How Personal Trainers Build Muscle

How do Personal Trainers structure training and manipulate volume so that you increase your muscle mass? We reveal the basic science behind forcing adaptation.

Muscle gain should actually be called muscle adaptation. Unfortunately, it just doesn’t sound as sexy as ‘gains’. Imagine that, “Hey bro, looking good, you’ve made some serious adaptations recently!”

… One can only live in hope of such a scientific world.

Let’s explain. During a personal training session that is focused on ‘gains’, you stress and cause micro-tears (literally, damage) within your muscles. Our bodies are clever systems that repair damaged muscle more capable so that they can deal with the next time they’re put under such stress. Luckily for those looking to increase their muscle mass, more capable tends to mean bigger.

This is our adaptive survival system and the foundation of evolution. Those that survived a deadly incident returned stronger and more capable of doing so the next time. Those that didn’t never returned, and thus we were left with the cream of the crop, in peak physical condition. That was until weapons (and computers) came into existence, and we somehow reversed nature to turn our population into a collection of large-brained sloths.

So we’ve adapted the trials of nature to the gym, and personal trainers have built systems of increasing the need for adaptation over time.

Imagine your body was simplified and comprised of 8 key muscles (we know, bear with us).

When you first start doing any kind of general exercise, all 8 theoretical muscles will be sore afterwards because they’re involved in most movements like running, jumping, squatting, climbing, pushing and pulling. However, over time you will adapt and the limited stress that has been spread out across all of these 8 muscles will no longer force new adaptation.

These muscles also aren’t being specifically challenged; they’re all getting generally used to working out but eventually what is holding back our ability to challenge them to grow is our cardiovascular ability to supply all muscles with oxygen. It’s also very hard to achieve maximum stimulation to specific muscles with full-body movements like these. At this point, you’re in a position of maintaining muscle mass.

Muscle-building (or forced adaptation) training targets specific muscles with movements in order to maximally stimulate them. Different movements have different levels of isolation, with maximum stimulation coming from movements that completely isolate a muscle. In our future article “Isolation vs Compound Training”, we look at the differences between the two and how they relate to each other, but it’s purely a matter of how many muscles are being challenged at once.

Without going into this, resistance training is basically coaches choosing to target specific muscles and increase the work that those muscles have to sustain on a regular basis. The variables in play are:

1. Weight moved – The amount of weight moved in kgs or lbs.
2. Number of Reps – The number of times one is able to move the weight.
3. Number of Sets – The number of times a set number of reps was carried out.
4. Total Volume – This is total when multiplying the weight moved and how many times it was moved.
5. Time under tension – The amount of time the muscle(s) was working for. The tempo of each rep affects this because reps done with slower control means a longer set.
6. Rest Times – How long one rests between sets.

With bodyweight movements, one can target numbers 2-6, but number 1 (and possibly the most important for increasing density of muscle fibres) is left out of the equation. Those who are seen to be getting “more ripped” and building muscle by training this way are rarely doing so significantly, they’re merely cutting body fat to the point where their underlying muscle looks more defined. There is an element of sarcoplasmic muscle gain, where muscles increase in size to store more glycogen, but little increase in fibre density.

To truly cause an increase of fibre population in muscles, the resistance provided and required to be produced by the muscle must increase. The clever part about how Personal Trainers isolate muscles to force this is they put the muscle in a disadvantaged position and remove the ability of other muscles to help it. 15 kilograms that was easy to pick up and put overhead using one’s arms, back and legs is now difficult to curl with only one arm, using the bicep.

The bicep is stressed close to (or to) the point of failing to be able to lift the weight for x-number of reps, and when we rest and recover our adaptive systems repair the bicep to be able to get that x-th rep next time. Adaptation has been forced, thanks to the hacks of knowing how to mechanically disadvantage the joints and muscles of our body.

Hey, presto.