First Post - Long time Lurker -

I'm not inactive but I have not been on a bike in over 30 years (I'm 52). I decided to get in a little better shape and purchased a Trek 8.5 DS last weekend. I also purchased a trainer for the winter months. We had an unexpected 50 degree (F) day today and I decided to hit the bike path. I went 22 miles out and 22 miles back for a total of 44 miles! I'm pretty happy with my performance. The last 3 or 4 miles were pretty tough and I'm a little sore, but all in all a good day.

A quick question....

My breathing, comfort on the seat and riding position were fine. My legs simply gave out around 40 miles. I did not eat anything during the ride but I did drink plenty of water. Is this normal for a first time rider? Does this go away with training? Thanks.