BMI-referenced cut points for pedometer-determined steps per day in adults

BACKGROUND

The goal of this study was to establish preliminary criterion-referenced cut points for adult pedometer-determined physical activity (PA) related to weight status defined by body mass index (BMI).

METHODS

Researchers contributed directly measured BMI and pedometer data that had been collected (1) using a Yamax-manufactured pedometer, (2) for a minimum of 3 days, (3) on ostensibly healthy adults. The contrasting groups method was used to identify age- and gender-specific cut points for steps/d related to BMI cut points for normal weight and overweight/obesity (defined as BMI <25 and >or=25 kg/m2, respectively).

RESULTS

Data included 3127 individuals age 18 to 94 years (976 men, age = 46.8 +/- 15.4 years, BMI = 27.3 +/- 4.9; 2151 women, age = 47.4 +/- 14.9 years, BMI = 27.6 +/- 6.4; all gender differences NS). Best estimated cut points for normal versus overweight/obesity ranged from 11,000 to 12,000 steps/d for men and 8000 to 12,000 steps/d for women (consistently higher for younger age groups).

CONCLUSIONS

These steps/d cut points can be used to identify individuals at risk, or the proportion of adults achieving or falling short of set cut points can be reported and compared between populations. Cut points can also be used to set intervention goals, and they can be referred to when evaluating program impact, as well as environmental and policy changes.

Cross-sectional comparison of physical activity and inactivity patterns in Chinese and Filipino youth

BACKGROUND

To compare and contrast youth physical activity (PA) and inactivity patterns in two developing Asian countries: the Philippines and China.

METHODS

Comparative analysis of 1997-1999 Cebu Longitudinal Health and Nutrition Survey and the 1997 China Health and Nutrition Survey, large-scale surveys that included questions on type, frequency and duration of: commuting mode to school, sports/exercise in and outside of school, select sedentary activities and chores.

RESULTS

Filipino data included 760 males and 872 females aged 14-16 years. The comparable Chinese sample consisted of 202 males and 197 females. Active commuting is proportionately high in both countries (70-71% in the Philippines vs. 77-90% in China), although commuting by bicycling is rare in the Philippines (<1%) vs. China ( approximately 35%). Patterns of school sport/exercise participation differ between countries by gender; more Filipino males report school sport/exercise than females (63 vs. 49%) vs. China, where more females participate than males (75 vs. 69%). Sport/exercise outside of school is proportionately low (6-12%) for youth from both countries with a single exception: 74% of Filipino males participate in extra-curricular sport/exercise. Although a higher percentage of Filipino youth report watching television >4 h/day (<10%) vs. Chinese youth (<1%), both are lower than comparable US reports.

CONCLUSION

In the Philippines, continued modernization augurs a decrease in local primary PA sources (chores and active commuting). In China, where youth already are not expected to perform chores, shifts to more passive commuting modes (i.e. increased motorized transportation) are anticipated.

Health-related quality of life, BMI and physical activity among US adults (⩾18 years): National Physical Activity and Weight Loss Survey, 2002

OBJECTIVE

To examine the association between health-related quality of life (HRQOL) and physical activity (PA).

METHODS

Cross-sectional data were obtained via a national telephone survey from 9173 respondents (30.9% response rate; 51.4% cooperation rate). Four indicators of HRQOL were measured: self-rated health, physically unhealthy days, mentally unhealthy days and activity limitation days. Prevalence estimates were calculated by body mass index (BMI) category and PA level. Logistic regression evaluated BMI as an effect modifier of the relationship between HRQOL and PA.

RESULTS

Inactive adults reported more fair to poor HRQOL than active adults, regardless of BMI category (P<0.001). BMI did not modify the association between PA and any of the four HRQOL indicators.

CONCLUSION

Prevalence of low HRQOL is inversely related to PA participation, and the relationship is not altered by BMI status. Regardless of their weight status, adults should be encouraged to engage in PA.

How many days of pedometer monitoring predict weekly physical activity in adults?

BACKGROUND

The study purpose was to establish the number (and type) of days needed to estimate mean pedometer-determined steps/day in a field setting.

METHODS

Seven days of data were collected from 90 participants (33 males, age = 49.1 +/- 16.2 years, BMI = 27.2 +/- 4.1 kg/m(2); 57 females, age = 44.8 +/- 16.9 years, BMI = 27.0 +/- 5.9 kg/m(2)). Mean steps/day were computed for all 7 days (the criterion), each single day, and combinations of days. Analyses included repeated measures ANOVA, intra-class correlations (ICC), and regression.

RESULTS

There was a significant difference (P < 0.001) between days. The difference was limited to Sunday and accounted for 5% of the variance. ICC analyses indicated a minimum of 3 days is necessary to achieve a reliability of 0.80. The adjusted R(2) was 0.79 for a single day (specifically Wednesday), 0.89 for 2 days (Wednesday, Thursday), and 0.94 for 3 days (Wednesday, Thursday, Friday). Sunday was the last day to enter the model.

CONCLUSIONS

Although there is a statistical difference between days, there is little practical difference, and the primary distinction appears limited to Sunday. Although a single day of collection is not acceptable, any 3 days can provide a sufficient estimate.

Physical activity and inactivity in Chinese school-aged youth: the China Health and Nutrition Survey

OBJECTIVE

To describe physical activity (PA) and inactivity levels and patterns in Chinese school children (aged 6-18 y).

DESIGN

PA and inactivity were assessed in a youth cohort enrolled in the China Health and Nutrition Survey (CHNS) in 1997.

SUBJECTS

A total of 1423 males (11.5+/-3.2 y) and 1252 females (11.5+/-3.3 y).

MEASUREMENTS

PA and inactivity were assessed by self-reported usual activity (questionnaire). Children under 10 y were assisted by parents.

RESULTS

Approximately 84% of Chinese youth actively commute to school for a median of 100-150 min/week. A total of 72% engage in in-school moderate/vigorous (MOD/VIG) PA for a median of 90-110 min/week. Relatively few children ( approximately 8%) participate in any MOD/VIG PA outside of school. A total of 72% engage in study-related activities outside of school for a median of 420 min/week. Only 8% of Chinese school children, regardless of gender, watch television > or =2 h/day; less than 1% watch > or =4 h/day. Chores related to housework are not a part of life for Chinese school children; fewer than 20% performed these tasks.

CONCLUSION

Chinese youth are unique compared to those in other developing countries because they do not perform household chores. Instead, they are under pressure to achieve scholastically. Participation in MOD/VIG PA outside of school is almost nonexistent. Current television watching habits are relatively low compared to developed countries and walking/biking is a common form of commuting. The descriptive analysis herein represents the foundation upon which future longitudinal studies of PA in this population will be based.

Physical activity in Filipino youth: the Cebu Longitudinal Health and Nutrition Survey

OBJECTIVE

To describe physical activity (PA) and inactivity levels of Filipino youth aged 14-16 y.

DESIGN

PA type and patterns were assessed in an adolescent cohort enrolled in the Cebu Longitudinal Health and Nutrition Survey.

SUBJECTS

A total of 1053 males (aged 15.6+/-0.5 y; body mass index (BMI)=18.6+/-2.6 kg/m(2)) and 990 females (aged 14.6+/-0.5 y; BMI=18.8+/-2.4 kg/m(2)).

MEASUREMENTS

PA was assessed by (1) self-reported usual PA (questionnaire); (2) 24-h objective monitoring (Caltrac accelerometer); and (3) 24 h recalls of PA during the objectively monitored time frame.

RESULTS

As measured by Caltrac, males expended 378.0+/-164.5 kcal and females 271.0+/-105.4 kcal. The measurement approaches employed agreed in expected ways, given the limitations of each. Together the approaches used indicated that the primary sources of PA for this population are chores and active commuting. In all, 40% of the sample walked to school, less than 1% rode a bicycle, 22% rode in/on motorized transport, and 37% used some combination of walking and motorized transport. Further, gender differences exist for type, frequency, and duration of physical activities performed by Filipino youth. Specifically, females report engaging in few leisure-time physical activities and more household chores. In total, 48% of Filipino youth report watching > or =2 h/day of television; relatively few youth (7%) report watching >4 h/day at this time. An 18% of males report no vigorous activities compared to 87% of females.

CONCLUSION

Clear gender differences in PA patterns and levels exist in Filipino adolescents. Nonsport/exercise type activities (eg chores and active commuting) currently provide a large proportion of daily activity for both males and females, however. It is anticipated that as modernization and technological advancement continue in this developing country, these primary sources of PA will decrease.

Omission of active commuting to school and the prevalence of children's health-related physical activity levels: the Russian Longitudinal Monitoring Study

BACKGROUND

Active commuting to school by walking or bicycle is a potential source of continuous moderate activity for children that has been largely ignored in surveys of physical activity. The purpose of this study was to evaluate the analytical impact of omitting active commuting to school (walking or bicycling) on conclusions about children's physical activity levels.

METHODS

The Russian Longitudinal Monitoring Study (RLMS) is the first nationally representative household survey in the Russian Federation. More than 6400 households from all regions of Russia were surveyed eight times between 1992 and 1998. Analysis was conducted using physical activity data (school physical education classes, out-of-school active pursuits and active commuting to school) obtained by parent-proxy on 1094 (572 boys, 522 girls) school-aged Russian children (mean age 10.2 +/- 1.9 years) participating in the November 1998 round of the RLMS. Data were examined according to prevalence of achievement of health-related physical activity guidelines, active commuting to school behaviours included then omitted.

RESULTS

Omitting active commuting to school resulted in a statistically significant decrease in the prevalence of achievement of health-related guidelines from 12% to 20%, similar for both genders. Likewise, the prevalence of sedentarism (defined as not meeting any of the guidelines) was increased by 17-22%.

CONCLUSIONS

The present findings suggest that, in order to avoid misclassification bias of children's physical activity levels, it is necessary to include questions about mode of commuting to school. The findings also carry practice implications: the commonplace need to get to and from school may be a missed opportunity for children's health-related physical activity in motorized societies.

The association between joint stress from physical activity and self-reported osteoarthritis: an analysis of the Cooper Clinic data

OBJECTIVE

The purpose was to evaluate the association between estimated joint stress from physical activity (PA) and hip/knee osteoarthritis (OA).

DESIGN

A nested case-control study was performed using data from the Aerobics Center Longitudinal Study. Participants without self-reported OA at baseline who attended the clinic between 1974 and 1993 and returned a follow-up questionnaire in 1990 or 1995 were eligible. Cases were those who reported a physician diagnosis of OA of the knee and/or hip at follow-up (N = 415). A random sample of persons in the remaining cohort were classified as controls (N = 1995). PA was measured at baseline by self-report and subjects were classified as 'moderate/high' or 'low' joint stress by PA type. Those reporting no PA were classified as sedentary with 'no' joint stress (the reference group). Men and women were analyzed separately. Stratified analysis and multiple logistic regression were used to assess the relationship between hip/knee OA and joint stress as predicted by PA.

RESULTS

After adjustment for age, body mass index, years of follow-up, and history of hip/knee joint injury, among men, there was no association between hip/knee OA and low joint stress while moderate/high joint stress was associated with reduced risk of hip/knee OA (adjusted odds ratio (OR) = 0.62, 95% confidence interval (CI) = 0.43-0.89). Among women, both levels of joint stress were associated with reduced risk of hip/knee OA (OR = 0.58, 95% CI = 0.34-0.99 for low and OR=0.24, 95% CI = 0.11-0.52 for moderate/high).

CONCLUSIONS

PA may reduce the risk of hip/knee OA, especially among women. Further research should assess the combined effects of frequency, intensity, duration and joint stress level of PA on incidence of hip/knee OA.

Agreement between participant-rated and compendium-coded intensity of daily activities in a triethnic sample of women ages 40 years and older

Participant-rated and compendium-coded intensity of daily physical activities were compared in 148 African American, 144 Native American, 51 non-Hispanic White women ages 40 to 91 years who completed 4 days of activity records. For compendium-coded intensity, reported activities were classified as light (< 3 metabolic equivalents [METS]), moderate (3-6 METS), or vigorous (> 6 METS) using the Compendium of Physical Activities (1), whereas these categories were self-assigned for participant-rated intensity. Minutes per day (min/d) spent in activities at each intensity level were computed. Relative to compendium-coded min/d, participants reported significantly greater time spent in light (+10 min/d; p < .01) and vigorous (+17 min/d; p < .001) activities, and less time spent in moderate activities (-27 min/d; p <.001). Similarly, compendium-coded estimates yielded higher rates ofparticipants meeting Centersfor Disease Control and Prevention-American College of Sports Medicine and Surgeon General recommendations than participant-rated estimates (11-18% differences) but substantially lower rates meeting American College of Sports Medicine vigorous recommendations (22% difference). Further, 247 greater kilocalories per day were estimated based on compendium-coded intensity. Kilocalories per day estimates based on compendium codings were more highly associated with pedometer counts than those based on participant ratings (p < .05). Studypatterns were generally seen across all sample subgroups. Discrepancies between participant and compendium estimates are likely to be most meaningful in studies estimating energy expenditure as it relates to health outcomes and in studies estimating vigorous activities.

Behavioral and demographic correlates of diabetes, hypertension and overweight among the Catawba Indian Nation

OBJECTIVE

In 1998, the Catawba Diabetes and Health Survey (CDHS) was conducted among adult members of the Catawba Indian Nation living in the Carolinas to determine the prevalence of diabetes and other health conditions, and to assess the population's health-related behaviors.

DESIGN

A population-based sample of adult members of the Catawba Indian Nation (N = 633) were surveyed by telephone or in person regarding health status and health-related behaviors. Logistic regression was used to determine demographic and behavioral correlates of diabetes, hypertension, and overweight among the Catawba.

RESULTS

Age-adjusted prevalence rates of self-reported diabetes, hypertension and overweight were 12.3%, 29.1%, and 63.8%, respectively. Older age was related to diabetes, hypertension, and overweight (P<.0001 each), and heavier weight status was related to diabetes (P = .026) and hypertension (P<.0001). Nearly 40% of the Catawba are physically inactive (29.5% men, 46.5% women). Physical inactivity was related to diabetes and hypertension among men only, and related to overweight among women only (P<.05 each). Current smoking was inversely related to overweight among men and women (P = .002). Dietary behavior was not associated with the health outcomes.

CONCLUSION

Given the high rates of overweight and physical inactivity, reducing the rates of both may be very important for the health of the Catawba, considering their association with diabetes and hypertension.

Limitations on the use of a single screening question to measure sedentary behavior

OBJECTIVES

This study explored the limitations of identifying sedentary individuals via an existing screening question in a state-based surveillance system.

METHODS

A national sample (n = 7529) of adults, selected by random-digit dialing between November 1999 and May 2000, responded about participation in leisure-time physical activity.

RESULTS

Of those who initially reported no leisure-time physical activity (25%), 85% were engaging in at least some activity, and 20% were engaging in enough moderate- or vigorous-intensity activity to meet health-related recommendations.

CONCLUSIONS

Public health programs that use only 1 screening question to identify sedentary behavior may not be able to target physical activity messages effectively, especially if physical activity is defined to include a broad range of activities beyond sports.

The relationship between pedometer-determined ambulatory activity and body composition variables

OBJECTIVE

To examine the relationship between pedometer-determined ambulatory activity (steps/day) and body composition variables body mass index (BMI) and percentage body fat).

DESIGN

: Secondary analysis of a cross-sectional objective activity monitoring study for up to 21 consecutive days.

SUBJECTS

A total of 109 apparently healthy adults (eight African American males, 23 African-American females, 33 Caucasian males, 45 Caucasian females), age 44.9+/-15.8 y, BMI=26.9+/-5.1 kg/m2.

MEASUREMENTS

Pedometer-assessed ambulatory activity (steps/day), height and weight, and percentage body fat by bioelectrical impedance.

RESULTS

Analyzed as both a continuous and a categorical variable (determined using 25th and 75th percentiles for distribution for steps/day), ambulatory activity was consistently related to body composition variables. Steps/day was inversely correlated with BMI and percentage body fat (r=-0.30, and r=-0.27, respectively, both P<0.01). The consistency of the relationship was also evident when examined using accepted BMI cut-off points for normal-weight, overweight, and obese categories.

CONCLUSIONS

Individuals in this small sample with values greater than approximately 9000 steps/day are more frequently classified as normal weight for height. Individuals with values less than approximately 5000 steps/day are more frequently classified as obese. These findings require further corroborative investigation but provide preliminary cutoff points for identifying individuals at risk who may benefit from appropriate physical activity intervention.

Estimation of energy expenditure from physical activity measures: determinants of accuracy

OBJECTIVE

To describe the determinants, specifically age, body mass index, percentage of body fat, and physical activity (PA) level, associated with over- and underestimation of energy expenditure (EE) using PA records and the Stanford Seven-Day Physical Activity Recall (7DR) compared with doubly labeled water (DLW).

RESEARCH METHODS AND PROCEDURES

We collected PA measures on 24 males eating a controlled diet designed to maintain body weight, and we determined EE from DLW and estimated EE from PA records and 7DR.

RESULTS

Absolute differences in the estimation of EE between DLW and PA assessment methods were greater for the 7DR (30.6 +/- 9.9%) than PA records (7.9 +/- 3.2%). In PA records, overestimation of EE was greater with older age and higher body fatness; EE was overestimated by 16.7% among men 50 years and older compared with only 5.3% among men <40 years of age. For percentage of body fat, EE was overestimated by 19.7% among men with a percentage of body fat > or =30% compared with only 5.6% among men with a percentage of body fat <25%. A trend for less overestimation of EE with higher levels of PA (measured by DLW/basal metabolic rate [BMR]) also was observed in the PA records. In the 7DR, the estimates of EE varied widely and no trends were observed by age, percentage of body fat, and PA levels.

DISCUSSION

Estimation of EE from the 7DR is considerably more variable than from PA records. Factors related to age and percentage of body fat influenced the accuracy of estimated EE in the PA record. Additional studies are needed to understand factors related to accurate reporting of PA behaviors, which are used to estimate EE in free-living adults.

Prevalence of physical activity among South Carolina adults

Participating in regular PA is associated with many health benefits. Overall, the prevalence of inactivity in South Carolina (33 percent) is among the highest in the Southeast and in the US as a nation. While few gender differences exist between the proportion of adults who report participation in sufficient PA (females 21 percent and males 23 percent), racial and age differences are apparent with ethnic minorities and older adults as the least active. The most popular PA among all adults is walking. Physicians can play a key role, through counseling, to help increase the prevalence of regular PA among those who are currently obtaining insufficient amounts of activity to derive optimal health benefits.

Association among physical activity level, cardiorespiratory fitness, and risk of musculoskeletal injury

To help public health practitioners promote physical activities with a low risk of injury, this study determined the relation among type and duration of physical activity, cardiorespiratory fitness, and musculoskeletal injury in a sample of adults enrolled in the Aerobics Center Longitudinal Study. Subjects included 4,034 men and 967 women who underwent a baseline physical examination between 1970 and 1985 and who returned a mailed follow-up survey in 1986. At baseline, a treadmill graded exercise test was used to measure cardiorespiratory fitness. At follow-up, subjects reported injuries and type and duration of physical activity in the preceding 12 months. Polytomous logistic regression was used to estimate the association among physical activity type and duration, cardiorespiratory fitness, and injury. The risk of sustaining an activity-related injury increased with higher duration of physical activity per week and cardiorespiratory fitness levels. Results suggest that cardiorespiratory fitness may be a surrogate for unmeasured components of physical activity, such as exercise intensity. Among walkers, increasing duration of activity per week was not associated with an increased risk of injury. Results suggest that, for most adults, walking is a safe form of physical activity associated with a lower risk of injury than running or sport participation.

Racial/ethnic health disparities in South Carolina and the role of rural locality and educational attainment

BACKGROUND

The prevalence of selected health indicators were compared among the Catawba Indians, African Americans, and whites in South Carolina, considering the possible role of rural locality and education.

METHODS

Catawba members were respondents of a 1998 survey (N = 808). Other South Carolina residents were respondents of the 1995-1997 Behavioral Risk Factor Survey (4,150 whites and 1,413 African Americans). Prevalence of cardiovascular disease, diabetes, hypertension, overweight, poor health, smoking, physical inactivity, and poor diet were compared among the racial/ethnic groups. Logistic regression analyses were conducted within strata of urban/rural locality and education to determine whether these factors were associated with the adverse health indicators.

RESULTS

Both Catawba and African Americans had higher prevalence of diabetes, hypertension, overweight, poor health, physical inactivity, and poor diet than whites. In addition, prevalence of diabetes, poor health, smoking, and poor diet were higher among the Catawba than among African Americans. Restricting the analyses to comparisons within urban/rural locality had little effect, whereas restricting the analyses to comparisons by education level eliminated many of the disparities among those with low education.

CONCLUSIONS

Prevalence of chronic disease and adverse health behavior are higher among the Catawba than among other residents of South Carolina, especially compared with white residents.

Environmental influences, physical activity, and weight status in 8- to 16-year-olds

OBJECTIVE

To assess the association between vigorous physical activity, participation on sport teams and in exercise programs, television watching, family environment, and weight status in youth.

DESIGN

Cross-sectional data from the Third National Health and Nutrition Examination Survey.

PARTICIPANTS

A group of 2791 youth between the ages of 8 and 16 years who were enrolled in the Third National Health and Nutrition Examination Survey.

MAIN OUTCOME MEASURES

Overweight was defined using age- and sex-specific 85th percentile of body mass index using Center for Disease Control and Prevention growth charts.

RESULTS

Both males and females who had an overweight mother and or father were more likely to be overweight compared with youth who did not have an overweight parent. Females who watched 4 or more hours of television were more likely to be overweight than those who watched less than 4 hours. Males and 14- to 16-year-old females who participated in sport team and exercise programs were less likely to be overweight than their counterparts who did not participate. Also, females with larger families and males from families with higher family incomes were less likely to be overweight.

CONCLUSIONS

These results suggest that family environment is associated with overweight in youth and that sport and exercise program participants are less like to be overweight and that, for females, increased television watching is related to overweight.

Quantifying energy expenditure and physical activity in the context of dose response

PURPOSE

Methods for assessing physical activity (PA) and energy expenditure (EE) were reviewed to identify potential limitations to evaluating and interpreting dose-response relationships between PA and health-related outcomes and to suggest future research directions in this area.

METHODS

Literature describing PA and EE assessment methodology was reviewed according to the reported validity, reliability, and feasibility of the measurement in epidemiologic studies. A summary of this review is presented for techniques applicable to studying PA or EE among free-living individuals.

RESULTS

Several methods with varying degrees of precision and feasibility have been used to assess PA and EE in free-living populations. Lack of a gold standard field measure of PA may explain some of the variability in precision among these methods. The most accurate field measure of EE appears to be doubly labeled water; however, this approach has limited feasibility in terms of cost and use in studies of total EE only. Electronic motion sensors and physiologic measures related with EE are limited in their ability to discriminate specific types of PA and by inconvenient measurement procedures. Self-reported PA records and surveys are low-cost, relatively unobtrusive methods of assessing PA and EE in field settings and vary in terms of their format, mode of administration, and degree of detailing habitual PA levels. Disparity in the metric used to quantify PA and EE exists within the current literature, which limits the interpretation and comparison of observed dose-response relationships.

CONCLUSIONS

Efforts to develop equated methods of assessing PA and EE in free-living populations are needed before a systematic evaluation and interpretation of dose-response characteristics between PA and specific health-related parameters can be undertaken.

Validation of the COSMED K4 b2 portable metabolic system

The purpose of this investigation was to assess the accuracy of the COSMED K4 b2 portable metabolic measurement system against the criterion Douglas bag (DB) method. During cycle ergometry on consecutive days, oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), and respiratory exchange ratio (R) were measured at rest and during power outputs of 50, 100, 150, 200, and 250W. No significant differences (P > 0.05) were observed in VO2 between the K4 b2 and DB at rest and at 250W. Though the K4 b2 values were significantly higher (P<0.05) than DB values at 50, 100, 150, and 200 W, the magnitude of these differences was small (0.088, 0.092, 0.096, and 0.088 L x min(-1), respectively). VCO2 and VE values from the K4 b2 were significantly lower than the DB at 200 and 250 W, while no significant differences were observed from rest through 150W. The slight overestimation of VO2 (50-200 W) combined with the underestimation of VCO2 (200 and 250W) by the K4 b2 resulted in significantly lower R values at every stage. These findings suggest the COSMED K4 b2 portable metabolic measurement system is acceptable for measuring oxygen uptake over a fairly wide range of exercise intensities.

Physical activity, physical fitness, and Framingham 10-year risk score: the cross-cultural activity participation study

PURPOSE

Although physical activity and physical fitness are inversely and causally associated with coronary heart disease (CHD) morbidity and mortality, available equations for estimating CHD risk do not include scores for activity or fitness. Therefore, this study evaluated the association of physical fitness and moderate-intensity physical activity with the 10-year Framingham CHD risk estimate.

METHODS

Cross-sectional analyses were performed on data from 137 healthy middle-aged women (53.9 +/- 9.9 yr; 28.3 +/- 6.0 kg/m2). Health histories, body composition, blood pressure, and blood samples were obtained from a clinical examination. Levels of moderate (3-6 METS) intensity physical activity, expressed as MET-minutes/day of energy expenditure, were derived from multiple 24-hour physical activity records. Physical fitness was quantified as duration of a symptom-limited maximal treadmill exercise test.

RESULTS

After adjustment for race, body mass index (BMI), and hormone replacement status, a graded reduction in the Framingham risk score was observed across low (5.8%), moderate (4.0%), and high (3.6%) fitness levels (P for trend = 0.009). Women in both the moderate and high fitness categories had a lower (P < 0.01) risk score compared with their low fit counterparts. Significant differences in risk were not seen among low (3.9%), moderate (4.9%), and high (4.4%) physical activity groups. The lack of association between the risk score by physical activity may have been due to the homogeneity of activity levels among participants. Our findings reinforce existing data that show enhanced levels of fitness are associated with lower risk for CHD.

Sociocultural perspectives on physical activity in the lives of older African American and American Indian women: a cross cultural activity participation study

Illuminating the diversity and sociocultural specificity of women's experiences may be important if healthy lifestyles and quality of life are to be achieved. The incidence of cardiovascular disease linked to physical inactivity is high among African American and American Indian women. If more is understood about the experience of physical activity involvement, healthier living might be encouraged. Therefore, the purpose of this study was to explore the sociocultural meanings of physical activity for older (over the age of 40 years) African American and American Indian women who participated in the Cross Cultural Activity Participation Study (CAPS). Through qualitative in-depth interviews, we explored how sociocultural perspectives are related to perceptions about physical activity. Gender and other sociocultural factors influenced physical involvement on a continuum from negligible to significant. Both groups interviewed showed evidence that opportunities for physical activity in their free time did not always exist for them. For African American women, history and daily living issues were important factors limiting their involvement. Marginality limited American Indian women, but their cultural pride was often a source of physical activity. The juxtaposition of cultural and personal values emerged as a determinant of physical activity involvement among the women in this study. A further expansion of cultural and personal life situation perspectives is recommended to help understand the complex dimensions of physical activity as it relates to healthy living.

Validation of the Stanford 7-day recall to assess habitual physical activity

PURPOSE

The ability of the Stanford 7-Day Recall (7-DR), a well known instrument for surveying work and leisure-time physical activity (PA) in epidemiologic studies, to assess levels of habitual PA in men and women was evaluated.

METHODS

The 7-DR was administered twice, one month apart. Its accuracy was studied in 77 men and women, aged 20-59 years, by its repeatability and comparison of both administrations of the 7-DR with: fourteen 48-hour physical activity records; fourteen 48-hour Caltrac accelerometer readings; peak oxygen uptake (VO(2) peak) determinations; and percent body fat. These criteria measures were obtained over a year's duration.

RESULTS

One month repeatability correlation coefficients for 7-DR total activity were r = 0.60 and r = 0.36 for men and women, respectively. Comparison of corresponding indices of activity between the 7-DR and the PA record indicated: 1) a closer relationship in men for total (r = 0.58 for visit 10 7-DR and 0.66 for visit 11 7-DR, p < or = 0.01), and very hard (r = 0.44 and 0.60, p< or = 0.05) activity then in women (r = 0.32 and 0.33, p < or = 0.05, and r = 0.21, ns and 0.43, p< or = 0.01, respectively); and 2) in general, lower and less consistent associations for hard, moderate, and light activity. Total PA by the 7-DR was significantly associated with Caltrac readings in men only. 7-DR results were more consistently related to VO(2) peak in men than women, but were significantly related to percent body fat in women only.

CONCLUSIONS

The ability of the 7-DR to assess habitual PA was greater for more vigorous than for lower intensity PA.

The association between physical activity, cardiorespiratory fitness, and lipoprotein(a) concentrations in a tri-ethnic sample of women: The Cross-Cultural Activity Participation Study

The purpose of this cross-sectional study was threefold: (1) to examine ethnic differences in plasma lipoprotein(a) [Lp(a)] concentrations; (2) to examine the relationship between physical activity levels (moderate, moderate-vigorous, and total MET-min/day) and Lp(a) concentrations; and (3) to determine the relationship between maximal treadmill time and Lp(a) concentrations among African-American, Native American, and Caucasian women (n=140, ages 40-70 years: 54.5+/-10.7). Physical activity records were kept for two 4-day periods, scheduled 1 month apart, a total of 8 days, and each activity was assigned a code from the 'Compendium of physical activity'. Subjects completed a graded exercise test to determine maximal treadmill time, and a fasted blood sample was collected to quantify Lp(a) concentration. Lp(a) concentrations were negatively skewed with a geometric mean of 28.3 mg/dl (25-75%: 10.4-43.1 mg/dl) in African-Americans (n=47), 2.9 mg/dl (25-75%: 1.2-7.4 mg/dl) in Native Americans (n=45), and 9.4 mg/dl (25-75%: 2.6-22.4 mg/dl) in Caucasians (n=48). African-American women had significantly higher (p<0.05) Lp(a) concentrations than either Native Americans or Caucasians. No relationships were observed among moderate, moderate-vigorous, and total MET-min/day of physical activity, maximal treadmill time, and Lp(a) concentrations. Significant ethnic differences in Lp(a) concentrations were found, with African-American women having higher Lp(a) concentrations than Native American and Caucasian women. Lp(a) concentrations were not associated with any physical activity variables. Therefore, physical activity and maximal treadmill time did not influence Lp(a) concentrations in this tri-ethnic population of women.

Active Commuting to School

The assessment and promotion of childrens' healthful physical activity is important: (i) to combat the international obesity epidemic that extends to childhood; and (ii) to establish an early habit of lifestyle physical activity that can be sustained into adolescence and adulthood. The primary focus of both assessment and promotion efforts has been on in-school physical education classes and, to a lesser extent, out-of-school structured exercise, sport and play. A potential source of continuous moderate activity, active commuting to school by means of walking or by bicycle, has been largely ignored in surveys of physical activity. Suggestive evidence of steep declines in the amount of childrens' destination walking can be gleaned from national transportation surveys. At the same time, there has been a dramatic increase in the reported use of motorised vehicles, including the use for chauffeuring children. There is very little evidence to support or refute active commuting to school as an important source of childrens' physical activity; however, this is largely because it has been overlooked in the stampede to assess time in more vigorous activities. The promotion of active commuting to school must be considered in the context of parents' real and perceived concerns for their children's personal and pedestrian safety. We certainly do not have a full understanding at this time of all the factors related to decisions about transportation mode, whether by child, parent, community, or school. Such information is necessary if successful and sustainable interventions can be implemented, important transport policy decisions can be made, and community and school designs can be modified. Practice rarely waits for research, however, and there are numerous examples of innovative programming, policies and environmental designs occurring internationally that can serve as natural experiments for enterprising researchers willing to push the envelope of our understanding of active commuting and childrens' physical activity. Since we know so little, there is much to learn.

Enablers and constraints to walking for older African American and American Indian women: the Cultural Activity Participation Study

Walking is a significant physical activity undertaken by a range of women from different ages, economic backgrounds, and family situations. The purpose of this analysis was to examine what conditions enabled walking to occur and what constraints prevented some older African American and American Indian women from walking as a physical activity. A descriptive analysis emerged related to three dimensions: the context of walking, how walking was enabled, and constraints to walking more or achieving greater satisfaction with walking as a physical activity. As more is known about how and why a behavior such as walking occurs, more can be done to raise the physical and mental quality of life for all people, regardless of race or gender.

Cardiorespiratory fitness and coronary heart disease risk factors: the LDS Hospital Fitness Institute cohort

BACKGROUND

Cardiorespiratory fitness is favorably associated with most modifiable coronary heart disease (CHD) risk factors. Findings are limited, however, by few data for women, persons with existing CHD, and low-risk populations. In the present study, we described cross-sectional associations between cardiorespiratory fitness and CHD risk factors in a large cohort of middle-aged men and women, of whom the majority were LDS Church members (Mormons), with and without existing CHD.

METHODS AND RESULTS

Comprehensive health examinations were performed on 3232 men (age 45.9+/-10.8 years) and 1128 women (age 43.8+/-12.8 years) between 1975 and 1997. Maximal treadmill exercise testing was used to categorize those with (12% of the men and 10% of the women) and those without CHD into age- and sex-specific cardiorespiratory fitness quintiles. After adjustments for age, body fat, smoking status, and family history of CHD, favorable associations were observed between fitness and most CHD risk factors among men and women, regardless of CHD status.

CONCLUSIONS

These data indicate that enhanced levels of cardiorespiratory fitness may confer resistance to elevations in CHD risk factors even in a low-risk sample of middle-aged men and women. Furthermore, these findings reinforce current public health recommendations that advocate increased national levels of physical activity and cardiorespiratory fitness for primary and secondary CHD prevention.

Physical activity patterns in women

Participation in regular physical activity provides numerous health benefits, including reduced risk of cardiovascular disease, colon cancer, obesity, and type 2 diabetes mellitus. Among women, regular physical activity also may reduce the risks for breast cancer and osteoporosis ((1)). The Healthy People 2010 goals for the United States are to increase the quality and years of healthy life and to eliminate health disparities among residents. Important components in reaching the broad goal are reducing the proportion of adults who engage in no leisure-time physical activity to 20% and increasing the proportion of adults who engage in at least 30 minutes per day of regular, moderate physical activity ((2)).

Evaluation of heart rate as a method for assessing moderate intensity physical activity

To further develop our understanding of the relationship between habitual physical activity and health, research studies require a method of assessment that is objective, accurate, and noninvasive. Heart rate (HR) monitoring represents a promising tool for measurement because it is a physiological parameter that correlates well with energy expenditure (EE). However, one of the limitations of HR monitoring is that training state and individual HR characteristics can affect the HR-VO2 relationship.

PURPOSE

The primary purpose of this study was to examine the relationship between HR (beats x min(-1)) and VO2 (mL x kg(-1 x -1) min(-1)) during field- and laboratory-based moderate-intensity activities. In addition, we examined the validity of estimating EE from HR after adjusting for age and fitness. This was done by expressing the data as a percent of heart rate reserve (%HRR) and percent of VO2 reserve (%VO2R).

METHODS

Sixty-one adults (18-74 yr) performed physical tasks in both a laboratory and field setting. HR and VO2 were measured continuously during the 15-min tasks. Mean values over min 5-15 were used to perform linear regression analysis on HR versus VO2. HR data were then used to predict EE (METs), using age-predicted HRmax and estimated VO2max.

RESULTS

The correlation between HR and VO2 was r = 0.68, with HR accounting for 47% of the variability in VO2. After adjusting for age and fitness level, HR was an accurate predictor of EE (r = 0.87, SEE = 0.76 METs).

CONCLUSION

This method of analyzing HR data could allow researchers to more accurately quantify physical activity in free-living individuals.

Compendium of physical activities: an update of activity codes and MET intensities

We provide an updated version of the Compendium of Physical Activities, a coding scheme that classifies specific physical activity (PA) by rate of energy expenditure. It was developed to enhance the comparability of results across studies using self-reports of PA. The Compendium coding scheme links a five-digit code that describes physical activities by major headings (e.g., occupation, transportation, etc.) and specific activities within each major heading with its intensity, defined as the ratio of work metabolic rate to a standard resting metabolic rate (MET). Energy expenditure in MET-minutes, MET-hours, kcal, or kcal per kilogram body weight can be estimated for specific activities by type or MET intensity. Additions to the Compendium were obtained from studies describing daily PA patterns of adults and studies measuring the energy cost of specific physical activities in field settings. The updated version includes two new major headings of volunteer and religious activities, extends the number of specific activities from 477 to 605, and provides updated MET intensity levels for selected activities.

Validity of four motion sensors in measuring moderate intensity physical activity

PURPOSE

This study tested the validity of four motion sensors for measuring energy expenditure (EE) during moderate intensity physical activities in field and laboratory settings. We also evaluated the accuracy of the EE values for selected moderate activities listed in the 1993 Compendium of Physical Activities.

METHODS

A total of 81 participants (age 19-74 yr) completed selected tasks from six general categories: yardwork, housework, occupation, family care, conditioning, and recreation. Twelve individuals performed each of the 28 activities examined. During each activity, EE was measured using a portable metabolic measurement system. Participants also wore three accelerometers (Computer Science and Applications [CSA], Inc. model 7164; Caltrac; and Kenz Select 2) and the Yamax SW-701 electronic pedometer. For the CSA device, three previously developed regression equations were used to convert accelerometer scores to EE.

RESULTS

The mean error scores (indirect calorimetry minus device) across all activities were: CSA1, 0.97 MET; CSA2, 0.47 MET, CSA3, 0.05 MET; Caltrac, 0.83 MET; Kenz, 0.96 MET; and Yamax, 1.12 MET. The correlation coefficients between indirect calorimetry and motion sensors ranged from r = 0.33 to r = 0.62. The energy cost for power mowing and sweeping/mopping was higher than that listed in the 1993 Compendium (P < 0.05), and the cost for several household and recreational activities was lower (P < 0.05).

CONCLUSION

Motion sensors tended to overpredict EE during walking. However, they underpredicted the energy cost of many other activities because of an inability to detect arm movements and external work. These findings illustrate some of the limitations of using motion sensors to predict EE in field settings.

Estimation of energy expenditure using CSA accelerometers at hip and wrist sites

PURPOSE

This study was designed to establish prediction models that relate hip and wrist accelerometer data to energy expenditure (EE) in field and laboratory settings. We also sought to determine whether the addition of a wrist accelerometer would significantly improve the prediction of EE (METs), compared with a model that used a hip accelerometer alone.

METHODS

Seventy participants completed one to six activities within the categories of yardwork, housework, family care, occupation, recreation, and conditioning, for a total of 5 to 12 participants tested per activity. EE was measured using the Cosmed K4b2 portable metabolic system. Simultaneously, two Computer Science and Applications, Inc. (CSA) accelerometers (model 7164), one worn on the wrist and one worn on the hip, recorded body movement. Correlations between EE measured by the Cosmed and the counts recorded by the CSA accelerometers were calculated, and regression equations were developed to predict EE from the CSA data.

RESULTS

The wrist, hip, and combined hip and wrist regression equations accounted for 3.3%, 31.7%, and 34.3% of the variation in EE, respectively. The addition of the wrist accelerometer data to the hip accelerometer data to form a bivariate regression equation, although statistically significant (P = 0.002), resulted in only a minor improvement in prediction of EE. Cut points for 3 METs (574 hip counts), 6 METs (4945 hip counts), and 9 METs (9317 hip counts) were also established.

CONCLUSION

The small amount of additional accuracy gained from the wrist accelerometer is offset by the extra time required to analyze the data and the cost of the accelerometer.

Comparison of three methods for measuring the time spent in physical activity

PURPOSE

Three methods for measuring time spent in daily physical activity (PA) were compared during a 21-d period among 83 adults (38 men and 45 women).

METHODS

Each day, participants wore a Computer Science and Applications, Inc. (CSA) monitor and completed a 1-page, 48-item PA log that reflected time spent in household, occupational, transportation, sport, conditioning, and leisure activities. Once a week, participants also completed a telephone survey to identify the number of minutes spent each week in nonoccupational walking and in moderate intensity and hard/very hard-intensity PA. Data were analyzed using descriptive statistics and Spearman rank-order correlations. Three equations developed to compute CSA cut points for moderate and hard/very hard PA were also compared with the PA logs and PA survey.

RESULTS

There was modest to good agreement for the time spent in different PA intensity categories between the three CSA cut point methods (r = 0.43-0.94, P < 0.001). Correlations between the CSA and PA logs ranged from r = 0.22 to r = 0.36, depending on the comparisons. Correlations between the survey items and PA logs were r = 0.26-0.54 (P < 0.01) for moderate and walking activities and r < 0.09 (P > 0.05) for hard/very hard activities. Correlations between the survey items and the CSA min per day varied according to the method used to compute the CSA intensity cut points.

CONCLUSIONS

The results were consistent with findings from other PA validation studies that show motion sensors, PA logs, and surveys reflect PA; however, these methods do not always provide similar estimates of the time spent in resting/light, moderate, or hard/very hard PA.

Evaluation of the kaiser physical activity survey in women

PURPOSE

The Kaiser Physical Activity Survey (KPAS) was evaluated for test-retest reliability and comparison with direct and indirect measures of physical activity (PA) in 50 women (ages 20-60 yr) with a broad range of physical activity (PA) habits.

METHODS

The KPAS, an adaptation of the Baecke usual physical activity survey, was designed specifically to assess activity in women. It provides four summary activity indexes: housework/caregiving, active living habits, sports, and occupation. Summary indexes were compared against direct (Caltrac accelerometer and PA records) and indirect (cardiorespiratory fitness (VO2 peak) and percent body fat) criterion measures of PA. Participants kept detailed PA records for two, 7-d periods, separated by 1 month. Caltrac accelerometers were worn concurrently with the PA records.

RESULTS

Intraclass correlations for 1-month test-retest reliability were high for all KPAS indexes (r = 0.79 to 0.91, P < 0.01). Age-adjusted Spearman rho correlations between the KPAS sports/exercise and active living habits indexes were of moderate magnitude for VO2 peak (r = 0.34 to 0.76, P < 0.01) and percent body fat (r = -.30 to -0.59, P < 0.05). KPAS caregiving and occupation indexes were related to Caltrac kcal x d(-1) (r = 0.30 to 0.44, P < 0.05). Correlations between similar activities from the KPAS and PA records ranged from r = 0.03 to 0.64. Daily, habitual activities from the KPAS and PA records had the highest correlations (r > 0.28). Correlations among infrequent activities were lower (r < 0.05).

CONCLUSION

The KPAS demonstrated good reliability and was reasonably accurate in detecting regular housework/caregiving, occupation, sports/exercise, and active leisure activities among women with a broad range of physical activity habits.

Issues in the assessment of physical activity in women

Women spend forty-plus hours a week at a full-time job and anywhere from twenty-five to forty-five hours a week working in the home. All this household work often seems unavoidable, like death and taxes." (Schor, 1992, page 83).

Measurement of daily walking distance-questionnaire versus pedometer

PURPOSE

This study compared measurements of daily walking distance on the College Alumnus questionnaire (CAQ) and a pedometer.

METHODS

A total of 96 men and women (25-70 yr of age) with a wide range of physical activity habits were studied. Physical activity index was computed from the College Alumnus questionnaire (PAI-CAQ) as the sum of the energy expended in stair climbing, walking, and sports and recreational physical activity. Data on walking distance were compared with values obtained from the Yamax electronic pedometer (DW-500B). Participants wore the pedometer for 7 consecutive days, except when sleeping, showering, or performing sports and recreational activities.

RESULTS

Subjects underestimated their daily walking distance on the CAQ, compared with the pedometer (1.43 +/- 1.01 vs 4.17 +/- 1.61 km x d(-1)). The energy expended in walking was correspondingly lower on the CAQ, compared with the pedometer-derived values (555 +/- 405 versus 1608 +/- 640 kcal x wk(-1)).

CONCLUSIONS

These findings suggest that electronic pedometers are useful for examining questions about walking distance on physical activity questionnaires.

Challenges in measuring physical activity in women

This article identifies challenges facing researchers when studying physical activity in women. The three issues include social and cultural differences influencing women's physical activity habits, measuring lifetime physical activity, and measuring moderate-intensity physical activity within the context of women's lives.

Moderate-intensity physical activity and fasting insulin levels in women: the Cross-Cultural Activity Participation Study

OBJECTIVE

The purpose of this study was to determine the association between moderate-intensity physical activity (PA) and fasting insulin levels among African-American (n = 47), Native American (n = 46), and Caucasian women (n = 49), aged 40-83 years, enrolled in the Cross-Cultural Activity Participation Study. Associations by race/ethnicity, levels of central obesity, and cardiorespiratory fitness were also examined.

RESEARCH DESIGN AND METHODS

Physical activity scores were obtained from detailed PA records that included all PA performed during two consecutive 4-day periods scheduled 1 month apart. Using MET intensity (the associated metabolic rate for a specific activity divided by a standard resting metabolic rate), PA was expressed as MET-min (the product of the minutes for each activity times the MET intensity level) per day of energy expended in moderate (3-6 METs) and moderate/vigorous (> or = 3 METs) PA. Fasting insulin levels were determined by radioimmunoassay. Data were analyzed by multiple linear regression analysis.

RESULTS

After adjusting for race/ethnicity, age, educational attainment, and site, an increase of 30 min of moderate-intensity PA was associated with a 6.6% lower fasting insulin level (P < 0.05). The association was similar among races/ethnicities, centrally lean and centrally obese women, and women with low and high cardiorespiratory fitness levels.

CONCLUSIONS

These findings lend support to the 1995 Centers for Disease Control and Prevention and American College of Sports Medicine recommendations for an accumulation of 30 min/day in moderate-intensity PA. They also contribute to the growing literature suggesting that moderate amounts of PA have a significant role in reducing the burden of hyperinsulinemia and diabetes among ethnic populations at highest risk for these conditions.

Physical activity and self-reported, physician-diagnosed osteoarthritis: is physical activity a risk factor?

This prospective study evaluated regular physical activity and self-reported physician-diagnosed osteoarthritis of the knee and/or hip joints among 16,961 people, ages 20-87, examined at the Cooper Clinic between 1970 and 1995. Among those aged 50 years and older, osteoarthritis incidence was higher among women (7.0 per 1000 person-years) than among men (4.9 per 1000 person-years, P = 0.001), while among those under 50 years of age, osteoarthritis incidence was similar between men (2.6) and women (2.7). High levels of physical activity (running 20 or more miles per week) were associated with osteoarthritis among men under age 50 after controlling for body mass index, smoking, and use of alcohol or caffeine (hazard ratio = 2.4, 95% CI: 1.5, 3.9), while no relationship was suggested among women or older men. These findings support the conclusion that high levels of physical activity may be a risk factor for symptomatic osteoarthritis among men under age 50.

Race/ethnicity, social class and their relation to physical inactivity during leisure time: results from the Third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

Physical inactivity is more prevalent among racial and ethnic minorities than among Caucasians. It is not known if differences in participation in leisure time physical activity are due to differences in social class. Thus, this paper provides estimates of the prevalence of physical inactivity during leisure time and its relationship to race/ethnicity and social class.

METHODS

This was a national representative cross-sectional survey with an in-person interview and medical examination. Between 1988 and 1994, 18,885 adults aged 20 or older responded to the household adult and family questionnaires as part of the Third National Health and Nutrition Examination Survey . Mexican-Americans and African-Americans were over-sampled to produce reliable estimates for these groups. Multiple assessment of social class included education, family income, occupation, poverty status, employment status, and marital status.

RESULTS

The age-adjusted prevalence (per 100) of adults reporting leisure time inactivity is lower among Caucasians (18%) than among African-Americans (35%) and Mexican-Americans (40%). African-American and Mexican-American men and women reported higher prevalence of leisure time inactivity than their Caucasian counterparts across almost every variable, including education, family income, occupation, employment, poverty and marital status.

CONCLUSIONS

Current indicators of social class do not seem to explain the higher prevalence of physical inactivity during leisure time among African-American and Mexican-American. More research is needed to examine the effect of other constructs of social class such as acculturation, safety, social support and environmental barriers in promoting successful interventions to increase physical activity in these populations.

Prevalence of physical inactivity and its relation to social class in U.S. adults: results from the Third National Health and Nutrition Examination Survey, 1988-1994

PURPOSE

This study examines the prevalence of physical inactivity during leisure time in a national representative sample of U.S. adults.

METHODS

Data were obtained from the Third National Health and Nutrition Examination Survey, conducted between 1988 and 1994. A total of 18,825 adults aged 20 yr and older participated in a home interview where information about physical activity, education, income, occupation, employment, and labor force participation was obtained.

RESULTS

The prevalence of physical inactivity among U.S. adults was 23%, with more women (28%) than men (17%) reporting being inactive during their leisure time. Additionally, inactivity is more common among in social class such as persons who are less educated, living below the poverty line, living in households with income below 20,000 dollars, and who are retired. In every category of social class, women experienced a higher prevalence of physical inactivity than men.

CONCLUSIONS

We conclude that social class is associated with physical inactivity and that more research is needed to better understand the effect that other social and environmental factors have on sedentary behaviors in our society.