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New Post 5/11/2008 4:34 AM
  PCexpress
6 posts
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What causes Hypertrophy? 
I am not looking for simple answers to this question, and I do realize that there are several different types of hypertrophy:  Transient (the "pump" after a workout), sarcoplasmic, and myofibrillar.  However, the answer to what causes hypertrophy still seems to be debated over, at least as far as I can tell.  However, the answers usually come in very vague terms, i.e.) High volumes of lifting at moderate intensities is the best way to acheive hypertrophy, or sometimes the complete opposite theory; low volume High Intensity Training (HIT) that people like Mike Mentzer and Arthur Jones swear by.

I was wondering if anyone had ever determined what happens to cause hypertrophy on a more scientific level.  Is hypertrophy caused by reaching a certain level of lactic acid accumulation in a muscle for a certain amount of time? Is it caused by the depletion of glycogen?  If all humans grow muscle tissue via the same physiological processes, why are some people able to get larger by working out with huge volumes of lifting and others are able to acheive the same results with a HIT program (<30 minutes/day and <3days/week)?  What do these two types of training have in common that result in hypertrophy?  Any insight on this would be greatly appreciated.

-Ed Miller
USA
 
New Post 5/14/2008 4:35 PM
  PMANDL
8 posts
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Re: What causes Hypertrophy? 
Hi Ed,

What you're going to find is that it's an overall increase in the accumulation of contractile proteins in the muscle fiber.

This is triggered by a handful of pathways, namely muscular tension and the acute metabolic demands created by that tension. The effects of stretching and deforming the muscle fibers, occurring somewhat tangentially to this process, also contributes.

In simple terms, it's a balance of tension-induced damage and the fact that this appears to be exacerbated further by acute lack of energy in the muscle tissues. This triggers the process of remodeling by a net increase in the overall protein balance of the muscle.

In even simpler terms, it means you need to lift heavy weights and lift them in a way that triggers an element of acute fatigue in the muscle mass. Throwing in some kind of lengthening under load (ie, eccentrics, high-force shock stuff, even isometrics, what have you) couldn't hurt. You also need to progressively improve the weight being trained, so that the body doesn't adapt to the current load. As long as the protocol keeps that in mind, the detail work doesn't seem to matter terribly much.

Hope that helped somewhat.

Matthew Perryman
Darwin, Australia
 
New Post 5/16/2008 2:53 AM
  ferreo
5 posts
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Re: What causes Hypertrophy? 

 PMANDL wrote
Hi Ed,

What you're going to find is that it's an overall increase in the accumulation of contractile proteins in the muscle fiber.

This is triggered by a handful of pathways, namely muscular tension and the acute metabolic demands created by that tension. The effects of stretching and deforming the muscle fibers, occurring somewhat tangentially to this process, also contributes.

In simple terms, it's a balance of tension-induced damage and the fact that this appears to be exacerbated further by acute lack of energy in the muscle tissues. This triggers the process of remodeling by a net increase in the overall protein balance of the muscle.

In even simpler terms, it means you need to lift heavy weights and lift them in a way that triggers an element of acute fatigue in the muscle mass. Throwing in some kind of lengthening under load (ie, eccentrics, high-force shock stuff, even isometrics, what have you) couldn't hurt. You also need to progressively improve the weight being trained, so that the body doesn't adapt to the current load. As long as the protocol keeps that in mind, the detail work doesn't seem to matter terribly much.

Hope that helped somewhat.

Matthew Perryman
Darwin, Australia

Matthew, when you talk about to bring about acute fatigue are you talking about perform enough volume to deplete glycogen and CP stores?.

Also, what books do you recomend regarding hypertrophy field?. It seems that there's no many serious books about this issue.

 

Thank you.

 
New Post 5/16/2008 5:18 AM
  Valentin
8 posts
www.thegympress.net
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Re: What causes Hypertrophy? 
The exact events that guide the process of hypertrophy is a huge topic. It is still being research, and its not something that can be covered in a post. However in short.

Hypertrophy as pointed out by PMANDL is really the remodeling of the muscle following an acute bout of resistance training. Aside from the different forms of hypertrophy that you point out PCexpress "Transient (the "pump" after a workout), sarcoplasmic, and myofibrillar" different types of fibers (Type IIa, Type IIb, Type I) respond differently and hypertrophy process occur differently between them.
Muscle remodeling involves the disruption and damage of muscle fiibers, an inflammatory response, hormonal interactions, and ultimately the synthesis of new proteins and their orderly incorporation in existing or new sarcomeres (Beachle & Earle, 2000). This stimulation of new protein starts at the gene level initiated by neural signaling for the release of a multitude of anabolic hormones (eg, testosterone, insulin, insulin-like growth factor, growth hormone) that all contribute to the stimulation of protein synthesis. All this occurs during the recovery period following exercise stress (as PMANDL said, from the tension-induced damage, and energy recovery). Research has shown that testosterone levels are highest after exercises has stopped. Remodeling also does not happen evenly across a single muscle fiber. Due to the multinucleated nature of a muscle cells, each nucleus is responsible for what is called its nuclear domain along the muscle fiber. This means that each nucleus is responsible for the regulation of protein metabolism in its domain along the length to the muscle fiber. Thus the more muscle fiber recruited during the performance of an exercise, the greater the extent for potential remodeling. This explains the benefits of doing full range of motion in all exercises for the accumulation of greater hypertrophy. It also explains why its possible to target hypertrophy in specific (well as specific as you can get) areas of muscle...spot bulking.
 
New Post 5/21/2008 2:14 PM
  PMANDL
8 posts
No Ranking


Re: What causes Hypertrophy? 
 ferreo wrote

Matthew, when you talk about to bring about acute fatigue are you talking about perform enough volume to deplete glycogen and CP stores?.

Also, what books do you recomend regarding hypertrophy field?. It seems that there's no many serious books about this issue.

Thank you.



When I say fatigue, the better word might be "ischemia". Although it's not strictly required for growth to occur, it seems that training a given pool of motor units to the point where they no longer have the energy to contract and become, effectively, "rigid" (the condition of ischemia) makes them more susceptible to further damage from eccentric actions. This in turn contributes to the remodeling process. But, so do other factors -- it seems that there's a continuum of sorts that denotes a dose-response relationship between exercise intensity/volume and the training response.

So it's not substrate depletion you're after, but rather the acute demand on energy supplies that allow the fibers to contract, if you're after maximum hypertrophy.

Sadly, there are no books on the matter that aren't drawn from the shall we say "less than scientific" viewpoints of Western bodybuilders. Your best bet would be an understanding of muscular physiology and a scan of research databases that deal with skeletal muscle protein synthesis and strength gains.

Matthew Perryman
Darwin, Australia
 
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