) or the wrist movement counter (r = 0.74). In estimating oxygen requirement (VO2) the standard error of estimate, based on 21 subjects and 14 activities, was 6.6 ml X min-1 X kg-1 for the accelerometer. This was also better (smaller) than for the waist movement counter (9.2 ml X min-1 X kg-1) or for the wrist movement counter (7.9 ml X min-1 X kg-1).

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 exercise to achieve health-related physical fitness components.

To improve health and fitness effectively through physical activity or exercise, we need to understand how this comes about. For many of these changes, the stimulus has been grossly defined in terms of type, intensity, duration, and frequency of exercise, but for others a dose-response relationship has not been determined. Physical activity that appears to provide the most diverse health benefits consists of dynamic, rhythmical contractions of large muscles that transport the body over distance or against gravity at a moderate intensity relative to capacity for extended periods of time during which 200 to 400 kilocalories (or 4 kilocalories per kilogram of body weight) are expended. For optimal health benefits, such activity should be performed daily or at least every other day and should be supplemented with some heavy resistance and flexibility exercises. The greatest benefits are achieved when the least active individuals become moderately active; much less benefit is apparent when the already active individual becomes extremely active. Overexertion or inappropriate exercise can produce significant health risks. Research is needed to characterize better the health-promoting features of physical activity and exercise.

Assessment of physical activity in epidemiologic research: problems and prospects.

More than 30 different methods have been used to assess physical activity. These methods can be grouped into seven major categories: calorimetry, job classification, survey procedures, physiological markers, behavioral observation, mechanical and electronic monitors, and dietary measures. No single instrument fulfills the criteria of being valid, reliable, and practical while not affecting behavior. The instruments that are very precise tend to be impractical on a population basis. Surveys are the most practical approach in large-scale studies, although little is known about their reliability and validity. Studies employing objective monitoring through heart rate, movement sensors, and doubly labeled water procedures appear promising, but are still experimental and costly. Despite the difficulty of measurement, relatively strong association has been found between physical activity and health, suggesting that, with improvements in assessment techniques, even stronger associations should be seen.

Comment on heart rate recording in field studies.

This is a report of our experience using the Uniq Heart Watch for recording the heart rate in epidemiologic settings. Relatively few heart rates are missed during occupational and leisure activities. However the mean daily heart rate among subjects is somewhat variable so that several week days and Saturday and Sunday should be monitored to obtain a representative daily average.

The validity of a portable accelerometer for estimating energy expenditure in bicycle riding.

The purpose of the investigation was to determine the validity of a portable vertical accelerometer and a Large-Scale Integrated Motor Activity Monitor (LSI) for estimating energy expenditure in riding a bicycle at various velocities. Instrument placement was either at the knee or ankle. Energy consumption, i.e. oxygen consumption (VO2) was determined during bicycle rides after steady state metabolism was reached. Standard errors of estimate were used to express the accuracy of estimating VO2 from accelerometer or LSI recordings. The reliability of the vertical accelerometer was found to be satisfactory. The vertical accelerometer was also effective for estimating VO2 in bicycling (standard errors of estimate = 3.3 to 4.4 ml.kg-1.min-1). The accuracy of the LSI was not as good; the standard errors of estimate being = 5.9 to 8.5 ml.kg-1.min-1.

The Longevity and Morbidity of College Athletes.

This well-designed study does not prove that athletic participation affects longevity and morbidity. Perhaps the same study of highly trained athletes would produce different results.