It is necessary to understand that, while the object of training is to develop your anaerobic capacity to exercise, this can only be done in relation to your oxygen uptake level and capacity to exercise aerobically. In other words, it is necessary to run as many miles or kilometers as you possibly can at economic or aerobic speeds to lift your oxygen uptake to your highest possible level as the foundation upon which to base your anaerobic or speed training.
To gain the best results for the time spent in training, it is important to run at your best aerobic speed: i.e. at speeds at a level just under your steady state or Maximum Oxygen Uptake. This is theory and can be applied in practice.
Even very slow running will effectively increase general cardiac efficiency and therefore raise the oxygen uptake. However, by running at speeds much below the maximum oxygen uptake level, it is going to take much longer periods of time to gain the same results than if the if the rates of speed were at faster aerobic levels. In other words: one can run too fast or too slow and it is important to control the running efforts as well as possible if the optimum results are to be achieved in the time spent exercising.
To train at speeds above the oxygen uptake is anaerobic exercising with the net results the development of lactic acid that causes a lowering of the blood pH with the ultimate results of neuromuscular breakdown in the working muscles. This means that the volume of exercising will be limited according to the oxygen debts being incurred. Seeing that, in this marathon conditioning phase, it is important to do a large volume of training and it has to be economic, or aerobic. The net results of the aerobic exercise is carbon-dioxide we breathe out; and water and salt we perspire. we are really endeavoring to lift the pressure by the heart upon the cardiac systems generally, to an economical level to bring about the development of the under-developed parts–the smaller arteries, arterioles, capillary beds and veins.
To carry out this ‘near best aerobic’ training practically, it is necessary to time your runs over measured courses, and to progressively increase the running efforts as fitness improves.
It can take many years to gradually and continually develop general cardiac efficiency. This is the reason why marathon runners are usually better performers at ages nearer forty rather than in their earlier years; that is if they continue with systematic long aerobic training.
I always tell runners that, “miles make the champions”, and that initially this grind of running all the mileage possible between the competitive seasons is of prime importance. The more miles that you are able to run aerobically in training, then the greater endurance you will be able to develop. So there is really no limit to the mileage that a coach should place upon his athletes, provided that the supplementary miles run above the required faster aerobic running are as easy effort at the lower aerobic speeds. In other words; it is wise to run once a day at faster aerobic speeds and supplementary to this running, to jog as many miles as you find time and energy for; even if it is only for fifteen minutes jaunt.
The fast aerobic running should be approached this way: Decide how much time you have daily for your training and balance your conditioning schedule upon this.