Table 1 4-STEPS sessions content

✓ Listen to patient complaints, with emphasis on fatigue.

✓ Illness perceptions.

✓ Exploration of patients' present physical activity behavior.

✓ Current health behaviors and other activities are explored (physical activity, sleep, pain, etc.).

✓ Discussion of the information on the booklet given previously (specially the relation between CF major symptoms and physical activity behavior and boom-bust pattern).

✓ Motivation and Confidence Scales: Exploration of the willingness to engage in physical activity (or adjust current physical activity behavior) and the confidence in one's own capability to achieve this behavior with success.

✓ Discussion of the pros and cons (not-) to change physical activity behavior (Decisional Balance).

✓ Social support network is addressed.

✓ Exploration of possible competing goals with physical activity (e.g. housework chores) and link to core values.

✓ Strategies to overcome obstacles to physical activity and competing goals are addressed.

✓ Based on the register of daily activities and steps taken (pedometer register) and GET scheme for physical activity, the patient establishes a personal physical activity goal for the following two months.

✓ Discuss the possible reasons for perpetuation of symptoms and difficulty to change health behaviors in CF patients, namely perfectionism, fear of movement, presence of stressful situations and boom-bust pattern. (some are already mentioned at the first motivational interview and are now emphasized).

✓ Exploration of emotion control importance and techniques (e.g. relaxation techniques).

✓ Revision of the physical activity goal planning (adequacy to the patients' present situation).

✓ Relapse prevention (strategies to overcome new or persisting difficulties to physical activity and emotion control strategies).