The aerobic phase, sometimes called “base training”, “foundation” or “conditioning”, consists mainly of long, steady distance (LSD) running mixed with fartleks, easy leg speed work (strides), slower easy runs when needed and a weekly faster aerobic run (such as “Out and Backs“).
The aim of the aerobic phase is to run as high a mileage as possible without overtraining and to increase gradually the average speed and distance of your training workouts.
Once you have achieved the basic technical ability to run for at least 60 minutes at a steady pace without injury you are ready for the aerobic phase of training.
The long steady running that I term marathon training is designed to create a state of fatigue, though not so great as to interfere with the next day’s program. You should be able to recover reasonably quickly. – Arthur Lydiard, Running the Lydiard Way
During the aerobic phase your raise your “steady state” to its highest possible level. You may enter the training with a maximum steady state of around 12kph. At the end you may have moved this up to 14kph. This means that you can now execute much higher quality workouts as part of the specific training ahead and that you will recover quicker from this because of your greater level of endurance.
The aerobic phase also helps mitigate injuries as the body get’s time to adapt before being thrown at very fast or intense workouts. If the runner has excellent technique, they will be almost impregnable to injury if they adapt a long period of aerobic training.
Because all events from 800m and upwards use predominantly the aerobic energy system for fuel, it needs to be trained to the greatest extent first for all of these events and there are only small differences in the aerobic training phase between 800m runners and marathoners.
Duration of the phase
Aerobic training can be beneficial up to 6 months, or even more, but generally takes up around 42% of our training programmes (10 out of 24 weeks). When envisioned by Lydiard, his runners generally spend 3 months on aerobic training followed by 1 months of hill work as a transition and 2 months specific track preparation.