Lydiard is out of date because athletics now is very much different from 50 years ago, but the principles of Lydiard are still at the base of every program.
Which are the main evident differences ?
Now, we don't have, and don't need anymore, to have long periods of general basic preparation.
This is true when we speak about beginners : the way for starting endurance events is the same of 50 years ago, and there are no doubts about the necessity to develop a long, continuous and gradual increase in what we call "general resistance", that is exactly what Lydiard did. At the same time, we need to continue to build strength, in all its forms, that is at the base of the development of the speed.
But many years ago, after a full season, athletes started again from the ground.
Michel Jazy, already record holder of 1500m (3'36"4), 2000m (5') and 5000m (13'24"), at the end of the season rested completely for one month, and his first 90 days of training included 3 hours of run at 5' per km pace (almost 8' per mile).
At the light of what we know today, this training was completely useless, and sometimes damageous.
At that time, we justified this training with the goal of increasing the number of vessels, calling this process "capillarization". This was correct for a certain period of time, but, after 2-3 years, we can't increase the number of vessels if we don't do long run at more intensive speed.
The athletics of 50 years ago didn't have the same number of opportunity there are today. There were not WCh, not many international meetings, no real money. The athletes were real "amateurs" (with some money under the table only, paying attention not to be discovered, otherwise could be DQ by the IAAF for being "professional"). Athletes belonging to Countries of Commonwealth had two windows every 2 years (the even years) : Olympics, and Commonwealth Games. Athletes not in Commonwealth Games, for example European, had Olympics and European Championships.
The odd years were practically empty, with only some match among National Teams.
In those conditions, to think of continuity in training at high level of intensity was something impossible, since the best athletes couldn't maintain the same motivation for very long time, without competition at maximum level.
For some Country like Ethiopia the situation was still worse : they didn't have other stimuli than every 4 years, looking at Olympics, and went to boycott two edition (1976 and 1984), with very long period agonistically empty.
With the change at the top of IAAF in 1979, when the Italian Primo Nebiolo became President, athletics changed, becoming professional. From 1983 we had, every 4 years, WCh, was created the Golden League, on the road the number of top Marathon grew every year, the number of indoor track became bigger, World Indoor Championships were created, and athletics became very much more popular. Also when we speak about Cross Country, I remember that the first time there was an African Team for juniores was in 1982, when World Cross Country Championships were in Rome, and the IAAF (for the will of Nebiolo) paid the travel to the full Ethiopian Team, that won ahead the strongest Italian Team ever.
Becoming more professional the athletic organization, also the athletes became more professional : their activity had to last all the season, and the training system had to change. So, one of the most important points was NEVER THEY HAD TO LOSE WHAT ALREADY THEY HAVE.
This means that every type of intensity, in any event, needed to be trained also out of season, and never had to decrease too much. For example, athletes for 1'43" in 800m MUST be able to run in 1'47" also in winter, and their training has to include specific speeds, not at the same intensity of the last specific period, but in any case at 90% of the max individual ability.
This was not true at the time of Lydiard.
Another source of confusion is the name we called the Lydiard system : Marathon Training. This system was good as basic for ALL THE EVENTS of endurance, ECCEPT the marathon. Lydiard produced, directly or indirectly, a lot of top runners on track in distance between 800 and 1500m, very little in 10,000 and nothing in Marathon (with the only ecception of Ron Dixon winning NY with a type of training not depending on Lydiard principles.
So, when I say that Lydiard is out of date, I mean that today, if somebody wants to follow Lydiard system, he has to look at an activity that is not professional and doesn't have all the MUSTS top athletes have today. Top athletes reduce the time dedicated to build up their base, for the simple reason that, after building already 5 floors of their aerobic house, their off season put them at the 4th floor only, and from there they start to build again some new floor, when in the past the best athletes, after already having the 5th floor, could start again the next preparation from the 1st floor only, needing a lot of time for rebuilding something, that they already had.
The history of the training methods can teach many things, because the development is based on what somebody was able to do in the past. In any case, always was clear the final goal for increasing the performances in any event of endurance : TO INCREASE THE VOLUME OF SPECIFIC INTENSITY.
This means NOT the volume at low intensity, like in Lydiard and first 70' years, when many athletes (of middle distances too) had a mileage of almost 200 miles per week (320 km) at low intensity.
This means NOT the intensity, like in the period 1990-2005, when in Europe and America athletes cut the volume looking at higher intensity only, with a continue decrease in the performances.
But the increase of the VOLUME of SPECIFIC INTENSITY, that needs, in any part of the year, extensive volume (from 180 to 230 km per week, in the period without competitions, depending on the event) and intensive training (always elements of the preparation at submaximal intensity).