There are at least four good reasons to schedule a non running day each week: 

• Reduces the possibility of over training - Physical fatigue is cumulative.  Providing an interuption every 7 days prevents an over accumulation of fatigue.  For any training program to be effective, the body must have regular periods of rest and recovery to "absorb" the tough physical conditioning. 
• Reduces the possibility of mental burn out - Month after month of everyday running can get stale.  Without a change in the routine, the training program may seem like a prison sentence.  Regular non running days can prevent this from happening.
• Encourages a high quality long run - If the non-running day follows the long run day, you have more of a tendency to "give it your all" on the last 20 or 30 minutes of the long run. After all, the next day is an easy day.  Finishing quickly is always a good strategy for the long run.
• Reduces the tendency to count miles - Many runners fixate on running "x" miles per week.  For most of us, the point is not compiling an impressive training log; it's all about running fast.  With a 6 day program, you'll never run the number of miles that a 7 day runner will. Thus, your focus will shift from counting miles to executing an appropriate series of workouts. 
  
  

So if you take one non running day per week, does this mean that you workout only six days out of seven?  Not necessarily.  Depending upon your goals, running twice per day on some days and/or cross training may be appropriate.  (Cross training and two-a-days will be discussed in future RunQuick articles.)