The most beneficial time to take a workday break is mid-morning.

Hunter and Wu found that rather than the typical culture of working hard all morning only to take a lunch-hour or mid-afternoon break, a respite earlier in the workday replenishes more resources -- energy, concentration and motivation.

"We found that when more hours had elapsed since the beginning of the work shift, fewer resources and more symptoms of poor health were reported after a break," the study says. "Therefore, breaks later in the day seem to be less effective."