INTERVENTIONS TO INCREASE WALKING BEHAVIOR
Walking is the most frequently reported activity in surveys of leisure-time physical activity (54,58) and is associated with numerous health benefits (25). Surveillance estimates among US adults indicate that about 30% of men and 47% of women report walking in their leisure time and about 50% report walking at least 3 d·wk−1 for 30 min per occasion or about 1.5 h·wk−1 (55). However, if one considers walking done at home, work, and during leisure time; about 80% of adults in the United States report walking for 10 min at a time on at least 1 d·wk−1 (2). In this survey of US adults, the median duration reported for purposeful walking for any reason was about 4 h·wk−1. Objective estimates of walking behavior in the US population indicate that adults accumulate 6000 to 7000 steps per day on average (57,59). In contrast, subgroups of North American adults who do not use the full complement of labor saving devices in their daily lives routinely accumulate 15,000 to 20,000 steps per day (1). In summary, walking is a highly prevalent form of activity that can be done at work, home, and during leisure time, which makes this form of activity a logical choice for intervention efforts (24,27).
Although researchers have made great strides in understanding the impact of physical activity on biological mechanisms that influence the natural history of chronic diseases, the current challenge is to continue to develop intervention programs that successfully target the psychological and the social-ecological mechanisms that mediate and moderate the adoption and the maintenance of physical activity. The purpose of this paper is to review studies of walking promotion interventions. Non-face-to-face (i.e., mediated) interventions that targeted overall physical activity are also briefly discussed, given their good fit for delivering home-based walking programs.
We searched PubMed and PsychINFO databases for studies from 1980 forward that included the word "walk" (including, for example, "walking," "walkers") in the study title. Study titles and abstracts were scanned. Because we wanted to distinguish walking promotion interventions from more general physical activity interventions, full text articles were obtained only for studies that specifically examined the effects of a walking promotion intervention on walking behavior change. Studies that measured walking outcomes but did not exclusively target walking behavior [e.g., Ref. (45)] were not included. Additionally, a number of studies that tested the effects of a walking program on one or more targeted health outcomes (e.g., obesity) were not included in this review if control groups were explicitly asked not to increase their walking [e.g., Refs. (13,42)]. In addition to our database search, we searched references from articles obtained via the search methods above and reference sections from other reviews of physical activity promotion interventions [e.g., Refs. (18,21,38)] and retrieved articles if they met the above inclusion criteria. Through this process, we obtained additional studies of walking interventions that did not include the word "walk" in the study title. Specifically, we located 14 randomized controlled trials (RCT) that randomized individual participants to one or more walking interventions and/or a control condition and examined walking behavior outcomes (Table 1). These studies are the focus of our review.
WALKING PROMOTION INTERVENTIONS
We found three RCT that tested the efficacy of walking promotion programs versus a control condition that did not include a physical activity program (23,44,49,56). Kriska et al. (23) found greater walking behavior at 1 and 2 yr, relative to no-treatment controls, among healthy postmenopausal women who received an intensive 8-wk face-to-face walking program, followed by continued face-to-face contact if desired, plus frequent phone prompts and monthly newsletters over 24 months. A follow-up analysis conducted 10 yr after the end of the initial 24-month period found that women in the treatment condition continued to walk significantly more than controls and significantly more than initial baseline values (49). Similarly, Mutrie et al. (44) found that previously inactive UK worksite employees who received a packet of print materials, including theory-based physical activity promotion booklets and maps highlighted with possible walking routes to each participant's worksite, were almost twice as likely to be walking to work 6 months later compared with participants in a wait-list control condition. A third trial, conducted by Talbot et al. (56), found significant increases in walking among adults over age 60 with diagnosed osteoarthritis of the knee who were given three brief walking promotion counseling sessions every 4 wk over a 12-wk period compared with participants who received arthritis education only. The walking increases were not maintained, however, at 24 wk. Taken together, the findings show that intensive walking interventions can increase walking behavior relative to no treatment, with one trial showing long-term maintenance of walking increases among healthy women.
All of the other RCT that we found tested the efficacy of one or more aspects of a walking program against other walking programs that varied with respect to the intervention components (8-11,19,20,28,47,50,53). The greatest number of studies examined the efficacy of telephone prompts as an intervention adjunct or as the primary intervention (10,28,20,47). Humpel et al. (20) found no additional benefit of three weekly telephone counseling sessions when added to print materials distributed over the same 3-wk period among adult clients of an Australian health care organization (20). However, both groups had significantly increased walking at the time assessments were conducted-1 month following the end of the 3-wk intervention-and because there was no assessment immediately posttreatment, it is not clear whether there were group differences at that time. Three additional studies each included a treatment arm that received brief physical activity counseling and/or educational materials at baseline only and compared this minimal treatment to multiple additional treatment arms receiving the minimal treatment plus different frequencies, durations, or types of phone prompts (10,28,47). Nies et al. (47) found increases in walking that were not different from the minimal intervention group among women receiving short-duration telephone prompts or an equal number of longer-duration telephone counseling sessions. In a 2 × 2 design plus a minimal intervention group, Lombard et al. (28) found that receiving telephone prompts versus no prompts and receiving more frequent prompts resulted in greater increases in walking behavior among women, although, consistent with Nies et al. (47), prompt duration (i.e., prompts vs counseling) had no effect on walking outcomes. Interestingly, Dubbert et al. (10) found larger increases in walking among older men (60-80 yr) receiving 10 personal and 10 automated phone prompts than participants receiving baseline counseling alone; however, no differences were found between men receiving 20 personal phone prompts and men receiving counseling alone. Findings from these studies provide preliminary evidence that telephone prompts may be helpful in increasing walking behavior and that number of contacts may be more important than type or duration (i.e., counseling vs brief prompt) of contacts. More research is needed though, given some null effects of phone prompts [i.e., Ref. (47)] and issues concerning personal versus automated prompts (10) and potential difference by gender.
In addition to phone prompting, two RCT tested the efficacy of using pedometers as a motivational tool and setting goals in terms of steps taken versus minutes walked (11,19). Hultquist et al. (19) found greater increases in walking among participants using pedometers to set step-based goals compared with a no pedometer, minute-based goal-setting group, whereas Engel et al. (11) found no difference between groups in a similarly designed study. A number of differences in the two study designs, however, may account for the different study outcomes. Hultquist et al. (19) assessed walking among middle-aged women (33-55 yr) over 4 wk with pedometers as the primary outcome measure, whereas Engel et al. (11) assessed walking among older men (50-70 yr) over 6 months, with self-reported time spent walking as the primary outcome measure. Moreover, in the Engel et al. (11) study, treatment for both groups was more substantial, involving individualized counseling and tailored goal setting, whereas in the Hultquist et al. (19) study, treatment involved a minimal contact intervention and goals based on national recommendations (i.e., 10,000 steps or 30 min·d−1). Thus, the more substantial intervention and individually tailored goals may have led to a lack of differences in the Engel and Lindner (11) study. More research is needed to determine the efficacy of pedometers as a motivational tool, including potential moderators such as age, gender, and goal type.
Two RCT examined the effects of various exercise prescriptions on walking behavior. In a 2 × 2 design, Perri et al. (50) found that prescriptions for walking at a higher frequency (5-7 vs 3-5 d·wk−1) and moderate intensity (vs vigorous intensity) resulted in more total minutes of walking among healthy adults. Complimentary to these findings, Coleman et al. (9) found no differences in increased walking among healthy adults who were asked to walk 30 min·d−1 6 d·wk−1 via either 30-min continuous sessions, three 10-min sessions per day, or sessions of any duration as long as they were at least 5 min in duration and summed to 30 min·d−1. Taken together, these studies indicate that prescribing high-frequency moderate intensity walking is most effective at increasing minutes of walking, but that daily walking can be accomplished in one or multiple bouts.
Finally, two RCT compared interventions that differed with respect to their theoretical basis. Chen et al. (8) found that among racial-ethnic minority women, an intensive, individually tailored, theory-based intervention resulted in similar increases in walking at 2 and 30 months compared with a less intensive intervention that was not theoretically based. Surprisingly, the participants in the standard intervention walked more at 5 months than participants in the more intensive, theory-based intervention. Rovniak et al. (53) tested a theory-based 12-wk intervention using specific modeling, goal-setting, self-monitoring, and performance feedback compared with a standard intervention using similar techniques and number of contacts, but without specific theory-based content. There were no differences in walking increases at 12 wk, but there was a trend for more walking among the theory-based group at the 1-yr follow-up. More RCT, similar to the Rovniak et al. (53) study, that control for contact time but have larger sample sizes are needed to test the efficacy of theory-based walking programs.
MEDIATED INTERVENTIONS AS A VEHICLE FOR WALKING PROGRAMS
A number of walking programs have used telephone prompts or telephone counseling to deliver walking promotion interventions (8,10,11,20,28,47). These programs are often referred to as mediated interventions because they deliver intervention content through non-face-to-face media. In addition to telephone, mediated interventions can be delivered via print or using information technology (i.e., e-mail, Internet) (37,41,45,53). Mediated interventions can be particularly helpful for promoting walking, as brisk walking is a form of moderate intensity physical activity for most people that can be performed without face-to-face supervision, special equipment, or special physician clearance. Moreover, mediated interventions can save time by reducing or eliminating face-to-face contact but can also provide information and support at the level that would normally be available only through face-to-face contact with an exercise specialist (36,37,39,41). This is especially important since lack of time and resources are the most often cited barriers to the adoption and maintenance of regular physical activity (31).
In addition to the few studies of mediated walking interventions (8,10,11,20,28,47,53), several studies have examined mediated interventions that promote overall physical activity rather than walking per se. Some programs have offered tailored, mediated physical activity programs based on theoretical models. Such interventions, which are sometimes delivered via a computer expert system, offer motivational tips and advice based on complex algorithms that account for each individual's standing on a number of theory-based variables. Thus, participants enrolled in expert system-driven interventions receive theory-based "counseling" in the context of a home-based, worksite-based, or primary-care-based physical activity program (14,30,32). Print and telephone-based interventions for physical activity, particularly those that have been shaped by theoretical perspectives such as social cognitive theory and the transtheoretical model, have been effective for promoting physical activity (6,28,30,32-34). These effects have been found in trials in which the recruitment was done in the community (22) as well as in primary care settings (15). Additionally, there have been a few studies that have examined Internet or e-mail alone or compared with print with mixed results. Two studies found no increases in physical activity among participants receiving an Internet physical activity promotion program (16,40), whereas a third showed increases in self-reported walking relative to a control condition but not increases in overall physical activity (45). In one of the studies showing no increases in physical activity, only 46% of participants reported visiting the Web site during the study period (26). In a recently completed study that used various features in an attempt to increase Web site usage, physical activity increased significantly and similarly among participants receiving Internet and print interventions (33,35).
Individual level interventions have been shown to be effective at increasing physical activity, but they only affect a small percentage of the population. Mass media campaigns, however, are able to reach a large number of individuals over a relatively short time period. Increasing walking is an ideal campaign message since walking can be performed, unsupervised, by most individuals. Although mass media campaigns do not lend themselves to RCT, a few recent mass media campaigns specifically targeting walking behavior were examined through quasi-experimental designs. One community-wide intervention targeted 50- to 65-yr-old sedentary adults living in a rural community in West Virginia (51,52). The 8-wk intervention combined elements of mass media and individualized intervention components, including paid advertising, public relations, community participatory planning, work site programs, and physician-based programs. A similar, 4-wk campaign was delivered at 11 months. A comparison community was located in the same geographic region and had a similar population in terms of size and demographics but did not receive any intervention. Random digit dial telephone surveys were conducted on a subsample in each community. Among adults who were sedentary at baseline, 32% met CDC or ACSM criteria (at least 150 min accumulated over at least 5 d·wk−1) at the 8-wk assessment in the intervention community versus 18% meeting these criteria in the comparison community. These relative increases were maintained at 12-month follow-up, with the intervention community members who were sedentary at baseline almost twice as likely to be meeting CDC or ACSM criteria at 12 months compared with the comparison community (52).
Another series of community-wide campaigns designed to promote walking was conducted in six rural Missouri communities with comparison communities in Arkansas and Tennessee that were matched on size, poverty level, and percentage of African Americans (4,5). The intervention included tailored newsletters sent to individuals who enrolled in the program, walking groups, physician-based programs, and community events. There were also six walking trails constructed in the Missouri communities and two of them had counting devices to track trail use. Some community members also received cards that allowed the research team to provide tailored feedback based on their own personal use of the trail. Results, however, indicated a slight decline in walking in the intervention communities relative to the comparison communities, although there was a nonsignificant trend indicating that individuals who received a higher dose of the intervention (combination of participating in various aspects of the intervention) were more likely to meet recommendations.
Similar to the campaigns conducted by Brownson et al. (4,5) that specifically targeted walking behavior, reviews of mass media campaigns attempting to promote overall physical activity show that, in the absence of additional components, most do not lead to population level increases in physical activity (7,12,21,37,41). Additionally, many studies of mass media interventions do not include a control group, so even if changes are noted, they cannot unequivocally be attributed to the mass media campaign and may be due to secular trends or other events occurring in the community at that time (17,43). Moreover, although recall of the awareness for many mass media campaigns has been fairly high, it is important to keep in mind that 15% to 20% of individuals will report recall of a campaign even before it has started (3). Nonetheless, more research is needed on mass media campaigns as a means for delivering walking promotion and overall physical activity programs, as they have the potential to successfully introduce new ideas, reinforce messages, attract attention, affect important antecedents of physical activity (knowledge, beliefs, intentions, social norms, attitudes, etc.), and act as a supplement to other interventions that are occurring in the community (7,29,48).
SUMMARY AND CONCLUSIONS
Increased walking on a population level has the potential to significantly decrease incidence of chronic disease (25). However, in order for this process to be set into motion, interventions must effectively promote walking behavior. Although few walking programs have been studied in the context of an RCT, findings show some promise for intensive walking promotion interventions relative to control groups (23,44,56), even over follow-up periods as long as 10 yr (49). Findings from studies examining various components of walking interventions have shown that brief telephone prompts may be helpful in increasing walking behavior (28), and that prescribing moderate intensity walking 5-7 d·wk−1 (50) in either single or multiple sessions per day (9) may be most effective for increasing minutes of walking. Preliminary evidence indicates that walking programs that are carefully tied to theoretical frameworks may be superior to atheoretical programs or programs loosely based on theory (53). More research is needed to determine the relative efficacy of various theoretical models, as well as the usefulness of programs based on multiple theoretical models.
Mediated interventions help circumvent the barriers of time and resources often associated with traditional face-to-face interventions (46). Mediated interventions that operate on the level of the individual have shown some success, especially when theory-based and tailored to individuals needs (30,32-34). Mass media campaigns often raise awareness but typically do not produce behavior change on a population level (12). One mass media campaign that did increase walking behavior used both mass media and face-to-face approaches, such as physician counseling and worksite programs (51,52). This highlights the potential benefit of combining mass media campaigns with more intensive intervention approaches. One avenue yet to be pursued is combining the strengths of mediated intervention approaches that operate at the individual and population levels. Although mediated interventions focusing on individual change are usually able to provide more intensive programs, they often lack the broad reach of mass media campaigns. This is usually because of the high costs associated with delivering an intensive, individually tailored campaign on a population level. However, Internet-based, expert system-driven programs have the potential to be highly cost-effective. Although relatively high costs are associated with initial development of expert systems and Web sites, incremental costs of program delivery to each additional user are small or nonexistent. Recent findings have shown some promise for changing physical activity patterns through Internet-based, individually tailored mediated interventions (33); however, additional research will be needed to successfully market and deliver these programs on a population level. Despite these challenges, theory-driven, mediated physical activity promotion programs show excellent promise for increasing walking behavior on a public-health scale.
This project was supported in part through a career development award (Dr. Williams, Scholar; Dr. Coustan, PI) from the National Institute of Child Health and Human Development (HD43447) and grants from the National Heart, Lung, and Blood Institute (HL69866 and HL64342 to Dr. Marcus). Special thanks to Barbara Doll for her assistance with manuscript preparation.
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