Effects of Caffeinated Chewing Gum on Muscle Pain during Isometric Exercise in Individuals with Fibromyalgia

Fibromyalgia (FM) is a chronic, widespread musculoskeletal pain condition that is typically accompanied by several comorbid symptoms (e.g., depression, fatigue, sleep disturbance). Research demonstrates that regular exercise helps individuals with FM improve their symptoms and physical function; however, individuals with FM often experience augmented muscle pain during exercise compared to healthy controls, which may serve as a behavioral determinant that keeps them less physically active. Previous research shows that caffeine ingestion reduces an intensity of muscle pain during exercise in healthy adults; however, the hypoalgesic effects of caffeine on exercise-induced muscle pain have not been tested in individuals with FM. PURPOSE: This study examined the effects of caffeinated chewing gum on muscle pain during submaximal isometric handgrip exercise in individuals with FM. METHODS: This study was conducted with a double-blind, placebo-controlled design. Twenty-three adults with FM (43.57± 18.49 yrs) completed a caffeine session where they consumed a caffeinated chewing gum that contains 100 mg of caffeine, and a placebo session where they consumed a non-caffeinated chewing gum. During the sessions, they completed isometric handgrip exercise at 25% of their maximal strength for 3 minutes, and muscle pain rating (MPR) was recorded every 30 seconds during exercise using a muscle pain rating scale. The order of the two sessions was counterbalanced across the participants. RESULTS: The primary analyses indicated that MPR gradually increased during exercise in both sessions (p < 0.001), but the caffeinated chewing gum did not attenuate the increase in MPR during exercise compared to the placebo gum (p > 0.05). However, the secondary analyses indicated that average MPR during exercise in the placebo condition was associated with a magnitude of the hypoalgesic effects of the caffeinated chewing gum (r = 0.570, p = 0.005). CONCLUSION: The results suggest that the hypoalgesic effects of the caffeinated chewing gum were limited to those who reported greater muscle pain during exercise in the placebo condition.