Well you're 69! - you warming up, post ride stretching all that? I'll be 50 in a month and I sure can't blast out of the door without warming up like I use to when I was 25. I also use a foam roller before every ride and usually after and if I forget it feels like I have no legs for first :15 minutes. I also like to stretch and roll the legs before bed, especially on nights before a ride, seems to help.