Top marathoners now have about 90-95% slow-twitch muscle fibers; it used to be 95-98%, but running 4:30 miles requires more speed. About half the population has 50% or less slow-twitch and I'm in that group. If you try to run marathons on fast-twitch fibers, you end up "hitting the wall," unless you run very slowly or you take steps to store as much glycogen as possible and use it as sparingly as possible.
In previous posts ("The Puzzle," parts 1-3), I pointed out that the standard carbohydrate loading program of three days may not be sufficient and should be made 7-10 days. I also pointed out that those who have adopted the "fat-adaptation" diet have decreased needs for glycogen, but that while full adaptation probably takes several weeks, major muscle adaptations occur after only 5 days. Lastly, I suggested that muscles don't care whether they lack glycogen because one's diet lacks carbohydrates or because one has depleted them through exercise.
This leads me to a training plan suited for 3K/5K specialists such as myself who are trying to run a marathon well under 4 hours (ideally under 3 hours). Those running slower should be training like ultramarathoners and those who are better at running longer distances have a multitude of training plans that they could try. It's a variation of "crash" training, with several difficult runs in a row, which must be carefully controlled to avoid burnout.
Saturday: 90 minutes, with 3-4 miles at half-marathon pace and 4-5 miles at marathon pace. This is a fast continuous run at anaerobic threshold pace and should deplete slow-twitch muscle fibers.
Sunday: 150 minutes long slow steady run. This keeps the slow-twitch fibers depleted and forces the body to use muscle fibers it reserves for when the "most-favored" muscle fiber bundles can't be used. This should be done slowly, to keep the fast runs separated by a day.
Monday: 75 minutes, with 3-5 x 6 minutes hard alternated with 3 minutes easy. The hard sections may range from 1200-2000 meters. These are maximal oxygen uptake intervals and the recoveries are incomplete, making each one harder than the previous one. The third should be difficult toward the end, the fourth should be difficult right from the start and one should fall apart on the fifth, as the fast-twitch "A" fibers are depleted.
Tuesday: 105 minutes of hill repeats. This is an extensive interval workout, done at an easy pace, where it is the sheer number of repetitions (15-30) that make it challenging. The hills require the muscles to be used in a different way than on flat ground, challenging them without running hard. Working against gravity causes an increase in heart rate on the uphill, making it an interval workout, even though it's run at a steady pace. This should be slow enough to separate the fast runs by a day.
Wednesday: 75 minutes with 6-10 x 400m at 1500m pace, with 5+ minutes (full) recovery. This is a lactate tolerance repetition workout. Each repetition should be hard to finish, but recovery should feel complete before the next one is attempted. The lack of glycogen in the muscles from previous runs will make this even more challenging. This workout is of less importance than the previous ones and the actual times run can be expected to be much slower than one would expect if running "fresh."
Thursday: 30 minutes with 8x100m strides or sprints. This works muscles much like weight lifting does and ideally does not use glycogen at all, but stores of another compound called creatine phosphate. This is a transitional run, moving one from glycogen depletion to glycogen storage.
Saturday 2: 90 minutes easy cross-training (hiking, power-walking)
Sunday 2: 150 minutes x-train
Monday 2: 75 minutes x-train
Tuesday 2: 105 minutes x-train
Wednesday 2: 75 minutes x-train
Thursday 2: 30 minutes x-train
Friday 2: off
If one can do these workouts without getting injured in the process, it should cause muscle glycogen depletion for 5-6 days, causing some fat-adaptation and then there is 8-9 days of recovery, which should be enough to be able to start the cycle again, with far more glycogen stored than in the previous cycle and an ability to run faster while using less of that stored glycogen. Progress is measured by comparison of times, distances and paces of similar workouts from one cycle to the next.
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