T Nation

Slow and Fast Twitch Fibers


Hi everyone, I'm 19, been training for roughly 10 months now and since then I've put on roughly 6-7kg of lean mass. I have a decent grasp of what bodybuilding is all about. So please bear with me, I need this clearing up.

I have read through many bodybuilding articles on the internet, including this website and Poliquin's concerning fiber muscle make up. Frustratingly, none of these articles have been crystal clear with exactly how you target all three fiber types (Type I(slow twitch), IIA and IIB(fast twitch)). Don't get me wrong, I understand which repetition ranges target which fibers. What I'm more concerned with is HOW you go about performing a rep; HOW those fibers are actually recruited.

For example, say I'm just beginning to train my chest. Today I'm following a relatively strength based protocol; long rest times, low reps & volume. My first exercise is incline dumbbell press. I've finished my warmup. I'm about to begin my working sets of 5 for 5 repetitions. Now how do I perform the press?

  • Which TEMPO do I adapt in order to target those type IIB fibers?
  • Do I explode for the concentric?
  • What about the eccentric? Do I lower the weight slowly (2,3,4 seconds?) Or lower it quickly?
  • Any pauses?

Another point to make. By using heavy weights, I find it difficult to 'explode' for the concentric; maybe for the first few sets but fatigue inevitably catches up. Surely the weight is too heavy in order for me to perform the concentric as fast as possible? Am I correct in assuming that as fatigue sets in, more slower twitch fibers are recruited in order to maintain motion?

Generally, during any concentric, what happens if motion is slow/fast? What about the eccentric?

It all really comes down to this. For each fiber type - what TUT, tempo, volume, rest times? I'd really appreciate any thorough respones. Thanks.


Beware of analysis by paralysis, simply reading too many opinions! Bodybuilding the forum you are in requires the following (amongst others)

  1. Consistency
  2. Excess calories
  3. Patience
  4. Effort

  5. If you're doing more strength based stuff, I wouldn't worry about making the descent very slow.

  6. If you're MORE focused on size they are a useful tool.
  7. If you can't accelerate a 5 rep weight, I wound't stress it too much - concentrate on trying though. PLs typically use 40-60% for speed work, a 5rep max is much heavier than these so don't sweat this again.


Please just stop and think about what you're actually saying in the context of a HUMAN BODY. Not a machine, or a computer with mysterious but measurable codes that can be pinpointed and formulated and manipulated with the tiniest little changes. It's a human body, an adaptive machine. Whatever you DO with it, repeatedly, it will become better at.

This would be like if someone came onto a chess website and made a post asking "I know there are short term memory and long term memory neurons in my brain, but how do I ACTIVATE them when I'm learning stuff!? If I only want to store this chunk of information short-term, should I slow down the memorization process, or just glance it? For long-term, what tempo should I use when going over the info to turn on my long-term memory neurons?? When I start to get sleepy, is it switching over to short-term neurons to compensate???"

I get the impression that you think you want to create in yourself some disproportionate amount of fast-twitch muscle fibers because you think it will make you a badass with highly tuned muscles like loaded rubber bands ready to snap at any time WAH CHA, HIYAHHHHHHHH! but that isn't how the human body works. This is the problem you run into when you only have one little sliver on information about a hugely complex system... you need to understand the context.


Stopped reading there.


Made me chuckle. Haha, thankyou for this, seriously. Kind of brought me back down to earth.


Thanks for the feedback mate, very helpful.


Sorry if I offended you chap, didn't see you up there on your horse.




mr popular - that analogy was hilarious, and henceforth i will be stealing it



I was expecting CB to reply, but I think yours turned out sounding nicer (sorry CB).


Thats why he's popular. I always just say debating muscle fiber type is mental masturbation best suited for people that dont go to gyms


Hey guys I want to target the fast twitch fibers in my anus, what method should I use?
Is the force-rectum-ramping method the way to go, or am I targeting to much of the slow twitch fibers
with it?


It depends how big he is; if quite small you'll want to target the type II fibres for more tightness


Basically what mr popular and plateau said, COMEONDIESEL.

Don't obsess over the little stuff. If you COULD make all 5 sets of 5 reps fast rep speed, it would mean you weren't pushing yourself hard enough/using heavy enough weight. It's about TRYING to push them as hard as possible. Stick to the basic for the time being man, you've got no business going crazy with tempo/negative speed/specific muscle fiber type recruitment etc. Just get strong, and keep on learning. From the big guys.


Okay I`ll take your word for it, because you have experience on this :wink: