The marathon is a demanding event that requires training on tired legs and doing workouts that simulate the fatigue and soreness you'll experience during the latter stages of the race. For almost all other race distances, you can come close in training to the intensity and distance of the race itself. Unfortunately, we need to be more creative to simulate the late race fatigue in the marathon, which is why it's important to schedule a version of the following workout in almost every runner's marathon schedule.
-5 or 6 miles (two times) at 10-20 seconds faster than marathon pace
-10 min rest
-Finish with a 1 mile cool down
The purpose of this workout is to run at your threshold pace for a total of 10-12 miles, which will help you: (1) increase your ability to burn fat as a fuel source when running at marathon pace; (2) practice running on tired legs; and (3) simulate the “dead leg” feeling many marathoners experience after 18 miles. This is why many of the runners who perform this workout call it the “best marathon workout.”
You should use this workout as one of your marathon simulation runs. This means you should eat your planned pre-race meal the night before, try and eat a similar breakfast to what you will use on race day, and implement your planned nutrition strategy.
Warm-up with an easy mile of running, some light stretching, and a few strides to get the systems firing on all cylinders.
Begin the first 5/6-mile interval at your target pace. Always start your workouts on the slower end of the suggested pace range and only increase the pace to the faster end of the range if you feel good. This is a long session and you don’t want to blow up and not be able to finish.
Take a 10-minute rest after the first interval. You can walk, very slowly jog (more a shuffle than a jog) or stand in place — whichever works best for you. The purpose of this 10-minute rest is to get your legs stiff and uncomfortable, which will help simulate how your legs will feel during the latter stage of the marathon.
Begin your second 5/6-mile interval at your target pace. Hold this pace as best you can, stay relaxed, and focus on good form and finishing strong.
The real secret to this workout is actually the 10-minute rest. As mentioned earlier, this 10-minute break will make your muscles stiff and make it harder to run pace the second half of the workout.
You will feel more tired on the second set, most likely from stiff or lethargic legs. This is planned, so focus on pushing through as best as you can. If you’ve never run a marathon before, this is similar to how you will feel late in the race.
If you’re struggling on the second set, don’t be afraid to slow the target pace down to something you can handle. However, do your best to finish the entire distance unless you’re injured or sick.