Ah, alright that make sense. The marathon has seen a wide range of temps in just the last few years, so who knows what will end up like. I really like it best because since it starts so early it means a majority of the race with me is before the sun rises and thus guaranteed to not be in the sun.
So I think there's definitely some confusion based on those conclusions. That was a very brief summary of the much more in-depth and explained review I did here:
Ian Williams: An Updated Race Equivalency Calculator Attempt
So read that one and it may answer some of your questions. But to address the immediate concern, no, you don't need to be doing 63 miles per week. That value in their conclusions comes from this statement:
-Has a 5L% of 9-11%. So if you do 100 miles as 5L (or five 20 milers), then you better be doing 1000 miles in the 16 weeks of training (or 63 miles per week on average). The more you diverge from this, the worse your HM conversion becomes. Although, you can still be successful at a lower 5L like 60 miles if the 5L% is still in the 9-11% range (or 600 miles total and 38 miles per week) as long as that duration is over 5-5.5 hours for your paces.
"5L" is your 5 longest runs in the entire 16 weeks leading up to the marathon. So let's say you did a classic 3x 20 miler, a 19 miler, and 18 miler. That means your 5 longest runs are 20+20+20+19+18 = 97 miles. The data they generated suggested that those who are the best converters are those who have a 5L as a percentage of the total training done during the 16 weeks around 9-11%. So essentially, how much of your total training you did in the 16 weeks leading up to the marathon was encompassed in those 5 longest training runs?
Let's say you did 600 miles in those 16 weeks. That would come out to 37.5 miles per week (600/16=37.5). Then the 5L of 97 miles (from the classic 3x 20 miler, a 19 miler, and 18 miler) divided by 600 miles total in training is 16% (97/600=16%). Their data suggested that 9-11% was optimal for conversion, and thus 16% would be outside that range. So let's say you were dead-set on getting in those 3x 20 milers, 19 miler, and 18 miler. How many miles in 16 weeks would it take to get it to fall in the 9-11% range of the totality of training?
97/0.09 = 1077 miles; Over 16 weeks that would be an average of 67.3 miles per week
97/0.11 = 881.8 miles; Over 16 weeks that would be an average of 55 miles per week
What's the punchline of this particular conclusion?
Don't focus on the long run. Focus on balance throughout the entire week and training plan.
My school of thought is use current fitness relative pacing and duration of workouts to determine what to do on each day of a training plan. The mileage of a training plan is simply a function of those two variables.
You recently ran a 10k at 1:12:34. For the sake of argument, let's say that race is reflective of your current fitness level. Here is a race equivalency chart:
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Here are training continuous runner training paces for someone at that fitness profile:
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Approximately 80% of all training would be at a 13:53 min/mile or slower (roughly 50% at 14:16 min/mile or slower). That would be about a 4.3 mph on a treadmill.
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For someone who run/walks, this would be my suggested starting point for run/walk durations and pacing. These are based on your 3.5 mph jog pace referenced earlier, although I tend to suggest what feels like a comfortable walk instead. In the case of run/walk, about 80% of training would be at Easy/LR.
So using these paces, to get to 5.5 hours of training would be about 23 miles per week. A peak LR at 150 would be 10.8 miles for continuous runner or 12.2 miles for run/walker.