An example of a third class lever in the body is?

A third-class lever is characterized by the effort being applied between the fulcrum and the load. In the context of human movement, this means that in a third-class lever setup, the muscle (acting as the effort) is located between the joint (acting as the fulcrum) and the load (the weight being moved).

In the case of a bicep curl, the elbow joint acts as the fulcrum. When the bicep muscle contracts to lift the forearm (the load), the muscle action occurs between the fulcrum and the load, fitting the definition of a third-class lever. As the biceps shorten during a curl, they apply force to lift not just the weight being held but also the forearm and any additional loads. This type of lever arrangement is advantageous for producing a greater range of motion and speed, even though it may require more effort to move the same load compared to other types of lever arrangements.

For the other options, while they describe movements involving levers in the body, they do not exemplify a third-class lever configuration. Leg extensions involve a first-class lever, push-ups exhibit a variation of a third-class lever, and squats primarily use the body as a more complex lever