Muscle

A muscle is a contractile tissue that generates force through tension, enabling movement or stabilizing the body. Strength training primarily focuses on the skeletal muscles – the muscles that can be controlled voluntarily, such as biceps, quadriceps, latissimus, or gluteal muscle. They consist of many individual muscle fibers, which adapt depending on the training: heavy training with high load promotes thicker, stronger fibers (muscle building), while longer sets or interval training improve fatigue resistance (muscular endurance).

No muscle works completely alone. Even during an isolation exercise like bicep curls, surrounding muscles provide support, and in basic exercises such as the Big 5, several large muscle groups often work simultaneously. This interaction ensures strength, stability, and functional mobility.

Muscles can work in three main types of contractions: concentric (shortening, e.g., during the push-up phase or dips), eccentric (controlled extension, e.g., during lowering in negative bench press), and isometric (holding without movement, e.g., in planks). All three forms are important to develop musculature holistically and prevent injuries.

For muscles to grow or become stronger, they need to be regularly challenged beyond their usual limits – this is called progression. This can be achieved by increasing weight, performing more repetitions, taking shorter rest periods, or trying new exercises. At the same time, muscles need rest to recover and build strength. Without this balance, the risk of overtraining and injury increases.

In short: Muscles are the foundation of every athletic performance – whether in cardio, muscle building, or maximum strength development. Those who understand how muscles work and adapt can train purposefully and ensure long-term progress.