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Metis and Bodybuilders

Hacker News - Wed Apr 7 20:46

Fitness researcher Menno Henselmans writes about optimal program design for bodybuilders. His thesis is that peer-reviewed studies prove bodybuilder lore is wrong in lots of places. For example:

Traditional bro wisdom holds short rest periods of 1-3 minutes are optimal for bodybuilding. There never seemed to be much of a formal argument for why other than that people traditionally trained this way. The real reason was probably that bodybuilders chased the pump and burn they get from shorter rest periods. Later the idea of chasing the pump was rationalized into the theory of metabolic stress. Yet there wasn’t a single study to support that shorter rest periods actually benefit muscle growth.

  • In 2005, Ahtiainen et al. found similar muscle growth when training with 5 vs. 2-minute rest periods. Importantly, this study was work equated, which meant the shorter rest period group performed an average of one extra set for each exercise to compensate for their lower work capacity.

  • In 2009, Buresh et al. actually found greater muscle growth in a strength training program with 2.5-minute rest periods than the same program performed with 1-minute rest periods.

  • In 2010, De Souza et al. found similar  muscular development in a group resting a consistent 2 minutes compared to a group gradually cutting their rest periods down to 30 seconds over the course of the program. These results were replicated by Souza-Junior et al. in 2011.

  • Later in 2014, Schoenfeld et al. compared 2 work matched programs – a ‘powerlifting type’ program of 7 sets of 3 reps with 3-minute rest periods and a more traditionally bodybuilding type program of 3 sets of 10 reps with 1.5-minute rest periods – and found similar muscle growth.

Yet the idea that short rest periods were best for bodybuilding lived on. Several review papers even recommended rest periods of 30-60 seconds and the American College of Sports Medicine recommended 1-2-minute rest periods with some exceptions up to 3 minutes. So in 2014 I wrote a review paper together with Brad Schoenfeld critiquing the theory of short rest periods for muscle growth and metabolic stress. In addition to a formal overview of the literature showing no empirical evidence that short rest periods maximize muscle growth, my critique was, in short, as follows. The benefits of short rest periods were theorized to result primarily from increased anabolic hormone production. However, production of the key anabolic hormone testosterone is overall unaffected by rest interval length. It is only growth hormone production that increased and only with rest intervals below 1 minute. Problematically, resting less than 2 minutes also increases cortisol production and thereby worsens the T:C ratio. Since there is good evidence the T:C ratio is related to muscle growth, whereas growth hormone is not anabolic in muscle tissue but mostly related to anaerobic fuel mobilization, the hormonal milieu resulting from short rest intervals is more likely to be detrimental than advantageous for muscle growth.

Our paper became very popular and is still in the 5% most popular scientific papers on Altmetric. But public opinion now swung in a direction we didn’t intend to: people concluded it doesn’t matter at all how long you rest.

To settle the matter, in 2015 Brad Schoenfeld et al. and yours truly performed a randomized controlled trial comparing strength training programs with 1 and 3-minute rest intervals. The 3-minute rest group achieved greater muscle growth. While the 1-minute rest group (presumably) achieved greater metabolic stress, it evidently didn’t lead to more muscle growth, less even.

Subsequent research confirmed that resting only a single minute compared to 5 minutes between sets of leg extensions blunts anabolic signaling and acute myofibrillar protein synthesis in the muscle cells in spite of higher metabolic stress in the short-rest group.

Then Fink et al. (2016) showed that when total work is equated, resting only 30 seconds with 20RM loads is just as effective for muscle growth as resting 3 minutes with 8RM loads. The short rest group experienced greater muscle swelling and growth hormone production post-workout, but this was not correlated with muscle growth.

In conclusion, your rest interval matters primarily because it affects your training volume. As long as you perform a given amount of total training volume, it normally doesn’t matter how long you rest in between sets. If you don’t enjoy being constantly out of breath and running from machine to machine, it’s fine to take your time in the gym.

I found this interesting because some people hold up (no pun intended) bodybuilders as an almost-perfectly-incentivized “scientific” community. Every bodybuilder has his own skin in the game - based on getting the science right or wrong, he’ll be better or worse at what he does. There’s a quick feedback loop - you can see if you’re gaining muscle or not. And success is easy to observe - check if the person giving you advice has arms that look like tree trunks. Taleb et al contrast this with the academic scientific community, whose incentive is to publish papers that have low p-values so they can get tenure - no skin in the game, no incentive to get anything right, no easy way to check success or failure.

In James C Scott terms, bodybuilders have metis - the practical wisdom that comes from being a tight-knit community sharing a common goal, watching each other succeed or fail, and passing down lore to the next generation. It’s the same wisdom that lets primitive tribes have almost supernatural knowledge of how to safely prepare plants in their environment or build a bow with exactly the right kind of mountain goat sinew. Way better than the on-paper numerical knowledge that Western science can produce.

But here’s what seems like an example of body-builders failing miserably, and needing normal academic science to set them right. Seems awkward for skin-in-the-game and metis fans.

II.

Before I take this too far: is there really “traditional bro wisdom” recommending short rest periods? I Googled “bodybuilding rest periods” and checked what the first three sites had to say about it.

The #1 result was How Long Should You Rest Between Sets For Maximum Growth?, which had been voted the best answer by users of bodybuilding.com. It said that people training for strength should wait 3-5 minutes, but people training for hypertrophy (bigger muscles) should wait 30 - 60 seconds. I interpret that as confirming Henselmans’ claim that short rest periods are consensus - except that the answer cites eleven scientific studies. The studies all show that various biological things that could correlate with muscle growth (eg anabolic hormone release) are higher after short rest periods than long ones, but they don’t directly prove that the the short rest periods cause more gains.

The #2 result was Hypertrophy Rest Times: How Long Should You Rest Between Sets at outlift.com. It says:

Recently, research has been coming out showing that long rest periods between sets are best for building muscle. With longer rest times, our muscles can better recover their strength between sets, allowing us to maintain more of our performance from set to set. More weight lifted for more sets means more mechanical tension, higher training volumes, and thus more muscle growth. Because of this, most bodybuilders rest 2–5 minutes between sets.

But a decade ago, short rest times were thought to be best for building muscle. Bodybuilders would rest just 30–60 seconds between sets because it gave them better muscle pumps, kept their workouts short, improved their fitness, and, they thought, helped them build more muscle.

What’s neat is that both approaches are correct. Using long rest times allows us to use heavier weights and gain more strength, helping us to build more muscle. Short rest times, on the other hand, help us to improve our work capacity and general fitness, also helping us to build more muscle.

Henselmans’ article came out in 2019, and the outlift article is from this year, so this is sort of compatible with Henselmans’ claim that people supported shorter rest times when his article was written. Outlift also cites a 2016 study by Fink, Kikuchi, and Nakazato showing clear benefits of shorter rest times, which turns out to be one of the same studies Henselmans cites as not showing clear benefits - I think the difference is that it showed a strong trend towards benefits (in fact, twice as much muscle growth after short rests!) but the study was so small that this wasn’t statistically significant. Not sure what to think here, but it sounds like even this site doesn’t really want to stand by the results of this one.

The #3 result was Chris Beardsley on Medium, Do Short Rest Periods Help Or Hinder Muscle Growth? He makes basically the same points as Henselmans’:

Although short (1–2-minute) rest periods are popular among bodybuilders, they do not enhance muscle growth, when the total volume (as defined by the number of sets to failure) done in each workout is the same. In fact, longer (3-minute) rest periods produce more hypertrophy than short (1-minute) rest periods, in strength-trained males.

But these are still big websites that seem really interested in the science. I added “forum” to my search query to see what people in bodybuilding forums were saying to each other.

The #1 result was this 2016 thread in forum.bodybuilding.com, where the most prominent response said:

If you are resting 2 minutes you are probably fine. There is scant evidence for any benefit of shortened rest periods. Most experts seem to be advising that you should take as long as you need between sets. If shorter rests reduce what you are capable of doing, you are probably leaving some gainz in the gym.

The #2 result was this 2011 thread from the same place, which said:

I can not think of a better way to ruin a workout then to be concentrating on the second hand of a clock between sets! Lifting weights is NOT an aerobic exercise! Using time as a variable in your workout is completely self-defeating (within reason, of course) Rest as much as reasonably needed between sets! This will enable you to recover between sets and better perform the lifting of the weight. which is the reason you are working out in the first place!

Some people objected that longer rests meant it took more time at the gym to lift the same number of weights, but nobody really seemed to object on biology grounds.

The #3 result was this 2019 thread, also from the same place, where the first person to respond said:

Short answer: yes.
Long answer: no.

…to which the original poster responded “You are garbage. And a dick.”

But then people started saying useful things, and a lot of people did mention that maybe shorter rest times between 1-3 minutes were better, including someone citing Arnold Schwarzenegger saying this. And then a user linked the Menno Henselmans article I started this post with.

So overall, sources seemed to agree that people used to recommend shorter rest times, and I was even able to catch a few people recommending shorter rest times personally.

But this wasn’t based on dumb bros not realizing science was a thing. It was based (at least partly) on older scientific studies providing circumstantial evidence for shorter rest times. Then those studies didn’t really pan out.

And once the newer, better studies came out, the bodybuilding community embraced them and updated its advice. This didn’t happen instantly, but it happened about as fast as anything happens in any science-consuming community anywhere, including academic science.

III.

The most important lesson I draw from this is that metis and a community doing practical work doesn’t put you above academic science and peer-reviewed results (or at least it doesn’t always put you there). The bodybuilders had lots of opportunities to experiment and tinker, with lots of skin in the game, but they were still getting things pretty wrong until researchers looked into some of their conclusions using the normal scientific method.

On the other hand, some of their failure seems to have come from taking past scientific studies too seriously. There is no pure untouched community of noble savage bodybuilders, forming an academic-science-free control group. So who knows? How do you avoid getting misled by bad science, while still being correctable by good science?

(also, I’m still not sure what to think about that one Fink/Kikuchi/Nakazato study. You’d think metis-having practical communities would be able to take advantage of obvious trends without splitting hairs over exactly what the p-value was. Maybe I’m misreading the paper, or taking it out of context.)

None of this should come as a surprise; it’s the same thing that happened to doctors fifty years ago. We thought we’d developed useful lore. Evidence-based medicine showed half of it was wrong.

I appreciate the many ways that science and evidence can go wrong, and the unique expertise held by communities of metis-possessing practitioners. But in most of the communities I look into, trusting the peer-reviewed academic studies still seems to be the way to go.