T he fantastic improvement in world records in all sporting events over the past 25 years is the result of advances in our knowledge about training methods, athletic injuries, and nutrition.
To develop great strength for competition, weight lifters must lift very heavy weights in practice1; to develop speed, runners must run very fast in practice. However, because no athlete can exercise intensely every day, intense workouts are done no more often than every other day. Every time muscles are exercised intensely, they are injured,2 and it takes at least 48 hours for muscles to heal.
Twenty-five years ago, athletes worked so intensively during training sessions they were unable to reach their maximal performance in competition. Today's athletes are faster and stronger because they substitute quality for quantity in their intense workouts. For example, 25 years ago a typical speed workout for a marathoner was to run a
Mirkin G, Shangold M. Sports Medicine. JAMA. 1985;254(16):2340–2343. doi:10.1001/jama.1985.03360160172052