Review of Primary Care-Based Physical Activity Intervention Studies

Methodology Rating

The methodology rating scores for the studies we included ranged from 4 to 9, with the majority receiving a score of 6 or 7 on the scale of 0 to 10. Overall, the study designs were strong, with the vast majority being randomized trials that studied relatively large samples, employed appropriate analyses, and reported on attrition rates. The methodologic areas in which studies were downgraded most often were for not reporting implementation results and failing to employ intention-to-treat analyses or imputation procedures to address attrition issues. There was not a strong relationship between methodologic quality and intervention effectiveness. Five of the 10 studies with significant effects had methodology ratings of 7 or higher.

Sample

Study sample sizes ranged from small (N = 63) to large (N = 6124). Although all but one study included both men and women, the percentage of women was greater in most studies. All studies focused on adults, with an age range of 18 years to 75 years and older. Four studies included only adults 50 years and older, and none demonstrated significant short-term results, though one achieved long-term outcomes. Seven studies included only sedentary patients, although the definition of sedentary was not consistent across studies; the other 8 studies included patients with a range of or unspecified baseline physical activity levels.

In 12 studies, the bulk of the physical activity (or multiple risk factor) intervention was delivered during a routine primary care visit. In the other 3, a portion of the intervention took place in classes or groups outside of the primary care setting. The intervention was delivered by physicians in 9 studies, by nurses in 3 studies, by a physician and a health educator in 2 studies, and by public health students in 1 study. No clear relationship emerged between type of interventionist and effectiveness. Of the 7 studies with significant short-term effects, 4 had physicians deliver the intervention, one used nurse delivery, and 2 used delivery by a physician and health educator combination. Of the 3 studies with significant long-term effects, one was delivered by physicians, one by nurses, and one by public health students.

Study Design and Physical Activity Intervention

Nine studies employed a randomized controlled trial. In 8 studies, physical activity was the sole focus of the intervention; in 7 studies, the physical activity intervention was part of a multiple risk factor intervention, including behaviors such as smoking, diet, alcohol and seat belt use. Physical activity-only interventions faired better in the short term than multiple risk factor interventions; 6 of the 7 studies with significant short-term effects focused on physical activity only. In contrast, all 3 of the studies with significant long-term effects were multiple risk factor interventions. Walking was the most common activity recommendation.

The length of the initial provider-delivered intervention varied greatly—from 3 to 10 minutes of physical activity counseling in 7 studies to 15 to 120 minutes of multiple risk factor counseling in 3 studies. Brief counseling may be as effective as more lengthy counseling, since 5 of the 7 studies with significant short-term effects involved 3- to 10-minute counseling sessions. The majority of the studies provided at least some details about the amount of provider training regarding the physical activity (or multiple risk factor) intervention, which ranged from 15 minutes of individual training and the provision of tip sheets to 2-hour workshops.

Ten of the 15 studies involved interventions that were tailored to patient characteristics, such as readiness to exercise, baseline levels of physical activity, or physical activity preferences. Tailoring seemed to affect short-term physical activity outcomes, with 6 of the 7 studies with significant short-term effects using some form of tailored intervention. Of the 3 studies with significant long-term effects, only one involved a tailored intervention. Eleven of 15 studies used written materials that ranged from brief physical activity tip sheets to more extensive physical activity manuals. The use of written materials also seemed to have an impact on short-term outcomes, with 6 of 7 studies with short-term effects offering them to their patients. Two of the 3 studies with significant long-term effects used written materials to accompany the intervention. Six of the 15 studies included some form of follow-up support for the patient—3 offered an additional physician office visit, one used a phone call from the health educator, and 3 used tailored mailed physical activity pamphlets. There was no clear advantage of the use of follow-up support; only 3 of the 10 studies with significant effects used them.

Theory-Based Interventions

Seven of the 15 studies described the theoretical basis of the physical activity intervention employed. All explicitly theory-based physical activity interventions used at least some of, if not all, the components of social-cognitive theory^23,24 or self-management/behavior change interventions (eg, assessment and feedback, goal-setting, identification of barriers to change, personalized problem solving, reinforcement, and supportive follow-up).^24-27 Four studies employed a transtheoretical model or “stages of change” theoretical perspective.^28,29 Three of these 4 studies failed to find significant short-term effects.^19,30,31 Overall, theory-based physical activity interventions were not any more effective than those not based on explicit theories of behavior change; only 4 of the 10 studies with significant effects were based on explicit theories of behavior change.