Gabe Mirkin, M.D.
In 1968, some of top distance runners in the country came to Ball State University to be tested for physical characteristics that made them champions. Lou Castagnola could jump only 13 inches off the ground, a distance that most junior high schoolers can do easily. Several years later he was tested again after having retired and having gained more than 30 pounds, and he could jump more than twice as high to 27 inches.
Running long, slow distances slows you down. Muscles are made up of two types of fibers, those that are used primarily for endurance and those that are used for strength and speed. Running long distances develops your endurance fibers at the expense of your strength and speed ones, inhibiting your ability to jump high and run fast. Basketball players and sprinters need to run very fast two or three times a week, and so do marathon runners. Otherwise they will be slow runners.
It makes no sense to run long distances if you compete in sports that require short bursts of speed, such as basketball, baseball, football and hockey. Running long distances slows you down. During a basketball game, the players rarely run more than 20 or 30 yards continuously. The best way for basketball players to improve their endurance for basketball is to play basketball and run a series of very short sprints, two or three times a week. Distance runners need to run long distances to train a greater percentage of their fibers, but to be able to run very fast in races, they also should run a series of very short distances (called intervals) at near maximum speed two or three times week. To compete in any sport that requires short bursts of speed, run short intervals twice a week.