Assessing moderate-to-vigorous physical activity in hip and knee osteoarthritis using accelerometers: Implications of different patterns and cut-points for health and well-being.

Objective: This cross-sectional study explored how using age-specific and non-age-specific cut-points to assess moderate-to-vigorous physical activity (MVPA) measured by GT3X accelerometers affected bouted and total volume MVPA associations with health and well-being.

Methods: MVPA correlations with physical function, BMI, joint pain, quality of life, anxiety and depression were tested. Steiger's z compared the strength of these correlations for each pair of cut-points.

Results: A total of 109 adults with hip/knee osteoarthritis [M= 63.8 years (±10.58), 63.3% women] participated. Applying age-specific cut-points resulted in significantly more time classified as MVPA (76/9.5min total volume/bouted) compared to non-age-specific (38.8/7min total volume/bouted). Only total volume MVPA correlations differed significantly as a function of cut-points for self-reported function, quality of life, anxiety and depression (p ≤ .05). For age-specific cut-points, more time spent in MVPA was associated with a worse psychological profile.

Discussion: Applying age-specific cut-points for MVPA assessment in older adults with lower limb OA had implications for MVPA associations with health and well-being when total volume, but not bouted, MVPA was considered. Age-specific total volume MVPA needs further understanding regarding patterns and affective responses it comprises. Bouted MVPA is an important pattern for MVPA accrual, but probably not an applicable PA target for many patients.