ACSM Personal Trainer Certification Practice Exam

Which movement is an example of a 3rd Class Lever?

1. Plantar flexion while walking

2. Shoveling dirt

3. Standing on tiptoes

4. Elbow flexion

The correct answer is: Elbow flexion

In a third-class lever system, the effort is applied between the fulcrum and the load. This configuration is characteristic of many movements that involve muscles acting through limbs, such as elbow flexion. During elbow flexion, the fulcrum is at the elbow joint, the effort is applied by the biceps muscle as it contracts, and the load is represented by the weight of the forearm and any objects it might be holding. This type of lever is particularly effective for producing a greater range of motion and speed at the end of the limb compared to the effort applied, which is why many arm actions, particularly those involving flexion and extension at the elbow, utilize a third-class lever system. The choice accurately reflects the biomechanics involved in elbow flexion, demonstrating how this lever system facilitates movement in our daily activities.