What is the best way to ensure a PB in 12km race 3 weeks after completing a marathon?

I am planning on completing a Marathon in a couple of months and had my heart set on a PB in a 12 km race which is 3 weeks later. I want to know how to train / recover during those 3 weeks to ensure a speedy 12km. I am currently following a Marathon training plan which includes one speedwork session a week (varied) but otherwise predominately endurance runs.|||You are asking for a lot :)





Are there going to be downhill portions in the marathon? If so, train for them. Uphill climbs are actually less taxing (from a recovery standpoint) on the body than running on level ground. Downhill running is very stressful on the body.





Walk at least 800 meters or better yet 1 mile immediately after you cross the marathon finish line. Much of the normally ensuing stiffness and soreness can be reduced by doing this. Head off to take a warm but not hot shower or bath. Begin icing your legs.





For the next four days walk one hour in the morning and one hour in the evening. Continue to ice your legs several times a day. Swimming and stationary cycling will also move blood through your muscles to repair damage while maintaining fitness. Find a massage therapist and get massages every other day. If you lack the funds learn self-massage or recruit a friend.





On the fifth day begin a running schedule that mimics what you did the week before the marathon - controlled, slow medium distance running 4-6 miles. Continue to ice your legs and receive massage.





No speed work during the entire three weeks. Sorry. If you feel the need for speed try running at just faster than marathon pace during half of one or two of your 6 mile runs two weeks after your marathon.





A good diet is particularly important for healing. Back off your training the moment soreness becomes pain.|||You're really setting yourself up for pain/suffering/injury. After my first M I was totally careful for weeks, and still managed to injure a hamstring (which took months to get over). You can't rest/recover and train at the same time.





SO ONE OF YOUR GOALS IS UNREALISTIC. Chances are, before long, you'll do something that may interrupt your M and 12k. i HOPE NOT, but you're settting yourself up for anguish.





IF your first love is the M, then concentrate on that and find another 12K later on, which is what I recommend. My experience is that after the M, and after my hamstring healed, I began doing speedwork and set PR at every distance I ran. But that was with plenty of recovery time after the M.





Ideally, you would concentrate on the M, finish and bask in the glory of having done that, then rest and recover a few weeks, then EASE into some speedwork.





But good luck whatever you do....|||...maybe hire a professional trainer...