Clinical Trial: Self-regulatory interventions to facilitate physical exercise maintenance

Nina Knoll, Ralf Schwarzer (Freie Universität Berlin)

Background: The main objectives for physical activity prescribed to persons at risk for knee osteoarthritis (OAK) are enhancing the mobility and required range of motion of the joint and increasing the strength and endurance of the muscles. This requires voluntary action and, therefore, becomes subject to adherence failure. There is no medical solution to this problem, but a psychological program could make a substantial contribution. Supervised individualized exercise therapy and self-management techniques have been shown to enhance exercise adherence. Using the Health Action Process Approach (HAPA) as a theoretical backdrop, SPP7 aims to develop and evaluate a theory-based psychological adherence program (PAP) that is performed on top of the main medical trial (MMT; SPP6, Felsenberg et al.) and is designed to strengthen long-term self-management in the maintenance of MMT-condition-specific physical activity throughout a 24-month period. Increased physical activity is proposed to be a behavioral predictor of reduced OAK symptoms (as assessed by the WOMAC). Primary hypothesis: Positive effects of a psychological adherence program on OAK symptoms (i.e., WOMAC scores; primary endpoint) will be mediated via increases in physical activity (objectively assessed; key secondary endpoint). The effect of physical activity on OAK symptoms will be further moderated by MMT-group membership.

Method: Following baseline and prior to randomization all participants (N=240) will receive a basic knowledge transfer/motivational treatment.  Participants from each MMT-condition (MMT-HIE, n=80; MMT-LIE, n=80; MMT-CTRL, n=80) will then be further randomized either to a control group (PAP-CTRL, n = 120) or a multi-phase psychological adherence program (PAP-I, n = 120) with several additional motivational (e.g., decisional balance, recall of mastery, goal setting) as well as volitional (e.g., action and coping planning, action control) intervention components implemented. The main intervention delivery modes will be written materials and computer-assisted telephone interviews (CATIs), conducted by trained research assistants. The control group will not receive further psychological treatment, only assessments. Over the course of 2 years, total of 5 measurement points in time will include self-report questionnaires as well as accelerometer-based assessments of physical activity. Assessments of self-reports will take place at months 0 (baseline), 6, 12, 18, 24; accelerometer assessments will take place at months 0, 12, 24. Primary efficacy endpoint are  OAK symptoms (i.e., WOMAC scores). Key secondary endpoint(s) include frequency and duration of moderate and vigorous physical activity using accelerometers; self-reported physical activity, log sheets of MMT-adherence in physical exercise sessions, several social-cognitive predictors of change in physical activity, emotional well-being, and pain.

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