Sensitivity to Physical Activity Predicts Daily Activity Among Pain-Free Older Adults.

Objective: Prior research indicates that older adults with knee osteoarthritis have increased sensitivity to physical activity (SPA) and respond to physical activities of stable intensity with increases in pain. Whether SPA is present in healthy older adults without chronic pain and predicts functional outcomes remains relatively unexplored. The purpose of this study was to determine the degree of SPA in healthy older adults in response to a standardized walking task, and whether SPA was associated with temporal summation of pain, pain-related fear of movement, and functional outcomes.

Methods: Fifty-two older adults without chronic pain completed self-reported measures of activity-related pain and physical function, completed the Six-Minute Walk Test (6MWT), underwent quantitative sensory testing to measure temporal summation of heat pain, and wore an accelerometer for one week to measure physical activity behavior. Subjects rated overall bodily discomfort (0-100 scale) prior to and during each minute of the 6MWT. An SPA index was created by subtracting the initial bodily discomfort ratings from the peak ratings.

Results: Repeated-measures analysis of variance indicated that bodily discomfort significantly increased across the walking task, with approximately 60% of the sample experiencing SPA. Hierarchical regressions indicated that greater SPA was associated with fewer average steps per day and greater activity-related pain. Additionally, analyses revealed that temporal summation of pain and pain-related fear of movement significantly predicted the degree of SPA on the walking task.

Conclusions: These findings shed light on potential mechanisms underlying SPA in older adults and suggest that SPA might be a risk factor for reduced physical activity.