I noticed when I turned 40ish, bruises and soreness would not heal nearly as well. I could still play sports OK, and get "into shape" in a few days, quasi shape. I basically quit trying as I neared 50 and got dumpy. Then when I retired I resolved to "get in shape", which has proven amazingly difficult. I do ten time the work for one tenth the gain. I didn't run while we were in Cincy and ran the last two days and really feel it.