Fitness As A Mechanism Underlying Mood Changes Induced By Exercise Withdrawal

Abstract

Withdrawal of exercise has been associated with depressed mood, whereas transient periods of reduced physical activity result in decreased fitness. However, the relationship between aerobic fitness and subsequent changes in mood has not been evaluated. PURPOSE To determine whether changes in negative mood that follow exercise withdrawal are related to decreases in fitness. METHODS Regularly active participants (N=40) were randomly assigned to either exercise withdrawal (EXW) or to continue their usual activity for two weeks (CTR). Participants visited the laboratory on three occasions: baseline, week 1, and week 2. At each visit, the Profile of Mood States (POMS) was completed and a progressive, submaximal bicycle ergometry test was performed to estimate VO2max. Participants pedaled at 60 rpm for 2 minutes at each of four different power outputs, with the starting power set at 30 W for women and 60 W for men. Power was increased by 30W per stage. RESULTS At week 2, EXW had significantly higher negative mood scores as compared to CTR, as measured by the POMS. Significant differences were noted for the subscales of fatigue (7.5±6.4 vs. 2.5±3.6; p=0.01), tension (7.6±5.5 vs. 4.5±4.5; p=0.04), and vigor (13.3±8.4 vs. 19.1±5.4; p=0.04). Although estimated VO2max did not show an overall decrease among EXW, baseline fitness was significantly related to reduction in fitness over the withdrawal period (r=−0.58, p=0.01). In contrast, no relationship was found between baseline fitness and changes in fitness among CTR (r=−0.08, p=0.74). Changes in fatigue were negatively (r= −0.37; p=0.02), and changes in vigor were positively (r=0.39; p=0.02), related to changes in VO2max. The association between changes in fatigue remained significant after adjusting for baseline fitness and group status (R2 change=0.19; p=0.003). CONCLUSION Individuals with greater reductions in fitness following exercise withdrawal may be more prone to subsequent mood changes, especially feelings of fatigue, as compared to those whose fitness changes minimally. These data may improve identification of individuals at risk for developing depressive episodes in response to a lack of exercise caused by injury, professional requirements, or recovery from medical procedures.