I had not been on a bike since my mid teens and several weeks ago took up cycling for fitness at age 65. It came back to me in a few minutes. Being able to ride a bike at least. The physical part took a few weeks. My first few rides were less than a mile with my heart almost pounding. Now about two months after those first few rides I am doing 13 ~ 15 miles a day at a reasonably good speed for a hybrid bike. I average between 14 and 15 mph most days for the entire ride. A stiff head wind still knocks the stuffing out of me, but I can feel myself getting stronger going into the winds.