Fatigability in osteoarthritis: effects of an activity bout on subsequent symptoms and activity.

Background: Older adults with osteoarthritis (OA) are more likely to experience increased fatigue following bouts of physical activity than those without OA. The highly "fatigable" nature of this population is problematic as it has been linked to OA severity and decreased function. This study examined the effects of engaging in standardized lab-based physical tasks on subsequent fatigue, pain, and activity in older adults with OA.

Methods: Thirty-five older adults with OA performed lab-based tasks (sweeping, grocery shopping, and walking) in 15-minute circuits until they felt too fatigued to continue. Fatigue and pain were self-reported (0-10 scale) following each circuit and at set intervals during a 4-day baseline (pretask) and a 5-day posttask home period. Activity was tracked via wrist-worn accelerometer. Multilevel modeling was used to examine levels and patterns of fatigue, pain, and activity across the study period.

Results: The lab-based tasks altered subsequent levels and patterns of fatigue and activity but had no effects on pain. Compared with baseline, on the day of the lab-based tasks, fatigue was higher and more stable, and activity was significantly lower and dropped steadily toward evening. Activity returned to baseline levels and patterns by the day following the lab-based tasks while fatigue was lower for 3 days following task performance.

Conclusions: Among older adults with OA, a bout of standardized physical activity resulted in increased fatigue and reduced activity, but effects were short-lived. Future studies will need to identify factors that differentiate people who are particularly fatigable in order to target interventions.