Muscle Fibre Training.

[SprintStar]

I've been training for strength/power for a while now, and plan on doing so until mid may. I'm training for power/strength at 4-7 reps and from what I've read this works type IIb fibres , obviously im going to lack endurance (for sprint swimming 50&100 meters). Obviously i'll be in the pool for 6-10 hours a week too.

How closely linked are muscle fibers? can I condition the type IIb fibres at all? Can I effectively incorporate conditioning gym sessions into my current routine without overtraining the muscles? (3 days on, one day off)

Obviously I know nothing on the subject so if anyone has any sources that would be good.

[craig1014]

Its quite complex, and ever evolving. My current understanding of the subject is as such:

* There are two main types of muscle fibre, slow twitch (type I) and fast twitch (type II)
* Within type II fibres, there are further sub-categories - Type IIa and IIb are the most well known, but there are others, such as IIx.
* Type IIa fibres are a "bridge type" fibre between type I and IIb, as in they can take on characteristics of both types depending on the training methods
* Type IIb fibre number is relatively fixed (I think, although this is contentious) - one theory is that the muscle fibres can get bigger (hypertrophy), but not get larger numerically (hyperplasia).

So, this is how I would approach your questions:
* You can condition type IIb fibres by making them larger, and so they can produce the same amount of force for less effort
* You can save the type IIb fibres from fatigue by allowing more type IIa fibres to do more work.
* Over training depends on how much work you do each day, and how hard/long the sessions are, etc.

I hope that helps - not sure quite how current my knowledge is.