I'm 54 and last week bought my first new bike in 40 years. I elected to buy a hybrid over a comfort bike anticipating doing some easy trail rides. Today I finally had a bit of time to ride and I put 12 miles on the new bike.
Boy, I don't remember bicycling being so much exercise! I did 12 miles in 55:43 for a 12.9 mph average. In the first half mile, I found myself huffing and puffing. So I settled down to a comfortable pace and enjoyed the ride. I certainly gained a new appreciation for the TdF bicyclists!
I'm still new to this forum and somewhere read something about spinning... and if my understanding of spinning is correct, I found my speed to jump significantly if I could keep my concentration on spinning vs pumping the pedals. But I found it hard to keep focused on spinning. I guess it's a learned thing. :-)
Also, I found that my hands tended to get numb after riding a while.. even changing my grip using bar ends didn't eliminate it. I could shake out the numbness but it was aggravating. FWIW, I had similar numbness when I rode motorcycles too. I was diagnosed with CTS some years back, but never had anything done about it since I could shake out the numbness with no lasting effect... and still can.
All in all, I really enjoyed getting some exercise this way... much better than using a treadmill or running. I look forward to becoming more involved in the sport and hope my interest survives the new bike syndrome. ;-)
The bike is a Marin Novato.