Effort magnitude is commonly thought to reflect motivation, but little is known about the influence of emotional factors. Here, we manipulated the emotional state of subjects, via the presentation of pictures, before they exerted physical effort to win money. After highly arousing pictures, subjects produced more force and reported lower effort sensation, regardless of monetary incentives. Functional neuroimaging revealed that emotional arousal, as indexed by postscan ratings, specifically correlated with bilateral activity in the ventrolateral prefrontal cortex. We suggest that this region, by driving the motor cortex, constitutes a brain pathway that allows emotional arousal to facilitate physical effort.