The addition of mobile elements to online physical activity programs for adults aged 50 years and older

INTERVENTION: Block randomization is applied, where each participant is randomly assigned to one of the research groups. The randomization procedure takes place automatically via a built‐in algorithm within the software of the used online intervention programs after inclusion procedures (inclusion criteria questionnaire and signing informed consent). Participants are randomly allocated to one of three experimental groups or to a waiting list control group. All participants are instructed to wear an ActiGraph accelerometer for 7 days at baseline (T0) and 6 months post‐baseline (T2). Online questionnaires are filled in at T0, three months post‐baseline (T1) and T2. Participants in the experimental groups follow the online physical activity stimulating intervention Active Plus or I Move with a duration of 12 weeks including one of the following three mobile elements: 1. Activity tracker 2. Ecological momentary intervention (EMI) 3. Chatbot Participants in the control group participate in the first 6 months only in the accelerometer and questionnaire measurements. No access is provided to the intervention during this period. Control group participants receive a combined tailored physical activity advice of the Active Plus intervention directly after completion of the T2 questionnaire. CONDITION: Stimulation of physical activity within adults aged 50 years and over ; Not Applicable PRIMARY OUTCOME: Moderate to vigorous physical activity (MVPA) measured via the self‐reported SQUASH questionnaire at T0, T1 and T2 and via ActiGraph accelerometers at T0 and T2 SECONDARY OUTCOME: ; 1. Commitment measured using a scale based on Webb et al. (2005) at T0, T1 and T2; 2. Self‐efficacy measured based on the self‐efficacy for exercise scale at T0, T1 and T2; 3. Intention measured based on Sheeran et al. (1999) at T0, T1 and T2; 4. Appreciation rates of the mobile elements measured using a self‐composed usability and experience questionnaire at T1; 5. Appreciation rates of the intervention program including mobile element measured using a self‐composed usability and experience questionnaire at T2; 6. Participation rates and drop‐out rates are measured via questionnaire participation rates (at T0, T1, and T2), accelerometer participation rates (at T0 and T2), Active Plus (at T0, 4 weeks post‐baseline, and at T1) and I Move (at T0, 3 weeks post baseline, 6 weeks post‐baseline and at T1) participation rates and process data (continuously); INCLUSION CRITERIA: 1. 50 years or older 2. Able to use a computer, laptop or tablet 3. Own a smartphone from 2012 or later