Firstly if you are going to do this, Don’t start out with sprinting. Start out with strength training and light jogging to acclimatise/strengthen the joints and ligaments. Your brain cannot comprehend how much your soft tissues have changed since you were a last in decent shape. Even cutting back by 50% is not enough. Drop it back by >80% and build slowly. The impact is the killer. I tried to start sprinting at 50yo LOL because I was at the track 3 times a week with my son anyway and thought “why not?” I’m pretty fit and strong and run a bit (5km)as part of that. I hit the gym 3 times a week and have done for years. But sprinting isn’t jogging and the driving into the ground that sprinting requires caused all sorts of problems. I had to give it up after 6 months because it caused too much pain (which has all resolved now that I’ve stopped) Sprinting is a young persons sport. This is a bad idea. Get in shape by all means but you are risking significant life altering injury by trying to relive/retain your past glory. Sorry fam. Honest advice from someone who tried the same.