The first four weeks should be used for the further development of the anaerobic capacity to exercise and speed.  When developing the capacity to exercise anaerobically, it is important to realize what you are trying to do and what physiological development you are trying to achieve.  It is possible to develop an ability to incur about a 15-liter oxygen debt, and this is done by exercising anaerobically.  Developing big oxygen debts in training stimulates the body's metabolism to create buffers against fatigue.  If this is understood, it will be realized that it does not really matter what form of running it takes, as long as you are making yourself very tired with the volume of anaerobic exercise; and finish the training session knowing that you could not do much more nor any better.  Therefore, it doesn't matter whether you use repetitions or interval training, over different distances with different intervals, you don't even need to time them; as long as you come off the track or from your training quite fatigued.  However, as a practical guide, it is advisable to get fast running into a total of about three miles, or 5,000 meters, or thereabouts; i.e. 12 x 400 meters, 6 x 800 meters, 5 x 1,000 meters, or 3 x 1 mile, etc.; with recovery jog of the equal distance in between.  If one athlete takes longer intervals or more volume of fast repetitions than another to gain the same reactions physiologically, then he will just need to train for a longer time.

So, in many ways, it is important to evaluate your training every day, so as to understand the effects of each day’s training; and not to follow some or any schedule blindly.

I advise athletes to run their hard anaerobic training during this period of four weeks by doing it for three days weekly on alternate days.  Never do hard anaerobic training on consecutive days, as it is wise to allow your blood pH to return to normal after the exhausting workouts.

The younger the athletes, the less anaerobic training should be used in the schedule; and the ratio of anaerobic to aerobic training only increases as the athletes get older and fitter.

-Taken from "Training the Lydiard Way: Training Summary"