People with big muscles have to be strong, right?

It is a very common and understandable thought to have. Most professional athletes are larger than your average population and come with bigger muscles, and they are all very strong!

However, in this article, I propose that muscular size does not necessarily mean muscular strength and vice versa.


First of all, how do we define muscular size and strength?

Obviously size is the actual physical size of the muscle, either measured by the circumference of the outside of the muscle or the physiological cross-sectional area.

A cross-sectional area (CSA) of a muscle divides the muscle at its largest point, usually perpendicular to the muscle fibers. This method is the most accurate way to measure a muscles size, because it only includes muscular tissue. Taking the diameter of say, your arm, would be including the size of not only your muscle, but fat and other soft tissue as well.

There are many aspects to consider when reviewing this question. Main fiber type, motor innervation and training technique all have to be included.

Type of muscle fiber and training technique

Muscular size and strength are related as we look at muscular fiber type.

muscle size and strength_2There are two main fiber types in muscles, type I and type II, or slow twitch and fast twitch. Fast twitch muscles are used more for quick power and sprint activities while slow twitch are used for longer endurance activities.

Type II have the potential for greater hypertrophy (size increase) as well as greater force output than type one.

In saying this, if a person has a greater genetic predisposition to have more type II fibers, they also have a greater likelihood of having bigger muscles and strength than a person who has a majority of their muscle fibers under the type I category.

This concept is further complicated because it is highly dependent on the type of training one does.

Type I and type II fibers can be “converted” or trained to make them act like the other

For instance, a person with a high percentage of type I fibers can train those fibers to act more powerful and quick like type II and vice versa.

Therefore, a person could predominately have fast twitch muscles and train them for hypertrophy, giving him or her greater size.

Another person could have a greater number of slow twitch, but train them for strength and power and be smaller than the first person but stronger.

There are staggeringly famous feats of strength performed by people are aren’t big and muscular – achievements that couldn’t be emulated by the person with the big muscles. Things like The Dragan Challenge are interesting. The task is to curl and shoulder press a dumbbell (20kg for men) repeatedly for as many reps as possible. Often it’s the smaller guys who clock up the 100’s while the really big boys are stuck in the 10’s.

The muscle size and strength vary individually and differently, all depending on the fiber type and how you train it.

Find out more about fiber types and motor innervation in Part 2 of my article tomorrow..

Connect with Expert Jon Kilian.

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