Maybe this is more individual. I am extremely inflexible. If I don't stretch, my knees hurt. Sometime I will feel my knees aching mid-run. I stop and stretch my

Maybe this is more individual. I am extremely inflexible. If I don't stretch, my knees hurt. Sometime I will feel my knees aching mid-run. I stop and stretch my quads, and it goes away. I suppose it could be the act of stopping, but it seems pretty cut and dry that stretching helps.