Background/Purpose: Adults with knee osteoarthritis with worse physical function are known to benefit more from therapeutic exercise than those with less limitation. However, there is limited evidence on whether those with worse physical function also have more improvement in physical activity in response to physical activity interventions. This study aimed to examine the interaction effects of baseline physical function on changes in steps/day among individuals participating in the 6-week Walk With Ease by Phone (WWE-P) intervention compared to a control group.

Methods: Baseline physical function was assessed using the 30-Second Chair Stand Test (30-CST) total repetitions. Study participants in the intervention received 6 weeks of WWE-P while those in the waitlist control received no intervention until 12 months. Daily step count were measured using an Actigraph GT9X Link, collecting at the baseline, and 6 months. We examined the interaction effects between baseline physical function categorized as high and low using mean 30-CST time and treatment group with changes in steps/day from baseline to 6 months.

Results: 267 participants (mean age = 64.1 years old, 92% female, 49.4% in the WWE-P group) were included in the overall analytic sample. The mean baseline 30-CST score for the WWE-P and control group were 8.83 ± 2.88 and 8.88 ± 3.02, respectively. No statistically significant differences were observed between groups at baseline. Baseline 30-CST significantly interacted with time and group in predicting changes in daily step count (p = 0.001). Those in the intervention and control groups with low 30-CST walked 1104 and 819 fewer steps/day over 6 months, while those with high 30-CST in the intervention and control walked 513 and 446 fewer steps/day.

Conclusion: The results of this research indicate the significant interaction between baseline 30-CST and changes in daily step count over time, such that those with low physical function walked fewer steps/day regardless of the intervention group over 6 months, while those with high physical function had less decline. These findings suggest that those with worse physical function may have the greatest decline in physical activity regardless of receiving a physical activity intervention.

Table 1. Daily step count according to function level

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/does-baseline-physical-function-moderate-change-in-steps-day-following-a-telephone-delivered-walk-with-ease-program/