Exercise motivations, behaviour and frontal brain asymmetry: assessing competing hypotheses

Background: Exercise dependence, while sharing some symptomology with behavioural addiction per the DSM-V, lacks a psychophysiological explanation. Until such an explanation is developed and tested, the consideration of exercise dependence as a clinical disorder is speculative. Asymmetric alpha band activity in the electroencephalogram (EEG), within frontal brain regions of a person at rest, has been suggested as a potential biological marker of individual risk for exercise dependence. Competing hypotheses have been proposed about the relationship between frontal brain asymmetry and exercise dependence. The first, affect regulation hypothesis, proposes that those with relatively greater right frontal activity, linked to negative affect, may become dependent on exercise as a means of improving their emotional state. The approach-motivation hypothesis proposes those with greater relative left frontal activity may become dependent exercisers as they are inherently drawn to the positive aspects of the approach-related behaviour. Studies to date have reported inconsistent results on the relationship between brain asymmetry and dependent exercise. Aims: The present study tested both hypotheses by measuring the relationships between self-reported, exercise-related motivations and behaviour, and asymmetry in alpha frequency power in the EEG; alpha power being inversely related to activity. Methods: Regular exercisers (N = 45) completed questionnaires measuring exercise activity and motivation, and addiction symptomology. Self-reported, state affect was measured before indexing the alpha activity in frontal homologous sites across hemispheres (F3/F4) during eight, one-minute resting trials of alternating open/closed eyes, via a 32-channel dry-electrode EEG cap. Participants were grouped by frontal asymmetry (i.e., left activity greater than right, or right greater than left). Results: There was no main effect of frontal asymmetry group on exercise activity, motivation scores, or exercise addiction symptom questionnaire scores. Scores on motivation subscales appearing to reflect either approach-related or emotion regulation processes did not differ across asymmetry groups. There was no correlation of state affect with any variable measured. Conclusions: We are unable to support either hypothesis proposed as a psychophysiological relationship between frontal asymmetry and exercise dependence, and the consideration of exercise dependence as a new form of behavioural addiction remains tenuous. Limitations related to small sample size and self-reports on exercise are discussed.