Training & Nutrition - Converting type IIb to IIa muscle.

How long does it take to convert type IIb muscle to IIa? Does it make sense to do a block of strength training followed by a block of endurance? A few weeks, months? Years?

Just speculate.

I think you have been reading too much shiat and should just
go ride instead of wondering about this.

How long does it take to convert type IIb muscle to IIa? Does it make sense to do a block of strength training followed by a block of endurance? A few weeks, months? Years?
Strength training will only build IIb, to change to IIa you need to do a lot of endurance. And IIa is not commonly found very much in humans, so its even harder. I'd say you need to train a lot

My speculation is years.

A quote from http://www.bodybuilding.com/fun/kelly13.htm seems to imply that the conversion takes place quite quickly.


Another reason that fiber typing may be largely disregarded is that studies in both man and animal have consistently shown a fast to slow conversion in response to training of any kind. That is, IIB fibers convert into the slower contracting and less powerful IIA.

In fact, guess what group of people has the highest percentage of the fastest contracting IIB fibers? COUCH POTATOES! With just about any type of training, the higher threshold fibers (IIB) change into slower contracting IIA fibers. When training is ceased these fibers once again revert back to IIB. The likely reason why this occurs is because of metabolic efficiency.

The body will deal with stress in the most efficient manner possible and a slow transformation is metabolically more efficient while it still allows the body to adapt to stimuli.

The part that's left out of that article is the percentage of your muscles that's type I, IIa, and IIb. While there are some conversions, you'll find that research into the actual amount of those fibres that's converted is relatively small. Rather what happens with training is you do exercises to target specific types of fibres, IIa or IIb and make the existing ones much more efficient. Yet the overall ratio remains roughly the same.... which appears to be determined genetically.

Here's an article with the exercise intensities targeted towards specific muscle-types:
Practical Application of Physiology to Bodybuilding (http://www.wannabebig.com/article.php?articleid=31&pageid=3)

Journal Applied Physiology
Effects of sprint cycle training on human skeletal muscle (http://jap.physiology.org/cgi/content/abstract/77/5/2385?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT)
Skeletal muscle myosin heavy chain composition and resistance training (http://jap.physiology.org/cgi/content/abstract/74/2/911?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT)
Plasticity of mammalian skeletal muscle (http://jap.physiology.org/cgi/content/full/90/3/1119?maxtoshow=&HITS=40&hits=40&RESULTFORMAT=&&andorexactfulltext=and&searchid=1&FIRSTINDEX=40&sortspec=relevance&resourcetype=HWCIT)

http://www.baybutt.net/pubs/musclefibre.html

I think you have been reading too much shiat and should just
go ride instead of wondering about this.

+1 get yourself on a pro team first before you start scratching around for 0.05% of an edge...

learn to to ride harder than 99% of the rest of us first :D

Thanks Danno. Top notch advice and links as usual.


+1 get yourself on a pro team first before you start scratching around for 0.05% of an edge...

learn to to ride harder than 99% of the rest of us first :D

You know what, I'm not looking for an edge. I'm looking for better understanding.

You know what, I'm not looking for an edge. I'm looking for better understanding.

while you go read those articles some guy is out on his bike...given the outcome of your understanding in this particluar topic isnt likely to lead to any performance gains all im saying is your better off out on your bike :p (in this instance).

while you go read those articles some guy is out on his bike...given the outcome of your understanding in this particluar topic isnt likely to lead to any performance gains all im saying is your better off out on your bike :p (in this instance).

Maybe, but it's dark outside, I don't bike race, and my focus is long distance ski racing right now. I'm pretty fit since I started training last year.