I'm so weak!

I was feeling pretty good about myself and my ride on Tuesday. 28 miles and no muscle soreness or tiredness that evening or the next day. But when I went to the gym Wednesday afternoon it was like someone had attached sandbags to my legs! I could barely manage the workout at all--still no pain, but just weak, weak, weak! I didn't feel tired, but that effort was just too much for me. I'm glad I didn't try cycling two days in a row. I'll have to work up to that. I remember the same thing from back when I was touring--the first day of cycling was pretty short (maybe a grand total of 15 or 20 miles) but it wore me out and took me a couple of days to recover. And it probably took me a good three or four weeks before I got to the point where I could cycle 40 miles a day a few days in a row. And I was half the age I am now.