The Theory of How to Build Strength without the Size

Are you an athlete who has to stay within a certain weight class? Maybe you’re a runner who wants to keep their weight down as much as possible to keep running at maximum speed? Just want to keep off any extra pounds? Getting stronger without getting bigger is sometimes crucial. Here are the FizzUp trainer’s tips on how to build strength without gaining weight.


To build strength without the size, avoid going over your daily calorie intake requirement and tweak your eating habits based on the weight you’ve lost or gained while you focus on building strength. In other words:

  • If you consume more calories than you burn, you’ll gain weight. This is called a “calorie surplus.”
  • If you consume fewer calories than you burn, you’ll lose weight. This is called a “calorie deficit.”
  • If you burn about as many calories as you eat, you’ll stabilize your weight. This is called your “calorie maintenance level.”

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Keeping your calorie maintenance level in check prevents weight loss and weight gain and promotes healthy recovery from exercise thanks to a sufficient calorie intake.


The first thing to remember is that muscle mass isn’t the only factor that creates strength. For most people, the strongest man in the world looks something like the Hulk. But strength doesn’t only come from muscle; it also comes from your nervous system. There are two main factors you should think about if you want to build strength:

  1. Muscle size: The more muscle mass you have, the more strength you’ll be able to exert. Clearly, this isn’t the best choice if you want to build strength without the size.
  2. Nervous system: Every muscle is made up of thousands of individual motor units (muscle fibers + motor neurons). When these motor units receive neural impulses, they immediately contract to exert strength depending on the type of innervated muscle fiber, which can be either fast or slow. In the human body, a muscle can only exert a small percent of its total possible strength, even when using maximum effort. In short, the number of motor units activated at any given time is far from maximum capacity.

What’s a motor unit? A motor unit is made up of a motor neuron and all the muscle fibers the motor neuron activates. Muscles are made up hundreds of muscle fibers that are activated by motor neurons as a response to brain signals telling them to contract or not to contract. A single motor neuron can control several hundreds of muscles fibers at the same time, depending on the muscle’s size and function.

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For someone who wants to build strength without the size, the goal of their workouts should be to increase their nerve impulse, improve their technique and motor neuron activation to build more strength.


The more motor units you recruit, the more muscle fibers you’ll activate and the stronger you’ll be.

Your muscles are controlled by nerves connected to your brain. Every nerve is connected to many individual muscle fibers, which means that a single neuron can contract several muscle fibers at the same time. But not all of a muscle’s motor units are activated at the same time, even when you try to contract your muscles as hard as you can. It’s a safety measure your body uses, but you could also see it as a physical limitation, due to the fact that your body doesn’t know what it’s capable of. Fortunately, this diminishes the more you work out.

For instance, you can contract one of your biceps, but this might only activate about 10% of its muscle fibers. When you engage in a low-intensity activity such as lifting a glass, your brain activates motor units that contract a small number of muscle fibers and a minimum amount of strength in order to lift the glass. Imagine what would happen if your brain told your muscles to fully contract every time you wanted to drink: you’d crush the glass.

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On the other hand, when you lift something that’s extremely heavy or when you use lots of strength, your body will activate more (i.e. strong) motor units in order to do that movement. This is called “motor unit recruitment.”

Now you know the theory of how to build strength without the size. Put this knowledge from the FizzUp trainer into practice during your next workout.

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