A Continuum of Readiness Exists.
One end consists of rank beginners with no physical preparation and at the other extreme there are Olympic or world-class level participants. At any given time each of us is somewhere between those extremes. Get an idea where you are and strive to improve from that point.

General Adaptive Syndrome.
We improve and adapt to new levels of performance by putting ourselves under some stress. Continual improvement needs a gradual application of more stress. This may involve longer or faster running. However, improvement requires the opportunity to recover from this stress. The body follows its own rhythm. There is a certain rate, and no faster, to which it will develop. This program gives you plenty of time to progress to the your desired level. Stress without recovery leads to breakdown (injury and impaired performance).

Specificity and Delayed Training Effect.
We perform better after practicing a particular act. A successful completion of the any distance is easier after you can run farther and faster. At times we introduce new types of preparation to maintain variety and help your development. A delayed reaction to improvement exists at this time. Stress from running and exercising causes our body to slightly break down. Then it recovers and performs at an improved level. It usually takes 10-14 days to note improvement.

Cross Training.
Specificity does not say that cross training does not have its place. Fatigue or soreness from running may require some other activity to relieve stress on the lower legs. The cross training activities most specific to running are riding a bicycle while in a standing position, running in an upright position in water and walking. You can recuperate and even enhance your running prowess with these activities. Reverse the Run/Walk Intervals as described below. Walk 9:00 and run 1:00. Cross training workouts should not be more strenuous than recovery workouts if you are using them for recovery.