When Muscles Contract Do They Become Longer or Shorter

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When Muscles Contract, Do They Become Longer or Shorter?

If you`ve ever wondered what happens to your muscles when you flex or workout, you`re not alone. It`s a common misconception that when muscles contract, they become shorter or tighter. However, this is actually not entirely true.

Muscle Contraction 101

Before we dive into the myth and reality of muscle contraction, let`s first understand what muscle contraction is. In simple terms, muscle contraction is the process by which muscle fibers generate tension and shorten in length.

There are two types of muscle contractions – concentric and eccentric. Concentric contraction occurs when the muscle shortens and contracts towards the center of the body against a resistance, such as lifting a weight during a bicep curl. Eccentric contraction, on the other hand, occurs when the muscle lengthens while under tension, such as lowering the weight back down during a bicep curl.

The Myth: Muscles Shorten When They Contract

It`s a widespread belief that muscles shorten when they contract. This is because when you flex your bicep, for example, it feels like the muscle is getting shorter and tighter. However, this sensation can be misleading.

In reality, during concentric muscle contraction, the muscle fibers are moving towards each other, but the muscle as a whole does not become shorter. Instead, the muscle belly bulges, and the muscle`s overall length remains the same.

The Reality: Muscles Do Not Change Length

During a concentric contraction, the muscle fibers do not change length – they slide past each other, overlapping to generate force. However, during an eccentric contraction, the muscle fibers do lengthen as they slide apart from each other, still under tension.

So, the next time someone asks you if your muscles get shorter when you work out, you can confidently say that they do not. Instead, they generate tension and force through the sliding of muscle fibers and the bulging of the muscle belly.

Benefits of Understanding Muscle Contraction

Understanding how muscle contraction works is crucial in bodybuilding or weightlifting. For instance, when performing eccentric training, the lengthening of muscle fibers can lead to muscle damage and soreness, which can help stimulate muscle growth and recovery.

Furthermore, knowing how your muscles work can help you perform exercises more effectively and avoid injury. For example, when doing squats, keeping your knees behind your toes can help engage your quads more effectively and reduce the strain on your knees and ankles.


In conclusion, muscles do not get shorter when they contract. Instead, muscle fibers slide past each other, leading to the bulging of the muscle belly, generating force and tension. Understanding how muscle contraction works is essential in optimizing your workouts and preventing injuries. Next time you flex, know that your muscles are not getting shorter – they`re just generating power!