Get your blood pumping, your brain will love you for it! A study conducted by the British Medical Journal found that the increase in blood flow to the brain during exercise leads to an immediate boost in concentration. According to John Rately, clinical professor of psychiatry at Harvard Medical School, this peak in concentration lasts for about two to three hours after a work out. So if your feeling a bit slow before a big test or deadline, try taking a power walk around the block instead of sitting at your desk in despair.