The law of diminishing returns, put simply is an economic law that states if one aspect of production is kicked up a notch while everything else remains static or constant, the returns will eventually decrease after a certain point. Thus, sometimes doing more work or giving more effort will yield a negative result as opposed to a positive one.
This law applies to training for one particular skill such as running. If you want to be a better runner, the last thing you should do is only run.
Interesting fact from the father of distance running- Arthur Lydiard “it takes only ONE carefully timed extra long run (2.5-3 hours) 5-6 weeks prior to race day to increase capillary beds in the muscles. For multiple runs over 3 hours, the law of diminishing returns kicks in as far as any cardio benefits. The mental benefit of knowing one can handle the distance must be weighed against the downtime required to recover”
-Running Times, Sept.2011-
The Lydiard training system is based on a balanced combination of aerobic and anaerobic running. Aerobic running means running within your capacity to use oxygen. Everyone, according to his or her physical condition, is able to use a limited amount of oxygen each minute. With the right kind of exercise, you can raise your limit.
More than 50 years and 20 Olympic gold medals on, the Master Coach is still producing champions over a wide range of sports.