This relates to the comment I made to you on FB.
When my older son had been riding a month, he went out with DH and I to do the same little ride I did yesterday, about 11 miles. Aside from the fact a spoke broke on his bike about 3 miles in, I realized quickly that he would be riding with DH, and I would be the sweep. I pictured a skinny little 28 year old, who told me he was out of shape! I know age is the difference, but still. When I started doing aerobics at his age, I had to pull over on the side of the road, because I thought I was going to pass out after the class. It took me at least 5 months to feel in shape. I was really shocked he was so fast.