Arm exercise promotion scale: Instrument validation

Aim.: This paper is a report of psychometric testing of the Arm Exercise Promotion Scale. Background.: Patients with breast cancer having mastectomy are taught postoperative arm exercises during hospitalization; however, clinical observations suggest that patients infrequently practise them. It is important to develop an instrument that can be easily applied to evaluate women's motivation for arm exercises. Method.: An instrument validation design with a cross-sectional survey was conducted during 2008-09. The previously developed 15-item Likert-type Arm Exercise Promotion Scale was further tested for test-retest reliability, internal consistency reliability, theoretically supported construct validity, and concurrent validity. A total of 94 patients with breast cancer were recruited to the study. Results.: The Arm Exercise Promotion Scale has satisfactory internal consistency reliability (Cronbach's alpha 0·88) and a test-retest reliability of 0·90. Three theoretically supported factors were abstracted by principal component analysis: perceived benefits, learning support and situational support. These factors were inter-correlated and statistically significantly correlated with arm exercise behaviour, indicating concurrent and construct validity. Conclusion.: There is strong evidence to further support the Arm Exercise Promotion Scale as a valid instrument in assessing factors which promote arm exercises with patients with breast cancer. Future longitudinal clinical studies using this scale could add knowledge about the experiences of carrying out arm exercises in patients with breast cancer across time.