Self-reported Home Exercise Adherence: A Validity and Reliability Study Using Concealed Accelerometers.

BACKGROUND: Accurate measurement of adherence to prescribed exercise programs is essential. Diaries and self-report rating scales are commonly used, yet little evidence exists to demonstrate their validity and reliability. OBJECTIVES: To examine the concurrent validity of adherence to home strengthening exercises measured by (1) exercise diaries and (2) a self-report rating scale, compared to adherence measured using an accelerometer concealed in an ankle cuff weight. Test-retest reliability of the self-report rating scale was also assessed. METHODS: In this clinical measurement study, 54 adults aged 45 years or older with self-reported chronic knee pain were prescribed a home quadriceps-strengthening program. Over 12 weeks, participants completed paper exercise diaries and, at appointments every 2 weeks, rated their adherence on an 11-point numeric rating scale. A triaxial accelerometer was concealed in the ankle cuff weight used for exercises. Self-reported adherence rating scale data over each 2-week period were analyzed using descriptive statistics, the Wilcoxon signed-rank test, and a Bland-Altman plot to assess agreement, Spearman correlations for validity, and intraclass correlation coefficients for test-retest reliability. RESULTS: Exercise adherence was significantly overestimated in diaries during the 12 weeks (diary median, 220 exercises; accelerometer, 176; P