Muscle fibres

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Kermithimself
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by Kermithimself

I was talking to a guy a couple of days ago about muscle fibres. He mentioned that you only have muscle fibres IIb to sustain about 5-6 minutes of work. Does anybody know at what range you usually use these types of muscle fibres? I'm guessing it's the higher end, but are we talking neuromuscular or even beyond that?
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devinci
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by devinci

Those type IIb muscle fibres come into play at high load. I do not recall their particular threshold which is pretty relative anyways but they do work at high intensities, think 110%+ FTP. These are very inefficient fibres aerobically anyways and their often acquires a more type IIa phenotype with training.

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Kermithimself
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by Kermithimself

Ok, so it would be right to assume that AC and Neuromuscular efforts(efforts higher than 110% of FTP), would require IIb fibres.

Reason why I'm asking is that I am uncertain of the trueness to his statement about only having IIb fibres to 5-6 minutes of work in a total workout. I have ridden plenty of races where I have 10+ minutes in my neuromuscular zone.
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devinci
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by devinci

Neuromuscular is not an effort intensity in itself. All it tells you is you've hit high torques and/or rpm. It is not an energy system and most of the time such wattage is back up by creatine phosphate and anaerobic glycolitic systems.

Im not sure at what point you can entierly fatigue and rule out the type iib fibres recruitment, but it should not make any difference in a roadie's training...

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devinci
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by devinci

We could add that you should see it as a sort of team work or continuum (even though there are recruitment thresholds) and all fibres type will contribute to most of your moderate/high to high/supramax intensities

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