Leisure Time Physical Activity Instrument and Physical Activity at Home and Work Instrument. Development, face validity, construct validity and test-retest reliability for subjects with fibromyalgia

Purpose. A new instrument measuring leisure time physical activity (LTPAI) in populations predominately engaging in low intensity activities and a new instrument measuring the Physical Activity at Home and Work (PAHWI) were designed.

Methods. Patients with long-lasting pain and expert physiotherapists participated in the development of the two instruments. Test-retest reliability was evaluated for the LTPAI and the PAHWI. Construct validity was evaluated for the LTPAI by comparing it with an instrument measuring physical activities for older people, six-minute walk test and aerobic capacity.

Population. 37 women with FM, with the mean age of 46 years (SD 8.4) and mean symptom duration of 11 years (SD 5.9) were recruited to the study.

Results. The mean time that the study population spent in physical activities during leisure time was 5.2 hours (SD 4.0) a week. Satisfactory test-retest reliability was found for the total score of LTPAI (ICC 0.86, CI 0.79 - 0.93) and for the PAHWI (ICC 0.91, CI 0.82 - 9.96). A significant association between the LTPAI and the six-minute walk test (r_s 0.40, p = 0.02) and another physical activity instrument (r_s 0.39, p = 0.02) was found. As expected, LTPAI did not have any association with aerobic capacity.

Conclusions. Face validity of the instruments was ensured during the development process. Satisfactory test-retest reliability was found for the LTPAI and the PAHWI. Significant but low associations were found between the LTPAI and the six-minute walk test and an instrument designed for older people, respectively, while no association was found between the LTPAI and aerobic capacity.