Some acute training variables for hypertrophy are essential, but what is even more important it’s the relationship between them. Let’s define them and see how to manipulate one to favor the other and viceversa.
1) The volume variable for hypertrophy
Training volume is the primary acute training variable for hypertrophy (Krieger, 2010), and leads to higher protein synthesis.
We can calculate training volume with a simple formula: sets x reps.
In powerlifting community, we also add the load to have a total amount of tonnage. In the bodybuilding community, often we only calculate the total number of sets per muscle group per week, since all loads above 40% can produce hypertrophy when volume is equated and the proximity to failure is similar (Lasevicius et al., 2018).
In fact, while the differences in training are evident between weightlifters, powerlifters and bodybuilders, if we examine the cross-sectional area of muscles used by all these athletes, over the long term, is very similar, even though they train at very different loads.
Why? Because over the years, the total amount of work performed (training volume) on the muscles is similar (Tesch et ak., 1985).
There is no set of specific volume to be performed, and it may vary widely between different muscles and different load used: volume and intensity have an inverse related relationship.
If we use medium loads, we can perform multiple sets and exercises per muscle group to induce hypertrophy (bodybuilding). If we use high or very high loads, the volume has to drop because of systemic fatigue and central nervous system issues that might arise. When training volume is too high, we might induce a reduction in the T:C ratio.
Author Israetel, in Scientific principles of Strength Training, proposes a model of periodization of volume in which, within a mesocycle, we start at a lower training volume, and we raise a set per muscle group per week, up to a certain point called MRV (Maximal Recoverable Volume), from which we then deload and start over.
This mechanism works well since we induce muscle mass gains from a multi-set approach, and we add volume over time (progressive overload principle), but not to a point of evident diminishing returns, or worse, overtraining. In the past, bodybuilders used to train with a very low frequency and very high volume.
Lately, many authors have been proposing a better method: splitting the total weekly volume per muscle group over multiple session.
This seems to work very well: an athlete can induce hypertrophic adaptations, while preserving better quality of movements, being fresher at every session.
If you train, for example, quads for 20 sets in a single session, the quality of the work done after the first 4-8 sets will be very low. To solve this, athletes are now splitting the volume over 2-3 days.
This gives us the opportunity of either doing more volume, which leads to further hypertrophy, or to perform the same amount of volume at a higher effort and quality.
From bodybuilding to powerlifting, athletes from all over the world are preferring medium to high volume of work per muscle group over 2 to 3 (at least) days of training per week.
2) Intensity of training variable for hypetrophy
As far as hypertrophic adaptations, a wide range of loads can be used.
The inverse relationship between intensity and volume has to be clear: the higher the intensity, the lower the volume, and viceversa.
We’ve been seeing this type of relationship since the days of professor Verkhoshansky, who described the conjugate sequence system which later gave birth to the concept of block training periodization, in which the first mesocycle of training has a high volume load, but low intensity, and then moves up to a high intensity and low volume load in order to peak an athlete with perfect timing.
Recently, a more undulating type of periodization has been used by many coaches: during the same week, we can target the same muscle with different loads and volume per session, achieving hypertrophy through multiple ways of training.
For advanced athletes, especially those looking for Type II fibre hypertrophy, there is some evidence suggesting that an 80% and above intensity is required to maximize the hypertrophic potential (Fry, A.C., 2004).
We can therefore use a wide range of intensities over the long term, starting from lower loads with higher volume, and progressing to higher loads and lower volumes.
This will ensure that we also get a great amount of mechanical tension on the muscles, and a decent amount of metabolic stress, the two main drivers of hypertrophy.
For athletes, we should focus on higher loads and mechanical tension rather than very low loads and very high repetitions: by doing so, we can target the type II fibres, which have a higher growth potential and are more relevant to strength & power athletes.
While peak tension on the muscle is very important, the time under tension is too. Therefore, only using very high loads, so high that we can’t complete more than 1-3 reps per set, may not be optimal for hypertrophic adaptations, since the tension is at it’s highest, but total time under tension will be very low.
3) Training frequency variable for muscle mass gains
Frequency is how often we train, in general, but in this specific context it’s how often we train the same muscle group or movement pattern.
All training variables are linked, but frequency is not an independent training variable, but only a way in which we can manipulate the two main variables such as volume and intensity.
If we train with very high-volume loads in a single session, we can’t train the same muscle again after only 24-48 hours, since we need to recover from the previous bout of training. If we train with lower volumes, we can increase the frequency.
Intensity, volume and frequency are therefore related: we can’t manipulate one without considering the other. In the Bulgarian method used by in weightlifting, for example, intensity and frequency is extremely high.
How can athletes handle these two variables being both so high? With very low volume of training. In Norwegian powerlifting, the volume is extremely high, and so is the frequency, but the intensity is medium. This interrelation is seen in strength training and hypertrophic focused training as well.
Those bodybuilders who like to train to muscular failure choose to keep frequency very low, while those who train with an RPE 6-8, meaning 2 to 4 reps in reserve, use a much higher frequency of training.
Frequency is also muscle-dependant: a posterior deltoid can be trained multiple times per week, while quads muscles can’t.
4) Rest periods for muscle mass gains
Rest periods refers to the amount of time between sets. As we have seen, we can induce muscle hypertrophy through different type of training, loads, frequency and volume.
As all these factors are interrelated, we also have to remember that high loads require longer (more than 90 seconds) rest between sets, while medium loads need medium rest (60-90 seconds), and low loads can handle short rests (30 seconds or less).
Since most of our training for hypertrophy will happen in the 6-12 rep range, since it will allow enough mechanical tension, metabolic stress, and medium to high amount of volume, a 2-minute rest seems to be ideal.
This doesn’t mean we can’t manipulate rest periods too, as much as we do with loads, frequency, and volume.
Having a short rest between sets has proven to cause the accumulation of metabolites and waste products in the muscle cells, muscle swelling, increased hormonal release and fibre recruitment, all leading to increased muscle protein synthesis.
Short rest periods will also cause a reduction in load and total volume per session: it’s not therefore not ideal to only use short rests.
All these training variables for hypertrophy are extremely important, but what’s even more important is how you manipulate one to make room for the other.
Training variables for hypertrophy | References
- Fry, A.C., 2004. The role of resistance exercise intensity on muscle fibre adaptations. Sports medicine, 34(10), pp.663-679.
- Krieger, J.W., 2010. Single vs. multiple sets of resistance exercise for muscle hypertrophy: a meta-analysis. The Journal of Strength & Conditioning Research, 24(4), pp.1150-1159.
- Lasevicius, T. et al. (2018) ‘Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy’, European Journal of Sport Science. Taylor & Francis, 18(6), pp. 772–780. doi: 10.1080/17461391.2018.1450898.
- MEDICA, E.M., 2017. Effects of drop set resistance training on acute stress indicators and long-term muscle hypertrophy and strength. The Journal of sports medicine and physical fitness.
- Tesch, P.A. and Karlsson, J., 1985. Muscle fiber types and size in trained and untrained muscles of elite athletes. Journal of Applied Physiology, 59(6), pp.1716-1720.