It is possible to maintain both your high-end speed and marathon speed given the long runs and cumulative fatigue coming your way. There's more than one way to crack this problem; here's how we recommend you do it. Please note that all of the math done below off is of a 16-week training calendar that includes three key speed sessions per week. None of these speed sessions should be done on back to back days, and that any specific "rest" intervals should be done at the easiest pace you can sustain without losing proper form.
Weeks 1 to 6: Building Strength & Volume
In the first phase, your main goal is to do the hard work required to build the foundational fitness that will allow you to truly train for the marathon. Your main goals are to build the requisite strength for the race as you start to add miles. As a result the speed work is very specific, and not all that "speedy."
The Long Run: As your long runs begin increasing, we put the emphasis on "work first" and distance second. In other words, we use this as a speed session with two to three mile repeats at 5K pace, each with full recovery (easy running until you feel ready to repeat), followed by the remainder of your long run. The pace of distance is about 20 to 30 seconds slower per mile than your goal marathon pace.
Example: 90 minutes as 15 minute warm up, 2 x 1 mile @ 5K Pace(full recovery), Remainder of time steady @ Goal Marathon Pace (GMP) + 30 seconds/mile.
The Tempo Run: Anywhere from 60 to 90 minutes with intervals done at half marathon pace, on flat terrain. The intervals should build up from eight minutes to sixteen minutes each, all with 50 percent rest.It's tempting to run faster and longer (because you can), but we need to conserve that energy for that next key phase. If you do have the bug to do "more"this early on, feel free to add in an easy run or two that lasts no more than40 minutes where you focus on good form and a nice high cadence.
Example: 60 minutes as 15 minute warm up, 2 x 12 minutes @ Half Marathon Pace (six minutes recovery), Remainder of time steady @ GMP + 30seconds/mile.
The Speed Run: Adding some speed at this stage is less about work as it is about skill. This will be a Strides session,where after a warm up of about 30 minutes of easy running, you'll do six to eight repeats of 20 seconds each at mile repeat pace (aka very fast but not all out). Your goal is to get in thirty steps; recovery is as simple as walking back to the starting point. Repeat as needed and then finish with an easy run home.
Example: 40 minutes as 30 minute warm up @ GMP + 30 seconds/mile,then a set of six strides.
Weeks 7 to 12: Converting Base Fitness
This is the period where you really find out whether or not you have the credentials to run the race you were hoping to have. Your focus is on both a quality long run and on a solid speed session, so make sure to nail both each week and plan on plenty of recovery.
The Long Run: The long run flips in the phase. Now you'll do distance first, speed second. Long runs broken into thirds, starting at 30 seconds slower per mile than your goal marathon pace.The middle section is about 15 seconds slower per mile. The final third is a push, where you aim to hit 15 seconds faster per mile. So a 15-mile run where your GMP for race day is 8:00/mile would be:
Example: 120 minutes as 15 minute warm up, then building 5 miles at 8:30/mile avg, 5 miles at 8:15/mile avg, 5 miles at 7:45/mile avg. Easy jogging and walking for remainder of time.
The Tempo Run: Tempo run done at half marathon pace on rolling hills with work intervals of six to eight minutes with25 percent rest. So the work continues but the rest is significantly reduced. You might progressively build this up to 30 minutes of total work at pace. This session should last no longer than 75 minutes.