I was thinking about your approach again the other night, and I've seemingly unconvinced myself. I thought about posting in your forum, but I thought it was appropriate for this thread. I also stopped following the Biomechanics of Speed thread on the Supertraining group, so forgive me if it was already delved into in some form.
With the DLing, 30 meter flyes, etc., the focus is primarily functional, rather than structural. I am sure structural adaptations will occur, but once sizeable strength has been achieved, further adaptations will occur primarily by means of neural or functional adaptations.
These adaptations will be in intermuscular coordination, intramuscular coordination, etc. I believe sprinting form improvements from DLing may be due to intermuscular coordination, but I would like to focus on intramuscular coordination. According to Supertraining,
intramuscular coordination includes the following:
- Number encoding, the control of muscle tension by activating or deactivating certain numbers of fibres.
- Rate (frequency) encoding, the control of tension by modifying the firing rate of active fibres.
- Pattern encoding, the control of tension by synchronisation or sequencing of firing of the different types of muscle fibre (e.g. slow or fast twitch fibres).
I believe your premise for not training speed endurance is that, by maximizing MSF, you will be able to recruit more higher threshold fibres, even as you fatigue. I am not 100%, but I believe in reference to number encoding, nearly 100% recruitment of fibres is possible in most trained athletes. Further neural improvements in terms of intramuscular coordination are determined mostly by rate encoding and somewhat by pattern encoding.
Once top speed is reached in sprinting, what makes having maximized MSF in training more beneficial than having worked on speed endurance? I do not believe maximizing MSF makes you able to recruit more higher threshold fibres.
Intuitively, it also seems that practicing longer distance sprints would be more beneficial for pattern encoding in the latter part of the race.
I am wondering whether this is addressed in Charlie Francis' new book as well.