Hypertrophy and Muscle Growth

A detailed look at myofibril and sarcoplasmic hypertrophy, and how to train using both to maximize muscle mass gains.

“Hypertrophy.” When that word is said everybody who works out has an opinion. General conversations go something like this:

Hypertrophy Noob Lifter

So what is the best way to achieve hypertrophy? The reality is that there is not a single kind of hypertrophy, and you must do different types of training to target the two broad types of hypertrophy. What are the two types? Hypertrophy can be broken down into two broad types:

Myofibril hypertrophy.

Myofibrils are essentially bundles of myofilaments (The contractile parts of a muscle, the parts that pull). They are found in each skeletal muscle fiber.

Each muscle cell contains many myofibrils. Myofibril hypertrophy occurs due to an overload stimulus (lifting more than your body is used to) that applies trauma to the individual muscle fibers. Your body treats this as an injury and as such overcompensates during the recovery process by increasing the volume and density of the myofibrils so that the “injury” does not occur again.

This is one of the reasons why you must maintain overload to continue making gains.

Sarcoplasmic hypertrophy.

The sarcoplasm is the fluid and energy sources that surround the myofibrils in the muscle. It includes things such as ATP, glycogen, creatine phosphate and water. Increase in size of blood vessels that provide blood to the muscles can also be included in sarcoplasmic hypertrophy and is commonly referred to as capillirisation.

This occurs much in the same way as myofibril hypertrophy, through your body overcompensating during the recovery phase after your energy sources have been depleted during a workout. It therefore increases energy stores such as ATP and glycogen to prevent depletion during training.Muscle Hypertrophy

Ok, so I know the two types. What are the best ways to achieve both?  Before I go on I want to stress that you:

Choose the weight for your reps NOT the reps for your weight.

Progressive resistance exercise or progressive overload refers to the practice of continually increasing the stress placed on the muscle as it becomes capable of producing greater force or has more endurance. (Fleck S. J. and Kraemer W.J.,1997). This means that you MUST use weights and rep ranges that you struggle with.

You should choose a weight that you can only just complete the desired reps for. Do not choose a weight and get nearly the reps that are required, or one that is too light that you could complete many more reps. So for a 12 rep exercise, choose a weight that you can only just complete those 12 reps.

Myofibril hypertrophy training:

Strength training with 80%+ of your 1RM and reps in the 3-8 range with 2-4 minutes rest produce the largest changes in myofibrillar volume and density. Therefore if you want to achieve myofibril hypertrophy you must lift heavy. The heavier the weights you lift the more muscle fibers are recruited and in turn damaged. However it is recommended to keep the reps between 3-5 as any lower and it is mainly neuro-muscular adaptations that improve the athletes strength rather than through myofibril hypertrophy (Zatsiorsky, 1995).

“In fact low reps are essential for achieving maximal growth” - Charles Poliquin 1997.

Sarcoplasmic hypertrophy training:

Sarcoplasmic hypertrophy is achieved through what is known as fatigue training. Fatigue training is training at an intensity ~75% of your 1RM with reps in the range of 10-15 and short rest periods 45-90 seconds. It is referred to as fatigue training as it rapidly and directly uses up a lot of the stored energy in your muscle cells and fatigues your muscles.

When choosing the amount of sets for your workouts you must take into account the time under tension. There is a minimum amount of time under tension required for muscle hypertrophy to occur. Due to this it is generally required to complete more total sets for your strength training routine than your higher rep fatigue training routine.

In fatigue training you want to time under tension to be greater than the immediate energy available. The most immediate energy sources for short term anaerobic exercise is your ATP and creatine phosphate stores. These however are very short term and as such will be depleted in 7-10 seconds. After this your body will break down glycogen for energy, which will produce lactic acid (the burn). Therefore you must maintain a time under tension of over 10 seconds per set in fatigue training. The inclusion of slower reps, or methods such as same muscle supersets are a great way to achieve this.

Why cant I train both in a single rep range?

There is a spectrum through which myofibril and sarcoplasmic hypertrophy occur:

  • 1-5 Reps - Lead to a maximum increase in relative strength and myofibril recruitment.
  • 6-8 Reps - Produce the best medium between myofibril and sarcoplasmic hypertrophy.
  • 9-12 Reps - Increase sarcoplasmic hypertrophy at the maximum rate.
  • >15 Reps - You move into the range of muscular endurance where hypertrophy gains slow.

Myofibril damage will not just cease to happen at >12 reps, but it will be to a lesser degree and with less muscle fiber recruited than at lower reps.

Put it this way, why would you want to train at a rep range in which you are not getting maximum gains in either sarcoplasmic or myofibril hypertrophy? When you can train both maximally without deceasing gains in the other. I will explain how this can be achieved further down.

Ok so myofibril hypertrophy is best achieved through strength training and sarcoplasmic hypertrophy through fatigue training. What is the best way to achieve both?

Bodybuilder performing lat pulldowns for hypertrophy.

I’m sure you are aware of the dominance of the Eastern Bloc countries during the 50’s, 60’s, 70’s and 80’s. This can attributed to many things, notably the use of periodization.

Periodization in the West was very basic and often unused in many cases until the release of information from the Eastern bloc coaches. Periodization is the method of training specific goals in a cycle. Periodization can be broken down into 3 main categories:

  • Microcycle: Is very short term, usually around a week.
  • Mesocycle: Longer term cycles usually several weeks.
  • Macrocycle: Long term cycles for several months, even years.

Now conventionally people use mesocycles for their training, they do a set program for 8-12 weeks, say a strength program. They then swap and do for example a cutting program for another 8-12 weeks. While this type of training can produce results in a single area, it is very linear and as such you will regress in certain areas. It is also difficult to maintain overload on a program done for many weeks/months.

This is where the Eastern Bloc training comes in. Many Eastern Bloc coaches used very short term microcycles for their training, they would train towards many different goals in a few weeks. For example:

  • Week 1: Relative strength training.
  • Week 2: Power and speed development.

These can be repeated for many months with only slight changes and overload can be achieved more easily as the body finds it more difficult to adapt to rapid changes in training style.

So to achieve maximal hypertrophy I recommend you use 2-3 week long microcycles e.g.

  • Week 1: Strength training, 4 day split.
  • Week 2: Fatigue training, 5 day split.
  • Week 3: Recovery, 2 day full body split.

It is also possible to use even shorter intra-workout cycles for example starting a routine with an upper body strength exercise with reps in the range of 2-6 for 5-6 sets then moving on to higher rep (8-15), lower rest training for another 3-4 exercises.

A good example of a routine like this is Westside for Skinny Bastards which trains both low rep max effort training alongside higher rep fatigue training. It is important to note that if you do decide to undertake or create such a program that you make sure you perform the heavier max effort lifts first. This is due to the advantage in exciting your nervous system before continuing for more exercises. To put it another way your nervous system is warmed up and working to maximum efficiency after completing some heavy sets.

A study comparing the effects of linear vs. periodization changes in college athletes showed that the linear trained athlete’s strength increased 14.15% over 12 weeks compared to 23.53% for the athletes using periodized training programs. (Prestes J, Frollini AB, 2009)

So there we have it, a different approach to achieving muscle hypertrophy. If you like the sound of this my recommendation is to try it. I have tried many different routines in the past and without a doubt short term strength/higher rep cycles have worked best for me. Many other professionals also use this type of training including pro natural bodybuilder Joe Ohrablo who frequents these forums.

  • Fahey, T.D., R.Rolph, P. Moungmee, J.Nagel and S.Morata. Serum testosterone, body composition and strength of young adults. Med.Sci.Sport Exerc. 8:31-34. 1976
  • Van Loon LJ, Goodpaster BH (2006). "Increased intramuscular lipid storage in the insulin-resistant and endurance-trained state". Pflugers Arch. 451
  • Steven J. Fleck, William J. Kraemer, Designing resistance training programs, 3rd ed, 2004.
  • Prestes J, Frollini AB, de Lima C, Donatto FF, Foschini D, de Cássia Marqueti R, Figueira A Jr, Fleck SJ. Physiological Sciences Department, Exercise Physiology Laboratory, Federal University of São Carlos, 2009

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About The Author
All my life I have been into sports. I am currently studying for a coaching and fitness degree and specializing in strength and conditioning.

32 Comments+ Post Comment

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Posted Tue, 01/03/2017 - 07:45

What is RM? in this context "Strength training with 80%+ of your 1RM and reps in the 3-8 range with"

JoshEngland's picture
Posted Tue, 01/03/2017 - 11:33


1RM - 1 Rep Max

Hope this helps!

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Posted Thu, 07/30/2015 - 21:53

Good article and I took some info away from it that I will be using. One thing though. You're perpetuating the myth that lactic acid produces "the burn." This is not the case.

Hydrogen ions.....aka Acid.....are what cause the burn. They form from the pyruvate turned acetyl co-A, which is run through the Krebs cycle, broken down, and used for energy, resulting in said Hydrogen ions.

Just thought that someone writing for this website should know.

MikeWines's picture
Posted Fri, 07/31/2015 - 09:13

That is correct, you make an excellent point. However, this article is roughly 5 years old so the research on the subject at the time was lacking and has evolved greatly since then.

Good looking out though.

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Posted Sat, 11/30/2013 - 05:53

What about High Intensity Training? This sounds like what you are describing in the article, low volume/ high intense sets with rep ranging between 3-8 for max hypertrophy.

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Posted Sat, 11/30/2013 - 04:58

So if I alter my workout to reflect this and do it on a 3 week rotation with the first week myofibril hypertrophy, the second week sarcoplasmic hypertrophy, and the last as recovery. What rep range should I am for on the 2 day split recovery week?

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Posted Mon, 07/22/2013 - 15:06

nice post. It's nice to see something that not necessarily from a scholarly source have posted research to back up the argument as opposed something posted that you're not sure how many facts that it was backed up with. so thanks

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Posted Thu, 07/11/2013 - 05:41
Stim Rx

Nice blog. Thanks for providing such a wonderful info

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Posted Mon, 06/17/2013 - 02:50
Jimmy P

What is fatigue training?

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Posted Thu, 06/06/2013 - 20:03

A well written article with encouragement for those like myself wanting to know what is happening with my muscles during training.

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Posted Wed, 04/24/2013 - 15:52

Informative and well written. I work with the American College of Sports Medicine and it is refreshing to see an article that is based on physiology and not just another muscle head spouting off what works for him. Good job.

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Posted Wed, 03/13/2013 - 21:18

If you don't know what the article is talking about then do more research. Like you said this is for someone that already knows what they're talking about. It's a great written article. It just wasn't written for you.

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Posted Sun, 02/24/2013 - 11:03

Single most confusing article I've read. Written very poorly. I mean, i guess is it's a good article if you're writing for an audience who already know what this stuff is?

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Posted Wed, 03/13/2013 - 21:20

Do your research if you don't know what the article is talking about. It was a very well written article. It just wasn't written for you.

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Posted Mon, 09/09/2013 - 14:31

This article is incredibly well written actually. I don't know this subject area at all, in fact I never studied physical education at school, and now at 37 years of age I'm only just starting to learn how to exercise properly. If you find this confusing, get some sleep and try and read it again!

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Posted Tue, 02/12/2013 - 05:27
swati joshi

hypertrophy is not healthy muscle.

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Posted Mon, 01/07/2013 - 16:05

Is it ok to do 5 compound exercises in a single session twice a week. In the first session i am going to lift heavy a low rep range and in the second session i am going to lift lighter for a moderate rep range.
my exercises for both days are as follows;
military press, back squat, bench press, deadlift,and rows.

Please reply

Thank you

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Posted Wed, 12/12/2012 - 00:30

great article explained periodization in a much simpler and easier to grasp manner than my issa text book

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Posted Sat, 08/11/2012 - 15:26
David T

There just aren't enough good articles on the internet like this one. I don't want someone to tell my WHAT to do, I want to know WHY I should do it. This article is just full of great, specific information based on muscle physiology. Bookmarked. I will have to go through it a couple more times and explore some of the details. Excellent work Will, well done!

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Posted Thu, 12/27/2012 - 19:35
Will Scudder

Thank you, glad I could help!

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Posted Mon, 06/17/2013 - 02:51
Jimmy P

What is fatigue training as stated in week 2?

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Posted Sun, 08/05/2012 - 17:50

Its a well written article, but I don't see a lot of research backing this approach. Can you find more references so I can read the studies?

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Posted Wed, 04/25/2012 - 12:40

More recent evidence indicates that if one trains to concentric failure, with a weight that induces failure after no less than than 1 min, & no more than 3 min, -all- myofibril -&- sarcoplasmic aspects will be optimally developed. The idea than one can contract their muscle against resistance to failure yet somehow not be stimulating contractile tissue due to a few extra reps was odd on the face of it.

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Posted Sun, 11/27/2011 - 08:31

why to do ho reps

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Posted Fri, 09/30/2011 - 03:20

A very balanced view and highly informative. Though it wasn't really your purpose, I would have liked to see some mention of adaptation for idiosyncratic differences. Due to our different physiologies, some might benefit more from different combinations and slight adaptations to the various forms of training for hypertrophy. The principles remain sound however, and overall this is the best article on the subject I have read to date.


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Posted Thu, 11/11/2010 - 09:27
john cena

thanks man!

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Posted Tue, 03/02/2010 - 15:14

i'm curious

so your saying one week of heavy, low rep high set. then one week of lighter, high rep low sets. then one week of light full body/recovery.

would there be any advantages to doing more than just one week? like say 4 weeks of heavy, 4 weeks of lighter, one week of rest?

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Posted Wed, 02/20/2013 - 02:56

I was thinking about that too but think about this although it mayn't change your thoughts...
Youre training one type for a full 4 weeks so youll be getting more benefits of each after your myofribrillar/sarcoplasmic phase is complete...but you may lose some or a lot of those gains after 4 weeks and those fibres will, after 2/3 weeks be accustomed to "resting". 1-2 weeks of each is optimal i'd say and if your goal is more so one over the other just do one for 2 weeks then the other for only 1. :)

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Posted Sun, 02/28/2010 - 10:12

Very well done! Thanks!

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Posted Wed, 02/24/2010 - 07:47

Very informative thanks

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Posted Fri, 02/19/2010 - 14:23

bookmarked. thanks bro, some serious information there for people looking to make muscles big, is such myself.

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Posted Fri, 02/19/2010 - 14:18

That's actually really helpful!

Thanks man good article.