The protocols and methods involved in inducing muscle hypertrophy can be a topic of confusion for many. Everyone, from trainers to lab technicians, seems to have a limited understanding of the processes and procedures involved. This makes coming to any real consensus around the correct and most efficient way to build muscle troublesome. This is in part due to the highly complex physiological processes that are still being researched and discovered, but also largely down to a constant battle between perfectly plausible concepts versus misconception, and in some cases outright silliness that continues to fill gyms, research labs and online forums across the world.
Reading between the lines and detecting flawed concepts can be a difficult task and while this article does not claim to know any one true answer, it will attempt to analyse and bring together some of the basic concepts of muscle hypertrophy so that we might have a better framework to understand its principles and applications in the gym. It will also call into question some of the current hypotheses and recommendations in the exercise science literature and how while interesting, these may not be the best methods practically, especially when dealing with a general populous clientele.
Currently, general consensus agrees that there are three main mechanisms involved in the process of inducing muscle hypertrophy. These are Muscular Damage, Metabolic Stress and Muscular tension. So let’s explore these concepts in a bit more detail and perhaps ask some questions along the way.
When we perform an activity that is harder in some way than our current ability, that activity produces stress within one or more body systems that consequently requires these systems to adapt. It does this in many ways, from chemical to structural alterations, but the underlying principle remains the same.
Stress causes an adaptation within a particular body system, which the body then responds to by reorganising and repairing itself to be better prepared for next time. In order to drive further adaptation, higher stress must be applied to signal to the system that an adaptation is required. The adaptation of the body system is specific to the stress applied, in other words, you adapt in a way that is directly related to the stress experienced. For example, calluses form on your hands as an adaptation to picking things up. They develop on your hands and not on your face because that is the area where the stress was applied. Gradual and planned increases in this cycle of stress, recovery and adaptation are what we refer to as progressive overload and it forms the basic principle of almost all human performance-based training around the world. The goal of building muscle is no different.
When we stress muscle tissue appropriately, either through the application of load, volume and time under tension, this creates a certain level of structural and systemic damage within the muscular tissue itself. As a result of that damage, the muscular system reorganises and repairs that tissue to a level above what previously existed. Muscular damage, often as a side effect, creates soreness and inflammation within the tissue and for years it was assumed that more soreness equated to more growth. Thankfully, we now understand that not to be the case, despite this misconception still being repeated in many places. That being said, while the level of soreness does not directly correlate to more muscular growth, the basic concept of stress, recovery and adaptation of the muscle tissue is still a factor that must be considered in the process. For years, muscular damage was the be-all and end-all of training, but we now understand several other important factors that contribute to the process of inducing muscle hypertrophy – metabolic stress and muscle tension.
Metabolic stress is the concept of eliciting an influx of metabolic products into the muscle through manipulating reps, sets and rest time in an exercise. More commonly referred to as the “burn” or “pump”, this concept has existed for many decades in bodybuilding styles of training but has only more recently been researched and understood on a scientific level. The hypothesis that currently exists reports that increased metabolic activity in the muscle tissue (specifically metabolite accumulation) improves motor unit recruitment and drives the release of anabolic hormones accelerating muscle hypertrophy.
This concept was established through numerous studies where various set and rep range protocols were manipulated at the results closely studied. It was established that the primary driver of metabolic stress is:
While this might seem simple on the surface, we do need to ask the important question of exactly how this can be applied on a practical level to our training, as well as identify some of the shortfalls that become apparent once you start to analyse these conclusions a little further.
The fundamental problem with the metabolic stress model (apart from turning each workout into a hellish nightmare) is that it is very difficult to practically apply during large compound lifts, which should always form the foundation of any good program. You simply cannot perform 6-8 sets of 12 reps with only 1 minute of rest with any meaningful amount of weight (certainly not a true 80% of a 1RM which is advocated in several studies), at the very least not without compromising the form and safety of the trainee. This means that this type of training typically limits itself to isolation-based exercises that neither utilise as much muscle mass nor provide the systemic stress that compound lifts do. This reduces their overall ability to make any substantial change to muscle mass. The danger with this is when programs are designed based purely on this principle and forget to factor in the other primary factors of muscle hypertrophy, we are leaving a huge amount of untapped potential in our training, especially for new trainees as well as leaving ourselves open to possible injury, overtraining and chronic soreness.
It is important to note that I am in no way dispelling or advocating the redundancy of the above methods, and in certain situations that require specific adaptations to occur in specific muscle groups, these can be utilised with good results. I am however questioning the use and practicality of these methods on trainees that are just starting out in their journey to building a better physique and how too much information often confuses and misguides new trainees into making poor decisions into the priority and organisation of their training. This is often where we see a breakdown between academia and reality where the research, despite perhaps its best intentions, does not necessarily correspond to practicality and efficiency in the gym.
The previously mentioned mechanisms of muscle hypertrophy cannot happen without the third being present. Increases in muscular tension are the only reliable and constant factor across all demographics that must be in place for hypertrophy to occur. Muscular tension is the contraction of the sarcomeres within the muscle tissue to produce force. Yet it should be noted that hypertrophy from muscular tension can be produced in the absence of both significant metabolic stress and muscular damage. How much muscular tension and under what conditions are where the debate lies.
Theoretically, muscular tension is produced whenever a muscle is under contraction, but in the gym, we typically solicit tension under two conditions.
These two events are similar in a sense that the repetitions involuntarily slow down the further through the set we move and both events can, and will, create fatigue in the trainee forcing them to exert more force and effort into finishing the set. However, there are some less obvious differences between the two in terms of their performance.
A heavy set of say 5 at 90% 1RM, requires more motor unit recruitment from the start of the set, due to the outright force production necessary to lift the weight in the first place. The more force the trainee must produce, the more motor units must be recruited (particularly the larger type II fibres). In a lighter, but still taxing 12RM set, the first 6 reps are submaximal, meaning that they do not require close to the maximal effort to move. However, as the set continues, the trainee must then call into recruitment of more motor units (type II) to complete the set. (Note this is different from the metabolic stress-based approach using light weights and limited rest to create metabolic environmental changes). Both events create similar amounts of muscular tension on the tissue, however, it is important to note that the amount of total force production needed for each event is quite different.
The question is then placed as to what method do we choose? Both can have significant results in the production of muscle hypertrophy and can generally be safely utilised by the most demographics. Of course, there are several things such as time, specific goals, and access to equipment, that all play into this. For me (and I don’t think I’m alone here!), I want to choose the method that gets me the most bang for my buck in the most efficient way possible.
Firstly, heavy sets feel heavy because they ARE heavy. They also give the added benefit of calling into contraction a higher number of motor units in order to move the weight. Secondly, we know that hypertrophy occurs as a result of more motor units being utilised, but also the ability to produce maximal force increases in those muscle fibres when they are called into contraction. In other words, the adaptation occurs in both the size of the muscle but also in its ability to produce force. In contrast, lighter weights taken close to failure may feel difficult, and in some cases, will produce a good hypertrophic response. However, this method pales in comparison to the increase in overall force production of heavier weights completed for lower reps. The problem here is that due to the limited amount of adaptation towards more force production, the weight quickly becomes the bottleneck to continued progress. If you are getting bigger, but are not able to go up in weight, how do you continue to drive progress without now changing the rep ranges away from those best suited to continue to build muscle? Hopefully, you can see the conundrum forming.
The point being made here is that a lot of time trainees looking to gain muscle will jump immediately into a highly complicated multi-factor program that is backed by “science” only to spend the next year on a hamster wheel making little to no progress. Getting the foundations right in any training regime is fundamental before you start debating the ins and outs or finer details, and anyone who has been training for any amount of time generally arrives at the same conclusion eventually.
As a hard and fast rule, the following points should be addressed before anything else is toyed with to induce muscle hypertrophy.
It is all too easy to get roped into the latest “fad” program, training methods or equipment pedalled by the current influencers or celebrities. The reality is that all you need at the beginning is a simple program that focuses on large compound lifts which utilise and progressively overload as much muscle mass as possible over the full range of motion.
For example, a program consisting of 15 variations to train the pecs or activate your abs will not have nearly the effectiveness as a correctly designed program with perhaps only 2 or 3 well-executed compound lifts, especially at the beginning. Many people (including myself) have wasted years in the gym only to find out that the answer was simple, not complexity. As your training progresses and goals become more clearly defined, then complexity can be added, but don’t waste precious time by trying to get complicated before you have to.
The stress, recovery and adaptation cycle are exactly those three things. We apply the stress through training, we recover by eating and sleeping, and as a result, we adapt to become better. It is a very simple concept, yet so many of us focus on the tiny details of the training that we forget the most important part. Recovery is finite, meaning that there is only so much activity your body can draw resources towards to replenish and repair. If you are in the gym, playing sports, running, swimming and all the while not fueling your body with enough calories or getting the required sleep to recover, then no matter what method of training you choose eventually your progress will stall and in many cases may regress.
Finally, intelligently designed progressive overload is the key to driving results. Monitoring and managing the stress that you apply to the system throughout your workouts and knowing when to push and when to back off is something that can take many years to learn. But the key is that the stress by biological law MUST gradually increase to cause further adaptation. The more adapted a trainee becomes, the harder it is to continue to drive progress which is where the complexity comes in to help. Not understanding this fundamental principle is frequently the cause of people’s frustration and inability to attain the desired results.
Hopefully this article has shed a little light and common sense towards the goal of building muscle. The takeaway point is to focus on the general before the specifics and to make sure the foundations are built before you start focusing on the wallpaper. Over time and as you gain experience you can start to dial in on the smaller details in training methodology that will hopefully continue to further progress you towards your goals.
De Freitas MC, Gerosa-Neto J, Zanchi NE, Lira FS, Rossi FE. Role of metabolic stress for enhancing muscle adaptations: Practical applications. World J Methodol. 2017 June 26;7(2):46-54. doi: 10.5662/wjm.v7.i2.46. PMID: 28706859; PMCID: PMC5489423.
Schoenfeld, Brad PhD, CSCS, CSPS, FNSCA1; Grgic, Jozo MSc2. Evidence-Based Guidelines for Resistance Training Volume to Maximise Muscle Hypertrophy. Strength and Conditioning Journal 40(4):p 107-112, August 2018. | DOI: 10.1519/SSC.0000000000000363
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