In case of musculoskeletal pain, a decreased physical activity (PA) could favor deconditioning and chronicity. However, several studies have failed to highlight low PA in people suffering chronic pain. To explore this issue further, we analyzed PA level of patients with chronic musculoskeletal pain (CMP) with an inertial sensor. The objective was to assess whether pain interference (PI) with physical functioning correlated with PA level.

We studied 267 CMP patients [age: 44 years (SD: 12)]. Pain sites were upper limbs (43%), spine (23%), and lower limbs (34%). The participants wore an accelerometer during two consecutive days. We assessed the daily duration of moderate-to-vigorous PA (MVPA), that is, all movements with an intensity above slow walking. We used the average score of the three interference items related to physical functioning in the brief pain inventory (BPI) questionnaire (0–10). We fitted a generalized linear mixed model (GLMM) with MVPA as the dependent variable. We defined PI as a continuous predictor, and pain site as a 3-level categorical covariate. Main effects and interaction (PI×Pain site) were included in the model.

The average duration of MVPA was 76min (SD: 51), that is, 10% as high as the accelerometer wear time (13h, SD: 2.6). Average PI score was 5.3 (SD: 2.2). GLMM shows that PI was significantly and negatively associated with MVPA. The interaction result shows that the percent change for each PI point was upper limbs: −2%; spine: −10%; and lower limbs −3%.

The results show that PA level correlates to how CMP patients perceived the interference between pain and physical functioning. The association is particularly strong in patients with back pain. This finding supports the hypothesis that chronic pain impairs PA through the interference with daily physical activities.