This relatively low intensity telephone and mail-based physical activity maintenance intervention is one of the first studies to attempt to maintain physical activity levels among adults ages 50 to 70 years who had recently increased their physical activity in a community setting. Focusing on maintenance instead of adoption of physical activity, the intervention was designed to increase the proportion of adults age 50 to 70 years who maintained physical activity levels in the recommended range. Compared to UC subjects, those who received the intervention had significantly higher mean energy expenditures (roughly 450 Kcal/week) 6 months after randomization, after adjusting for baseline energy expenditure. The magnitude of the difference in PA between groups is statistically significant and sufficient to be clinically meaningful. We observed modest weight losses that were comparable between intervention and control subjects. Within the intervention group, those who completed the phone coaching course lost significantly more weight than those who did not complete the course.
Client satisfaction with the intervention was high with low dropout in both in the intervention (3.4%) and control (4.8%) groups, indicating that differences observed were unlikely due to differential drop out, and that the intervention strategy may have wide appeal to eligible adults.
The intervention is based on a theoretical model specifically developed to address issues related to PA maintenance. This model included consideration of factors that predispose those who are physically active to quit, including injury, changes in motivational level, lack of accountability, and lack of encouragement. This model appears to be relatively effective as a guide for successful intervention strategies, which could be developed for other target groups of adults and adapted to other behavioral outcomes. By focusing on maintenance of PA, we intentionally recruited subjects to the study who were at a more advanced stage of change and who may have been more highly motivated than is typical of participants in prior PA interventions. By contrast, our use of direct mail recruitment as the first line recruitment strategy may have reduced the volunteer bias that often results from less proactive, more traditional recruitment strategies such as use of advertisements. Although we, too, made use of advertisement and self-referrals as a second line recruitment strategy, only 21% of those enrolled came to the study through self-referral.
Thus far, only one published randomized controlled study has demonstrated a long-term (2 year) improved activity outcome following a lifestyle intervention approach (versus a traditional structured exercise approach) to increase PA(Dunn et al., 1999
). In this study, previously sedentary healthy adults effectively increased their lifestyle based PA over the first 6 months of treatment and subsequently maintained this gain over the following 18 months. This study was limited to middle-aged adults, and participants were required to attend weekly meetings for the first 16 weeks, then biweekly until week 24. This relatively resource intensive approach is not likely to meet the cost and penetration criteria for a successful population-based intervention,(Glasgow et al., 1999
) suggesting the need for alternative methods. Telephone-based counseling is one promising alternative approach with an increasing evidence base(Eakin et al., 2007
). As emphasized earlier, maintaining PA in those already active may be as important, or more important, than effective interventions to initiate activity in the sedentary. For this reason, the intervention we report, with its promising short-term results, represents an important advance in the overall effort to raise levels of PA in the U.S. population. In addition, while the success of health care providers at increasing
physical activity among patient populations has been mixed, our findings suggest a possible role for health care providers in maintaining
physical activity gains by encouraging continued PA efforts among their currently active patients through efforts such as verbal support and encouragement and positive role modeling. Given the time pressure and demands already placed on primary care physicians, implementing sustainable phone based coaching programs will likely require the development of parallel support systems, integrated with primary care, but with dedicated staff specially trained to perform these functions to whom clinicians may refer their patients.(O'Connor and Pronk, 1998
, Pronk and O'Connor, 1997
, Pronk et al., 2002a
) Examples of attempts to accomplish this include the work of HealthPartners own Health Behavior Group, and at a national level, the Green Prescription program in New Zealand.(Kerse et al., 2005
) Clearly, at this point, dissemination research is a logical next step in moving such programs into population health practice(Eakin et al., 2007
), one component of which includes building the business case for such programs by documenting the costs of behavioral factors such as inactivity and overweight/obesity.(Pronk et al., 2002b
, Pronk et al., 1999
, Anderson et al., 2005a
, Jeffery et al., 2003
, Martinson et al., 2003
, Sherwood et al., 2006
The interpretation of the data are limited by several factors. First, the intervention requires evaluation over longer follow-up periods, which is now underway. Second, generalization of results to other populations should be done with caution due to the likelihood of self-selection that is a threat to external validity in most clinical trials, as well as the added potential for self-selection stemming from the fact that our inclusion criteria required participants to be currently physically active at an increased level relative to some point in the recent past. Third, although the intervention appealed to a large number of those eligible to enroll in the study, multiple strategies are needed to assure the broad population penetration needed to increase overall population levels of PA. Fourth, it should be noted that the comparisons of subgroup results within the intervention condition presented in are observational, precluding inferences about causation. Finally, although this was a low-intensity intervention, the costs of it are not negligible, affordability should be considered for those identified as potential payers, and the significance of the results will be need to be assessed in the context of a planned cost-effectiveness analysis, once longer term impact on PA is fully assessed.
Despite these limitations, the results are interesting and have important clinical and public health implications, because they demonstrate both the practicality and the short-term efficacy of an intervention specifically designed to maintain PA in those who are already active. It is likely that the only feasible way to reach national PA goals is to couple interventions that maintain activity with others that effectively encourage initiation and adoption of PA among the sedentary. Thus, the demonstration of a promising and conceptually coherent approach to PA maintenance adds a potentially efficacious strategy to the relatively few proven strategies already available for increasing PA in the adult population.