All I know is at 40 yo I suddenly felt like the shit hit the fan. First I fall off a loading dock and get a herniated disc. Just as I'm feeling better from that I had a low side where my left leg got trapped under the bike breaking my fibula and tearing the ligaments in my ankle. So I'm told I need a plate and screws above my ankle to hold the bone in place while the ligaments heal. Then I get blood clots from the surgery, my blood pressure is way up because of my lack of physical activity and weight gain. Over a year later, diet and a strict physical fitness routine has gotten me back on the bike, off the blood pressure meds and feeling much better. So 40 sucked, but 41 is much better so far and the riding is more fun.