What is an example of a fusiform muscle?

A fusiform muscle is characterized by a spindle-like shape that is wider in the middle and tapers at both ends. This structure allows for a greater range of motion and helps to generate powerful contractions. The biceps brachii is an excellent example of a fusiform muscle because it has this distinctive shape and is designed to facilitate bending the elbow and lifting the forearm.

In contrast, the other muscles listed present different shapes and functions. The pectoralis major is a broad, fan-shaped muscle that is involved in movements of the shoulder and arm but does not exhibit the fusiform characteristics. The rectus abdominis, also known as the "abs," has a strap-like appearance and is structured for stability and support rather than for the characteristics of fusiform muscles. Lastly, the rectus femoris, part of the quadriceps group, has a more straight and linear shape, suitable for its role in contraction and movement but not fitting the fusiform designation. Understanding these distinctions clarifies why the biceps brachii is classified as a fusiform muscle.