SPEED is a quality depending from the following factors :
a) Percentage of Fast Fibers (something genetic)
b) Level of muscular strength (fundamental for the length of the strides)
c) Power of the nervous system (fundamental for the frequency of the action)
d) Technique of running (fundamental for the efficiency)
e) Ability in relaxation
At least, we speak about BIOMECHANICAL qualities. In the case of short distances, the main problems is HOW TO INCREASE THE MAX SPEED.
Instead, when we speak about ENDURANCE, we speak about BIOENERGETIC and METABOLIC qualities. In the case of EVERY event of ENDURANCE, the main problem is HOW TO LAST LONGER AT A HIGHER POSSIBLE PERCENTAGE OF YOUR MAX SPEED.
This means that there is a correlation between the SPEED OF THE RACE and the SPEED OF TRAINING. When we speak of SPECIFIC SPEED ENDURANCE, we have the problem to chose the system for running more distance at the specific pace of the race.
For every different speed, our muscles produce different level of lactate. When we run at our max speed, we recruit the most part of our FAST FIBERS, and we produce in very short time high quantity of lactate, so we are in the area of LACTIC POWER. This is, for example, the area where we have to work for coaching a specialist of 100m when we want to prepare 200m, and when we want to prepare a specialist of 400m. WE NEED TO INCREASE THE LACTIC POWER, BUT WE ARE NOT INTERESTED IN INCREASING THE LACTIC CAPACITY, because the duration of the race doesn't require the ability in producing a lot of lactate, but the ability to produce in short time more lactate possible.
When we want to extend the distance, for example moving to 800m, we need to train our lactic system to produce HIGH QUANTITY OF LACTATE IN SHORT TIME (Lactic Capacity). This is connected with the LACTIC POWER, and there is no any real connection with the Aerobic System.
For giving clear ideas about training, if LACTIC POWER is the result of a race of 400 / 600m (for example, 46" / 1'16"), LACTIC CAPACITY is the ability to run in training 3-4 times the same distance, using an intesity of 90-95% of your Lactic Power, with long recovery (for example, 4x400 in 50" with 5' recovery, or 3x600 in 1'19" with 7'/8' recovery.
In all these cases, we speak about SPECIFIC SPEED ENDURANCE, of course specific for the distance of 800m.
When we look for a longer distance, we need, obviously, to reduce the speed. In this case, the direct intervention of the AEROBIC SYSTEM becomes more and more important, growing with the length of the race.
Reducing the speed, we can't recruit all our FAST FIBERS, but only a percentage of them. Longer is the race, less intervention of fast fibers there is.
In methodology, we don't consider CORRELATED with any specific training speed that is 10% faster of the speed of the race. So, when we speak about SPECIFIC SPEED ENDURANCE we speak of speeds that are between 100% and 110% of the speed of the race.
Some example :
800m in 1'48" :
100% speed = 13"5 every 100m. 10% of 13"5 is 1"35, and 110% of speed is (13"5 - 1"35) 12"15 for 100m.
We can train the SPECIFIC SPEED ENDURANCE using speed between 12"15 and 13" every 100m, of course in different distances : 10x200 in 24"8 is SPECIFIC SPEED ENDURANCE TRAINING, the same 7x300m in 39", or 5x400m in 53", or 3x600m in 1'20".
Every speed FASTER than 110% is SPECIAL SPEED, but doesn't have any specific function. If I go for 3 times 200m in 23", or 6x100m in 11"5, this is part of my mechanical training, BUT DOESN'T HAVE ANY PARTICULAR INFLUENCE ON THE BIOENERGETIC AND METHABOLIC SYSTEM. So, if I have an athlete running fast (for example 46" in 400m), that doesn't have any training of SPECIFIC SPEED ENDURANCE (more volume at a slower but specific pace), he's not able running a fast 800m NOT BECAUSE HIS LACK OF SPEED, BUT BECAUSE HIS LACK OF SPECIFIC ENDURANCE.
This kind of percentage works for every distance. So, if we speak of a 10000m runner able to run 26'40" (16" every 100m), we can say that the Specific Speed Endurance is to extend the durantion of a speed of 14"4 every 100m (28"8 in 200, 43"2 in 300, 57"6 in 400, 1'12" in 500, 1'26"4 in 600, 1'55"2 for 800, 2'24" for 1000m). To develop a high volume of km in one session (for example 12/14 km) using these type of speed, mixing the distances, is an example of SPECIFIC SPEED ENDURANCE for a specialist, like when we run 7x3000m in 8'30" for a marathon runner able running 2:04:00 this is a workout of SPECIFIC MARATHON SPEED ENDURANCE.
So, stop looking at SPEED like an ABSOLUTE CONCEPTION, but start to look at speed like something RELATED WITH THE SPECIFIC SPEED OF THE RACE.
You must understand that, in middle and long distances, there is an INTERACTION between volume and intensity, and the first effect in increasing SPECIFIC VOLUME is to increase the BASIC SPEED OF THE EVENT (not the max speed !).
For example, if I'm able to run 10x400m in 60" with 60" of recovery, and I finish this training with 15 mml of lactate, when I becoma able to run 13x400 in 60" with 60" of recovery finishing at the same level (15 mml), obviously I have more SPECIFIC ENDURANCE, because I'm able to last longer at the same speed (so, this is a training of ENDURANCE). But this 2 workouts (possible for example to improve from 10 till 13 times in one month), if at the end produce the same level of lactate, are carried on AT THE SAME INTERNAL LOAD.
So, when I'm able to run 13 times instead 10 times in 60", at the same internal load, I can try to run again 10 times only, finishing at the level of 15 mml, AND I DISCOVER THAT I CAN RUN IN 58"5 INSTEAD 60".
This means that, using a training of Endurance, I AM ABLE TO INCREASE MY BASIC SPECIFIC SPEED.
This is the reason because we speak about the FINAL OF AEROBIC ATHLETES. You need to think that EVERY COMPETITION IS A COMPETITION OF SPEED, because at the end ALWAYS the winner is the fastest ON ALL THE DISTANCE. But the winner can only be the fastest AMONG ALL THE ATHLETES HAVING THE SAME LEVEL OF ENDURANCE, so the priority is ALWAYS to look for increasing the SPECIFIC ENDURANCE.
At least, what can you do with all your speed when you are not able to arrive in the last lap with the leaders ?