I give you an example, from my personal experience.
At the beginning of December 1999, I went to Kenya for controlling the training of my first African athletes (I went Kenya the first time one year before) : Paul Kosgei, John Korir, Kenneth Kimwetich, David Lelei, Wilson Boit Kipketer, Christopher Koskei (that, after winning gold medal in Seville, without any problem, quitted completely to train till June 2000...). When I arrived in Ngong, I went to the camp in the house of Wilson Boit Kipketer (World Champion of steeple in 1997 and WR holder before Barmasai). I educated all my athletes to write their training, because their results don't depend on the program you give them, but on what they REALLY DID, and normally I never knew an athlete able to follow a written program for more than 70%.
Of course, in September I gave them different schedules : one for Kimwetich (1'43"03) and Lelei (3'31"57), one for Wilson and Christopher (that, how I said before, didn't do anything...), one for Paul Kosgei and John Korir, looking for 10000m. The program for them was part of a project for running around 27' (also if Paul Kosgei supposed to be still a specialist of steeple, but I wanted to change moving to longer distances).
After controlling what they really did in their training, Paul introduced me to two for me unknown and new athletes. He told me : These two athletes are still very young, one (Robert Kipchumba) is 16 years old, the other (Wilberforce Talel) is 20, and are very strong, because they are with me in training. I asked : Which kind of training, and how many times they train with you ? And Paul answered : ALWAYS, in the last 2 months.
So, I explained to the group two things :
1- The fact that new athletes are able, in short time, to train with one of the best in the World, means that they have a lot of talent
2- The fact that are very young means that, if they continue to use the same system, they go to finish themselves in very short time.
This fact can also explain WHY many African athletes are able to obtain, from nothing, a top result, and the next season disappear : they go to burn themselves.
In Kenya, there are 2 different type of young runners :
a) Students of Primary or Secondary School. If they are regular in their studies, Primary (8 years) last from 6 to 14 years, but, expecially in the case of people living in villages on the mountains, many times they go to school not before being 10 years old or more. Secondary last other 4 years (from 15 to 18). The daily period of school in Kenya lasts 8 hours, so there is no too much time for training. Because the most part of these young people didn't have any official document (now the situation is better, but we are speaking about people born about 30 years ago), for AK the only way for controlling their age was to know the class in the school. So, if you were a student at the first year of Secondary, you were supposed to be 15, but many times you were already over 20 (in this situation, for example, there were many of the best Kenyan of the past, like Noah Ngeny or Japhet Kimutai, where the difference between their real and official age is between 4 and 6 years).
When a young Kenyan goes to school, his training is very little. For example, Brother Colm, the Catholic Priest that produced the most part of World Champions in Athletics when young (he worked with the athletes till when they were students, only), introduced the best students/athletes of Iten / Eldoret and part of Rifet Valley, to a very simple training plan, not too much heavy, not with high volume (may be 60 km of mileage in case of 800m, till 100 km in case of long distances, per week), but with clear concepts of progressivity, graduality and continuity. In other words, a propaedeutic plan for preparing them to the REAL HARD TRAINING of the future.
b) Athletes that don't go to school, or never finished their school. Also in 2010, there are many boys and girls only starting tyhe Primary, but never finishing. In these cases, they are free to train all the day. So, when somebody thinks to have some attitude for running, he, WITHOUT ANY PERSONAL PROGRAM and without any coach (please, don't speak about Kenyan coaches... may be there are 5 coaches in all Kenya, the others are old athletes with the passion for athletics, able to recruit young runners but not to develop till their top), joins the group of the top athletes in his village (and any village has some very strong athlete). In this case, they try to do what the best athletes do : same intensity till when they die, same volume till when are able, without having any idea to build the base for a full career.
But this way, of course very naif and not correct, has one advantage : who remains alive after 3 months of training, is very strong and can become a champion, IF SO LUCKY TO FIND A REAL COACH ABLE TO ROUTE HIM IN THE RIGHT DIRECTION.
Many times, I meet in Kenya some, for me, unknown athlete, coming to me telling me "Thank, your program are very good", but I never gave any program : they are using a plan that I gave, may be 5 years before, to another athlete, for a specific period of the season !
When we speak about long distances (from 10000m to Marathon) the most part of athletes come from the group running a lot of km when very young, that in many cases never could finish their Primary.
When we speak about short distances (800/1500m) we have more athletes coming from Secondary School.
This means that, in the case of shorter distances, what they are able to do in training (not yet too much mileage but in any case with the prevalence of Aerobic Training, and some test of Lactic Power, for example 3-4 times 300m fast with long recovery) is the basis for the development, instead, in case of long distances, nothing can replace the mileage, also when you are very young.