It may seem strange to suggest, but the three weeks prior to a marathon are best spent taking it easy.
That's assuming you've got a solid few months of training behind you.
This period is called tapering and while it does involve some running, all athletes benefit from letting the body recover for the big day.
The Academy finds out why:
WHAT IS TAPERING?
Put simply tapering is the phase in an athlete's programme where the volume of training is reduced.
Tapering is often done in preparation for a big event like a marathon so that the body is in prime condition.
Generally 2-4 weeks is needed, to give the body time to recover from training and to store energy for the race itself.
Charlie Pedlar, physiologist at the English Institute of Sport, says: "When you train hard you improve your ability to access the fuel you need to run and the ability to recover afterwards.
"As you reduce your training you take away the need to have a high level of fuel in your body.
"And the idea is that your body will then store that fuel.
"The damage to the body is also recovered so tapering allows you to start from 100 per cent fitness which is quite important."
"The problem is that lots of people don't taper their training and they should," says Sam Murphy author of Marathon: From Start to Finish.
"Not tapering is a mistake that even experienced runners make. It's a bit of insecurity thing. They think: 'Oh I've still got three weeks so I could get in another good session'.
"It's been proven that the ideal amount of time you need to fully recover and be prepared for the marathon is three weeks, which sounds like quite a long time.
"In that time your muscles are repairing all the tiny amounts of damage that are done each time you go for a run.
"Your glycogen stores, which is where you store your energy in your muscles, are being refilled to their maximum.
"So you're just recovering mentally and physically so you perform to your optimum on the day.
"If you don't taper for the race it's like starting with half a tank of petrol."
HOW DO YOU TAPER?
Tapering for three weeks doesn't mean you literally stop running for three weeks before a marathon.
Pedlar says: "What you'll find is that people will reduce the duration of their runs but maintain the intensity.
"So they'll keep their speed and power but they simply store up fuel - they won't stop their bodies being fit."
If you are planning a three-week tapering period, the week before, you should be embarking on your longest training run.
Murphy says: "If you're longest run is going to be about three hours, then after the first week you should cut that in half.
"Then the week after that I'd cut in half again, so you'd only be doing a quarter of your longest run.
"Saying that, it is also really important not to forget about your speed work during the last week of training.
"For the two weeks prior to the race you want to cut down the quantity of your other sessions.
"Keep the quality. So take a threshold run for example, you'd still work at an uncomfortable pace, but you wouldn't do it for as long."
WHAT SHOULD YOU DO IN THE FINAL WEEK?
It's tempting to keep yourself ticking over in the final seven days before the marathon.
But really it's all for effect. You've done the training, the main thing is not to get injured now and ruin it all.
"There's absolutely nothing you can do in that last week which will make you run better," Murphy says.
"During the last week I'd go out for a light run on the Tuesday and Thursday but it's more of a psychological thing.
"You might feel a bit sluggish during the last week because your body's become used to running. A couple of runs will get rid of that feeling.
"Within those runs I'd do a few strides where you pick up the pace for 25 metres or so. But I wouldn't do that if you've never done it before.
"And that goes for anything during the last week.
"You often see advice to go swimming or cycling which has less impact on your joints.
"But you don't want to do a half an hour swim if you never normally swim because that will be a quite a stress to your body if you don't normally do it.
"The same thing goes for yoga or things like that."