Table 2.

Example mapping of barrier behavior change technique messages following the behavior change wheel framework.

Barrier	COM-Ba category	TDFb domain	Intervention function	BCTc	SMSd content
Forgetfulness	Psychological capability	10. Memory, attention and decision processes	Training	8.3 Habit formation	[Name], it can be hard to remember. We suggest making the exercises a habit. Set aside the same time each day to do them. It’s much harder to forget when something is a daily routine.
Concern exercise (causing) pain	Reflective motivation	6. Beliefs about consequences	Enablement	1.2 Problem Solving	Remember mild pain with knee exercise is okay but significant pain’s discouraging. Figure out the cause! Use a log book this week, record how you feel after EACH exercise. Identify the exercise linked to your concern. Modify that ONE exercise & keep doing your program 3x week.

^aCOM-B: Capability, Opportunity, Motivation model of behavior.

^bTDF: Theoretical Domains Framework.

^cBCT: behavior change technique.