For my experience, the ability to use very short recovery between short and fast tests is one of the keys for running very fast in 800 and 1500m. The greatest specialist of 1500m, for example, come from 2 schools having the same "specialistic" characteristics : BRITISH (Coe, Cram, Ovett) and NORTH AFRICAN (Algerian and Maroccan, Aouita, Morceli, El Guerrouj). These two schools have, in common, the IDEA to run very fast using short intervals. This is the classic "Stamina" that English coaches continue to emphatize.
The fact that NEVER Kenyans had top champions in this events (the case of Ngeny is an exception, and in any case he was not able to last too long time) in the modern era, in my opinion is due to the lack of specific training in that direction. This happens because, living in altitude, IN ANY CASE THEY CANNOT USE VERY SHORT RECOVERY for the lack of oxygen, SO THEY MAINTAIN THIS BEHAVIOR AT SEA LEVEL TOO.
The real problem is another : supposing that the use of fast short tests with very short recovery can be the winning key for this distance, HOW IS IT POSSIBLE TO PREPARE THE BASE FOR THIS TYPE OF TRAINING ? In other words, the basic training for preparing the SPECIFIC TRAINING of short tests with short recovery, depends on THE LACTIC SYSTEM or on the AEROBIC POWER ?
The examples of the above athletes explain clearly that THE AEROBIC POWER IS THE KEY. All these athletes (with the exception of Coe, that never ran longer distances at top level) were able to run very fast 5000m (Aouita and El Guerrouj winning OG in this event), everybody very fast 3000m, also if, of course, their times in 800m were very good. Everybody of them started, when junior, from longer distances. Coe won EChjr in 1500m, Cram in 3000, Ovett ran road races, Aouita and El Guerrouj were in the National Team for Cross Country, and Morceli was able to run 3000m very fast when young.
Another example can be the Swiss Andre Bucher, starting from 10000m and steeple when junior, and later becoming World Champ in 800m.
When you are able to run very fast in competitions like 200 and 400m when young, YOU HAVE THE PHYSIOLOGY OF A SPRINTER. Konchellah (45.1 at 18), Fiasconaro (45.49 at 22), Juantorena (44.26 at 25), Courtney, Crothers, or in the past Whitfield and Harbig, WERE ATHLETES WITH A HIGHER PERCENTAGE OF FAST FIBRES. So, their mytochondrial attitude was not very high. In these cases, the phylosophy is the same (to extend your speed, moving to higher specific volume and reduction of recovery), but the speed is still very much higher than the speed of the race, the number of repetitions is not very high and recovery times are, in any case, open. If, for example, you are able to run 3 x 300 in 34.0 with 8 min recovery, you move to 6 x 300 in 36.0 with 6 min as final goal. If you become able to run in 1'42" (speed of 12"75 every 100m), the speed of 300m (12.0) is 5,88% faster than the speed of the race (0"75 : 12"75). Instead, in case of AEROBIC ATHLETES, with a very strong enzymatic system, we use the same speed, or also something slower. The 10 x 300 in 39.0 of Cram with 30.0 of interval are a clear example of this, and already 39.0 is the speed for 1'44".
Personally, I was curious to try a different type of training with some African runner, if I had time. For example, alternating 3 weeks at sea level with very tough training in lactic direction, followed by 3 weeks in altitude with training for Aerobic Power and Lactic Power (high speed with very open recovery), for competing at sea level again IMMEDIATELY AFTER THAT PERIOD, COMING BACK AT SEA LEVEL. I used this type of methodology, when I was the national Italian responsible, few times, having good results (for example, a PB with a very young Giuseppe D'Urso in 1989, from 1'47"17 to 1'46"30 going directly from Sestriere to Cesenatico, on the sea), but never like real project, with top athletes.
If the most important quality for 800m runners could be the speed, why the 90% of the athletes in top 50 all-time have also good times in 1500m, and only 10% in 400 ? And, if we look for Juantorena, Fiasconaro, Everett, Ereng, Konchellah and others, running 400/800, why they are not in top position in 800, but we find specialists of 800/1500 like Coe, Cruz, Cram or pure specialists of 800 (Kipketer, in any case more talented for 1500 than for 400, Sammy Kosgei, Bungei, Mulaudzi, Borzakovskiy, etc... ?).
The perfect specialist is an athlete having the MORPHOLOGY of a top 400m runner (like Juantorena) and his biomechanical attitudes, and the ORGANIC ABILITY of a top specialist of 1500m (El Guerrouj). When we find an athlete like this, to look for 1'39" becomes possible.