Not sure if it is the same for you, but I don't remember being sore from running when I was a teenager, maybe I was simply in better shape :).
These days I find myself with heavy legs after a long run or a track workout. Tart cherry juice has helped me to reduce the post run pain.
I know it sounds funny, but what is so special about tart cherry juice? Cherry juice has natural anti-inflammatory powers, which are also giving the cherry the bright red and pretty color. Cherry juice can be purchased as a concentrate. I have been taking 1-2 table spoons, added to a 12 oz glass of water after a run or other activities. Some sites refer to taking the juice 2x a day. You can obviously play with the amount you are taking. You can find several different research studies providing more scientific information regarding the reduced acidic levels measured in athletes taking the juice vs. placebos after a marathon or other running events.
Here is one, more recent article: Tart Cherry Juice Reduces Muscle Pain and Inflammation
Enjoy your run!