Understanding the Intricacies of Muscle Actions: A Key to Effective Personal Training


Muscles are the workhorses of the human body. They support our every movement, from the most mundane to the most strenuous. As a personal trainer or fitness enthusiast, understanding how muscles function can be a game-changer in creating effective training programs and achieving optimal results. This knowledge is so fundamental that it forms a core part of the curriculum in the IFBB Nordic Academy Personal Trainer course starting this September.

The Anatomy of Muscle Contraction

Muscle fibers are designed to shorten when stimulated. This phenomenon is facilitated by crossbridges in the muscle fibers that pull the protein actin towards the sarcomere's center, leading to muscle shortening. However, muscle actions are rarely without external resistance. Whether it's a dumbbell at the gym or just the force of gravity, muscles are often contracting against an opposing force. The type of muscle action that results is determined by the interplay of these forces.

The Three Types of Muscle Actions

  1. Concentric muscle action: This occurs when the force produced by the muscle is greater than the external resistance. As a result, the muscle overcomes the resistance and shortens. A practical example of this is lifting a dumbbell, where the muscle force exceeds the weight of the dumbbell.
  2. Eccentric muscle action: If the external resistance surpasses the force generated by the muscle, the muscle lengthens despite its inherent drive to contract. This is known as an eccentric muscle action. For instance, when you lower a weight slowly and under control, your muscles are undergoing an eccentric contraction.
  3. Isometric muscle action: When the muscle force and the external resistance are equal, the muscle does not change in length, resulting in an isometric or static muscle action. This is the kind of muscle action that occurs when you're holding a plank position or carrying a heavy load without moving.

Interplay of Muscle Actions in Exercise

All three muscle actions—concentric, eccentric, and isometric—are crucial during exercise and are employed during a typical resistance training session. The classic back squat exercise provides a great example. Isometric muscle actions stabilize the barbell at the start, eccentric actions allow the weight to be lowered, and concentric actions help stand back up. Coordinated muscle actions like these allow a person to exercise effectively while also protecting against injury.

Understanding Muscle Actions for Better Training

Often, trainees find the concentric phase of an exercise more challenging than the eccentric phase. For example, lifting the barbell off the chest during a bench press (a concentric action) is generally perceived as more difficult than lowering it (an eccentric action). This perception can lead to the erroneous assumption that the eccentric phase is less important than the concentric phase. However, research suggests that emphasizing both concentric and eccentric actions is crucial to maximize resistance training benefits.

As a personal trainer, understanding these different types of muscle actions can significantly enhance the effectiveness of your training programs. This knowledge allows you to design workouts that leverage the benefits of concentric, eccentric, and isometric actions, and helps you guide your clients to a better understanding of their own bodies. And this is exactly the kind of knowledge that will be imparted in the upcoming IFBB Nordic Academy Personal Trainer course, proving once again that a deep understanding of the human body forms the bedrock of great personal training.