The marathon, or indeed a half marathon like the Great North Run, has a pretty major breakdown effect on the body.
You'll have a lot of little tears in the muscle fibres, you'll lose about 2cm in height and you'll also be very dehydrated.
Sam Murphy, author of Marathon: From Start to Finish, explains how you can speed up the recovery process.
KICK-OFF THE REFUELLING
The important things to do are to eat something as soon as you finish and to start rehydrating - ideally not down the pub!
Your glycogen stores will be empty at the end of the race so it's important to get carbohydrate on board within half an hour of the end.
But have some protein too. This will enhance the amount of carbohydrate which will be taken into your glycogen stores.
There have been studies which claim that Vitamin C and Vitamin E help you to recover more quickly but eating fruit and vegetables is probably a good way of getting this rather than taking supplements.
KEEP WARM AND KEEP MOVING
Keep warm because you'll lose body heat very quickly. That's why they give you a foil blanket at the end so you should use it.
Foil blankets: Use them!
Don't stop still suddenly. Keep moving around for a bit after the race. And you shouldn't stretch too much for the same reasons as not having a massage - your muscles will be too damaged and sore.
Get out of your running kit and take in the atmosphere at the end of the race. Sit down, eat something, have a drink and enjoy the feeling of finishing.
DON'T LET THE BUGS GET YOU DOWN
A day after the race is not the best time to book a massage.
If you want one, leave it a few days because you need to give your muscles time to recover to get the benefit from a massage.
Your immune system will be very low for a few days after the race too, so if there's any bugs or colds going round you'll probably get them.
So spend a few days taking it easy. Ideally have a few days off work if you can and maybe take something that will boost your immune system like echinacea.
CELEBRATE YOUR ACHIEVEMENT
Don't be surprised if you feel a bit flat after the initial elation of finishing.
You've had this thing for four or five months of your life and everything's been gearing up for this day. Then when you cross the finish line - it's all over.
You can end up feeling a bit empty and depressed. So it's quite good if you can arrange to do something a couple of days afterwards like a celebratory drink or dinner or even a weekend away to give yourself something to look forward to.
It gives you a focus beyond the day because it can be quite a shock.
The other option is to look for your next marathon or half marathon to run in!