Honestly, I'm not positive myself. All I can say is that overworking your joints without enough cool-down time will put you at high risk for arthritis.
The best surface for a beginner to run on is smooth and soft so that it can cushion the stresses of running. For a more advanced runner, hills could be beneficial in improving their training and cardiovascular endurance.
Im gonna D because its the only one that actually sounds helpful so makes the lungs able to fill more completely etc, etc
The term is sperm for the male reproductive cellar
