kevinG:
Charlie, I do not believe this to be true. Simply because an athlete increases his maximum speed does not mean that he will experience a corresponding improvement in speed reserve. During sub-maximal running (i.e. 200m or 400m pace), to which speed reserve is most relevant, maximum velocity is not the limiting factor in the first place. The real issue is energy production capacity. To run at a given speed requires a fixed amount of energy regardless of the athlete’s maximum speed. The fact that the output task decreases is irrelevant. Therefore, even if an athlete improves his maximum velocity, he will still fatigue just as quickly when running at any given speed.
Let me clarify my concept of speed reserve, which would actually be better described as “motor unit reserve”.
I believe that speed reserve primarily has to do with the “pool” of fast-twitch fibers available to contribute to a sprint effort. The nervous system recruits motor units on a rotating basis, replacing fatigued fibers with fresh fibers to delay fatigue by distributing the workload among as many fibers as possible. The more fast-twitch fibers an athlete possesses, the more he will have in “reserve” when running at a given speed.
When you improve maximum speed through sprint training, you don’t increase your number of motor units - you merely improve your nervous system’s ability to recruit them for a brief few seconds.
If speed is trainable (which it demonstrably is) then appropriate work must be done to train it. This additional work is also reflected in the speed reserve picture.