Association Between Pain And Physical Activity In Individuals With And Without Patellofemoral Pain

PURPOSE: To evaluate the association between daily pain and daily PA levels in individuals with and without PFP over a two-week period. METHODS: Fifty-five individuals with PFP (23.1 ± 4.0 y) and 38 pain-free controls (23.9 ± 4.1 y) completed the study. Participants wore an ActiGraph wGT3X-BT for two weeks to assess minutes of moderate to vigorous physical activity (MVPA) and recorded daily measures of worst pain, sleep quality, mood, and medication use. We performed separate linear mixed effect models, by group, while treating MVPA as response variable. Daily observations of MVPA and pain were nested to the participant level. Key predictors for a day’s MVPA were used with the two previous days’ MVPA, previous day’s pain, and indicator of pain, while including sex, age, BMI, sleep quality, mood, and medication use as individual-level covariates. A between-within model was conducted with random intercept and slope of within-individual MVPA. Statistical tests were conducted in R and alpha was set a priori at p < .05. RESULTS: In both groups, one day’s MVPA was a significant predictor of the next day’s MVPA, but pain did not influence the next day’s MVPA. In the PFP group, a 1-unit increase in one day’s MVPA resulted in an increase of .11 (within-individual) and 1.83 MVPA (between-individual) the next day. The pain-free group also had significant predictions of .23 and 2.0 MVPA, for within-individual and between-individual, respectively. The PFP group’s MVPA from two days prior showed a significant negative within-individual effect, with a reduction of -.163 MVPA. Individuals with PFP who took medication had a 12.66 increase in the next day’s MVPA. CONCLUSIONS: Individuals with PFP and pain-free controls who increased their PA predicted the next day’s MVPA; however, the PFP group had a negative within-individual effect 2 days prior, suggesting that an increase in MVPA may decrease future PA engagement. Pain medication use resulted in greater engagement in PA for those with PFP.