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Strength & Conditioning Gym Brisbane - Group Fitness Classes & Personal Training - ATHLETIX

Hypertrophy main - Strength & Conditioning Gym Brisbane - Group Fitness Classes & Personal Training - ATHLETIX

Lifting weights is – and always should be- a science-supported activity, so that can be practiced with safety and scientific back-up.

In general terms, there are specific protocols to improve physical qualities: Max Strength (lift the most amount of weight), Hypertrophy (gain the most muscle mass) or Power (greatest force production over a short period of time).

How much you lift, for how long, how often and how much you rest, will determine the type of adaptation (or lack thereof) you will experience (2); we call this “dose-response”.

Also, some people who simply do not respond at all to training stimuli (non-responders) like the average does, as well as some others who responds incredibly well (high responders).

There will always be some individual variations to the protocols’ outcome, as well as in the participants of the studies used as reference below.

Which is why among the most widely used words in this blog (and any other discussing sport science topics) there are “depends” and “conflicting evidence”.


After 2 decades of working in gyms, I heard some frequently asked questions, especially regarding building muscle mass.

As usual, we have looked at several papers published in the past 10-15 years to try and give you some ground info on how to make the most of your weight training.

The number of papers published on the topic is large, so this is not a comprehensive guide, but rather a good overview of the topic, which might help even our ATHLETIX members understand why we approach our LIFT classes the way we do!


Few definitions to make sure the read is smooth:

  • Reps = repetitions, as in how many times in a row you perform a movement
  • Muscle fibre types: there are a few muscle fibres in the body; for simplicity let’s just call them type I and II. Type 1 are the ones that take over during longer and less intense exercises (slow oxidative), while the type 2 are more engaged during short and higher intensity activities. Further subdivided in II a (fast oxidative) and II x (fast glycolytic). There is an overlap between the fibre types.
  • RM = Repetition Max. When testing for strength, practitioners may choose to test for 1 or 3 Reps Max. This helps to set a benchmark and choose the right amount of weight to use depending on the goal.


Note for the readers: I left the last 2 questions for the more in-depth explanations related to muscle development and hormones. If you are not interested, just skip them 😉.

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   1. How many sets do you recommend to trigger hypertrophy during a workout?

Research has shown that when it comes to hypertrophy, total volume is key.

When it comes to increasing muscle mass, about >10 sets per muscle group per week elicited greater hypertrophy than < 10 sets, according to Schoenfeld in his study from 2016 and 2017 (2, 3).

Now, this does not mean that if you do less than 10 weekly sets you won’t have results. Schoenfeld in his 2017 study (2) shows that even as little as 4 weekly sets per muscle group can trigger significant muscle growth. So, this is great news for those who are pressed for time or older populations. However, IF you can add more sets, evidence shows how the results are greater.


    2. How many reps help with hypertrophy?

Although the science is still unsure about the number, emerging evidence indicates that there may be a fibre type specific response to training in different rep ranges. What does this mean?

When lifting heavy loads, it appears that highest threshold motor units (type II x) fibres show greater hypertrophy. With lighter loads instead, the hypertrophic response happens more in the type I fibres (4).

Assuming this is proven true, if the goal is general hypertrophy (non -performance based), then there might be a benefit to training with both high and low loads to maximize muscle growth, so that all fibre types get exposure to hypertrophic stresses.

As general guidelines, valid for most populations (from recreational lifters to advanced ones) a range of 6-12 reps is considered a happy medium between, allowing for good physiological and anatomical adaptations, with less time needed to rest, compared to heavy loads and lower reps (9,10).

hypertrophy article - Strength & Conditioning Gym Brisbane - Group Fitness Classes & Personal Training - ATHLETIX

   3. What is a good training intensity (load) for hypertrophy?

There is conflicting evidence as to how much effort is required for maximal growth. Research generally suggests that you don’t need to train to all-out failure to achieve a maximal benefit (6).

In fact, according to Schoenfeld (3) for untrained individuals a load of <60% of 1 RM (Repetition Max) is sufficient to promote substantial increases in muscle strength and hypertrophy.

Another study advised for intensities between 60 and 80% of 1RM (10) is best to promote the best hypertrophic adaptations. I generally bring the intensity up during a hypertrophy cycle, dropping reps

For elite athletes, coaches should consider integrating advanced resistance training techniques and methods to provide an additional stimulus to break through plateaus, prevent monotony, and reduce the time of training session (10).

With my Rugby high school boys, I like to adopt the Reps in Reserve (RIR) approach, which gives an indication of how many reps should be left in the tank, at the end of each set. This not only allows for a more correct use of the “strength on the day” (fluctuating capability due to overtraining, stress, sleep quality etc), but also helps them gauge the correct load if they have not yet been tested for their 3-rep max on the given lift.

Personally, after reading all the papers in this post, it seems that failure training can have a place for advanced lifters to maximize hypertrophy.

In practice, with more advanced lifters, and/or towards the end of a hypertrophic block, I have no problems in having an RIR of 2-3 on the first set, 1-2 on the second set, and then going to failure on the final set (9).


   4. What should the rest be in between sets?

A study from 2009 (7) showed that when the training goal is hypertrophy, short rest intervals of 30–60 seconds might be most effective due to greater acute levels of growth hormone during such workouts (5,7).

As per everything discussed so far, the variation among individuals is a reality and always depends upon several factors, among which training age, training frequency and nutrition play a huge role.

   5. How does RT influence muscle growth?

Lifting weights makes people stronger and/or bigger depending on the type of hormonal response they go through.

In Layman’s terms, the stress coming from lifting pushes the body to produce specific hormones, that lead to building muscles.

The mechanism is made by 4 main points:

  • Exercise induced muscle damaged: during eccentric activities the contractile elements (actin and myosin) produce resistance to the movement, which in turns creates small tears in the muscle fibres. During the recovery, the tears are repaired, and the muscle gets stronger to withstand a similar stress (adaptation)
  • Metabolic stress results from the build-up of various metabolites (e.g., lactic acid, inorganic phosphate, etc.), primarily because of training in the fast glycolytic energy system where carbohydrates are used anaerobically to fuel performance.
  • Mechanical stress, it is the amount of force/tension generated in the muscle fibres in response to a stimulus. This stress triggers the protein synthesis and therefore muscle size. The goal is to activate as many muscle fibres as possible to maximize the response.
  • Fascia Stretch Training. When the muscles are pushed to work with specific resistance and work/rest ratios (see below) there is an increase of oxygenated blood in the soft tissue in a short time. This forces the fascia to stretch and expand, packing nutrient and oxygen rich blood into and around the muscle cells to promote repair and growth.

hypertrophy 3 - Strength & Conditioning Gym Brisbane - Group Fitness Classes & Personal Training - ATHLETIX

   6. What are the hormones most involved in the muscle growth process?

The hormonal response is generally initiated by the type of training, which after exercise, produces a series of enzymatic responses, triggering anabolic and catabolic signals, leading to a shift in the protein balance towards the synthesis (5).

Most studies on hypertrophy generally focus on IGF-1 (Insulin-like Growth Factor), Testosterone, and GH (growth hormone)

Let’s see what they are and where they come from to try and have a better understanding.

  • IGF-1 (Insulin-Like Growth Factor-1)

It is a peptide with structural similarities to insulin. primarily derived from the liver. Exercised muscles are the primary producers of systemic IGF-1 during intense physical training. Interestingly the same working muscles are the major users of that circulating IGF-1. (5). Research has shown that humans have 3 distinct IGF-1, one (IGF-1Ec) is mechanically activated; for such reason is also called a Mechano-Growth-Factor (MGF) (5). Furthermore, it is defined as a Myokine* rather than a hormone.

*Myokines are peptides synthesised and released in the muscles in response to muscular contraction (8).

  • Growth Hormones

It is secreted by the Pituitary gland and released in waves (pulsated). The greatest non-exercise production happens during the sleep. GH has many tasks (fat metabolism, uptake of amino acids, etc). When it comes to muscles, the GH is believed to mediate the hypertrophic adaptation via the IGF-1 actions. Several studies showed increase of circulating IGF-1 after growth hormone administration (6)

  • Testosterone

Testosterone is a steroid hormone synthesized from cholesterol. Men have around 10 times higher amount of testosterone that women, which explains the huge difference in post-puberty muscular accrual. It should be noted that factors such as gender, age, and training status profoundly influence testosterone release. (5)

Although the hormonal hypothesis is still not fully validated and supported by science, there is a growing belief on the acute effect of transient hormones following a resistance training bout that seems like supporting the narrative. More research is needed.


Final considerations:

After all the above, the take-home message for those who want to train to gain muscle mass is to remember that protocols high in volume, moderate to high in intensity, using short rest intervals and stressing a large muscle group, tend to produce the greatest acute hormonal elevation and outcome in cross-sectional area, across majority of the studies.

The table below may serve as quick guideline (with the due considerations already discussed about training age, gender, nutrition etc).

Sets Reps Intensity Rest
>10 weekly set per muscle group 6-12 repetitions per set* 60-80%1RM, 3-1 Reps in Reserve (RIR) ** 30-60sec after each set *,**
*Depends on the load
**Depends on which set of the block

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  1. Kraemer WJ, Ratamess NA. Hormonal responses and adaptations to resistance exercise and training. Sports medicine. 2005 Apr;35(4):339-61.
  2. Schoenfeld BJ, Ogborn D, Krieger JW. Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. Journal of sports sciences. 2017 Jun 3;35(11):1073-82.
  3. Schoenfeld BJ, Wilson JM, Lowery RP, Krieger JW. Muscular adaptations in low-versus high-load resistance training: A meta-analysis. European journal of sport science. 2016 Jan 2;16(1):1-0.
  4. Grgic J, Schoenfeld BJ. Are the hypertrophic adaptations to high and low-load resistance training muscle fiber type specific?. Frontiers in physiology. 2018 Apr 18;9:402.
  5. Schoenfeld BJ. Postexercise hypertrophic adaptations: a re-examination of the hormone hypothesis and its applicability to resistance training program design. The Journal of Strength & Conditioning Research. 2013 Jun 1;27(6):1720-30.
  6. Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. The Journal of Strength & Conditioning Research. 2010 Oct 1;24(10):2857-72.
  7. Freitas de Salles B, Simao R, Miranda F, da Silva Novaes J, Lemos A, Willardson JM. Rest interval between sets in strength training. Sports medicine. 2009 Sep;39(9):765-77.
  8. Pedersen BK, Steensberg A, Fischer C, Keller C, Keller P, Plomgaard P, Febbraio M, Saltin B. Searching for the exercise factor: is IL-6 a candidate?. Journal of Muscle Research & Cell Motility. 2003 Apr;24(2):113-9.
  9. Helms ER, Cronin J, Storey A, Zourdos MC. Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength and conditioning journal. 2016 Aug;38(4):42.
  10. Krzysztofik M, Wilk M, Wojdała G, Gołaś A. Maximizing muscle hypertrophy: a systematic review of advanced resistance training techniques and methods. International journal of environmental research and public health. 2019 Dec;16(24):4897.

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