Table 2 4-STEPS Materials content

✓ Overview of Chronic Fatigue: CDC diagnosis criteria, epidemiology information, etiology, possible factors that contribute to a better or words prognosis (e.g. physical inactivity/activity).

✓ Physical activity: current physical activity guidelines for adults in general population, physical and psychological benefits of physical activity, benefits of physical activity for CF. Information about different types of physical activities (that are appropriated for CF) such as walking as well the importance and illustration of relaxation training.

✓ Link between CF symptoms and physical (in-) activity (deconditioning cycle) and boom-bust pattern (erratic pattern of rest and activity).

STEP 1 - "Am I ready to start?"

✓ Motivation and Confidence Scales: Patients' willingness and confidence to do adjusted levels of physical activity is assessed on a scale for ranging from 0% (not at all) to 100% (very much).

✓ Decisional Balance: list of the pros and cons (not-) to change in relation to physical activity.

✓ Competing goals with exercise: information on the importance o analyzing possible competing goals (or conflicting activities) with exercise that may be refraining patients from physical activity. List of two main activities (e.g. other leisure activities).

✓ Activity/Rest Diary and Pedometer log - instructions to use for two weeks (interval between MI sessions) and the importance of the pedometer as a motivational strategy.

STEP 2 - "My physical activity goal":

✓ GET Scheme and daily activity management: information on the importance of increase physical activity level gradually, consider the way patients feel in different days (different levels if patients is feeling good or bad), importance of rest during physical activity, importance of adjusting physical activity levels to the amount of effort spent in that day (balance between activities and rest).

✓ Goal setting activity: explanation of how to set a goal (SMART - specific, measurable, achievable, realistic and timely), formulation of a personal physical activity goal to achieve in 2 months time (e.g. to do brisk walking four days per week for 30 minutes (plus 10 minutes break), implementation intentions (type of activity, frequency and intensity, period of the day, with whom, where) and a goal ladder (patients formulate goals for every 2 weeks until reaching the two months time and main goal.

✓ Information on self-rewarding for each step goal achieved.

✓ Tips for managing daily activities and incorporate physical activity on the daily routine

STEP3 - "Overcoming obstacles":

✓ Problem solving activity: List two main physical activity barriers and a strategy to overcome it.

STEP 4 - "I am physically active...and I want to keep that way":

✓ Relapse prevention information and strategies

Resources and support for CF and physical activity.

✓ Similar to the record used for the assessment (day of the week and number of steps for each day).

✓ Record containing the days of the week and hours each day. Patients fill the activities they do in each hour of day. The options are: physical activities, other activities (activities requiring mental effort) and rest. Each option is explained in detail.

✓ Facts about CF.

✓ Brief information on the relation between physical activity and CF.

✓ Tips for partners or other relatives to support patients with CF.