Last Updated 2 years ago
One of the most common misconceptions about muscle growth is that you have to lift heavy, all of the time.
The reality is that there’s a time and place for all kinds of lifting and that there’s not one single best way to build muscle.
In this article we’re going to look at what the science says about muscle growth, then use that information to tell you the scientifically proven ways to build muscle.
Skeletal Muscle Fibre Physiology
To understand more about muscle growth, we have to look at how a muscle functions and how its physiology works.
The best way to do this is to show you what skeletal muscle looks like at various depths.
This is important because you’ll see how a muscle is structured and you’ll learn that there are many different fibres within a muscle.
The smallest units of muscle are myofibrils and myofilaments (the contractile units of muscle).
When we weight train, we increase the quantity, size and density of the myofibrils. This process makes the muscles bigger and allows them to handle more weight.
There are different types of muscle fibres and they have different capabilities.
They also react to different types of training…
Slow and Fast Twitch Muscle Fibres
Our muscles are essentially made of two different fibre types, known as ‘slow twitch’ and ‘fast twitch’, although there are two types of fast twitch fibres.
For now, let’s work with these two, because our goal here is to explain muscle building, not physiology!
Slow twitch fibres (Type 1)
Slow twitch fibres are built for endurance.
They have much greater endurance capacity than fast twitch fibres and will respond better to medium to light weight training, with a lot of volume.
They not especially strong or powerful fibres, but they take a long time to tire.
Fast Twitch (Type 2A and 2B)
Fast twitch fibres are bigger and more explosive. They generate a lot of speed, a lot of power and are capable of carrying heavy loads.
They grow bigger than slow twitch fibres and respond to heavy weight training.
They do however, fatigue quicker.
Type 2A fibres almost sit in a middle ground, where although they have most of the characteristics of the fast twitch fibres, they don’t produce the absolute maximum force and strength.
They also have better endurance characteristics than the type 2B fibres.
Type 2B fibres are the strongest, biggest and most powerful fibres.
They generate the most force of all, but they tire quickly and have limited capacity for repeated bouts of movement. They’re at the extreme end of fast twitch.
The fibres types respond to different types of training in terms of weight, volume and rest.
Why you should mix high and low weights for muscle growth
We have a mixture of all of the fibre types, so in order to really grow the maximum amount of muscle, you have to train across different rep ranges and weights.
In this 2019 review of the research surrounding resistance training for muscle gain, the investigators concluded that the most effective way to gain muscle was to go for medium-high volume sets and reps (3-6 sets, 12 reps) with short rest periods (not exceeding 60 seconds).
This makes perfect sense, because the volume would ensure that the slow twitch muscles would be trained and the short rest periods would make the most of the capacity of the fast twitch muscle fibres.
Further supporting evidence of the high volume approach can be found in this study from 2019, where the high volume approach resulted in a lot of muscle gain. It didn’t however, result in much strength improvement.
That contrasts with another volume study that showed muscular strength endurance improved significantly in higher volume training programmes.
What this means is that a high volume approach appears to be the best way to build the most muscle, but might not be the best from a performance point of view.
There is a place for strength training in muscle building programmes too though, because although high volume training will benefit type 1 and 2A muscle fibres, it tends to neglect the type 2b fibres which are only recruited with the heavy load, high power movements.
This study suggests that heavy loads can be as effective as high volume for muscle building in certain strength-trained individuals, but they’re also far better for building strength.
Mixing light weights and heavy weights in a muscle building programme
From the scientific evidence it’s clear that any muscle building programme should be based in high volume training, with 4-6 sets of 12, with short rest periods (around 60 seconds).
If this approach makes up the bulk of the training, the next question is how should we be training each muscle group?
Again, the evidence tells us that the most effective way to build muscle is to follow a full body training programme, rather than split routine.
This is because when training this way, you train more muscle, more often. This also ties into the frequency of training evidence we shared earlier in the article.
As a good rule, 4-5 full body workouts per week would be sufficient – it’s frequent enough to train the muscles regularly, but also allows for rest days in the training week.
Breaking up the training week effectively would look like this…
- Day 1
Medium weight, high volume (4-6 sets of 12 per exercise)
- Day 2
Medium weight, high volume (4-6 sets of 12 per exercise)
- Day 3
Rest
- Day 4
Heavy weight, low volume (5-10 sets of 1-5 reps per exercise)
- Day 5
Light weight, high volume (4-6 sets of 20 per exercise)
- Day 6
Rest
- Day 7
Rest, OR Medium weight, medium volume (3-5 sets of 8-10 per exercise)
This breakdown of the weekly training cycle allows you to mix different volumes and weights, whilst still allowing for rest. It’s the perfect blend of work and recovery, which will be shown in your results!
Follow this approach, train hard, eat well, sleep well and watch your physique transform!
References
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950543/ [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6303131/ [3] https://pubmed.ncbi.nlm.nih.gov/25546444/ [4] https://pubmed.ncbi.nlm.nih.gov/24714538/ [5] https://pubmed.ncbi.nlm.nih.gov/25932981/
Steve Hoyles is the owner of MyGym, a strength and conditioning facility in Stockport. He has almost 20 years experience in the fitness industry and writes extensively on fitness, nutrition and personal training.