Table 4 Changes in self-reported BCT use from pre-intervention (T1) to post-intervention (T3) by group. Numbers indicate mean (SD)

BCTs sumscore (for general BCTs)

Control

2.9 (0.9)

2.6 (1.5)

Intervention

2.6 (1.0)

3.3 (1.0)

BCT sumscore (for frequency-dependent BCTs)

Control

2.6 (0.6)

2.1 (0.7)

Intervention

2.5 (0.8)

2.8 (1.1)

I have set PA goals for myself (“goal setting, behaviour” 1.1)

Control

3.8 (1.1)

3.5 (1.6)

Intervention

3.1 (1.3)

3.8 (1.1)

I have made a detailed plan to carry out PA (“action planning” 1.4)

Control

3.0 (1.6)

2.7 (1.7)

Intervention

2.6 (1.3)

3.3 (1.2)

I have written down my plan (in e.g. my calendar) (“action planning”, 1.4)

Control

2.4 (1.6)

2.0 (1.6)

Intervention

2.2 (1.4)

2.9 (1.3)

I have divided large PA goals into smaller goals (“graded tasks”, 8.7)

Control

1.3 (0.7)

1.6 (1.0)

Intervention

2.0 (1.1)

2.7 (1.3)

I have thought about what positive consequences regular PA would bring into my life (“keeping in mind/reminding oneself of positive consequences of PA”^a)

Control

3.8 (1.1)

3.0 (1.2)

Intervention

3.1 (1.4)

3.3 (1.3)

I have thought about my PA goals (“thinking about own goals”^a)

Control

3.9 (1.0)

3.1 (1.3)

Intervention

3.3 (1.5)

3.4 (1.2)

I have monitored my own PA, e.g. by logging bouts of PA in my PA diary or mobile app (“self-monitoring of behaviour” 2.3)

Control

2.1 (1.5)

1.7 (1.1)

Intervention

1.9 (1.3)

2.4 (1.4)

I have compared my actual PA with the PA goal that I had set (“discrepancy between current behaviour and goal”, 1.6)

Control

2.2 (1.3)

1.8 (1.0)

Intervention

2.4 (1.3)

2.6 (1.1)

If I have not reached my PA goal, I have considered what went wrong (“barrier identification a)”^a)

Control

2.1 (1.3)

2.1 (1.1)

Intervention

2.2 (1.4)

2.6 (1.6)

I have thought about what reasons for PA are important for me personally (“thinking about /reminding oneself of one’s own motives”^a)

Control

3.5 (1.2)

2.7 (1.6)

Intervention

3.1 (1.2)

3.2 (1.2)

I have considered what kind of situations prevent me from realizing my PA plan (“barrier identification b)”^a)

Control

2.9 (1.4)

2.4 (1.5)

Intervention

2.6 (1.1)

2.8 (1.0)

I have planned ways to overcome barriers to being physically active (“problem solving”, 1.2)

Control

2.3 (1.2)

1.7 (0.9)

Intervention

2.7 (1.2)

2.9 (1.3)

I have tried out new ways of being physically active (“behavioural experiments”, 4.4)

Control

2.3 (1.3)

1.8 (0.6)

Intervention

1.9 (0.9)

2.3 (1.2)

I have asked my family or friends to be physically active with me (“obtaining social support”, 3.1)

Control

2.3 (1.3)

1.9 (1.3)

Intervention

2.4 (1.0)

2.8 (1.2)