What are the two main classifications of muscles?

The primary classifications of muscles in the context of their function are flexors and extensors. Flexors are muscles that decrease the angle between two parts of the body, such as bending an arm at the elbow or a leg at the knee. Extensors, on the other hand, work to increase the angle between body parts, straightening out the arm or leg. This functional classification is crucial in understanding how muscles work together to facilitate movement and maintain posture.

Flexors and extensors play a vital role in coordinated movements and are often paired in opposing muscle groups. For example, when flexors contract to bend a joint, extensors must relax, and vice versa, which highlights the intricate balance and coordination required for smooth physical activity.

Other classifications, such as major and minor muscles, refer more to size rather than function, while the category of fast-twitch and slow-twitch muscles relates to muscle fiber composition and performance characteristics, such as endurance vs. quick bursts of power. While these are important distinctions in muscle physiology, they do not represent the main functional categories of muscles focused on movement.