Remco Arensman

34 Chapter 2 Table 3 Patient characteristics of the reliability study of the exercise adherence scale quality of performance score. n % Mean (SD) Range Total sample 50 Age, in years 50 100 25.6 (7.37) 18–55 Male 31 62 Female 19 38 Height (cm) 50 100 177.1 (11.3) 151–200 Weight (kg) 50 100 73.3 (11.6) 50.4–106.1 Education Vocational school 1 2 College or university 49 98 EXAS Quality of performance 200* 4† 1–5 n: number of participants in sample; SD: Standard Deviation; cm: centimeters; kg: kilograms; EXAS: Exercise Adherence Scale; *: quality of performance scores from the first assessment only; †: Mode reported instead of mean. Table 4 Associations between the exercise adherence scale and lack of time to exercise, lack of motivation to exercise, pain, and the Quebec back pain disability scale. Lack of time to exercise Lack of motivation to exercise Pain QBPDS n 27 27 27 26 EXAS 0.47* 0.48** 0.24 0.005 QBPDS: Quebec Back Pain Disability Scale; n: number of participants in sample; EXAS: Exercise Adherence Scale; *: p < 0.05; **: p < 0.001; Spearman’s rho was used for all associations Validity For convergent validity, the association between lack of time to exercise and the EXAS was rho = 0.47 (p = .013), and the association between lack of motivation to exercise and the EXAS was rho = 0.48 (p = .011) (Table 4). For divergent validity, the association between pain and the EXAS was rho = 0.24 (p = .22), and the association between disability and the EXAS was rho = 0.005 (p = .98). Reliability For intrarater reliability, Cohen’s kappa using quadratic weights was Kqw = 0.87 (95%-CI 0.83–0.92), p < .001, with a total of 200 observations of four exercises performed by 50 healthy subjects. In 200 observations, disagreement between repeated ratings of the same video by the same therapist occurred in 41 ratings. Out of these 41 ratings, only one

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