T Nation

Physiological Reasons Why Muscles Hypertrophy?


Now we all know that being consistent in the gym working out with intensity and eating enough will produce results.
But I want to start a discussion on why muscle hypertrophies whether it involves the nervous system, mechanical stress, muscle break down etc, etc... as relevant to bodybuilding.


probably easier to go to a library and or buy a book - might get some good discussion though idk

Im pretty sure you can download "Science and practice of strength training" by Zatsiorsky and Kraemer.... off google maybe. Thatll give you a gooood head start.


Wow I thought this thread would get flamed anyways Ill check out those books. I thought this thread would be more popular due to certain authors saying that a certain style of training is more effective for hypertrophy than another training style for whatever physiological reasons even though the traditional training style is known to produce good results and is used by the majority of successful bodybuilders. An example would be Total Body Training vs Body Part Splits.


There's too many topics I wouldn't even know where to start - I thought you were talking protein degradation, neural adaptations etc etc but you mentioned training splits so idk?

You could start a thread on individual topics maybe...or just do some research... and find out what you actually want to know.


I'm studying exercise science and from everything I have read and been taught so far it seems that the jury is out. There are a whole heap of contributing factors it seems and it is difficult to attribute a cause and effect relationship between any one factor and hypertophy.

One example is a study I was refered to a couple of weeks ago which was looking at circulating hormones and hypertrophy. It is well known that higher levels of circulating hormones induced by exercise such as GH and testosterone are associated with hypertrophy but does it actually contribute to growth? apparantly not.
I will have to find the study and have another read, if anyone is interested I can post it up.

Obviously one study doesn't prove anything but it just goes to show that a lot of the things people take as fact still don't have a clear scientific basis and are more theoretical.

That is why you will notice that a lot of the big guys on here talk a lot more about the simple stuff and less about studies even though they have probably read more than the skinny kid with 100 quotes. The simple stuff has been tried and proven (anacdotely) over decades.


i would "like" that if it was facebook haha.

Also i dont know if the "jury is out" - there are a lot of known variables, the problem is tying everything together. A really simple example would be that we know the difference in affect between no. of reps and weights and the physiological response that it has on muscle adaptation...but what works for one person might no work for another. So thats where the anecdotal and clinical knowledge has to be combined. In other words, the most successful trainers will combine both knowledge sets, and without either, you're basically walking in the dark.

knowledge reigns supremeeeee


Sure post it, is it that study where they had one group do curls and the other group do curls after they squatted and took a biopsy of the bicep muscle to see if the hormones released from squatting had any measurable effect with curling vs just curling?


@ Joab, yeah that sounds like the one. Interesting stuff considering how many authors were talking up different exercises because they increase GH more or whatever. I noticed in a recent article on here the author was downplaying the importance of increased GH due to particular exercises, I wonder if it's in response to the recent research.
I should be able to get it up tomorrow.


I think you might be more successful in your search if you start looking at it from the bottom instead of from the top. Hypertrophy is the result - but what produces this result? A major factor is increased synthesis of contractile proteins. Almost always opposing processes in our body happen simultaniously. So we have breakdown of contractile proteins vs. synthesis of contractile proteins. If the first pathway is more strongly activated we achieve atrophy, if the second one dominates the result will be hypertrophy.

So it might be intresting to look what causes an increas in contractile protein synthesis and a decrease in contractile protein breakdown (e.g. hormons, look factors, etc.) And then go up a notch and look what causes this , etc.

But personally I do not believe that this search will lead anywhere. In such cases I always think back to the first semester and what a physics professor said in his first lecture: "We understand the real small process, llke intramolecular interactions and the huge ones like gravity and the lever rule but we are not nearly smart enough to extrapolate the big ones from the small ones."

So basically it would help you more to study training results or to study physiology and not "waste" time trying to draw training conclusions from physiology.


or just go to a gym and lift some fucking iron then eat BULK amounts of food!


^ This pretty much.

I look at it from a enviromental/physiological perspective. Muscle growth is a stress response to facilitate your bone structure moving increasingly heavy external (environmental) load. The whole reason your have muscles is to move about, and interact with, your environment. they will adapt to their environment much like the rest of your physiology to a degree. Muscle tissue is effectively modified Neural tissue (derived from the neuroectoderm). The most basic way of interpreting your nervous system is that it evolved to enable you to interact and respond to your environment.


Probably one of the most concise posts ever written on this site.


(PS: Would take an Englishman :D)


Itz all about teh sarcoplazmzzz!!


Pl33se sorc sacraplazmazz. I cant bye it at teh GNC.


Mechanical loading under conditions of cell fatigue causes the actin and myosin filaments to pull apart and tear slightly. The exposed frayed filaments attract satellite cells, growth factors, nutrients, etc. and are repaired thicker and stronger than they were before.


Seems like a thread for nerds


My advice would be to go to your local community college library and read an anatomy textbook on how the muscle works, a real, in depth study on what muscles are made of, what the different parts do, and how they interact with each other, and the whole body in general. Learn about the innervation, and how that whole system works together with the muscle. Then, once you learn all that, if you still want to find physiological reasons that make it hypertrophy....you probably wanna become a scientist, not a bodybuilder.


lol jesus you guys are gonna be miserable ol' C's when youre older...whats wrong with people trying to gain a bit of knowledge...

On topic though - I was reading today about the mechanics of reversibility in training, ie the opposite to hypertrophy adaptation... so basically why you "use it or lose it" - google it if you're interested, pretty cool stuff.


Also, a few topics for OP.

old school thoughts for muscle adaptation (but i think they are disregarded now, interesting none the less)

  • blood over circulation hypothesis
  • muscle hypoxia hypothesis
  • ATP debt theory

A more likely theory - energetic theory of muscle hypertrophy (talks about protein synthesis vs mechanical work)

ie rate of protein degradation x mechanical work = total degraded protein. ie 5RM x 1 rep < 5RM x 5 reps. (obviously)

  • Protein and carb intake post exercise and the effect on testosterone binding to androgen receptors. "up-regulation"

  • Neural factors...intramuscular coordination ie rate coding, recruitment, synchronisation.

-hyperplasia vs hypertrophy

There's just so many topics(which is a positive thing) its not funny but I hope this is helpful bud


Its called adaptive response, and it is sustainable provided all the bases (food, sleep, progressive overload) are covered