Physical activity patterns among adults in Georgia: results from the 1990 Behavioral Risk Factor Surveillance System

Cardiovascular factors explain genetic background differences in VO2max

The purpose of this study was to further explore factors that may be related to ethnic differences in the maximum rate at which an individual can consume oxygen (VO2max) between 20 African American (AA) and 30 European American (EA) sedentary women who were matched for body weight (kg) and fat-free mass (FFM). VO2max (l/min) was determined during a graded treadmill exercise test. Submaximal steady-state heart rate and submaximal VO2 were determined at a treadmill speed of 1.3 m/sec and a 2.5% grade. Hemoglobin (Hb) was determined by the cyanide method, muscle oxidative capacity by 31P magnetic resonance spectroscopy (ADP time constant), and FFM (kg) by dual-energy x-ray absorptiometry. Genetic classification was self-reported, and in a subset of the sample (N = 32), the determinants of ethnicity were measured by African genetic admixture. AA women had significantly reduced VO2max, Hb levels, and muscle oxidative capacity (longer ADP time constants, P < or = 0.05) than EA women. Submaximal oxygen pulse (O2Psubmax), ADP time constant, Hb, and ethnic background were all significantly related to VO2max (ml/kg/min and ml/kg FFM/min, all P < or = 0.01). By multiple regression modeling, Hb, O2Psubmax, muscle oxidative capacity, and ethnicity were found to explain 61% and 57% of the variance of VO2max in ml/kg/min and ml/kg FFM/min, respectively. Muscle oxidative capacity and O2Psubmax were both significantly and independently related to VO2max in all three models (P < or = 0.05), whereas Hb and ethnicity were not. These results suggest that mitochondrial muscle oxidative capacity and oxygen delivery capabilities, as determined by O2Psubmax, account for most if not all of the ethnic differences in VO2max.

Resources for physical activity participation: does availability and accessibility differ by neighborhood socioeconomic status?

The purpose of this study was to determine whether the availability and accessibility of physical activity resources differed by neighborhood socioeconomic status (SES) in a small U.S. city (population = 133,046). U.S. census tracts (N =32) were used to represent neighborhoods and categorized into high, medium, or low SES on the basis of the percentage of unemployed individuals, per capita income, and percentage of the population below the poverty threshold. We developed a geographic information system to generate a comprehensive list of physical activity resources available within each census tract in the city. We identified 112 parks, 33 sport facilities, 15 fitness clubs, 11 community centers, and 5 walking/biking trails. The total number of physical activity resources varied by neighborhood SES (p <.05); low-SES (M =4.5-/+2.3) and medium-SES (M =4.9-/+2.6) neighborhoods had significantly fewer resources than high-SES (M =8.4-/+3.5) neighborhoods. Low-, medium-, and high-SES neighborhoods did not differ on the number of pay-for-use facilities; however, low-SES (M =3.1-/+1.5) and medium-SES (M =3.8-/+1.6) neighborhoods had significantly fewer free-for-use resources than high- (M =6.1-/+2.4) SES neighborhoods (p <.01). Data suggest that individuals from lower SES neighborhoods may have limited ability to control their physical activity in the face of inaccessible environments. Community research and promotion efforts should include assessment and targeting of available and accessible physical activity resources.

Participants' evaluation of a weight-loss program

OBJECTIVE

The purpose of this study was to evaluate participants' perceptions of the weight-loss intervention used in a hypertension prevention clinical trial.

DESIGN

A total of 308 overweight and moderately obese subjects participated in the weight-management intervention. After the 18-month program, 281 participants completed a questionnaire designed to evaluate their perceptions of the program's effectiveness.

SUBJECTS/SETTING

Adult participants (224 men and 84 women) in the weight-loss modality of the Trials of Hypertension Prevention Phase I, surveyed in 1991.

STATISTICAL ANALYSES PERFORMED

chi 2 Analyses were used to test for statistical significance of group differences.

RESULTS

Intervention components that were most useful are presented. Older participants (older than 50 years) were most likely to attend sessions and women were most likely to identify stress and frustration because of disappointing results. Successful participants were more likely to incorporate exercise into their daily activities, exercise regularly, and use self-monitoring strategies. Few participants found group exercise to be useful.

CONCLUSION

These findings suggest that interventionists in weight-loss programs need to find flexible and creative ways to maintain contact with participants, continue to develop better methods of self-monitoring, obtain the skills needed to recognize frustration and provide timely support, continue to couple the message of diet and exercise, and emphasize helping participants develop their problem-solving skills. This may require training outside the traditional field of dietetics.

What is the optimal type of physical activity to enhance health?

This review examines the potential of active daily living as a means of gaining the cardiovascular and health rewards previously sought through vigorous aerobic fitness programmes. Cross-sectional studies of occupational and leisure activity show encouraging associations between such activity and good health; in workers, the gross intensity of effort needed for health benefits has seemed to be 20 kJ/min. There has been less unanimity on the threshold intensity needed in leisure activities, but various recent "position statements" have decreased the recommendation to 50% of an individual's maximal oxygen intake, sustained for one hour three to five times per week. Life-style activities such as walking seem likely to reach this intensity in older individuals, but are unlikely to do so in young adults. A growing number of controlled longitudinal studies of walking programmes have demonstrated gains in aerobic fitness, modest reductions in blood pressure, improvements in lipid profile, increased bone density, and enhanced mood state, with less consistent reductions of body fat. However, gains have been greatest in the elderly, sedentary, and obese populations. The main component of active living, fast walking, seems likely to enhance health in such populations, but it is unlikely to be effective in young adults who are in good initial health.