Mechanisms Of Hypertrophy
Muscular hypertrophy is a relatively common goal with most people in the fitness world. It’s a less common goal in Crossfit as opposed to body building but there are still a tonne of benefits from increasing muscle mass that aren’t just a case of getting jacked! In this two part blog series we’re going to dive into all things hypertrophy. Today I will dive into what hypertrophy actually is, the benefits of seeking muscle hypertrophy for functional fitness, what’s going on at the muscle itself and how we can stimulate muscle hypertrophy.
Then in the second blog we’ll be talking about nutrition for hypertrophy so that you can fuel your sessions, provide the building blocks for muscle hypertrophy and achieve those GAINS.
What is Hypertrophy and why do we care?!
So what actually is muscle hypertrophy and why do we care?! Muscle hypertrophy is simply an increase and growth in muscle cells. We know for a fact that the force that can be generated by a muscle is proportional to the size of that muscle. So bigger muscles=bigger force. On top of that, the type of training that elicits a hypertrophic response in the muscle (i.e. resistance training), is one that has a knock on effect on a tonne of different systems in our physiology. For example, we know that resistance training can also develop the central nervous system, improve bone density and positively affect the pulmonary system. Training for hypertrophy is something that I believe everyone should focus on at some point in their lives or training season.
Before we dive into how to elicit hypertrophy, we need to understand what is actually going on in the muscle, and to do that we need some background on muscle structure. We’ll keep it simple here and focus on the parts we care about most for muscle hypertrophy. We essentially need to understand that the muscle is made up of bundles of individual muscle fibres. Zooming in more we can see that each individual muscle fibre also contains organelles called myofibrils which contain actin and myosin, the proteins that work together to create muscle contractions. Actin and myosin are organised into repeating units called sarcomeres. There are other organelles at the muscle fibre but we don’t need to worry about them too much right now.
Ok sweet, muscle structure sorted! Now we want to look at what is actually happening at the muscle. Which aspect of it is getting bigger when hypertrophy occurs? There are 2 main possibilities but different ways to achieve them. The muscle can either get longer, or it can get wider. This is laid out fantastically by Jorgenson et al (2020) in their recent review paper below.
We can see from the macroscopic view that the fascicles (which is what the bundle of fibres in the muscle cell are called) are either getting longer or wider. If each individual muscle fibre is getting longer we would see a growth in the size of the muscle. This is called increasing sarcomere “in series”.
There are more ways to increase the diameter of the muscle. We can increase the number of muscle fibres or we can simply increase the diameter of the muscle fibres. Increasing the number of muscle fibres occurs by either hyperplasia (literally creating new fibres) or the splitting of existing fibres.
Hyperplasia was previously thought to be impossible, turns out it is possible, but extremely unlikely and only really occurs in certain situations such as growth throughout adolescence. Splitting is also highly unlikely so it’s essentially just a case of the muscle fibres getting larger!
We don't necessarily know for sure how they get larger but it’s likely a combination of more actin and myosin being added to the fibre, it could be sarcoplasmic hypertrophy (an increase in the cell size from NON-contractile components) it could also be myoFIBRIL hyperplasia i.e. creating more of smaller components inside the muscle fibres.
How to elicit hypertrophy
So now we know what happens, it's time to dive into how it happens. Muscle hypertrophy is essentially a four-step process at the cellular level. The stimulation for muscle hypertrophy needs to occur, this then results in the signalling pathway to essentially tell the nucleus of the cell to express the genes that control protein synthesis. Stimulus, signalling, gene expression and then protein synthesis! From our side of things we want to put the muscle in the best possible situation to go about this process and that starts of course with the stimulus.
To create a stimulus for muscle hypertrophy we need one, or a combination of 3 things. In 2010 Brad Schoenfeld proposed that we need either mechanical tension of the muscle, metabolic stress at the muscle cell and muscle damage to elicit hypertrophy.
Turns out, resistance training creates all of these stimuli, hence why it works for hypertrophy. Now the amount of volume and intensity of resistance training needed to grow is ultimately an individualised thing! The research suggests that equal amounts of hypertrophy can occur when using loads of between 30-85% of your 1RM.
This is when it’s worth considering other adaptations too. For example if strength and hypertrophy are the goal, then higher loads with slightly less volume may be more appropriate.
Which leads us on to volume.....And again, the amount of volume needed to achieve muscle hypertrophy is individual and dependent on someone's ability to recover.
But it’s believed that 5 sets per muscle per week is the amount by which muscle mass can be maintained. Meaning that any more than this is likely to result in some form of hypertrophy. For untrained individuals, you can likely get away with a slightly lower amount of volume than trained individuals so around 10-20 sets per muscle group per week seems to be a common recommendation that covers both trained and untrained!
Final thoughts
The recommendations for hypertrophy are pretty wide but this is good reason....it really depends on your training age, genetics and the type of training you are doing.
If you are untrained then don't get caught up in the details...just get training!
If you are more experienced then identify your goal. If it is strength + hypertrophy use slightly lower reps with a higher percentage of 1RM and do more sets.
If you are just looking to get bigger then ensure you are creating metabolic stress, mechanical tension and muscle damage!
Keep an eye out for the next blog diving into nutrition for hypertrophy.
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