Prevalence of Total Daily Walking Among US Adults,

original research Journal of Physical Activity and Health, 2008, 5, 337-346 2008 Human Kinetics, Inc. Prevalence of Total Daily Walking Among US Adults, 2002 2003 Jared P. Reis, Caroline A. Macera, Barbara E. Ainsworth, and Deborah A. Hipp Background: Walking for exercise is a popular leisure-time activity pursuit among US adults; however, little information is available about total daily walking. Methods: A nationally representative random sample of 10,461 US adults (4438 men and 6023 women) was surveyed via telephone between 2002 and 2003. Weekly frequency and daily duration of walking for all purposes in bouts of at least 10 min were measured. Regular walking was defined as walking 5 d/wk, 30 min/d. Results: Overall, 49% of adults (51% of men and 47% of women) were regular walkers, and approximately 17% reported no walking. Regular walking was significantly higher in employed adults and decreased with increasing age in women and body mass index in both sexes. Total walking was significantly higher among adults with lower levels of educational attainment and did not vary significantly by race/ethnicity. Conclusions: These results affirm the popularity of walking in the United States. Keywords: surveillance, exercise, epidemiology, correlates Walking is not only a fundamental form of daily physical activity (PA) but is also the most highly reported leisure-time PA pursuit among US adults, 1-5 including older adults 6 and those who are trying to lose weight. 7 Walking is something most people can do without special training or equipment and is an attractive target for the promotion of PA among characteristically sedentary populations. 2,4 Walking occurs in all domains of daily PA including leisure time, occupation, transportation, and household work; however, much of the published research regarding the descriptive epidemiology of walking for PA in the United States has been focused solely on walking for exercise during leisure time. 2-5 In addition to intentional walking for exercise, it is important to capture walking that occurs in nonleisure contexts because this type of walking contributes significantly to the overall amount of walking accumulated throughout a typical day. 1,8 More recent surveillance studies have begun to provide data on walking for purposes other than merely exercise; Reis and Macera are with the Division of Epidemiology and Biostatistics, San Diego State University, San Diego, CA 92101. Reis is also with the Dept of Family and Preventive Medicine, University of California, San Diego, CA 92186. Ainsworth is with the Dept of Exercise and Wellness, Arizona State University, Mesa, AZ 85212. Hipp is with the Centers for Disease Control and Prevention, Atlanta, GA 30341. 337

338 Reis et al however, these studies have either included small numbers of adults, 9 excluded occupational walking, 9 or have failed to report national estimates of walking using a definition similar to current health promotion objectives for PA (ie, walking 5 d/wk, 30 min/d). 1 Total daily walking activity in the form of time spent walking or daily walking distance, and independent of the intensity of walking, has been shown to be inversely associated with coronary heart disease, 10 cardiovascular disease, 11,12 and all-cause mortality. 13 This evidence is further strengthened by studies that have used pedometers to measure total walking activity in the form of steps per day with no information regarding intensity. Higher accumulated daily step totals have been significantly associated with lower percent body fat, body mass index (BMI), waist and hip circumferences, blood pressure, and other components of the metabolic syndrome. 14-18 Small experimental studies promoting an increase in total daily walking with the aid of pedometers have also shown promise in improving metabolic and cardiovascular variables among at-risk populations. 19-22 Based on accumulated evidence, state and national campaigns (http://www. americawalks.org) have been organized to promote walking within all domains of daily PA in populations. Little is known, however, about the prevalence of total daily walking behaviors in the Unites States. To provide descriptive information regarding the total daily walking of US adults, we used data collected on a national sample in 2002 to 2003 during the National Physical Activity and Weight Loss Survey (NPAWLS). Survey Method Methods The overall purpose of NPAWLS was to collect detailed, cross-sectional information regarding preventive health behaviors, frequently used weight control practices, and PA in a nationally representative, random sample of civilian, noninstitutionalized adults living in the United States. Non-Hispanic Black and Hispanic adults were oversampled to provide greater representation from these subpopulations. The survey and sampling design were similar to the Behavioral Risk Factor Surveillance System (BRFSS), a yearly state-based data collection system used by public health professionals for planning, implementing, and evaluating health promotion and disease prevention programs under the guidance of the Centers for Disease Control and Prevention (CDC). The final survey consisted of approximately 85 questions and took roughly 18 minutes per respondent to complete. Over 92% of the interviews were conducted in English, with the remainder administered in Spanish. The survey response rate was calculated according to the methodology described by the Council of American Survey Research Organization (CASRO) and was based on the product of completed interviews to the sum of the completed interviews, refusals, and a proportion of numbers that were ring-no answer, busy-no answer, and those who answered but terminated the interview before respondent selection. 23 The calculated CASRO response rate was 30.9%. The cooperation rate, defined as the proportion of all respondents interviewed of all eligible units that were actually contacted, was 51.4%. The Institutional Review Board for human subjects research at the University

Total Walking in the United States 339 of South Carolina approved the sampling methodology and questionnaire, and each respondent was read an informed consent agreement before completing the survey. Participants The telephone survey was administered between September 2002 and February 2003 to 11,211 respondents. We excluded 750 (6.9%) respondents who provided incomplete information regarding their total walking activity. The final analytic sample consisted of 10,461 adults (4438 men and 6023 women). Total Walking Total daily walking behavior within all domains of daily PA was assessed with the following question, In a usual week, do you walk for at least 10 minutes at a time while at work, for recreation, exercise, to get to and from places, or for any other reason? Respondents replying positively to this initial question were asked to report their usual weekly frequency and daily duration. Respondents were classified as regular walkers if they reported 5 days of walking for 30 min/d, occasional walkers if they reported some walking but at a level insufficient to meet the definition of a regular walker, or never walkers. Test retest reliability over a median of 16 days has been reported as fair to moderate (intraclass correlation coefficient =.40) for this total walking survey administered via telephone to a sample of 106 adults living in the southeastern United States. 24 Sociodemographic Characteristics The demographic module of the 2001 BRFSS survey (available for download at www.cdc.gov/brfss) was used to assess the characteristics of each NPAWLS respondent. BMI was calculated as self-reported weight in kilograms divided by the square of self-reported height in meters. Employment status at the time of the survey was dichotomized as employed or unemployed, the latter category also including those respondents who identified themselves as a homemaker, student, or retiree. Data Analysis The SUDAAN statistical software package v9.0 (Research Triangle Institute, Research Triangle Park, NC) was used in all analyses to adjust for the complex sampling methodology of NPAWLS. Data were weighted by the product of the inverse of the probabilities of selection at the household and intrahousehold levels and a poststratification factor adjusting to the 2000 US census population by age, sex, and race. Weighted prevalence estimates were calculated to provide a better representation of the overall population prevalence because telephone surveys tend to overrepresent certain subpopulations such as women and the elderly, nonresponse tends to be unequally distributed across subpopulations, and non-hispanic Blacks and Hispanic adults were oversampled. Sex-specific multivariate logistic regression models were used to predict the odds of regular walking behavior while simultaneously adjusting for age, race/ethnicity, BMI, education, and employment status. Statistical significance was defined at the P <.05 level.

340 Reis et al Results Table 1 displays the demographic characteristics of the current study sample. No differences were noted when comparing the current analytic sample with the 11,211 respondents to the NPAWLS survey (data not shown). Approximately 40% of those included in the current study were age 35 to 54 years. Approximately 22% were non-hispanic Black or Hispanic. Nearly 57% were overweight or obese, and approximately 38% had a high school education or less. More than two-thirds (69%) of men and 54% of women were employed. Age, race/ethnicity, and educational status were similar between men and women. About one-third (35%) of men and one-half (52%) of women were in the normal weight category, whereas 45% of men and 27% of women were overweight. The prevalence of regular, occasional, and never walking among men and women according to age, race/ethnicity, BMI, education, and employment status are displayed in Table 2. Overall, 49% (SE = 0.59; 51% of men and 47% of women) Table 1 Demographic Characteristics of US Adults Responding to the National Physical Activity and Weight Loss Survey (NPAWLS), 2002 2003 Men, % (n = 4438) Women, % (n = 6023) Total, % (n = 10,461) Age (y) 18 34 33.9 30.9 32.4 35 54 40.5 39.4 39.9 55 25.7 29.6 27.7 missing (n = 217, 2.1%) Race/Ethnicity non-hispanic White 72.5 71.9 72.2 non-hispanic Black 10.3 12.0 11.2 Hispanic 11.3 10.2 10.7 other 5.9 5.9 5.9 missing (n = 195, 1.9%) Body mass index normal (<25.0 kg/m 2 ) 34.7 51.8 43.2 overweight (25.0 29.9 kg/m 2 ) 44.8 27.2 36.0 obese ( 30.0 kg/m 2 ) 20.6 21.0 20.8 missing (n = 718, 6.9%) Education high school graduate 37.2 38.4 37.8 some college 26.4 28.8 27.6 college graduate 36.4 32.8 34.6 missing (n = 65,.6%) Employment status employed 68.7 54.0 61.2 not employed 31.3 46.0 38.9 missing (n = 27,.3%)

Table 2 Prevalence of Total Daily Walking a Among Men and Women by Sociodemographic Characteristics, National Physical Activity and Weight Loss Survey (NPAWLS), 2002 2003 Demographic group Regular Men Women Occasional Never Regular Occasional Never Total 51.3 (0.86) 31.6 (0.8) 17.2 (0.64) 47.0 (0.8) 36.5 (0.77) 16.5 (0.58) Age (y) 18 34 55.6 (1.59) 30.7 (1.49) 13.7 (1.07) 50.9 (1.57) 37.8 (1.54) 11.3 (0.95) 35 54 52.0 (1.33) 30.6 (1.22) 17.4 (1.02) 47.3 (1.27) 37.5 (1.24) 15.2 (0.89) 55+ 43.9 (1.58) 34.7 (1.52) 21.5 (1.30) 42.3 (1.36) 34.6 (1.29) 23.2 (1.18) Race/Ethnicity non-hispanic White 50.6 (1.0) 32.0 (0.93) 17.3 (0.74) 47.5 (0.92) 36.4 (0.89) 16.2 (0.67) non-hispanic Black 49.5 (3.08) 31.9 (2.88) 18.7 (2.37) 41.7 (2.44) 41.0 (2.43) 17.3 (1.67) Hispanic 56.4 (2.53) 29.3 (2.33) 14.3 (1.8) 48.2 (2.79) 35.2 (2.61) 16.6 (2.0) other 51.2 (3.60) 32.0 (3.34) 16.8 (2.80) 50.3 (3.45) 31.6 (3.21) 18.1 (2.73) Body mass index normal (<25.0 kg/m 2 ) 53.4 (1.51) 31.7 (1.42) 14.9 (1.05) 51.4 (1.16) 35.0 (1.11) 13.6 (0.78) overweight (25.0 29.9 kg/m 2 ) 50.3 (1.28) 33.1 (1.21) 16.6 (0.95) 46.3 (1.60) 37.2 (1.55) 16.6 (1.17) obese ( 30.0 kg/m 2 ) 49.3 (1.92) 29.9 (1.74) 20.8 (1.55) 39.4 (1.78) 39.3 (1.78) 21.3 (1.41) Education high school graduate 55.0 (1.41) 25.8 (1.25) 19.2 (1.11) 46.0 (1.32) 35.2 (1.27) 18.8 (1.0) some college 51.9 (1.72) 32.8 (1.64) 15.4 (1.20) 50.0 (1.51) 34.9 (1.45) 15.2 (1.03) college graduate 47.0 (1.38) 36.6 (1.33) 16.4 (1.03) 45.8 (1.33) 39.5 (1.31) 14.8 (0.96) Employment status employed 56.2 (1.03) 27.7 (0.92) 16.2 (0.76) 51.6 (1.09) 34.2 (1.03) 14.3 (0.75) not employed 40.7 (1.51) 40.1 (1.52) 19.2 (1.18) 41.6 (1.17) 39.3 (1.16) 19.1 (0.91) a Total Walking: Regular walker = walking 5 d/wk, 30 min/d; Occasional walker = some walking, however, less than a regular walker; Never walker = no reported walking. 341

342 Reis et al of respondents were regular walkers, 34% (SE = 0.56; 32% of men and 37% of women) were occasional walkers, and 17% (SE = 0.43) were never walkers. Regular walking decreased with increasing age (from 56% to 44% among men and 51% to 42% among women) and BMI (from 53% to 49% among men and 51% to 39% among women). Regular walking was highest among Hispanic men (56%) and similar among non-hispanic White (51%), non-hispanic Black (50%), and other racial/ethnic (51%) men. Among women, the prevalence of regular walking was similar among non-hispanic Whites (48%), Hispanics (48%), and other racial/ ethnic groups (50%), and lowest among non-hispanic Blacks (42%). For men, regular walking increased with decreasing education, from 47% of those with a college degree to 55% of those with a high school education or less. For women, regular walking was highest among those with some college education (50%) and lower among those with a high school education (46%) or a college degree (46%). For both sexes, regular walking was highest among employed respondents (56% among men and 52% among women). Table 2 shows that in both men and women, never walking increased with increasing age (from 14% to 22% among men and 11% to 23% among women) and BMI (from 15% to 21% among men and 14% to 21% among women), decreased with increasing education (from 19% to 16% among men and 19% to 15% among women), and was higher among the unemployed (19% of men and women). With regard to race/ethnicity, never walking varied from a low of 14% among Hispanic men to 19% among non-hispanic Black men and 16% among non-hispanic White women to 18% among women of other racial/ethnic groups. Sex-specific adjusted odds ratios for the association between regular walking and demographic characteristics in men and women are shown in Table 3. The odds of regular walking decreased significantly with advancing age in women and BMI in both sexes. For both sexes, the adjusted odds ratios for regular walking increased with decreasing levels of education and were significantly higher among respondents who were currently employed. Discussion The results of the current study show that an estimated 49% of US adults walked regularly, on average (ie, 5 d/wk, 30 min/d) in 2002 to 2003. Our data also show that regular walking decreased significantly with advancing age in women and BMI in both sexes and was higher in men, the employed, and those with less education. In the 1990 National Health Interview Survey, 44.1% of men and women reported walking as their main form of leisure-time exercise. 6 In 2005, Bates et al 1 identified the prevalence of total walking at 80.5% among 6000 US adults participating in a random sample telephone survey. However, total walking was defined by Bates et al 1 as walking for 10 minutes at a time for any purpose, and therefore, a higher estimate of total walking as compared with the current study would be expected because we defined regular walking as 5 d/wk, 30 min/d. Addy et al 25 used the same questions employed in the current study to assess total daily walking among 1194 men and women living in a southeastern US county and reported a prevalence of regular walking ( 5 d/wk, 30 min/d) of 39.6%. Eyler et al 9 measured nonoccupational walking among a national sample of 1186 men and

Total Walking in the United States 343 Table 3 Adjusted a Odds Ratios for Regular Walking b Among Men and Women, National Physical Activity and Weight Loss Survey (NPAWLS), 2002 2003 Men (n = 4181) Women (n = 5296) Demographic group OR (95% CI) OR (95% CI) Age (y) 18 34 1.0 (ref) 1.0 (ref) 35 54.89 (0.75 1.05).86 (0.72 1.02) 55+.86 (0.70 1.05).83 (0.69 1.00) P (trend).12.04 Race/Ethnicity non-hispanic White 1.0 (ref) 1.0 (ref) non-hispanic Black.89 (0.68 1.15).85 (0.67 1.07) Hispanic.99 (0.79 1.26) 1.02 (0.79 1.32) other.96 (0.70 1.30) 1.17 (0.87 1.57) Body mass index (BMI) normal (<25.0 kg/m 2 ) 1.0 (ref) 1.0 (ref) overweight (25.0 29.9 kg/m 2 ).88 (0.75 1.03).83 (0.70 0.97) obese ( 30.0 kg/m 2 ).81 (0.67 1.00).63 (0.53 0.76) P (trend).04 <.0001 Education high school graduate 1.51 (1.28 1.79) 1.23 (1.04 1.45) some college 1.31 (1.09 1.57) 1.29 (1.08 1.53) college graduate 1.0 (ref) 1.0 (ref) Employment status employed 1.89 (1.59 2.25) 1.46 (1.26 1.70) not employed 1.0 (ref) 1.0 (ref) a Adjusted for all variables shown. b Regular walking = walking 5 d/wk, 30 min/d. women and found a prevalence of regular walking ( 5 d/wk, 30 min/d) of 33.6%. Other surveillance studies have reported prevalence estimates of regular walking ranging from 21% to 46%; however, these estimates were based solely on walking for exercise. 2,4,5 In this study, we report the prevalence of total regular walking at 51.3% for men and 47.0% for women. Our data indicate a significant inverse relationship between total daily walking activity and education, with the adjusted odds of regular walking 51% (OR = 1.51, 95% CI = 1.28 1.79) and 31% (OR = 1.31, 95% CI = 1.09 1.57) higher in men with a high school education or less and some college, respectively, compared with men with a college degree and 23% (OR = 1.23, 95% CI = 1.04 1.45) and 29% (OR = 1.29, 95% CI = 1.08 1.53) higher among similar women. These findings are in contrast with previous studies 2,5,9 that show physical inactivity is inversely related with education level. This study is unique, however, in that the definition of walking included occupation and transportation walking, whereas other studies consider walking for exercise only. 2,5,9 Because education, job type, and occupational PA are

344 Reis et al closely linked, 26 it is likely that the inclusion of occupational walking resulted in an increased prevalence of regular walking among those with lower education. Additional sociodemographic comparisons showed that total walking decreased with increasing age in women and BMI in both sexes and was higher in men and employed adults. These observations have been reported in previous studies that have described the epidemiology of nonoccupational walking 9 and objective, pedometer-determined ambulatory activity. 27 In 2001, Tudor-Locke et al 27 recruited 209 adults living in the southeastern United States by telephone to wear a pedometer for 1 week and record their daily ambulatory activity on a standardized data collection form. Results showed that the number of steps per day was lower in older adults, women, and the overweight and obese. Our results, however, are contrary to several reports of sociodemographic walking trends among US adults that show that walking increases with age and is higher among women than men. 2,3,5 These differences may be explained by the walking domains assessed. The discrepant studies used the BRFSS PA module employed before 2001 and, therefore, queried only leisure-time walking or walking for exercise. Older adults of retirement age would also be expected to report less occupational related walking. Although walking for exercise might be the choice for women and older adults, total daily walking seems to be higher in men and younger adults. Although we measured total walking as opposed to walking only for exercise or leisure, we did not ask about the intensity of walking. Thus, we cannot estimate the prevalence of moderate- or vigorous-intensity walking sufficient to meet the recommendations of the Surgeon General 28 and the Centers for Disease Control and Prevention/American College of Sports Medicine. 29 Research since the release of these landmark reports has documented the benefits of total daily walking on the incidence of cardiovascular disease and premature death. 10-13 Furthermore, ambulatory monitoring (ie, pedometer) studies support the health-related benefits of increased total daily walking in addition to current health promotion strategies that focus on a lifestyle approach to behavior change by accumulating PA throughout the day. 14-22 Despite these research and promotion efforts aimed at increasing total daily walking, additional evidence from large studies is necessary to document the health-related benefits of total daily walking independent of intensity. The strengths of the current study include its large nationally representative sample population and the measurement of walking within all domains of daily PA. However, there are limitations of the current study that should be considered. First, the self-report of PA habits might be subject to social desirability bias and might thus be overreported. 30 Second, the total walking survey used in the current study provided an estimate of walking by grouping all-purpose walking into a single survey item making it impossible to study domain-specific walking patterns. Further, this grouping of total walking into a single survey item and response might have been cognitively challenging for some respondents to respond appropriately and accurately. Although no study has investigated the validity of the total walking survey, test retest reliability has been shown to be acceptable among a population of African American and White men and women living in North Carolina and Mississippi surveyed via telephone. 24 Their population was less physically active and included a higher percentage of African Americans by design. Age and level of education were similar. We do not know how this would influence the test retest reliability of the walking survey if performed on our study population. The change in the seasons does influence physical activity behavior; however, we do not believe

Total Walking in the United States 345 we can adequately describe the cross-sectional seasonal variation in walking behavior in this study population because we did not collect data throughout an entire year. We collected data only between September and February. In addition, the rather low response rate for NPAWLS might limit the external validity of our findings; however, the cooperation rate was similar to that reported by the BRFSS in 2001. 31 In conclusion, this study affirms the popularity of walking in the United States and suggests that when total daily walking within all domains of PA is assessed, nearly half of all adults walk regularly. Among subpopulations of adults, total walking is slightly higher in men, decreases significantly with increasing age in women and BMI in both sexes, and is higher in employed adults and those with lower levels of formal education. The popularity and health-related benefits associated with increased walking should continue to make walking an attractive mode of PA for adult intervention programs. Acknowledgments This study was supported by a Cooperative Agreement from the US CDC, SIP-20-01, U48/CCU409664, awarded to Dr. Ainsworth. The findings and conclusions in this report are those of the authors and do not necessarily represent the CDC. References 1. Bates JH, Serdula M, Khan LK, Jones DA, Gillespie C, Ainsworth BE. Total and leisure-time walking among US adults: Should every step count? Am J Prev Med. 2005;29:46 50. 2. Rafferty AP, Reeves MJ, McGee HM, Pivarnik JM. Physical activity patterns among walkers and compliance with public health recommendation. Med Sci Sports Exerc. 2002;34:1255 1261. 3. Rafferty AP, Reeves MJ, McGee HB. Compliance with physical activity recommendations by walking for exercise Michigan, 1996 and 1998. Morb Mortal Wkly Rep. 2000;49:560 565. 4. Siegal PZ, Brackbill RM, Heath GW. The epidemiology of walking for exercise: implications for promoting activity among sedentary groups. Am J Public Health. 1995;85:706 710. 5. Simpson ME, Serdula M, Galuska DA, et al. Walking trends among US adults: the Behavioral Risk Factor Surveillance System, 1987 2000. Am J Prev Med. 2003;25:95 100. 6. Yusuf HR, Croft JB, Giles WH, et al. Leisure-time physical activity among older adults: United States, 1990. Arch Intern Med. 1996;156:1321 1326. 7. US Department of Health and Human Services, Centers for Disease Control and Prevention. Prevalence of leisure-time physical activity among overweight adults: United States, 1998. Morb Mortal Wkly Rep. 2000;49:326 330. 8. Whitt MC, Dubose KD, Ainsworth BE, Tudor-Locke C. Walking patterns in a sample of African American, Native American, and Caucasian women: the Cross-Cultural Activity Participation Study. Health Educ Behav. 2004;31:45S 56S. 9. Eyler AA, Brownson RC, Bacak SJ, Housemann RA. The epidemiology of walking for physical activity in the United States. Med Sci Sports Exerc. 2003;35:1529 1536. 10. Lee IM, Rexrode KM, Cook NR, Manson JE, Buring JE. Physical activity and coronary heart disease in women: is no pain, no gain passe? JAMA. 2001;285:1447 1454. 11. Sesso HD, Paffenbarger RS Jr, Ha T, Lee IM. Physical activity and cardiovascular disease in middle-aged and older women. Am J Epidemiol. 1999;150:408 416.

346 Reis et al 12. LaCroix AZ, Leveille SG, Hecht JA, Grothaus LC, Wagner EH. Does walking decrease the risk of cardiovascular disease hospitalizations and death in older adults. J Am Geriatr Soc. 1996;44:113 120. 13. Lee IM, Paffenbarger RS Jr. Associations of light, moderate, and vigorous intensity physical activity with longevity. Am J Epidemiol. 2000;151:293 299. 14. Thompson DL, Rakow J, Perdue SM. Relationship between accumulated walking and body composition in middle-aged women. Med Sci Sports Exerc. 2004;36:911 914. 15. Iwane M, Arita M, Tomimoto S, et al. Walking 10,000 steps/day or more reduces blood pressure and sympathetic nerve activity in mild essential hypertension. Hypertens Res. 2000;23:573 580. 16. Tudor-Locke C, Ainsworth BE, Whitt MC, Thompson RW, Addy CL, Jones DA. The relationship between pedometer-determined ambulatory activity and body composition variables. Int J Obes Relat Metab Disord. 2001;25:1571 1578. 17. Hornbuckle LM, Bassett DR Jr, Thompson DL. Pedometer-determined walking and body composition variables in African-American women. Med Sci Sports Exerc. 2005;37:1069 1074. 18. Chan CB, Spangler E, Valcour J, Tudor-Locke C. Cross-sectional relationship of pedometer-determined ambulatory activity to indicators of health. Obes Res. 2003;11:1563 1570. 19. Sugiura H, Sugiura H, Kajima K, Mirbod SM, Iwata H, Matsuoka T. Effects of longterm moderate exercise and increase in number of daily steps on serum lipids in women: randomised controlled trial. [ISRCTN21921919] BMC Women s Health. 2002;2:3. 20. Swartz AM, Strath SJ, Bassett DR Jr, et al. Increasing daily walking improves glucose tolerance in overweight women. Prev Med. 2003;37:356 362. 21. Yamanouchi K, Takashi T, Chikada K, et al. Daily walking combined with diet therapy is a useful means for obese NIDDM patients not only to reduce body weight but also to improve insulin sensitivity. Diabetes Care. 1995;18:775 778. 22. Moreau KL, Degarmo R, Langley J, et al. Increasing daily walking lowers blood pressure in postmenopausal women. Med Sci Sports Exerc. 2001;33:1825 1831. 23. Frankel L. The report of the CASRO task force on response rates. In: Wiseman F, ed. Improving Data Quality in a Sample Survey. Cambridge, MA: Marketing Science Institute; 1983: 1 11. 24. Evenson KR, McGinn AP. Test retest reliability of adult surveillance measures for physical activity and inactivity. Am J Prev Med. 2005;28:470 478. 25. Addy CL, Wilson DK, Kirtland KA, Ainsworth BE, Sharpe P, Kimsey D. Associations of perceived social and physical environmental supports with physical activity and walking behavior. Am J Public Health. 2004;94:440 443. 26. Evenson KR, Rosamond WD, Cai J, Pereira MA, Ainsworth BE. Occupational physical activity in the Atherosclerosis Risk in Communities Study. Ann Epidemiol. 2003;13:351 357. 27. Tudor-Locke C, Ham SA, Macera CA, et al. Descriptive epidemiology of pedometerdetermined physical activity. Med Sci Sports Exerc. 2004;36:1567 1573. 28. US Department of Health and Human Services. Physical Activity and Health: A Report of the Surgeon General. Atlanta, GA: Centers for Disease Control and Prevention; 1996. 29. Pate RR, Pratt M, Blair SN, et al. Physical activity and public health: a recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA. 1995;273:402 407. 30. Adams SA, Matthews CE, Ebbeling CB, et al. The effect of social desirability and social approval on self-reports of physical activity. Am J Epidemiol. 2005;161:389 398. 31. Centers for Disease Control and Prevention. Behavioral Risk Factor Surveillance System: 2001 Summary Data Quality Report. Atlanta, GA: Centers for Disease Control and Prevention; 2002.