Suppose I consider the silver back gorilla as an example. I cannot imagine ever seeing one in the wild intentionally doing something akin to weightlifting like humans solely for the purpose of getting stronger (if I'm wrong about this, that would be fascinating to know as well). However, last I checked a male silver back can easily lift several times its own body weight. I used to workout heavily and used to hold my high school bench press record (330 lbs in the 160-171 lb weight class). However, even then I would have struggled to do more than a few pull ups with a 170 lbs strapped to my waste. Meanwhile, I've watched various types of monkeys and apes do handfuls of seemingly effortless pull ups at zoos as part of their play.

So do animals like gorillas have muscles that either start and stay stronger than humans or just atrophy much more slowly? Or is it just a matter of constant use? Or is it just a different proportion of fast vs slow twitch muscles as this study suggests?

I am skeptical of this last part because some estimates of gorilla strength suggest they can lift upwards of 10 times their body weight [e.g., https://storyteller.travel/how-strong-is-a-gorilla/]. I also recall reading a study in grad school of an orangutan pulling over 600 lbs with one arm clearly not straining according to the article (though I failed to find the reference while searching today, unfortunately).

If anyone has some useful references with quantitative data, that would be great as well.

  • $\begingroup$ No matter how much I excercise, my musculus maximus will be stronger than my abductor policis brevis by the virtue of being anatomically different musles. Why would you expect an animal with clearly different body proportions and anatomy to have the same strength as humans? $\endgroup$
    – BagiM
    Feb 9, 2021 at 6:40
  • $\begingroup$ Well, it's more a matter of confusion. Hafþór Júlíus Björnsson, for instance, is over 400 lbs and one of the strongest humans on the planet. He weighs more than most apes. Yet I would pick the apes in just about any strength contest over him and they never work out. Plus, male humans have a larger fraction of our body mass as muscle than apes yet they are still stronger. $\endgroup$ Feb 9, 2021 at 14:28
  • $\begingroup$ @honeste_vivere: You might consider that the normal activities of an ape are equivalent to a human "working out". Likewise for that subset of humans whose normal activities include a lot of physical work. $\endgroup$
    – jamesqf
    Feb 9, 2021 at 18:36
  • $\begingroup$ @jamesqf - True, they are more physically active. However, how often do mountain gorillas go out of their way to lift up more than 2000 lbs? I am guessing almost never yet they can certainly do that without risking serious injury. Hafþór Júlíus Björnsson has to constantly train and eat an absurd amount of food just to barely be able to lift that much weight. His job is to get stronger and he wouldn't even be able to compete against a gorilla. $\endgroup$ Feb 9, 2021 at 19:11
  • 1
    $\begingroup$ Few more points regarding anatomical differences: 1. A muscle can only exert so much force on tendon and bone until something breaks. Look at side by side comparison of gorilla and human skeleton. Look how much sturdier an wider are the bones and joins. Wide bone surface allows for wider and stronger tendon-bone binding area. 2. A short and wide muscle can have the same total mass as a long and thin muscle and be stronger since exerted force solely depends on cross-section area of the muscle. 3. Number of filaments in a muscle is already determined at birth. This limits what exercise can do. $\endgroup$
    – BagiM
    Feb 10, 2021 at 13:24

1 Answer 1


Animal muscle does atrophy and gain depending on use.

First, animal muscle does atrophy if the animal is too sessile. However in nature it is hard to be sessile. Consider how physically fit hunter-gatherer humans are in terms of their cardiovascular systems. If you are constantly active you don't need to "exercise" to build muscle - you are getting loads of physical activity. Walking 10km a day or more is normal for most humans without advanced technology. We used to see atrophy in animals a lot more, but with animal welfare laws we usually don't keep animals in tiny cages that prevent them from moving anymore.

Some animals are less lazy than humans: many animals will also instinctively stay active even when provided with the conditions to be sessile, but when forced to not be active we do indeed see muscle atrophy. This is especially true of less intelligent species, because the conditions to be sessile are too rare to waste "instinct space" on, but humans who have a much more broader range of behaviors with far more learning behaviors, so we can become very sessile. The downside of intelligence is that you can use it in self-destructive ways.

Just like humans, animals can also build extra muscle by doing the same thing over and over again: a draft horse will build different muscles than a race horse just because it is using them differently.

Many animals also have physiology that makes atrophy harder. Hibernating bears are known to have special adaptations to prevent atrophy because hibernation is defined as long periods of inactivity. But we only only see this in animals that have something like hibernation or have drastically different muscular systems.

So why is a gorilla so much stronger?

Well to start, wild male gorillas mass between 130 to 260 kg. Note that gorillas in captivity often become overweight weighing even more. They have short legs so we don't realize how much bigger than us they are. For scale, Andre the giant (a human far outside the normal range) masses about as much as a large but normal range male gorilla. But there are several other factors.

Humans’ muscles are weaker than other primates’ in significant ways. We have traded strength for much better endurance and fine control of muscles - we do indeed have a significant difference in muscle composition and possibly muscle fiber recruitment, although it is hard to test the latter - you can't tell a gorilla to contract one muscle as hard as they can. As a gain however humans have amazing endurance for any animal and far finer motor control than any other primate. An active human can have better endurance than almost any other terrestrial organism, humans can walk a horse to death, that is a human walking side by side with a horse can keep going long past the point the horse has died from exhaustion.

Gorillas are only stronger in some aspects, a gorilla upper body is certainly stronger, gorilla have large arms and a deep chest drastically increasing the muscle mass of the arms compared to a humans. But the best human could probably beat the best gorilla at kicking power, gorilla legs are comparatively small. To use Andre the giant again, Andre has a lot more muscle mass in his legs than a gorilla and the gorilla has a lot more in the arms, humans have long well-muscled legs. Like all things, genetics can set you up with better musculature, and you will keep it as long as it gets some use.


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