Study indicates better results by periodically alternating training program— published: 09-21-2010
It has been known to trainers that alternating higher intensity and lower intensity training sessions is the most effective means for conditioning athletes.
As reported in the September 20, 2010 edition of the Tauton Daily Gazzette (Tauton, MA), recent research indicates that it is not necessary to train at high-effort levels every exercise session. In other words, a combination of higher intensity and lower intensity exercise is recommended for a sensible and successful fitness program. The full article can be accessed here.