I see training broken up as neural adaptation and hypertrophy. One type of training allows your nervous system to fire at a maximum level while the latter allows you to build size and muscle.

The question is does hypertrophy training assist for a greater eventual neural output? Meaning if one gains muscle and gets bigger, do you believe there is a greater potential for that muscle to fire or is your neural ability entirely dependant by your genetics? I mean you can't have a donkey win a Kentucky Derby...but could a low level genetic human being be trained correctly through hypertrophy and neural training to become a professional athlete?

  • I think this is a very interesting question, but it might need editing. As it stands, I think it's a VERY broad question that is going to produce extended debate.
    – JohnP
    Commented Jul 11, 2012 at 21:36
  • @JohnP please let me know what you believe I should edit or single out which would interest you more. This question can get very broad...I agree. Commented Jul 11, 2012 at 21:40
  • 1
    I think you have two different thrusts of your question when you add the proviso about the professional athlete. There are tons of examples of athletes on both sides, the gifted and the not so gifted.
    – JohnP
    Commented Jul 11, 2012 at 22:43
  • The answer to the last part would likely depend on the sport. Almost anyone could become a professional MMA fighter, as the barrier to entry is mainly a matter of guts (and inherrent stupidity? - I'm only half kidding there), but a professional football player, unless you've got the genetic advantages you wouldn't even get scouted.
    – Robin Ashe
    Commented Jul 11, 2012 at 23:50
  • @Andreas I agree with JohnP that the last question you pose diverges radically from the rest of the question. That said, the central part of your question seems to be answered in some others: fitness.stackexchange.com/questions/5704/… fitness.stackexchange.com/questions/4666/… fitness.stackexchange.com/questions/2017/… Commented Jul 12, 2012 at 0:26

2 Answers 2


Question 1: Does hypertrophy training assist for a greater eventual neural output?

Hypertrophy training probably does not help to increase neural drive. That is because of the anatomical properties of the muscles.

enter image description here

Muscle fibers are innervated in groups, called motor units, by a single motor neuron (above figure shows a single motor unit).

By doing hypertrophy-type training, the neural output is fairly low (as compared to power training) and is not sufficient to simulate the motor neurons to "bud" (increase the number of muscle fibers in the motor unit they innervate). In simple terms, hypertrophy-type training doesn't increase the number of muscles fibers in a motor unit. Comparing to sedentary individuals, I would guess that there is an increased neural drive, however, this effect in later training is negligible.

What is interesting, however, is if we flip the coin and ask ourselves:

Can training to increase neural output, influence the effect of hypertrophy training?

indeed that is the case.

When beginners start going to the gym, their intramuscular coordination is fairly low. The contractions that the muscles produce are inefficient, and few motor units are activated. After months and years of power training, such as in professional athletes, that coordination is much better, the motor units are bigger (more fibers are innervated by each motor neuron) and more motor units are activated. What does this mean for the athlete?

Imagine a muscle of a beginner: 100 muscle fibers; it consists of 10 motor units, each consisting of 10 muscle fibers. During a contraction (of set intensity), only 3 motor units are activated (the muscle tension equals that produced by 30 muscle fibers; 3*10).

Through power training, the size of the motor units increases (from 10 to 15 in this case) (there is overlap between motor units; one muscle fiber can be innervated by more than one motor neurn), and the number of activated motor units is increased as well (from 3 to 5).

These changes lead to the activation of 75 muscle fibers (15*5), instead of the original 30.

Automatically, the 1RM is higher. And when you then perform hypertrophy training, the training stimulus is more than double the original. This is the reason why power lifters and sprinters gain mass extremely quickly when entering a hypertrophy phase at the beginning of their macrocycles.

As for your second question, your genetic makeup only determines your potential. For example, if your parents have 60% and 70% fast twitch fibers on average, then your genetic potential is in the range of 55-75%. By doing long distance aerobic training for 30 years, you will end up with 55% slow twitch fibers, not less. The same goes for explosive training; you will never get the 80-85% fast twitch muscles needed to become an Olympic sprinter.

Bear in mind that all figures stated are artificial for explanatory value. It could very well be that your genetic potential in the above case is 30-90%; to my knowledge there is no research yet on that.

  • There is no "ask to answer" here like in quora. But can you answer this question? fitness.stackexchange.com/questions/18443/… coming from a medical background, probably you can give a better answer. On a side note, I've gone through your profile and I'm really inspired by your track record. I bow you :)
    – claws
    Commented Aug 5, 2014 at 18:45
  • Thank you! :) I actually thought of writing an answer when I saw the Q today, but I dont have time now. Saved it on my desktop as a reminder; I'll try to answer it as soon as I find the time :) Commented Aug 5, 2014 at 20:50

Interesting question. Personally, I don't think that neural training would specifically help with hypertrophy training, except in a general sense, which I'll explain.

You can train neural pathways to the point where they approach the speed of a reflex. I'd have to dig up the studies, but they tested reflex transmission time against transmission times for martial artists doing various activities. You can get very close with highly trained individuals doing repetitive tasks. But, a faster transmission speed won't really facilitate hypertrophy, as it isn't causing a higher amount of stress to the muscle tissues, they are just a nanosecond or two quicker in responding.

Muscle memory {hereafter MM} (which is a bit of a misnomer, since it's not stored in the muscle) is probably a better fit, but is somewhat independent of neural transmission as far as speed is concerned. Muscle memory is attained through many many repetitions of a task (Such as reaching for a doorknob. You can find a doorknob in the dark because almost all US doorknobs are a standard height.)

Where MM would facilitate hypertrophy in my opinion is in better execution of a task. A neophyte in the gym is going to wobble around, their bench press won't groove in the same "track" so to speak for each rep, things like that. That takes away from the quality of the work being done, and you get less out of the workout. As your muscle memory grows, you get more out of the work being done.

What I completely don't know is if neural improvement would lead to better recruitment in the fibers, my blind guess would be probably not, as IIRC recruitment is a function of the type of exercise, but it would be an interesting avenue to explore.

  • first off thank you for your response. this is an excellent analysis where you couple neural training to become basically a reflex. Yes after doing the exercise over and over again the body becomes accustomed to the levels of stress and that's when big breakthrough and personal records can occur in events such as track and field. Your last paragraph is exactly what I am looking for but didn't have the words like you did to explain. Basically if you gain more muscle through hypertrophy training, can that result in a higher magnitude of fast twitch muscle fibers? Commented Jul 11, 2012 at 23:37
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    No. Your fast twitch and slow twitch are pretty much set at birth. They have shown that of the IIa and IIx fast twitch fibers, you can convert one to the other, but studies and attempts of converting slow twitch fibers to fast or vice versa have been murky and ambiguous at best.
    – JohnP
    Commented Jul 11, 2012 at 23:50
  • Research has shown that body builders have almost the same percentage of fast twitch fibers as long distance runners; in the range of 30-40% (Andersen et al, 2000). This could be because they are a self selecting population. That is, mesomorphs with a low percentage of fast twitch fibers fo not become power lifters, but body builders. Also, the proportion of fast and slow twitch fibers is not entirely set at birth. For example, studies have shown that immobility for short periods increases the protein isoforms with fast twitch characteristics. Refer to "Supertraining" by Mel Siff Commented May 6, 2014 at 12:58

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