Eli5: Why are bigger muscles not automatically stronger?



For example huge bodybuilders lifting a lot less than significantly smaller powerlifters

In: Biology

The same way that if you read 10 books about something you wont learn as much as if you read the same book 10 times, on average at least.

Simplest answer is that the body wants the minimal amount of “tissue (by this I mean anything that needs calories to keep functioning)” to achieve the demands placed on it. Those who do Mr. Olympia contest, etc. will tell you that to gain muscle size “hypertrophy” you have to over stuff your daily caloric load and work out like a man possessed. This doesn’t correlate to strength bc of a loss of function/range of motion. A pitcher can throw the ball 100mph due to his mechanics and wont throw the ball 1mph faster if he bulks up bc his mechanics will suffer. Yet, put the same increased muscle mass on a 9′ tall person and teach them the proper mechanics and they might throw the ball 130mph. Once you put all that muscle on a frame not meant to support it (from steroids, etc.) you lose a lot of “function.” It’s not to say you lose all of it. Ronnie Colman was squatting something like 800+lbs in his prime. If you put his muscle mass on a 10′ tall person he’d prob have squatted like 1,200lbs (pure guess).

tl;dr If you put in the work the body will respond but past a certain point the additional muscle takes away function (mobility). This is why to build size body builders cannot just keep increasing the amount they lift and continue to do 5 reps w 5min breaks in between, they have to keep the weight “lower” and do more reps w less rest in between bc they cannot maintain proper form to mitigate injury w the heavier weight due to not having the proper frame for the large muscles they are building.

Muscles are made up from a lot of muscle cells, on the cell level, the bigger cell is the stronger one.

If you look at a whole muscle the coordination of the contraction of all those cells also becomes important. This is called intramuscular coordination.

When it now comes to a specific exercise the so called intermuscular coordination (the coordination between individual muscles) also plays an important role.

Bodybuilder train mainly for size so the other two componets are lacking compared to a powerlifter who tries to train every component to get the maximal lifting number.

Muscles only contract and relax. So having a huge muscle is great but it can only do one extremely specific function. And that function is determined by how that specific muscle is anchored by tendons and ligaments. Almost any task that you do requires a combination of muscles and those muscles are ultimately limited by the ligaments and tendons not by the size of the muscle – in other words when building muscle you’ll hit a point of diminishing returns.