A reply to the question by Eugene Levin, Research Analyst in Hypertrophy & Sports Science posted on Quora.
Spoiler alert: building muscle has nothing to do with “microtears” and muscle damage. It’s not metabolic stress or time under tension. Here is the raw truth:
(TLDR at the end, but you will miss a lot of interesting knowledge. In order to figure out the best way to build muscle, we must understand HOW muscle is built.)
First, of all, where do these factors come from, and why does everyone believe them?
Well, let’s start with muscle damage. Who hasn’t heard the story that during training muscle gets damaged, and a bit more muscle is provided by your body to replace the damaged tissue? Or, in scientific terms:
Once damage is perceived by the body, neutrophils migrate to the area of microtrauma and agents are then released by damaged fibers that attract macrophages and lymphocytes. Macrophages remove cellular debris to help maintain the fiber’s ultrastructure and produce cytokines that activate myoblasts, macrophages and lymphocytes. This is believed to lead to the release of various growth factors that regulate satellite cell proliferation and differentiation. (Toigo et al. 2006, Vierck et al, 2000) – Schoenfeld 2010.
So a few clever bros read something like this and created the story which you have heard countless times.
Although this is correct, the cited studies never showed any net hypertrophic response (muscle growth) from the subjects. It may have been that anabolic effect occurred strictly to repair the damaged muscle, not to build new muscle. And why would your body even do that? Muscle damage is just that – damage. Have you ever stopped to wonder why that doesn’t work with regular cuts? If you cut your muscle, why doesn’t it get bigger? If you did, good job, you were on to something.
In fact, Damas et al. 2016 actually compared hypertrophy in 2 groups doing the same total work, but one group was designed to have more muscle damaged. And the result: no correlation between muscle damage and hypertrophy. And Damas is the leading expert in the field of muscle protein synthesis. The reason we avoid bro splits and train each muscle more than once a week is widely contributed to his research.
And in 2018 (2 months ago) another study was published by Damas et al. and here is a quote:
“We argue that the initial increases in MPS (muscle protein synthesis) post-RT (resistance training) are likely directed to muscle repair and remodelling due to damage, and do not correlate with eventual muscle hypertrophy.”
And their conclusion: “Thus, we conclude that muscle damage is not the process that mediates or potentiates RT-induced muscle hypertrophy.” which proves my aforementioned hypothesis.
All the previous studies which supported muscle damage as a factor for hypertrophy did not account for total weekly volume, and the one which did (Moore & Phillips 2011) showed no correlation. Remember total work volume. I will mention it later.
Given all the evidence, we can say that muscle damage not only has nothing to do with muscle growth, but it’s detrimental to it! It extends the recovery time and forces the body to repair damaged tissue instead of building new muscle. (Also Damas et al, 2018, Henselmans & Schoenfeld 2017 lecture)
Next up: metabolic stress.
Why do people believe this? Simple. You can feel the pump and getting nutrients to your muscles certainly sounds compelling. Unfortunately, it’s wrong.
First of all, we know cardio causes metabolic stress. (Conrado de Freitos et al, 2017). We also know that combining cardio with resistance training is detrimental to hypertrophy and strength, very detrimental. (Wilson, 2012) Strike one.
We know resting less causes more metabolic stress. (Also Conrado de Freitos, 2017) But a meta-analysis by Henselmans & Schoenfeld 2014 showed no difference in hypertrophy between those who rested longer and those who rested shorter when total work was equated. But total work is not always equated, as when you rest shorter, you do less reps due to fatigue. And that’s what Schoenfeld 2016 examined, and showed hypertrophy in favor of the group which rested longer. Strike two.
We know that doing more reps (8–15) vs less reps (1–5) causes more metabolic stress. (Also Contado de Freitos et al. 2017) But every study which equated for total work volume showed no difference in high rep vs low rep groups (Most notably, Campos et al. 2002) And Schoenfeld, Contreras & Peterson 2015 showed no difference between 8–12 and 25–35 (!!) reps when it comes to hypertrophy, slightly greater strength gains for strength in the 8–12 group and slightly greater endurance gains in the 25–35. But muscle growth: the same. Strike three. (However, there are still benefits of including both in your training, just not because of metabolic stress)
And finally, surely, training to failure is optimal for metabolic stress and hypertrophy. Right?
There is even a study called “Strength Training with Repetitions to Failure does not Provide Additional Strength and Muscle Hypertrophy Gains in Young Women”. Martorelli 2017. Nóbrega et al. showed the same muscle growth in both groups: 1 going to failure and 1 not. And Morán-Navarro et al. showed that training to failure leads to more fatigue early on, resulting in less total volume and less hypertrophy. Strike four.
Conclusion: on itself, metabolic stress has nothing to do with hypertrophy.
What is left? The only other factor – mechanical tension.
What is it? Well, it’s just tension on your muscles though contraction or stretch. The greater the stretch/contraction – the greater the tension.
Mechanical tension has been unfailingly shown to lead to hypertrophy. (Schoenfeld 2010) When tension occurs though contraction and/or stretch, a signal gets sent to your body to start the process of muscle growth (to put it very simply). This makes sense, as unlike damage, your body would want to adapt to tension. Not a single quality study has disputed mechanical tension as a huge factor of hypertrophy.
Notice how I mention stretch all the time? Well, stretch has been shown to directly lengthen the muscle fibers (Toigo et al. 2006). And doing that is exactly how hypertrophy occurs (rarely though the actual increase in muscle fibers, which is called hyperplasia) (Vierck et al, 2000). Again, makes sense. It also explains why rack pulls are so effective (Conteras for T Nation) at activating traps and lats with virtually no contraction. And some of you may know a very interesting study on birds, but that’s a story for another time.
So. What should I make of all this?
- Work out more frequently, especially when you get more advanced. This is to avoid muscle damage, which you now know is a bad thing, and to maximize MPS, which in some cases is just 12 hours! (See my previous answer here for more information). I will also make an answer regarding frequency alone.
- High reps aren’t better than low reps and 8–12 is not the magic number. But make sure to include a bit of more to work both types of fibers.
- Don’t buy occlusion bands, etc and don’t bother with metabolic stress and time under tension. It doesn’t seem to be important at all.
- EDIT: new point. To maximize mechanical tension, choose the exercises with the highest EMG activation. You can google “Bret Contreras EMG” to find his articles for T-nation with an absurd amount of exercise comparisons.
- Total weekly volume matters. I kept highlighting its importance throughtout my answer. Maximize it through progressive overload. It’s the most important aspect of strength training.
- Finally, don’t take anything for granted. If you disagree, analyze the evidence or carry out your own research. Try things for yourself in the gym. That’s how science was born in the first place: a few curious people noticed something, didn’t take the others’ word for it, and discovered the truth.
Please note: This answer is already incredibly long, so I was only able to cover so much. Obviously, the best way to build muscle MUST include nutrition, hormonal levels, rest, and exercise selection. But these are all separate incredibly complicated topics which I will absolutely cover in the future. Please let me know if any you want me to cover any of these preferentially.
I wish you the best, smart gains.
