My shape is round, the calendar places me well into the 50s and have to be gentle on my knees.
I Tour. Echoing above comments- Tour does not equal race.
I think Earnest Hemingway is attributed to this quip-
“It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle. “

It helps to have a bike that fits you well you are comfortable riding and confident on.
If you use panniers- put 10 lbs of stuff in each rear one and 5 lbs in each front one.
Then commute to work as many days as it is possible, important to ride each day.
IMHO- while many indicate "I was only a commuter etc", that day after day riding
helps you get comfortable with your bike and helps acclimate your body to a tour.