Response to
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If you believe those Touring books and articles, your first days ride should be the longest. It will usually be the day that is met with the most anticipation and energy. As the ride progresses, your miles should drop by anywhere from 15 to 25% per day, to a simple minimum. Stay on that minimum for the rest of the ride.
Judging by some of the responses here, that theory is out the window.
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The theory is sound, for IBA-type BIG mileage rides. The assumption is that you are trying to make maximum miles in minimum days. If the plan is for 200-300 mile days, then you are completely outside of the parameters of the theory. The theory addresses the question of maximum safe. alert mileage per day, on consecutive hard days, from a standpoint of physiology rather than personal preference.
More theory: First day you are freshest, so you can go the longest. After that, fatigue sort of accumulates, and you are progressively less rested each day for 4-5-6 days, then you bottom out around 70% of your maximum day and stay there until you get some heavy rest days. Assumes IBA levels of saddle time, like 16-20 hours daily. Anybody with a few 1000+ mile days under their tank will be able to confirm that.
The first 1000+ mile day is the easiest. So is the first 700+mile day. Or even the first 250+ mile day. The last day is typically the most dangerous, since we are usually pushing to get home.
saxman