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Muscle Activation: Definition and Types

What is Muscle Activation?

Muscle activation occurs when the brain sends instructions for muscles to contract and tighten up. This is possible because nerves can interact with muscles through neuromuscular junctions (NMJ)––connections between the end of a motor nerve and muscle tissue. As a result, the muscle can produce force and create movement at its insertion point.

Are There Different Types of Muscle Activation?

There are three types of muscle activation (contraction):

  • Eccentric – where the muscle lengthens under load, such as when lowering the weight during a bicep curl
  • Concentric – where the muscle shortens as it contracts, such as when performing hip adduction
  • Isometric – where the muscle contracts but doesn’t increase or decrease its length

Some coaches prescribe activation exercises to temporarily improve the communication between the muscles and nervous system, leading to better performance.


1. How to better feel muscle activation?

Reducing resistance and slowing the tempo is a simple and effective strategy. This allows trainees to focus on their technique and activate the target muscles more effectively.

2. How to measure muscle activation?

Electromyography (EMG) is one common way of measuring muscle activation, typically by attaching electrodes to the skin. The downside is that EMG is biased toward the concentric contraction and short muscle lengths, which means the data doesn’t necessarily help predict muscle growth or strength development.

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