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How does a big muscle be a weak muscle?

I think this has been covered before but i have completely forgotten, how is it that someone with a bigger muscle can not lift as heavy as someone with a smaller muscle? I have seen this many times. Any logic behind it?
Thanks.

This is not a complete answer, but heavy lifting is as much neurological as psyiological. (Maybe that’s the wrong term.) It’s about training the nervous system as well as the muscles.

There’s also the consideration of muscle insertion points, lever advantages, hydration, etc.

Sometimes what looks like a big muscle is really one with a lot of embedded fat.

There are two different types of muscular hypertrophy. Sarcoplasmic hypertrophy is when noncontracile elements grow in size, this type will not create gains in strength, just size. Then you have myofibril hypertrophy, this is when the actual contractile fibers hypertrophy, and strength is gained.

Each of the answers you have received have touched on a part of the reason why larger doesn’t always mean stronger. Strength is a function of many things. Leverage clearly plays a part. So too does the type of hypertrophy (sacroplasmic versus myfibrillar). So too does the role of the CNS. Highly trained athletes (strength and power) are able to recruit upwards of 85% of their muscle fiber in an instant (explosive and starting strength) and leave those fibers “turned on” throughout the movement (acceleration strength). Thus, two people (even with identical levers) may exhibit very different levels of strength. Trainee A may have larger muscles than trainee B but, trainee A’s hypertrophy may be primarily through increased fluid retention (which does provide somewhat of a mechanical advantage in and of itself from what I have read) instead of thickening of the contractile portions of the muscle fibers. Thus, (even if the two have identical fast-twitch/slow-twitch fiber make-ups percentage-wise) trainee B’s muscle fibers will exhibit a stronger “pull” than trainee A’s muscle fibers. Additionally, if trainee A is an average member of society, he will only be able to use about 40% of his muscle fibers. If trainee B has trained his CNS extensively (both through maximal effort lifts and speed work) he may be able to recruit 80% of his muscle fibers all at once. Thus (hypothetically) trainee A may have 150 muscle fibers whereas trainee B only has 100 muscle fibers. Assuming for the sake of argument that the fibers are of equal strength, and that equivalent amounts of rate coding exist between the two (i.e., both can use equal amounts percentage-wise of available muscle fibers in synchronization and leave them on) and that their is no significant leverage advantage possessed my either trainee, if trainee A can only tap into 40% of his available muscle fiber he would use 60 muscle fibers (.4 x 150) whereas if trainee B can use 80%, he would tap into 80 muscle fibers (.8 x 100). Thus trainee B would be stronger than trainee A despite the fact that trainee A has 50% more muscle fibers. This is a crude example, at best, but I think you get the point.

Sincerely,

Matthew A. Levy

Thanks heaps guys.