Unless you're a high-mileage runner, don't do any running the day after a race. There is no fitness to be gained, and much recovery to be lost, in forcing yourself to stagger through even a short training run within 24 to 30 hours of racing at any distance. Just walk and stretch for circulation. If you've run a marathon, don't run for at least three days, no matter who you are.
The Next Week
How quickly you return to normal training depends on the length of the race you've just completed, your fitness level, and when you plan to race next. If the race you've just completed is the last one in your current training cycle, you should feel no rush to return to normal training.
More: 5 Phases to Speed Up Your Running Recovery
In fact, you'll be better served in the long run if you allow your body and mind to rejuvenate through a brief span of inactivity followed by a period of informal, just-for-kicks workouts, perhaps featuring some alternative modes of exercise.
Having said that, however, we do recommend that you have some idea as to what your next running goal will be even before your climactic race, as this will help you overcome the post-peak blues runners normal feel following a much-anticipated race, whether they've raced well or poorly.
After shorter races, up to 10K, you can do your next hard run within as few as three days, if you're a high-mileage runner. Otherwise, wait about five days. After a 10-miler or half marathon, fitter runners can go long or fast again after four or five days, while more casual runners should wait at least a full week.
More: 7 Post-Race Recovery Tips
And after a full marathon, all runners wishing to maintain a high level of fitness should do little or no running for four to seven days followed by a week of only low-intensity running. Then you can return to your normal regimen.
Cross-training is a great way to maintain fitness without slowing the recovery process in the first few days after a longer race. Walking, swimming, cycling and inline skating are all good choices, as long as you keep the intensity low. Remember, replenishing glycogen stores is as important to the recovery process as overcoming muscle soreness, and high-intensity exercise performed in any mode too soon after racing will retard it.
More: 4 Cross-Training Activities for Runners
In Summary
Unless your next race is your "retirement" race, you'll want to execute a proper recovery plan afterward. By following the guidelines I've provided here, you can accelerate your body's return to homeostasis and get a jump-start on your preparations for the next race.
Sign up for your next race.