A marathon taper is a gradual decline in mileage that precedes the event, giving the athlete time to rest, recover and allow proper absorption of their final build phase of training (generally speaking this means your final 20- to 22-mile long run). Every marathon training routine should end with a taper roughly two to three weeks heading into the race.
The taper has been scientifically proven to help improve performance between three to five percent (which can be the difference between a PR or a Boston Qualifying time for many runners!). During this phase, your training is not geared toward physical improvement, in fact, there are very little fitness gains you can make this close to race day. It’s more about allowing your body to catch up to itself. In other words, you will be cutting back your mileage to allow muscle improvement as well as allowing your internal system to achieve optimal levels prior to race day.
When a taper starts, your body is somewhat depleted. You would have put in a lot of work as you approach this stage. Remember: the taper is meant to re-energize you so enjoy it and take it while you can!!
Like anything else in training, your taper process needs to be personalized. You might want to go the route of a three-week taper versus two weeks or cut back drastically on mileage while maintaining intensity. Another option is to tweak your mileage just enough and cut back on intensity. For the best results, you should be following a marathon training plan or working with a coach (like me ). But if you are on your own, you can choose what works for you. It might take some trial and error, but once you figure it out, you will be golden.
The hardest thing about tapering particular if this is your first time is the mental side of it. You've went from working your balls off for the last 12-14 weeks to doing easier efforts and days on the lead up to the big event. You'll feel you are losing fitness and speed but in essence you are doing the exact opposite. My advice- TRUST THE PROCESS and don't do anything stupid!!