Training for fiber type

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Also read the Training for Fiber Type - article by Bryan Haycock

You can't isolate fiber types in training for hypertrophy (or strength for that matter). All the notions of training for different fiber types is a misunderstanding of how muscle fibers are activated, or recruited.

Slow twitch fibers are activated first, followed by fast twitch fibers in any muscle contraction. This is a function of small "motor units" (slow twitch fibers) being activated first for small precise movements/contractions of low force, followed by large motor units (fast twitch fibers) for large and powerful movements of relatively high force. All fibers are generally activated in a muscle at 85% of 1RM, but this may actually be as low as 50% of 1RM for some muscle groups.

So the argument about training specifically for different fiber types is wrong from the very foundation. It is simple misinformation based on a lack of understanding about motor units and their recruitment patterns. What those programs you have come across aimed at training for specific fiber types are actually doing is training for different metabolic pathways (e.g. ATP>Glycolytic>beta-oxidative).

In order to make a muscle grow you must apply high forces. This requires high loads. This requires that the body activate ALL fiber-types/motor-units during a contraction that is against sufficient load to induce microtrauma and hypertrophy.

ANY biomechanics or kinesiology text book will explain in great detail the correct properties, functions, and recruitment patterns of different fiber types and motor units. Anyone with this basic knowledge of functional anatomy could not possibly claim that isolation of fiber types is possible with loads required for muscle hypertrophy. In essence, it would be like saying that you could rev a motor at 1,000 RPM without reving it at 500 RPM.

If you have a high makeup of slow twitch fibers, all that changes is the relative %ages of 1RM you can do a certain amount of reps with. Just lay out your HST program, get your diet in order, and you will grow....day by day. Just like everybody else.

 

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...but there is still a lot of controversy over this

In response to:

"A. Jones, in particular, has argued that an individual's muscle fiber recruitment and fatigue characteristics are largely genetically determined, so that there may exist an optimal TUL for each exercise, where one's musculature receives optimal growth stimulation (30). In fact, MedX technicians often incorporate the use of a "Fatigue Response Test" as a way of finding out one's particular fatigue and fiber-type characteristics. More recently, this theme has been repeated by several other authors who contend , "that (even) the concept of double progression (increasing weight and reps) is actually mistaken. Instead one should find the signature TUL for a given person in that movement and then carry out single progression. That is, progress weight at a fixed TUL as is determined by a particular fiber type and MU recruitment pattern. Once you know the ideal TUL, single progression (increasing resistance) appears to be the way to rapid gains."

- Gus Karageorgos


I've been there done that and everybody threw a fit and said I was blind (and presumably stoopid) and that I was saying things contrary to what everybody already knows and accepts about fiber types and training.

I am addressing this very issue in the next HS:Report so I will only touch on it briefly here.

First of all, if Gus Karageorgos is "GusK", I thoroughly enjoy reading his articles. I really like the way he writes and wish he would donate something to ThinkMuscle. My comments here have nothing to do with him or his views on fiber types.

Here is a statement as simple as I can make it on fiber types and training: “All muscle fibers undergo hypertrophy with increasing loads.”

That’s as simple as I can make it. There is no need to train “according” to some presumed ratio of fiber types that one is guessing they have. Besides, fiber types (MHCs) are “induced”. The type of MHC that a given fiber produces is a result of what you make that fiber habitually do through neural activity. MHC characteristics of any given muscle are constantly changing according to what it is forced to do. So if you begin to train with higher exhausting reps thinking you are making your type-Is grow, all you are doing is creating greater type-I fiber characteristics in your muscles.

Now, I will refer people to a study that was done comparing 3 different routines. (Campos GE, Luecke TJ, Wendeln HK, Toma K, Hagerman FC, Murray TF, Ragg KE, Ratamess NA, Kraemer WJ, Staron RS. Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. Eur J Appl Physiol. 2002 Nov;88(1-2):50-60.) They used an 8-week high-intensity training program for the legs. Workouts were performed 2 days/week for the first 4 weeks and 3 days/week for the final 4 weeks. The subjects used one of three different regimens. The different training regimens were designed to be approximately equal in volume (resistance x repetitions x sets) with the rest periods between sets and exercises adjusted according to the strength-endurance continuum. Therefore, those individuals working on the high-rep end of the continuum performed fewer sets and had shorter rest periods compared with the other training groups.

The exercises were performed in the fixed order of leg press, squat, and knee extension. After warming up:

· The Low-Rep group used their 3-5RM for four sets with 3 min rest between sets and exercises.

· The Intermediate-Rep group used their 9-11RM for three sets with 2 min rest.

· The High-Rep group used their 20-28 RM for two sets with 1 min rest.

During the study, the resistance was progressively increased as subjects were able to perform more reps in order to ensure subjects were always using their true RM for each rep range.

So what happened? Did the type-I fibers increase most in the high-rep group? Did only the type-II fibers hypertrophy in the low rep group? If you believe you must do high reps for type-I fibers to grow and low reps for type-II fibers to grow then that’s exactly what should have happened!

On the other hand, if hypertrophy is a matter of load, and all fibers hypertrophy in response to increasing load, then hypertrophy should go up as load goes up. In other words the group that lifted the heaviest relative weight should have experienced the greatest amount of hypertrophy in ALL fiber types irrespective of the number of reps (within reason). And that is exactly what happened.

Here is a breakdown of the hypertrophy caused by each rep range. [Remember, each group trained to failure regardless of RM used so muscular fatigue was equal between groups.]

High-Rep (20-28RM)
Type-I
· pre = 3894 post = 4297 (10.3% increase)
Type-IIA
· pre = 5217 post = 5633 (8.0% increase)
Type-IIB
· pre = 4564 post = 5181 (13.5% increase)

Med-Rep (9-11RM)
Type-I
· pre = 4155 post = 4701 (13.1% increase)
Type-IIA
· pre = 5238 post = 6090 (16.3% increase)
Type-IIB
· pre = 4556 post = 5798 (27.3% increase)

Low-Rep (3-5RM)
Type-I
· pre = 4869 post = 5475 (12.4% increase)
Type-IIA
· pre = 5615 post = 6903 (22.9% increase)
Type-IIB
· pre = 4926 post = 6171 (25.3% increase)

Should this surprise anybody? No! Higher loads with equivalent volume leads to greater hypertrophy regardless of fiber type. It also doesn’t surprise me that these researchers were confused by the fact that the low rep group had as much or more hypertrophy that the other groups. They too have the idea cemented in their brain that you can’t use heavy weight to stimulate hypertrophy. The strength training dogma of the past has deeply influenced even the research community with regard to hypertrophy. This has done nothing but hinder their progress in understanding it because they end up designing studies on false premises.

I’m not sure why people are so hesitant to accept the preeminence of load for producing hypertrophy. Perhaps it is that they fear not growing as fast as they think they can.

It would be of much greater benefit for people to discuss issues of fiber type with regard to muscle “performance” (i.e. strength/endurance/power). After all, the very distinctions themselves are based on how the fibers used fuel, not how they respond to load. Hence, basing predicted hypertrophic outcomes on the metabolic characteristics of a fiber will never lead anybody to a correct understanding of the mechanisms of hypertrophy.

- Bryan Haycock