Table 2 Measurement of the behavioural and psychological outcome measures
Outcome measure | Item(s) | Scale / Response categories | Scale’s Cronbach’s alphaa | Time of measurement |
|---|---|---|---|---|
Behavioural outcomes | ||||
 Physical activity | IPAQ short form: 6 items to assess weekly time spent in: ▪ vigorous intensity activities ▪ moderate intensity activities ▪ walking | Days per week/ Hours and minutes per day/ ‘Don’t know/not sure’ |  | T0, T2 |
 Sitting time | IPAQ short form: 1 item to assess daily sitting time | Hours and minutes per day/ ‘Don’t know/not sure’ |  | T0, T2 |
 Perceived increase in physical activity | ▪ Have you changed your physical activity behaviour in the past two weeks? If yes, what have you changed? | Yes, namely: … / No |  | T2 |
Psychological outcomes | ||||
 Intention | ▪ Do you plan to become more physically active? | Yes / No |  | T1 |
 Intention strength | ▪ How strong is your plan to become more physically active? | 1 (no strong plan at all)—10 (very strong plan) |  | T1, T2b |
 Active choice | In making this choice [about whether or not to become more physically active], I have… ▪ … taken into account the advantages of my current physical activity behaviour ▪ … taken into account the disadvantages of my current physical activity behaviour ▪ … taken into account the advantages of being more physically active ▪ … taken into account the disadvantages of being more physically active ▪ … thought about the advantages and disadvantages that are most important to me ▪ … thought about how important my health is to me ▪ … thought about the difference between ‘how important my health is to me’ and ‘how much time, effort and energy I spend on it’ ▪ … taken into account the time, effort and energy it takes to become more physically active ▪ … taken into account barriers to become more physically active | 1 (totally disagree)—5 (totally agree) | 0.77 | T1 |
 Autonomous choice | ▪ To what extent does your plan to become more physically active/ not become more physically active feel as your own plan? ▪ To what extent does your plan to become more physically active/ not become more physically active feel as imposed by others or society? | 1 (not at all as my own plan) – 10 (very much as my own plan) 1 (not imposed at all) – 10 (very much imposed) | 0.54c | T1 |
 Commitmentb | ▪ To what extent are you willing to put time, effort and energy in being more physically active? | 1 (not willing at all) – 10 (very willing) |  | T1, T2 |
 Self-efficacyb | ▪ How confident are you that you will succeed in being more physically active? ▪ How confident are you that you will succeed in being more physically active when faced with barriers, such as bad weather, lack of time and tiredness? | 1 (not confident at all) – 10 (very confident) | 0.85 | T1, T2d |
 Satisfaction | ▪ To what extent are you satisfied with you plan to become/not become more physically active? | 1 (not satisfied at all)—10 (very satisfied) |  | T1 |
 Alignment of choice with personal values | ▪ To what extent does your plan to become/ not become more physically active correspond with what you consider important? | 1 (not at all) – 10 (very much) |  | T1 |