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Prevalence of transportation and leisure walking among U.S. adults
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Preventive Medicine 47 (2008) 329 – 334 www.elsevier.com/locate/ypmed
Prevalence of transportation and leisure walking among U.S. adults ☆ Judy Kruger a,⁎, Sandra A. Ham a , David Berrigan b , Rachel Ballard-Barbash b a
b
Division of Nutrition, Physical Activity and Obesity, Centers for Disease Control and Prevention, Atlanta, Georgia, USA Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, Maryland, USA Available online 10 March 2008
Abstract Objective. This paper aims to contrast the demographic correlates of leisure and transportation walking. Methods. Using data from the 2005 National Health Interview Survey (n = 31,482), this paper reports on the prevalence of transportation walking and leisure walking for U.S. adults and examines the variation in prevalence across different socio-demographic groups. The prevalence of transportation walking and leisure walking for U.S. adults (≥5 days/week for ≥ 30 min/day) was calculated using data from the 2005 National Health Interview Survey. Results. In the United States, 41.5% of adults walked for leisure and 28.2% walked for transportation in intervals of at least 10 min. The highest prevalence of transportation walking was among black non-Hispanic men (36.0%) and Asian/Native Hawaiian/Pacific Islander women (40.5%). The highest prevalence of leisure walking was among Asian/Native Hawaiian/Pacific Islander men (42.0%) and white non-Hispanic women (46.6%). Leisure walking was most prevalent among respondents with higher incomes and education levels, whereas transportation walking increased in prevalence with education level but decreased with income level. Based on the findings, 6% of U.S. adults were considered regularly active (≥ 5 days/week for ≥ 30 min/day) by walking for transportation and 9% were regularly active by walking for leisure. Conclusion. Leisure and transportation walking have distinctly different demographic correlates. These differences should guide interventions aimed at influencing walking for different purposes. Published by Elsevier Inc. Keywords: Walking; Physical activity; Transportation
Introduction Physical inactivity is associated with multiple adverse health outcomes, including increased risk for cardiovascular disease, diabetes, and cancer (USDHHS, 1996). Most Americans are not active enough to obtain all or most of the health benefits associated with physical activity (USDHHS, 1996). The physical activity and public health recommendations are that every adult should accumulate 30 min or more of moderate-intensity physical activity on most, preferably all, days of the week (USDHHS, 1996; Pate et al., 1995). Brisk walking is a form of physical ☆
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention. ⁎ Corresponding author. Physical Activity and Health Branch, Division of Nutrition, Physical Activity and Obesity, 4770 Buford Highway, NE (MS K-46), Atlanta, GA 30341, USA. Fax: +1 770 488 5473. E-mail address: [email protected] (J. Kruger). 0091-7435/$ - see front matter. Published by Elsevier Inc. doi:10.1016/j.ypmed.2008.02.018
activity that adults can use to meet these recommendations (USDHHS, 1996). Walking is one of the most common and accessible forms of physical activity and requires no special equipment, facilities, or training (Dunton and Schneider, 2006). Thus, it seems clear that understanding who walks and why could be useful in the design of walking related interventions aimed at increasing physical activity. The CDC has recommended some evidence-based interventions to increase walking (CDC 2005). However, knowledge about how to target these interventions is lacking (Saelens et al., 2003). National statistics on walking trends come from three surveillance systems and are based entirely on self-reports. The National Health and Nutrition Examination Survey (NHANES) estimated walking sessions over a 30-day period (http://www.cdc. gov/nchs/nhanes.htm). The National Health Interview Survey (NHIS) collected information on participation in habitual walking or biking for transportation in 2000 (http://www.cdc.gov/nchs/nhis. htm). The National Household Transportation Survey (NHTS)
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measured walking for transportation on one day (http://nhts.ornl. gov/). These surveys use different data collection methods, use different time units to measure walking (i.e., day, week, and month) and occur in different contexts. Thus, comparisons of the prevalence of walking for different reasons have been difficult (Troiano et al., 2001). Moreover, none of these surveys queried walking for leisure and transportation measured as days per week, the frequency units that are used by the physical activity recommendations (USDHHS, 1996). Recently, questions concerning both leisure and transportation walking were added to the NHIS, allowing direct comparisons of the prevalence of transportation and leisure walking. This paper reports estimates of the prevalence of walking for both transportation and leisure among U.S. adults aged N=18 years based on survey questions that addressed each type of walking separately. Our objectives were to: 1) report on the prevalence and
correlates of walking for transportation; 2) report on the prevalence and correlates of walking for leisure, and 3) estimate the prevalence of adults who were regularly active based on walking for transportation or leisure (≥5 days/week for ≥30 min/day). Methods These results are based on the 2005 National Health Interview Survey (NHIS) conducted by the National Center for Health Statistics and administered by the U.S. Census Bureau. The survey is a continuing in-person survey of approximately 40,000 households in the civilian non-institutionalized population with a multi-stage area probability design covering the 48 contiguous states. Walking questions were contained in a Cancer Control Module (CCM), administered to one adult aged 18 years or older in each household (N = 31,428). The main body of the survey included queries concerning diverse demographicand socioeconomic-related variables as well as other health-related questions. The response rate for adults was 69.0% (ftp://ftp.cdc.gov/pub/Health_Statistics/ NCHS/Dataset_Documentation/NHIS/2005/srvydesc.pdf).
Table 1 Percentages of adults who walked for transportation a Men
Overall Demographics Age, years 18–34 35–49 50–64 65–74 ≥75 Race/ethnicity White, non-Hispanic Black, non-Hispanic Hispanic Asian/Native Hawaiian/Pacific Islander Other, multiracial SES related variables Education level bHigh school High school Some college College graduate Income-poverty ratio b100% 100–b200% 200–b300% ≥300% Work status Working Not working Physical and health status Self-rated health Good, very good, excellent Fair, poor Body mass index b25.0 25.0–b30.0 ≥30.0 Activity limitation No Yes
Women
n
%
95% CI
n
%
95% CI
12,858
30.3
(29.1, 31.4)
16,621
26.4
(25.3, 27.4)
3628 3880 3097 1254 999
35.2 30.5 28.2 23.4 20.2
(33.1, 37.3) (28.8, 32.3) (26.5, 30.0) (20.8, 26.3) (17.5, 23.3)
4631 4686 3846 1641 1817
30.8 28.3 24.6 20.9 15.1
(28.9, 32.7) (26.6, 30.0) (23.0, 26.3) (18.6, 23.4) (13.3, 17.2)
8453 1522 2293 415 161
29.3 36.0 31.0 34.4 21.2
(28.0, 30.5) (33.2, 38.8) (28.4, 33.6) (29.0, 40.2) (14.8, 29.3)
10,619 2427 2873 455 232
25.0 26.8 30.9 40.5 20.1
(23.8, 26.2) (24.5, 29.2) (28.7, 33.2) (35.9, 45.3) (15.1, 26.2)
2369 3608 3433 3360
26.9 25.1 32.2 36.1
(24.7, 29.3) (23.4, 26.9) (30.2, 34.2) (34.3, 38.1)
3105 4757 4790 3845
24.9 20.5 28.0 32.7
(22.9, 26.9) (19.0, 22.0) (26.3, 29.8) (30.8, 34.7)
1568 2422 2213 6656
35.0 28.7 27.3 30.7
(31.3, 38.9) (26.3, 31.3) (25.0, 29.8) (29.3, 32.2)
2944 3718 2818 7141
32.4 23.4 24.5 26.6
(29.8, 35.1) (21.4, 25.5) (22.5, 26.6) (25.3, 27.9)
8661 4188
30.9 28.8
(29.7, 32.1) (26.9, 30.8)
8830 7771
28.5 23.8
(27.2, 29.8) (22.4, 25.2)
11,185 1665
31.7 19.1
(30.5, 32.9) (17.0, 21.4)
14,072 2544
27.9 16.7
(26.7, 29.1) (15.0, 18.4)
4064 5482 3139
32.4 30.5 27.8
(30.6, 34.2) (29.0, 32.1) (25.8, 29.9)
7105 4563 4193
29.7 24.8 22.7
(28.3, 31.2) (23.1, 26.5) (21.1, 24.3)
10,835 2017
31.8 20.6
(30.6, 33.0) (18.4, 23.0)
13,532 3072
28.4 15.9
(27.2, 29.6) (14.4, 17.6)
National Health Interview Survey, 2005. a Walking for transportation refers to get some place such as work, school, or restaurant.
J. Kruger et al. / Preventive Medicine 47 (2008) 329–334 Walking for transportation was measured by the questions, “During the past seven days, did you walk to get some place that took you at least 10 minutes?” Those who said ”yes” were asked, “During the past seven days, on how many days did you walk for at least 10 minutes at a time to get some place such as work, school, or restaurant?” Those who responded that they walked for at least one day were then asked “How much time did you usually spend on one of those days walking to get from place to place?” Respondents who reported a regular pattern of walking for transportation (i.e., N=5 days per week for N=30 min each day), were considered regularly active. Walking for leisure was assessed by the questions, “Sometimes you may walk for fun, relaxation, exercise, or to walk the dog. During the past seven days, did you walk for at least 10 minutes at a time for any of these reason? Please do not include any walking that you already told me about?” Those who said ”yes” were asked, “During the past seven days, on how many days did you walk for at least 10 minutes at a time for fun, relaxation, exercise or to walk the dog?” Those who responded ”yes” were asked to report the number of days per week and the average total time per day spent in these activities. Respondents were classified as being regularly active by walking for leisure using the same criteria described above for walking for transportation.
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The prevalence of walking was examined by demographic characteristics, socioeconomic status (SES), and health status. Income was reported using an income-poverty ratio in the following four categories: b100%, 100–200%, 200– 300% and N300% (an income-poverty ratio of b100% indicated that a family was at or below the poverty level). These variables accounted for differences in family size and were standardized for inflation and other factors (http://www.census.gov/ hhes/www/poverty/poverty.html). Respondents were classified as working last week (e.g., working for pay at a job or business, working but not for pay at a job or business) and not working last week (e.g., not working at a job or business, with a job or business but not at work, looking for work, and not looking for work). We calculated respondents' body mass index (BMI) from self-reported height and weight (kg/m2) and divided the sample into three BMI categories: normal weight (18.5 to b25.0), overweight (N25.0 to b30.0), and obese (N30.0). Respondents who were missing information were excluded from our analysis. Data were analyzed using SUDAAN (Version 9.0; Research Triangle Institute, Research Triangle Park, NC) with appropriate weighting to account for the complex sample design. Prevalence (%) and 95% confidence intervals were reported for walking for transportation and walking for leisure, stratified by gender and categorized by several demographic, SES, and health-related measures.
Table 2 Percentages of adults who walked for leisure a Men
Overall Demographics Age, years 18–34 35–49 50–64 65–74 ≥75 Race/ethnicity White, non-Hispanic Black, non-Hispanic Hispanic Asian/Native Hawaiian/Pacific Islander Other, multiracial SES Related Variables Education level bHigh school High school Some college College graduate Income-poverty ratio b100% 100–b200% 200–b300% ≥300% Work status Working Not working Physical and health status Self-rated health Good, very good, excellent Fair, poor Body mass index b25.0 25.0–b30.0 ≥30.0 Activity limitation No Yes
Women %
95% CI
%
95% CI
12,860
38.9
(37.8, 40.0)
16,620
43.9
(42.8, 45.0)
3637 3880 3097 1246 1000
36.1 40.0 40.4 43.3 37.2
(34.2, 37.9) (38.2, 41.8) (38.5, 42.3) (40.1, 46.6) (33.9, 40.6)
4635 4689 3850 1636 1810
46.6 48.2 43.4 38.6 27.1
(44.7, 48.6) (46.5, 49.8) (41.4, 45.4) (35.9, 41.4) (25.0, 29.4)
8445 1524 2295 417 165
40.4 32.5 36.2 42.0 29.0
(39.1, 41.7) (29.5, 35.6) (34.0, 38.5) (37.0, 47.2) (22.2, 36.8)
10,617 2429 2877 450 232
46.6 31.6 39.2 46.2 40.7
(45.3, 47.9) (29.4, 33.8) (36.9, 41.5) (41.3, 51.1) (30.6, 51.6)
2375 3612 3433 3352
31.7 32.2 38.7 51.1
(29.5, 34.1) (30.4, 34.0) (36.7, 40.6) (49.2, 53.1)
3102 4757 4797 3842
30.5 37.9 46.8 56.4
(28.4, 32.8) (36.1, 39.8) (45.1, 48.6) (54.5, 58.3)
1575 2422 2210 6653
30.6 33.2 35.2 43.3
(27.4, 34.1) (30.7, 35.8) (32.8, 37.8) (41.8, 44.8)
2938 3727 2818 7137
31.9 34.6 42.1 51.3
(29.7, 34.2) (32.6, 36.6) (39.7, 44.5) (49.8, 52.8)
8675 4,177
39.2 38.3
(37.9, 40.5) (36.6, 40.1)
8838 7763
47.5 39.5
(46.1, 48.9) (38.1, 40.9)
11,190 1664
40.2 28.8
(39.0, 41.4) (26.2, 31.6)
14,072 2543
47.1 23.1
(46.0, 48.3) (21.3, 25.1)
4060 5480 3145
38.7 41.5 35.8
(36.9, 40.6) (39.9, 43.2) (34.0, 37.6)
7112 4563 4183
48.5 44.2 36.5
(47.0, 50.1) (42.4, 46.0) (34.8, 38.2)
10,835 2019
40.1 31.8
(38.9, 41.2) (29.3, 34.4)
13,541 3062
47.5 25.3
(46.3, 48.7) (23.6, 27.1)
National Health Interview Survey, 2005. a Walking for leisure-time refers to fun, relaxation, exercise or to walk the dog.
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Results The nationally representative sample of U.S. adults included 13,762 men and 17,666 women. About one-third were aged 18– 34 years; 26.6% were college graduates; 64.4% were nonHispanic whites, 62.7% had BMIs ≥ 25.0, and 15.5% had income-poverty ratios of b 100%. In 2005, an estimated 28.2% (95% CI = 27.3, 29.1) of U.S. adults engaged in walking for transportation. Men (30.3%) were more likely to walk for transportation than women (26.4%) (Table 1). The median frequency of walking for transportation for both men and women was 3 days/week, and the median duration was 20 min/day. Adults aged 18–34 years had the greatest prevalence of walking for transportation compared with other age groups. Among racial/ethnic groups, black nonHispanic men (36.0%) and Asian/Native Hawaiian/Pacific Islander women (40.5%) were most likely to walk for transportation. Transportation walking was highest among college graduates (36.1% men; 32.7% women) and lower among lesseducated respondents. In contrast, transportation walking was highest in the lowest income groups, with 35% of men and 32.4% of women reporting transportation walking. Among those who were working, 30.9% of men and 28.5% of women walked for transportation. Most adults who reported good, very good, or excellent health walked for transportation. Walking for transportation was slightly more prevalent among respondents with normal BMI for both men and women and substantially more prevalent among respondents reporting no activity limitations. For example about 32% of men without activity limitations reported transportation walking compared with only 21% with such limitations. Approximately 41.5% (95% CI = 40.7, 42.4) of adults walked for leisure (38.9% men; 43.9% women) (Table 2). The median frequency of walking for leisure for both men and women was 3 days/week, and the median duration was 30 min/ day. The prevalence of leisure walking increased with age until age 74 among men and until age 49 among women. For both genders, leisure walking was most common among nonHispanic whites and Asian/Native Hawaiian Pacific Islanders and least common among Hispanics. Leisure walking was also low among men of other or multiple races. Leisure walking was highest among more educated adults; with N 50% for those who were college graduates, and lower among less-educated respondents. Results showed that leisure walking was highest among respondents with incomes N =300% of the poverty level (43.3% men; 51.3% women) and was reported by about 30% of adults with incomes at or below the poverty level. Among adults who were working, 39.2% of men and 47.5% of women engaged in leisure walking. The prevalence of leisure walking was lowest among adults with higher BMIs. Lastly, among those without activity limitations, men (40%) were less active than women (48%); among those with activity limitations, men (32%) were more active than women (25%). When we analyzed walking for transportation alone, 6% of adults were regularly active (N5 days/week for N30 min/day) (data not shown). Men were more likely to be regularly active based on walking for transportation than women (6.6% vs. 4.7%
respectively). The percentage of adults who were regularly active by walking for leisure was 9% (8.7% men; 9.5% women). We do not report estimates based on both types of walking combined because the survey did not determine whether transportation and leisure walking occurred on different days. Discussion We estimated that in 2005, just over 40% of U.S. adults walked for leisure, and almost 30% of adults walked for transportation. However, a much smaller percentage of the U.S. population was considered regularly active from either walking for transportation (6%) or walking for leisure (9%). Because walking is so commonly reported and has measurable health benefits, the need for interventions to increase the amount and prevalence of leisure and transportation walking is great (USDHHS, 1996; Saelens et al., 2003). Our findings add to the literature and confirm that walking is a common form of physical activity. Direct comparisons with past studies are difficult, but our estimates are qualitatively similar to those obtained from past in-person and telephone health surveys that relied on standardized survey questions (Berrigan and Troiano, 2002; Eyler et al., 2003). In NHANES III (1988–1994), 54.7% of U.S. adults reported walking 1 or more miles per month for any reason, and 14.6% reported 20 or more such walks (Berrigan and Troiano, 2002). Data from the 1998 Behavioral Risk Factor Surveillance System (BRFSS) indicated that 38.6% of U.S. adults reported walking for physical activity (Rafferty et al., 2002). In the 2001 NHIS, another in-person interview survey, self-reported prevalence of “usual” walking/biking for transportation ranged from 12.9% among non-Hispanic whites to 20.2% among Hispanics (Berrigan et al., 2006a). By contrast, 41.2% of Californians report any non-leisure time transportation walking or bicycling (Berrigan et al., 2006b). The NHTS results indicate that in 2001, 21.1% of all trips less than 1 mile were made on foot (Ham et al., 2005). The literature includes studies that used various time frames and survey methods. Results from this study show consistency with previous reports in walking for leisure. However, we found that walking for transportation increased with education level, whereas the NHTS data showed that walking for transportation has a J-shaped relationship with education level and that those with the least education are least likely to have access to private vehicles. It is possible that the context of the health survey elicited overreporting among the more educated adults. Further research is needed to identify the best methods for measuring walking for transportation and for leisure (http://appliedresearch.cancer. gov/tools/paq/). Nevertheless different survey methods do result in somewhat different estimates of walking prevalence. The interview mode, the temporal domain associated with survey questions, and the survey context can influence self-reported prevalence of walking for different reasons (Tourangeau et al., 2000). Health surveys and transportation diaries use different approaches to assess time spent in various activities and present different cognitive challenges in assessing past behavior. Validation
J. Kruger et al. / Preventive Medicine 47 (2008) 329–334
studies relating responses to travel surveys, time use surveys, standardized survey questions, and direct measurements of walking, particularly in specific bouts, are lacking; however, responses to both travel and health surveys are correlated with measures of total levels of physical activity based on pedometers, accelerometers, and heart rate monitors (Ainsworth et al., 2000). Equivalent thresholds for steps/day measured by pedometers to classify people as walking or not walking are not available because pedometers capture all ambulatory activities in addition to walking behaviors that are measured by selfreport. Therefore, best practices have not yet been identified for how to measure actual levels of walking and walking intensity in different domains among non-institutionalized adults. Ideally, relative levels of walking could be estimated by using a single instrument to measure walking for different purposes, and this instrument might allow satisfactory estimation of national prevalence and evaluation of the effectiveness of interventions, even if the absolute levels of walking are not measured precisely. These concerns have significant implications for the evaluation of interventions that aim to increase walking as well as other forms of physical activity, such as bicycling. Only about 5–10% of respondents were regularly active solely by walking for transportation or leisure. This finding is consistent with previous reports of the prevalence of adults who engage in sufficient levels of regular walking. The 1997 Australian Bureau of Statistics showed that 7.3% of adults were active at levels sufficient to meet Australian recommendations by walking for exercise, and 6.6% were active at levels sufficient to meet recommendations by walking for transportation (Tudor-Locke et al., 2004). Among U.S. adults, our findings for walking for leisure are similar to those from the 1996 to 1998 BRFSS, which showed that 6.4% of Michigan residents walked for leisure at patterns that approximate. There are no physical activity recommendations (CDC, 2000) for walking alone. However, because walking is so predominant, clear messages encouraging walking for transportation and walking for leisure could help to increase activity rates (Beaudoin et al., 2007; Wray et al., 2005). Such targeting could be more cost effective than generic campaigns to increase walking, but data are lacking. The Community Guide to Preventive Services has identified three evidence-based strategies to increase physical activity at the community level, including 1) increased access combined with informational approaches; 2) interventions providing behavioral, and social support to individuals and community-wide campaigns, and 3) environmental and policy approaches (CDC, 2005). Our study highlights the need to match interventions related to walking and the function of walking trips. One path towards this goal might involve encouraging developers to design residential environments that promote walking routes that could assist in meeting recommendations by walking, given that the prevalence of walking varies for adults living in suburban (39.8%), urban (35.6%), and rural (27.0%) environments (Eyler et al., 2003). In addition, a number of research tested intervention programs to increase physical activity are available from the internet (http://cancercontrolplanet.cancer.gov/physical_activity. html).
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This study has several limitations. First, data are based on selfreports and could include reporting errors related to recall bias and bias associated with social desirability of physical activity (Sallis and Saelens, 2000). Second, these data are cross-sectional and therefore no causal associations between levels of walking and demographic/SES variables in this study can be demonstrated. Third, data on intensity of walking was not collected. Walking for transportation or for leisure can be done at light or moderate intensities, thus we cannot make the assumption that all reported walking was of moderate intensity. Moreover, to assess whether people meet public health recommendations, it is important to ascertain frequency, intensity, and duration of physical activity. Fourth, although the survey questions were reviewed by experts, cognitively tested in a small sample of U.S. adults, and pilot tested for clarity, the items were not formally validated. Similar questions have been subject to reliability and validity testing; thus, it seems likely that these questions would show similar levels of validity (Sallis and Saelens, 2000). Conclusion Walking may help adults meet public health guidelines related to physical activity. These data provides a snapshot of walking behavior in a large and representative sample of U.S. adults and suggests that if respondents are only asked to report their leisure-time activities, the potential gain in health benefits derived from walking for transportation could be overlooked by health surveys. Since walking for leisure and transportation is among the most common forms of physical activity, collecting data on the proportion of adults who engage in these types of activities may help guide the design of interventions aimed at increasing physical activity. References Ainsworth, B.E., Bassett Jr., D.R., Strath, S.J., Swartz, A.M., O'Brien, W.L., Thompson, R.W., Jones, D.A., Macera, C.A., Kimsey, C.D., 2000. Comparison of three methods for measuring the time spent in physical activity. Med. Sci. Sports Exerc. 32 (9 Suppl), S457–S464. Beaudoin, C.E., Fernandez, C., Wall, J.L., Farley, T.A., 2007. Promoting healthy eating and physical activity: short-term effects of a mass media campaign. Am. J. Prev. Med. 32 (3), 217–223. Berrigan, D., Troiano, R.P., 2002. The association between urban form and physical activity in U.S. adults. Am. J. Prev. Med. 23 (2 Suppl), 74–79. Berrigan, D., Dodd, K., Troiano, R.P., Reeve, B.B., Ballard-Barbash, R., 2006a. Physical activity and acculturation among adult Hispanics in the United States. Res. Q. Exerc. Sport 77 (2), 147–157. Berrigan, D., Troiano, R.P., McNeel, T., Disogra, C., Ballard-Barbash, R., 2006b. Active transportation increases adherence to activity recommendations. Am. J. Prev. Med. 31 (3), 210–216. CDC, 2000. Compliance with physical activity recommendations by walking for exercise-Michigan, 1996 and 1998. Morb. Mort. Wkly Rep. 49 (25), 560–565. CDC, 2005. Task Force on Community Preventive Services. Guide to community preventive services. Physical activity. US Department of Health and Human Services, Atlanta, GA. Available at http://www.thecommunityguide.org/pa/ default.htm. Dunton, G.F., Schneider, M., 2006. Perceived barriers to walking for physical activity. Prev. Chronic Dis. [serial online] Available from: URL: http://www. cdc.gov/pcd/issues/2005/oct/05_0185.htm. Eyler, A.A., Borwnson, R., Barcak, S.G., Housemann, R.A., 2003. The epidemiology of walking for physical activity in the United States. Med. Sci. Sports Exerc. 35 (9), 1529–1536.
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Ham, S.A., Macera, C.A., Lindley, C., 2005. Trends in walking for transportation in the United States, 1995 and 2001. Prev. Chronic Dis. [serial online] Available from: URL: http://www.cdc.gov/pcd/issues/2005/oct/04_0138.htm. Pate, R.R., Pratt, M., Blair, S.N., Haskell, W.L., Macera, C.A., Bouchard, C., Buchner, D., Ettinger, Heath, G.W., King, A.C., et al., 1995. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 273, 402–407. Rafferty, A.P., Reeves, M.J., McGee, H.B., Pivarnik, J.M., 2002. Physical activity patterns among walkers and compliance with public health recommendations. Med. Sci. Sports Exerc. 34, 1255–1261. Saelens, B.E., Sallis, J.F., Frank, L.D., 2003. Environmental correlates of walking and cycling: findings from the transportation, urban design, and planning literatures. Ann. Behav. Med. 25 (2), 80–91. Sallis, J.F., Saelens, B.E., 2000. Assessment of physical activity by self-report: status, limitations, and future directions. Res. Q. Exerc. Sport 71 (2 Suppl), S1–S14.
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Preventive Medicine 47 (2008) 329 – 334 www.elsevier.com/locate/ypmed
Prevalence of transportation and leisure walking among U.S. adults ☆ Judy Kruger a,⁎, Sandra A. Ham a , David Berrigan b , Rachel Ballard-Barbash b a
b
Division of Nutrition, Physical Activity and Obesity, Centers for Disease Control and Prevention, Atlanta, Georgia, USA Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, Maryland, USA Available online 10 March 2008
Abstract Objective. This paper aims to contrast the demographic correlates of leisure and transportation walking. Methods. Using data from the 2005 National Health Interview Survey (n = 31,482), this paper reports on the prevalence of transportation walking and leisure walking for U.S. adults and examines the variation in prevalence across different socio-demographic groups. The prevalence of transportation walking and leisure walking for U.S. adults (≥5 days/week for ≥ 30 min/day) was calculated using data from the 2005 National Health Interview Survey. Results. In the United States, 41.5% of adults walked for leisure and 28.2% walked for transportation in intervals of at least 10 min. The highest prevalence of transportation walking was among black non-Hispanic men (36.0%) and Asian/Native Hawaiian/Pacific Islander women (40.5%). The highest prevalence of leisure walking was among Asian/Native Hawaiian/Pacific Islander men (42.0%) and white non-Hispanic women (46.6%). Leisure walking was most prevalent among respondents with higher incomes and education levels, whereas transportation walking increased in prevalence with education level but decreased with income level. Based on the findings, 6% of U.S. adults were considered regularly active (≥ 5 days/week for ≥ 30 min/day) by walking for transportation and 9% were regularly active by walking for leisure. Conclusion. Leisure and transportation walking have distinctly different demographic correlates. These differences should guide interventions aimed at influencing walking for different purposes. Published by Elsevier Inc. Keywords: Walking; Physical activity; Transportation
Introduction Physical inactivity is associated with multiple adverse health outcomes, including increased risk for cardiovascular disease, diabetes, and cancer (USDHHS, 1996). Most Americans are not active enough to obtain all or most of the health benefits associated with physical activity (USDHHS, 1996). The physical activity and public health recommendations are that every adult should accumulate 30 min or more of moderate-intensity physical activity on most, preferably all, days of the week (USDHHS, 1996; Pate et al., 1995). Brisk walking is a form of physical ☆
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention. ⁎ Corresponding author. Physical Activity and Health Branch, Division of Nutrition, Physical Activity and Obesity, 4770 Buford Highway, NE (MS K-46), Atlanta, GA 30341, USA. Fax: +1 770 488 5473. E-mail address: [email protected] (J. Kruger). 0091-7435/$ - see front matter. Published by Elsevier Inc. doi:10.1016/j.ypmed.2008.02.018
activity that adults can use to meet these recommendations (USDHHS, 1996). Walking is one of the most common and accessible forms of physical activity and requires no special equipment, facilities, or training (Dunton and Schneider, 2006). Thus, it seems clear that understanding who walks and why could be useful in the design of walking related interventions aimed at increasing physical activity. The CDC has recommended some evidence-based interventions to increase walking (CDC 2005). However, knowledge about how to target these interventions is lacking (Saelens et al., 2003). National statistics on walking trends come from three surveillance systems and are based entirely on self-reports. The National Health and Nutrition Examination Survey (NHANES) estimated walking sessions over a 30-day period (http://www.cdc. gov/nchs/nhanes.htm). The National Health Interview Survey (NHIS) collected information on participation in habitual walking or biking for transportation in 2000 (http://www.cdc.gov/nchs/nhis. htm). The National Household Transportation Survey (NHTS)
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measured walking for transportation on one day (http://nhts.ornl. gov/). These surveys use different data collection methods, use different time units to measure walking (i.e., day, week, and month) and occur in different contexts. Thus, comparisons of the prevalence of walking for different reasons have been difficult (Troiano et al., 2001). Moreover, none of these surveys queried walking for leisure and transportation measured as days per week, the frequency units that are used by the physical activity recommendations (USDHHS, 1996). Recently, questions concerning both leisure and transportation walking were added to the NHIS, allowing direct comparisons of the prevalence of transportation and leisure walking. This paper reports estimates of the prevalence of walking for both transportation and leisure among U.S. adults aged N=18 years based on survey questions that addressed each type of walking separately. Our objectives were to: 1) report on the prevalence and
correlates of walking for transportation; 2) report on the prevalence and correlates of walking for leisure, and 3) estimate the prevalence of adults who were regularly active based on walking for transportation or leisure (≥5 days/week for ≥30 min/day). Methods These results are based on the 2005 National Health Interview Survey (NHIS) conducted by the National Center for Health Statistics and administered by the U.S. Census Bureau. The survey is a continuing in-person survey of approximately 40,000 households in the civilian non-institutionalized population with a multi-stage area probability design covering the 48 contiguous states. Walking questions were contained in a Cancer Control Module (CCM), administered to one adult aged 18 years or older in each household (N = 31,428). The main body of the survey included queries concerning diverse demographicand socioeconomic-related variables as well as other health-related questions. The response rate for adults was 69.0% (ftp://ftp.cdc.gov/pub/Health_Statistics/ NCHS/Dataset_Documentation/NHIS/2005/srvydesc.pdf).
Table 1 Percentages of adults who walked for transportation a Men
Overall Demographics Age, years 18–34 35–49 50–64 65–74 ≥75 Race/ethnicity White, non-Hispanic Black, non-Hispanic Hispanic Asian/Native Hawaiian/Pacific Islander Other, multiracial SES related variables Education level bHigh school High school Some college College graduate Income-poverty ratio b100% 100–b200% 200–b300% ≥300% Work status Working Not working Physical and health status Self-rated health Good, very good, excellent Fair, poor Body mass index b25.0 25.0–b30.0 ≥30.0 Activity limitation No Yes
Women
n
%
95% CI
n
%
95% CI
12,858
30.3
(29.1, 31.4)
16,621
26.4
(25.3, 27.4)
3628 3880 3097 1254 999
35.2 30.5 28.2 23.4 20.2
(33.1, 37.3) (28.8, 32.3) (26.5, 30.0) (20.8, 26.3) (17.5, 23.3)
4631 4686 3846 1641 1817
30.8 28.3 24.6 20.9 15.1
(28.9, 32.7) (26.6, 30.0) (23.0, 26.3) (18.6, 23.4) (13.3, 17.2)
8453 1522 2293 415 161
29.3 36.0 31.0 34.4 21.2
(28.0, 30.5) (33.2, 38.8) (28.4, 33.6) (29.0, 40.2) (14.8, 29.3)
10,619 2427 2873 455 232
25.0 26.8 30.9 40.5 20.1
(23.8, 26.2) (24.5, 29.2) (28.7, 33.2) (35.9, 45.3) (15.1, 26.2)
2369 3608 3433 3360
26.9 25.1 32.2 36.1
(24.7, 29.3) (23.4, 26.9) (30.2, 34.2) (34.3, 38.1)
3105 4757 4790 3845
24.9 20.5 28.0 32.7
(22.9, 26.9) (19.0, 22.0) (26.3, 29.8) (30.8, 34.7)
1568 2422 2213 6656
35.0 28.7 27.3 30.7
(31.3, 38.9) (26.3, 31.3) (25.0, 29.8) (29.3, 32.2)
2944 3718 2818 7141
32.4 23.4 24.5 26.6
(29.8, 35.1) (21.4, 25.5) (22.5, 26.6) (25.3, 27.9)
8661 4188
30.9 28.8
(29.7, 32.1) (26.9, 30.8)
8830 7771
28.5 23.8
(27.2, 29.8) (22.4, 25.2)
11,185 1665
31.7 19.1
(30.5, 32.9) (17.0, 21.4)
14,072 2544
27.9 16.7
(26.7, 29.1) (15.0, 18.4)
4064 5482 3139
32.4 30.5 27.8
(30.6, 34.2) (29.0, 32.1) (25.8, 29.9)
7105 4563 4193
29.7 24.8 22.7
(28.3, 31.2) (23.1, 26.5) (21.1, 24.3)
10,835 2017
31.8 20.6
(30.6, 33.0) (18.4, 23.0)
13,532 3072
28.4 15.9
(27.2, 29.6) (14.4, 17.6)
National Health Interview Survey, 2005. a Walking for transportation refers to get some place such as work, school, or restaurant.
J. Kruger et al. / Preventive Medicine 47 (2008) 329–334 Walking for transportation was measured by the questions, “During the past seven days, did you walk to get some place that took you at least 10 minutes?” Those who said ”yes” were asked, “During the past seven days, on how many days did you walk for at least 10 minutes at a time to get some place such as work, school, or restaurant?” Those who responded that they walked for at least one day were then asked “How much time did you usually spend on one of those days walking to get from place to place?” Respondents who reported a regular pattern of walking for transportation (i.e., N=5 days per week for N=30 min each day), were considered regularly active. Walking for leisure was assessed by the questions, “Sometimes you may walk for fun, relaxation, exercise, or to walk the dog. During the past seven days, did you walk for at least 10 minutes at a time for any of these reason? Please do not include any walking that you already told me about?” Those who said ”yes” were asked, “During the past seven days, on how many days did you walk for at least 10 minutes at a time for fun, relaxation, exercise or to walk the dog?” Those who responded ”yes” were asked to report the number of days per week and the average total time per day spent in these activities. Respondents were classified as being regularly active by walking for leisure using the same criteria described above for walking for transportation.
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The prevalence of walking was examined by demographic characteristics, socioeconomic status (SES), and health status. Income was reported using an income-poverty ratio in the following four categories: b100%, 100–200%, 200– 300% and N300% (an income-poverty ratio of b100% indicated that a family was at or below the poverty level). These variables accounted for differences in family size and were standardized for inflation and other factors (http://www.census.gov/ hhes/www/poverty/poverty.html). Respondents were classified as working last week (e.g., working for pay at a job or business, working but not for pay at a job or business) and not working last week (e.g., not working at a job or business, with a job or business but not at work, looking for work, and not looking for work). We calculated respondents' body mass index (BMI) from self-reported height and weight (kg/m2) and divided the sample into three BMI categories: normal weight (18.5 to b25.0), overweight (N25.0 to b30.0), and obese (N30.0). Respondents who were missing information were excluded from our analysis. Data were analyzed using SUDAAN (Version 9.0; Research Triangle Institute, Research Triangle Park, NC) with appropriate weighting to account for the complex sample design. Prevalence (%) and 95% confidence intervals were reported for walking for transportation and walking for leisure, stratified by gender and categorized by several demographic, SES, and health-related measures.
Table 2 Percentages of adults who walked for leisure a Men
Overall Demographics Age, years 18–34 35–49 50–64 65–74 ≥75 Race/ethnicity White, non-Hispanic Black, non-Hispanic Hispanic Asian/Native Hawaiian/Pacific Islander Other, multiracial SES Related Variables Education level bHigh school High school Some college College graduate Income-poverty ratio b100% 100–b200% 200–b300% ≥300% Work status Working Not working Physical and health status Self-rated health Good, very good, excellent Fair, poor Body mass index b25.0 25.0–b30.0 ≥30.0 Activity limitation No Yes
Women %
95% CI
%
95% CI
12,860
38.9
(37.8, 40.0)
16,620
43.9
(42.8, 45.0)
3637 3880 3097 1246 1000
36.1 40.0 40.4 43.3 37.2
(34.2, 37.9) (38.2, 41.8) (38.5, 42.3) (40.1, 46.6) (33.9, 40.6)
4635 4689 3850 1636 1810
46.6 48.2 43.4 38.6 27.1
(44.7, 48.6) (46.5, 49.8) (41.4, 45.4) (35.9, 41.4) (25.0, 29.4)
8445 1524 2295 417 165
40.4 32.5 36.2 42.0 29.0
(39.1, 41.7) (29.5, 35.6) (34.0, 38.5) (37.0, 47.2) (22.2, 36.8)
10,617 2429 2877 450 232
46.6 31.6 39.2 46.2 40.7
(45.3, 47.9) (29.4, 33.8) (36.9, 41.5) (41.3, 51.1) (30.6, 51.6)
2375 3612 3433 3352
31.7 32.2 38.7 51.1
(29.5, 34.1) (30.4, 34.0) (36.7, 40.6) (49.2, 53.1)
3102 4757 4797 3842
30.5 37.9 46.8 56.4
(28.4, 32.8) (36.1, 39.8) (45.1, 48.6) (54.5, 58.3)
1575 2422 2210 6653
30.6 33.2 35.2 43.3
(27.4, 34.1) (30.7, 35.8) (32.8, 37.8) (41.8, 44.8)
2938 3727 2818 7137
31.9 34.6 42.1 51.3
(29.7, 34.2) (32.6, 36.6) (39.7, 44.5) (49.8, 52.8)
8675 4,177
39.2 38.3
(37.9, 40.5) (36.6, 40.1)
8838 7763
47.5 39.5
(46.1, 48.9) (38.1, 40.9)
11,190 1664
40.2 28.8
(39.0, 41.4) (26.2, 31.6)
14,072 2543
47.1 23.1
(46.0, 48.3) (21.3, 25.1)
4060 5480 3145
38.7 41.5 35.8
(36.9, 40.6) (39.9, 43.2) (34.0, 37.6)
7112 4563 4183
48.5 44.2 36.5
(47.0, 50.1) (42.4, 46.0) (34.8, 38.2)
10,835 2019
40.1 31.8
(38.9, 41.2) (29.3, 34.4)
13,541 3062
47.5 25.3
(46.3, 48.7) (23.6, 27.1)
National Health Interview Survey, 2005. a Walking for leisure-time refers to fun, relaxation, exercise or to walk the dog.
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Results The nationally representative sample of U.S. adults included 13,762 men and 17,666 women. About one-third were aged 18– 34 years; 26.6% were college graduates; 64.4% were nonHispanic whites, 62.7% had BMIs ≥ 25.0, and 15.5% had income-poverty ratios of b 100%. In 2005, an estimated 28.2% (95% CI = 27.3, 29.1) of U.S. adults engaged in walking for transportation. Men (30.3%) were more likely to walk for transportation than women (26.4%) (Table 1). The median frequency of walking for transportation for both men and women was 3 days/week, and the median duration was 20 min/day. Adults aged 18–34 years had the greatest prevalence of walking for transportation compared with other age groups. Among racial/ethnic groups, black nonHispanic men (36.0%) and Asian/Native Hawaiian/Pacific Islander women (40.5%) were most likely to walk for transportation. Transportation walking was highest among college graduates (36.1% men; 32.7% women) and lower among lesseducated respondents. In contrast, transportation walking was highest in the lowest income groups, with 35% of men and 32.4% of women reporting transportation walking. Among those who were working, 30.9% of men and 28.5% of women walked for transportation. Most adults who reported good, very good, or excellent health walked for transportation. Walking for transportation was slightly more prevalent among respondents with normal BMI for both men and women and substantially more prevalent among respondents reporting no activity limitations. For example about 32% of men without activity limitations reported transportation walking compared with only 21% with such limitations. Approximately 41.5% (95% CI = 40.7, 42.4) of adults walked for leisure (38.9% men; 43.9% women) (Table 2). The median frequency of walking for leisure for both men and women was 3 days/week, and the median duration was 30 min/ day. The prevalence of leisure walking increased with age until age 74 among men and until age 49 among women. For both genders, leisure walking was most common among nonHispanic whites and Asian/Native Hawaiian Pacific Islanders and least common among Hispanics. Leisure walking was also low among men of other or multiple races. Leisure walking was highest among more educated adults; with N 50% for those who were college graduates, and lower among less-educated respondents. Results showed that leisure walking was highest among respondents with incomes N =300% of the poverty level (43.3% men; 51.3% women) and was reported by about 30% of adults with incomes at or below the poverty level. Among adults who were working, 39.2% of men and 47.5% of women engaged in leisure walking. The prevalence of leisure walking was lowest among adults with higher BMIs. Lastly, among those without activity limitations, men (40%) were less active than women (48%); among those with activity limitations, men (32%) were more active than women (25%). When we analyzed walking for transportation alone, 6% of adults were regularly active (N5 days/week for N30 min/day) (data not shown). Men were more likely to be regularly active based on walking for transportation than women (6.6% vs. 4.7%
respectively). The percentage of adults who were regularly active by walking for leisure was 9% (8.7% men; 9.5% women). We do not report estimates based on both types of walking combined because the survey did not determine whether transportation and leisure walking occurred on different days. Discussion We estimated that in 2005, just over 40% of U.S. adults walked for leisure, and almost 30% of adults walked for transportation. However, a much smaller percentage of the U.S. population was considered regularly active from either walking for transportation (6%) or walking for leisure (9%). Because walking is so commonly reported and has measurable health benefits, the need for interventions to increase the amount and prevalence of leisure and transportation walking is great (USDHHS, 1996; Saelens et al., 2003). Our findings add to the literature and confirm that walking is a common form of physical activity. Direct comparisons with past studies are difficult, but our estimates are qualitatively similar to those obtained from past in-person and telephone health surveys that relied on standardized survey questions (Berrigan and Troiano, 2002; Eyler et al., 2003). In NHANES III (1988–1994), 54.7% of U.S. adults reported walking 1 or more miles per month for any reason, and 14.6% reported 20 or more such walks (Berrigan and Troiano, 2002). Data from the 1998 Behavioral Risk Factor Surveillance System (BRFSS) indicated that 38.6% of U.S. adults reported walking for physical activity (Rafferty et al., 2002). In the 2001 NHIS, another in-person interview survey, self-reported prevalence of “usual” walking/biking for transportation ranged from 12.9% among non-Hispanic whites to 20.2% among Hispanics (Berrigan et al., 2006a). By contrast, 41.2% of Californians report any non-leisure time transportation walking or bicycling (Berrigan et al., 2006b). The NHTS results indicate that in 2001, 21.1% of all trips less than 1 mile were made on foot (Ham et al., 2005). The literature includes studies that used various time frames and survey methods. Results from this study show consistency with previous reports in walking for leisure. However, we found that walking for transportation increased with education level, whereas the NHTS data showed that walking for transportation has a J-shaped relationship with education level and that those with the least education are least likely to have access to private vehicles. It is possible that the context of the health survey elicited overreporting among the more educated adults. Further research is needed to identify the best methods for measuring walking for transportation and for leisure (http://appliedresearch.cancer. gov/tools/paq/). Nevertheless different survey methods do result in somewhat different estimates of walking prevalence. The interview mode, the temporal domain associated with survey questions, and the survey context can influence self-reported prevalence of walking for different reasons (Tourangeau et al., 2000). Health surveys and transportation diaries use different approaches to assess time spent in various activities and present different cognitive challenges in assessing past behavior. Validation
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studies relating responses to travel surveys, time use surveys, standardized survey questions, and direct measurements of walking, particularly in specific bouts, are lacking; however, responses to both travel and health surveys are correlated with measures of total levels of physical activity based on pedometers, accelerometers, and heart rate monitors (Ainsworth et al., 2000). Equivalent thresholds for steps/day measured by pedometers to classify people as walking or not walking are not available because pedometers capture all ambulatory activities in addition to walking behaviors that are measured by selfreport. Therefore, best practices have not yet been identified for how to measure actual levels of walking and walking intensity in different domains among non-institutionalized adults. Ideally, relative levels of walking could be estimated by using a single instrument to measure walking for different purposes, and this instrument might allow satisfactory estimation of national prevalence and evaluation of the effectiveness of interventions, even if the absolute levels of walking are not measured precisely. These concerns have significant implications for the evaluation of interventions that aim to increase walking as well as other forms of physical activity, such as bicycling. Only about 5–10% of respondents were regularly active solely by walking for transportation or leisure. This finding is consistent with previous reports of the prevalence of adults who engage in sufficient levels of regular walking. The 1997 Australian Bureau of Statistics showed that 7.3% of adults were active at levels sufficient to meet Australian recommendations by walking for exercise, and 6.6% were active at levels sufficient to meet recommendations by walking for transportation (Tudor-Locke et al., 2004). Among U.S. adults, our findings for walking for leisure are similar to those from the 1996 to 1998 BRFSS, which showed that 6.4% of Michigan residents walked for leisure at patterns that approximate. There are no physical activity recommendations (CDC, 2000) for walking alone. However, because walking is so predominant, clear messages encouraging walking for transportation and walking for leisure could help to increase activity rates (Beaudoin et al., 2007; Wray et al., 2005). Such targeting could be more cost effective than generic campaigns to increase walking, but data are lacking. The Community Guide to Preventive Services has identified three evidence-based strategies to increase physical activity at the community level, including 1) increased access combined with informational approaches; 2) interventions providing behavioral, and social support to individuals and community-wide campaigns, and 3) environmental and policy approaches (CDC, 2005). Our study highlights the need to match interventions related to walking and the function of walking trips. One path towards this goal might involve encouraging developers to design residential environments that promote walking routes that could assist in meeting recommendations by walking, given that the prevalence of walking varies for adults living in suburban (39.8%), urban (35.6%), and rural (27.0%) environments (Eyler et al., 2003). In addition, a number of research tested intervention programs to increase physical activity are available from the internet (http://cancercontrolplanet.cancer.gov/physical_activity. html).
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This study has several limitations. First, data are based on selfreports and could include reporting errors related to recall bias and bias associated with social desirability of physical activity (Sallis and Saelens, 2000). Second, these data are cross-sectional and therefore no causal associations between levels of walking and demographic/SES variables in this study can be demonstrated. Third, data on intensity of walking was not collected. Walking for transportation or for leisure can be done at light or moderate intensities, thus we cannot make the assumption that all reported walking was of moderate intensity. Moreover, to assess whether people meet public health recommendations, it is important to ascertain frequency, intensity, and duration of physical activity. Fourth, although the survey questions were reviewed by experts, cognitively tested in a small sample of U.S. adults, and pilot tested for clarity, the items were not formally validated. Similar questions have been subject to reliability and validity testing; thus, it seems likely that these questions would show similar levels of validity (Sallis and Saelens, 2000). Conclusion Walking may help adults meet public health guidelines related to physical activity. These data provides a snapshot of walking behavior in a large and representative sample of U.S. adults and suggests that if respondents are only asked to report their leisure-time activities, the potential gain in health benefits derived from walking for transportation could be overlooked by health surveys. Since walking for leisure and transportation is among the most common forms of physical activity, collecting data on the proportion of adults who engage in these types of activities may help guide the design of interventions aimed at increasing physical activity. References Ainsworth, B.E., Bassett Jr., D.R., Strath, S.J., Swartz, A.M., O'Brien, W.L., Thompson, R.W., Jones, D.A., Macera, C.A., Kimsey, C.D., 2000. Comparison of three methods for measuring the time spent in physical activity. Med. Sci. Sports Exerc. 32 (9 Suppl), S457–S464. Beaudoin, C.E., Fernandez, C., Wall, J.L., Farley, T.A., 2007. Promoting healthy eating and physical activity: short-term effects of a mass media campaign. Am. J. Prev. Med. 32 (3), 217–223. Berrigan, D., Troiano, R.P., 2002. The association between urban form and physical activity in U.S. adults. Am. J. Prev. Med. 23 (2 Suppl), 74–79. Berrigan, D., Dodd, K., Troiano, R.P., Reeve, B.B., Ballard-Barbash, R., 2006a. Physical activity and acculturation among adult Hispanics in the United States. Res. Q. Exerc. Sport 77 (2), 147–157. Berrigan, D., Troiano, R.P., McNeel, T., Disogra, C., Ballard-Barbash, R., 2006b. Active transportation increases adherence to activity recommendations. Am. J. Prev. Med. 31 (3), 210–216. CDC, 2000. Compliance with physical activity recommendations by walking for exercise-Michigan, 1996 and 1998. Morb. Mort. Wkly Rep. 49 (25), 560–565. CDC, 2005. Task Force on Community Preventive Services. Guide to community preventive services. Physical activity. US Department of Health and Human Services, Atlanta, GA. Available at http://www.thecommunityguide.org/pa/ default.htm. Dunton, G.F., Schneider, M., 2006. Perceived barriers to walking for physical activity. Prev. Chronic Dis. [serial online] Available from: URL: http://www. cdc.gov/pcd/issues/2005/oct/05_0185.htm. Eyler, A.A., Borwnson, R., Barcak, S.G., Housemann, R.A., 2003. The epidemiology of walking for physical activity in the United States. Med. Sci. Sports Exerc. 35 (9), 1529–1536.
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