I have always been told that it’s better to vary your mileage throughout the week. I’m wondering what the difference is between running 6 miles 6 days a week and a long run vs running varied mileage throughout the week, but the same long run. Both scenarios add up to the same amount of miles. Why is the varied schedule better? This is just base running no workouts.
Long run = 20%-25% of weekly mileage
75%-80%of weekly mileage to be divided in the next 6 days
Sun 20%
Mon through sat 10% to 15% of weekly mileage per day.
For a hundred mile week:
Sun 18
Mon 14 ( am 6 pm 8)
Tues 14 ( am 4 pm 10 x 1k)
Wen 14 ( am 6 pm 8
Thurs 14 ( am 4 pm 10 mile progression run)
Fri 14 ( am 6 pm 8
Sat 12 ( am 6 pm 6)
But, why is it better to vary mileage?
Because you want rest and recovery. It helps you make better adaptations to run some of your runs faster or further as you see fit. Running the same thing every day just makes you marginally better at doing the same thing every day. You'll make better improvement by stressing your body within adequate risk limits, getting ideal and healthy response adaptations, and then repeating this process optimally. If your end goal is to brainlessly jog 6 miles, then by all means keep right on doing that 6 easy miles every day. If your goal is a fast race at a particular distance or set of distances, then you need to progressively get faster through a series of quality workouts with an underlying support of decent volume. This will more optimally give you the mechanics, engine, and efficiency to race well.
There is no difference between the two schedules you described. More important would be to vary the intensity and effort on different days and that usually leads to adjusting the mileage as well.
To get faster, you need to have some runs that are very difficult. They need to be so difficult that you simply wouldn't be able to run them again the next day. Instead, you run the next day at a much slower pace or not at all as you recover, thus introducing variation in your schedule.
Your body responds to different stimuli.
You can get good at running 6 miles at a moderate pace very quickly. Running the same moderate pace will take less effort and burn fewer calories. If that is your only goal, then there is nothing wrong with doing the same thing every day.