Just arrived from NY, with very much interest I read this new argument. I fully agree with tinman. I'm not able to be so deep in the argument because my knowledge of English language isn't so precise while talking about scientific arguments, but I want to confirm what practically happens FOR ALMOST ALL TYPES OF RUNNERS : when you are able to improve in "stamina", meaning the base of specific endurance, ALWAYS YOU IMPROVE IN YOUR PERFORMANCES. When my athletes (not only Kenyans, but also European) go for long EXTENSIVE-INTENSIVE RUN, always some days later they feel an important benefit in other types of workouts too.
Coaching my athletes, normally they are able to reach their best performance IN THE SHORTER EVENT DIRECTLY CONNECTED (for ex., 5000 if runners of 10000, 10000 if runners of HM, HM if runners of Marathon, but also 1500 if runners of 3000 or of steeple) about one month before the main race. At the same time, coming back to more quality after the main race, THEY ARE ABLE TO IMPROVE THEIR BEST IN SHORTER EVENT AGAIN 2-3 weeks after the most important event.
An example : Paula Radcliffe was able running fastest than ever in cross (2002) one month before her Marathon debut in London, but her first race after London was her PB in 3000 with 8'22", never run before.
This happens because the phylosophy of training is not TO REPLACE A TYPE OF TRAINING WITH ANOTHER during different periods of the season (for example, long run during winter season with crosses of 12 km, and speed during summer season without running over 6-7 miles in training), but is TO ADD SOMETHING THAT PREVIOUSLY YOU DIDN'T DO.
If you follow this phylosophy, it's clear that endurance is a basic work for speed, and speed a basic work for endurance. So, these two works must go on at the same time, of course with a correct modulation.
In training, there is a SPECIFIC TRAINING, directly connected with the performance, and a TRAINING FOR SPECIFIC TRAINING, that has the task to improve your basic qualities in order to do MORE and BETTER SPECIFIC TRAINING.
If, for instance, you connect 3 x 600m in 1'20" with 10' recovery with a performance like 1'45" in 800m, is clear that if you are able running 3 x 600 in 1'18"5 with the same recovery, or 3 x 600m in 1'20" with 6' recovery, you can run in 1'43". The problem is : how is it possible running in 1'18"5 instead 1'20", or with a shorter recovery ?
Is possible if we can play with SPEED, RECOVERY, VOLUME.
For ex., running 5x600 in 1'23" with 8' recovery, then 7x600 in 1'25" with 6' rec., till 10 x 600 in 1'28" with 2' rec.
But we can run more volume if we are able running 2 x 1000 in 2'25" with 10', then 4x1000 in 2'30" with 6', then 8x1000 in 2'36" with 3'.
But, for doing this work, we must use 2 x 2000 in 5'15" with 8', then 3x2000 in 5'20" with 6', then 4x2000 in 5'30" with 3'.
For doing this, we must run 5k in 13'45" or less, and for running so fast 5k, we must run 10k in 30' improving till 29'.
At the same time, we can go for improving speed, running 3x400 in 50" with 8', then 2 x 400 in 49" with 8', then 3x300 in 35" with 6', for example.
When we are able to improve in ENDURANCE, of course is easier to run one more interval at the same speed of before, WITH THE SAME RECOVERY. But, if you are able running 4x600 at the same speed that before you used for running 3x600, of course you are able running 3x600 a little bit faster. SO, ENDURANCE IS GOOD FOR INCREASING SPEED.
When we are able to improve in SPEED, of course is easier
to run a little bit faster the same number of intervals with the same recovery. SO, IF YOU USE THE SAME SPEED, YOUR EFFORT IS MINOR, AND YOU CAN RUN ONE MORE TEST.
SO, SPEED IS GOOD FOR INCREASING ENDURANCE.
The connection of these two type of works is the only secret of training.