Even elite runners take a break after a grueling marathon, but how many weeks before you can race again at your peak level? The science of exercise recovery is somewhat sketchy. Few studies provide a clear indication of how long to rest before tackling your next race, let alone what recovery really means. It takes about 24 hours to replenish the body’s energy—glycogen—stores. You can easily do this by eating carbohydrates and some protein after the race. Muscle soreness takes about a week to go away, although the exact time varies among people. Feeling good and replenishing your energy stores, though, may not mean that you are ready to run at full speed or strength. Elite marathoners run only one or two races a year, taking six months off in between. Ultra-runners who do 55 miles in mountainous terrain require 18 months or more to recover. Many of them report needing to give the mind a break between races. Clearly there’s a psychological component to recovery. There are a few studies that indicate that something happens during a race beyond muscle soreness and mental fatigue. One Danish study showed that while the muscles of marathoners had largely recovered five days after a marathon, the maximum contraction—power—was still reduced. Based upon this, it’s likely that some fatigue will linger long after the pain of your race is gone. Experience–and good coaching–can go a long way toward helping you find a recovery plan that works for you. Expect, though, at least three to four weeks of recovery after a marathon before you are feeling your mojo again.