1) Sleep. Tom Brady slept 9 hours/night while in training and that is part of what kept him going in the NFL to such an advanced age. Christian McCaffrey, young as he is, during off-season training periods, sleeps 9 hours/night AND takes a two-hour nap before dinner (yes, he spends about half the time asleep). While a lot of people say they can't sleep enough because they're so busy with work, these folks see sleeping a lot as PART OF their job.
2) General rest. Every body is different in how it recovers. Even in high school, I didn't recover from workouts the way my peers did. Sadly, my coaches never understood this -- even as I was always slower at the end of the season than at the start -- and just told me to work harder (compounding the problem). If you still feel it 2 or 3 days after a hard workout, then you need to be waiting 3 or four days between workouts.
3) Protein. For a 40+-year-old person who is actively training, you should crank it up to approximately 1 gram of protein per pound of body weight, daily. Personally, I take 5 grams of pure leucine as a supplement daily (half before workout, half after) because it is the most important amino acid for muscle repair. 5 grams of pure leucine (of 10 grams of BCAA mix) may take the place of about 50 grams of whole protein in that 1 gram per pound allocation.
4) Creatine. Particularly if you are training for sprints, you need to be taking this. It is one of the few "wonder supplements" that actually has strong scientific evidence of effectiveness.
5) Recovery therapies. Keep a heating pad on your legs. Get massage. Soak your legs in hot water. These are all ways to drive blood flow to the affected areas so all that good leucine that do its work where you need it.