Table 1 Outline of the interview protocol (APEF tool)

Active participation

Group formation

1. We, as exercise group, choose who participates in the exercise group.

Since when have you been exercising together?

How are participants recruited?

Do you ever bring a friend or a neighbour?

Content activity class

2. We, as exercise group, choose the activities for the exercise class

What does your physical activity program look like?

Were you involved in the choice of activities, and if so, how did that work?

How important is that for you?

Community initiative

3. Some participants within the exercise group take the initiative to exercise together elsewhere

Can you give an example of somebody taking the initiative?

Enjoyment

Enjoyment of physical activity

4. Exercising in the exercise group ensures that I like being physically active

What physical activity do you like most?

Is the program consistent with your preferences?

How do you ensure that everybody can enjoy the physical activity class?

Feelings of safety

5. The exercise group offers me safety to be physically active

What comes to your mind if we talk about safety?

How does the group support safety?

Fostering group processes

Social support

6. Exercising in the exercise group offers me support to be physically active

What comes to your mind if we talk about group support?

In what way does the group offer support to physical activity behaviour?

How do you deal with factors that make physical activity difficult?

Role exercise trainer

7. Within the exercise group, the exercise trainer is an example for me to be physically active

In what way is the exercise trainer an example?

Learning achievements

8. By exercising in the exercise group, I learn how to be more physically active in my daily life

Can you give examples of what you learned in the exercise group?

What have you discovered since you joined the exercise group?

What is your benefit or achievement?