I suppose you are speaking about something you don't know.
A lot of Kenyans don't use any training of AEROBIC POWER. All the athletes use running (usually on Monday) for long time (over 1 hr 30'), but at very slow pace. IF IT'S TRUE THAT NOBODY RUNS FAST LIKE KENYANS OR ETHIOPIANS IN TRAINING, IT'S ALSO TRUE THAT NOBODY RUNS SLOW LIKE THEM.
When you read something about training 3 times per day, this is a total bullshit. The first training is at 6:00am, most part of times without light, and athletes run in the darkness helped by the lights of the car of the coach, the few occasions that they have a coach, otherwise their pace is between 7' and 6' per km for the first 3 km. So, when they say "I run 1 hr fast", it means 3 km in 20' jogging, 15' increasing speed, 10' moderate and last 15' at 3' / km, using progressive running. The second training is again in the morning (about 10:00 o'clock), and is the best of the day (track or fartlek). The 3rd session (almost some time) is in the afternoon, consisting in very easy jogging (45' / 50' for 10 km).
This means that THESE ATHLETES REMAIN FAR FROM THEIR AEROBIC POSSIBILITY.
Of course, normally they have a natural aerobic power higher than white runners born and living at sea level, BUT THE LEVEL THEY CAN REACH IS VERY MUCH HIGHER IF THEY WORK IN THAT DIRECTION, also if runners of 1500m.
If you are Kenyan, the problem is not to train for beating some European (possible also with a soft aerobic training), but to beat the other Kenyans and Ethiopians. If you can become the number one, you cannot be satisfied to be the number 20 (but better than the European).
So, we are speaking about THE BEST SYSTEM FOR REACHING THE MAX POSSIBLE LEVEL ACCORDING WITH THE TALENT THEY HAVE.
Under this point of view, there are no differences between European and African, or between strong and week athletes. If you want to reach your personal best, the key is to reach the higher possible level of Aerobic Power, and this is not possible without adequate volume that is the base for the "volume of intensity".
Why two Marathon runners (one, Geoffrey Mutai, full time because already able running under 2:05:00, the other, Wilson Kiprop, having a preparation for Prague Marathon started in January, using that training for increasing the volume of "specific training" for 10000m) were able to beat in Kenya ALL THE ATHLETES FASTER THAN THEM PREPARING NATIONAL TRIALS IN TRADITIONAL WAY ?
When Paula Radcliffe was able to run her PB in 3000 (8:22), 5000 (14:31) and 10000 (30:01) after many years of specific training for track ? Some month after running her first marathon in 2:18 (2002).
When Maura Viceconte was able to beat the Italian Record of 10000m (31:05.54) ? Two months after beating the National Record of Marathon (2:23:47 in 2000).
You have to answer to this question : do you think more possible running a marathon preparing 5000m with a lot of training of speed but without long and fast run, or running a 5000m preparing Marathon with long and fast run, including some specific workout of speed ?
And also : which type of speed you need for running, for example, a 5000m in 13' (2'36" per km = 62"4 every 400m) ?
If you are able running in training 10 times 400m in 56" with 2'/3' of recovery in between, the next goal in order running a fast 5000m is running 10 times in 55", or it's better running 10 times in 56" reducing recovery to 1' (in this way, increasing the ability in running with high saturation of lactate in your muscles), or also 15 times in 56" with the same recovery of 2' / 3' ?
In other words, is it better to continue to push for increasing speed, or, when you are comfortable with a speed faster of 5% than the specific speed of the race (in the above case, 62"4 less 3"1 = 59"3), to try to EXTEND THE SPECIFIC ENDURANCE AT THAT SPEED, increasing the volume of training at a speed between 90% and 105% of the specific speed (in this case, per km, between 2'51" and 2'28", obviously using distances in training till 8-10 km at 90%, and distances of 400-800m at 105% ?
The final goal, for every distance, is not TO INCREASE THE SPEED, but TO EXTEND THE ABILITY TO LAST AT THE SPEED OF THE COMPETITION.
In this way, you increase the special volume, and this provokes a decrease of the level of lactate at the same speed. Consequentely, WHEN YOU WANT TO RUN A SHORT DISTANCE AT THE SAME PERSONAL INTERNAL LOAD, YOU CAN RUN FASTER (so, the first effect of an increase in specific volume is to enhance the speed).
You make confusion between MECHANICAL ENGINE (we have to work for bettering muscular strength, reactivity and elasticity, but this has nothing to do with BIOENERGETICAL FACTORS, that are the real limit in every competition of endurance) and METABOLIC ENGINE. For all the activity of endurance, the cake are workouts having a Metabolic goal, the sherry on the cake workouts having a Mechanical goal.