This is an annual ride in Michigan's Thumb area, meaning lots of flat, open farmland and small rural towns. My previous long ride was 40 miles on my comfort bike a year ago, so I figured 65 on my fast new road bike would be no problem. Unfortunately I made two rookie mistakes: going out too fast and not accounting for the wind that turned into enough of a breeze to stiffen flags on the many flagpoles that I saw. "Flat and open" also means "can't hide from the wind." Last year I rode with a small group at a casual pace and with a lot of breaks; this year I was alone on the road the whole time and got in too much of a hurry to get to the next turn or landmark.
Anyway, I found myself at the 50/65 decision point after riding the last 4 miles right into the wind. A glance at the map told me that the 65-mile route meant another 5 or 6 in the same direction, so I took a right turn onto the 50-mile route. That was a good decision, as I finally ran out of steam at about 40 miles and pretty much limped to the finish after that (luckily with the wind at my back for once). My time in the saddle was 3:20 for an average of about 14.5mph, which is probably not bad considering.
Being in good condition for the running that I do, I was not stretched aerobically at all and did not even work up much of a sweat (it was in the mid-50s), but it was my legs that were giving out. Obviously cycling uses some different muscles, or uses the same muscles differently, or whatever, but today felt like I used to feel after running a marathon. It will probably take more than a day or two to really recover.
But I have another event in three weeks, and with what I've learned, and if the wind stays away, I might manage to "ride my age" on their 60-mile route just a couple days after my 60th birthday.