Overactivation of the Reward System and Deficient Inhibition in Exercise Addiction

PURPOSE: Behavior studies have found that exercise addiction is associated with high impulsivity. In other addictions, neural mechanisms of impulsivity reflect abnormalities in the reward and inhibition systems. In this study, we determined whether abnormalities existed in the reward and inhibition systems of exercise addicts. METHODS: Three groups of male participants (15 exercise addicts, 18 regular exercisers, and 16 exercise avoiders) completed the Mini International Personality Item Pool (Mini-IPIP), the classic go/no-go task, and the exercise-related go/no-go task. Event-related potentials (ERP) were recorded during the go/no-go tasks, and correctly performed trials were analyzed. RESULTS: Exercise addicts scored lower for extraversion and higher for neuroticism, reflecting a poor capacity for emotional regulation and impulse control, and had larger N2 and P3d amplitudes during the exercise-related go/no-go task. Exercise addicts and exercise avoiders demonstrated impaired accuracy in the exercise-related go/no-go task and had larger N2 amplitudes compared with regular exercisers during the letter–digit go/no-go task. Exercise addicts and regular exercisers showed larger Go-N1 and Go-P2 amplitudes compared with exercise avoiders during the exercise-related go/no-go task. Exercisers (exercise addicts and regular exercisers) demonstrated higher activation in response to exercise-related stimuli as reflected by larger N1 and P2, and addicts (exercise addicts) demonstrated poorer inhibition as reflected by larger N2 and P3d amplitudes. Go-N1 and Go-P2 were significantly correlated with no-go accuracy in exercise-related task. CONCLUSIONS: Exercise addicts scored higher for the neuroticism personality trait and exhibited overactivation of the reward system and underactivation of the inhibition system. Overactivation of the reward system may be related to long-term exposure to exercise. Underactivation of the inhibition system may be a crucial factor in exercise addiction.