November 9th, 2012

Another Tip from Your Philadelphia Personal Trainer: Why Do Heavier Weights Build More Muscle?

Freeweight DumbBells

Why do heavier weights build more muscle?

In this short post, I’m going to address the question above, which is one I’ve been asked many times over the years from clients just starting out.

All muscles in the body are made up of muscle fibers. Each muscle will vary in terms of how many muscle fibers it has. Some may have thousands, some millions, etc. The larger muscles have the most. The smaller – such as the muscles surrounding the eyes – have the least. To complicate matters further, genetics plays a large role in strength training. Some folks are just born with more muscles than others.

In order to increase mass, muscles have to pushed continually to what’s called their adaptation threshold. In other words, in order to get bigger, you have to be constantly asking your muscles to ‘try harder.’ When you lift heavier weights, you ask your body to use more muscle fibers, and push it towards that ‘adaptation threshold.’

One other point to understand about strength training is that your body is actually made up of two types of muscle fibers. These two types are called slow twitch fibers and fast twitch fibers. The two have evolved to perform different tasks, namely the ability to perform repetitive tasks requiring endurance (such as running away a lion) vs. the need to perform explosive tasks requiring great strength (like pushing a rock in front of the cave, to keep the lion out…) Not surprisingly, slow twitch muscle fibers tend to predominate in the legs, while fast twitch fibers are found in greater numbers in the chest and back.

The takeaway from all this is to understand that, in order to get bigger, the fast twitch fibers are the ones you need to be focusing on. They respond to lifting by getting larger and, if you don’t lift enough – or possibly move the weights in a quick enough manner – you don’t use the muscle cells that are responsible for making you stronger.

Wanna learn more about the types of training that are best for you? Stop by one of our personal training studios in Philadelphia or write us to set up three free training sessions with us!

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