Overview

Levers are fundamental to human movement. In biomechanics, a lever is a rigid structure that rotates around a fixed point called a fulcrum. In the human body, bones act as the levers, joints serve as the fulcrums, and muscles provide the force to move them. Understanding how levers work—both inside the body and in equipment used outside of it—helps explain how we produce movement, generate force, and maximise efficiency in sport and exercise.

A lever system consists of three main components:

The fulcrum – the pivot point (usually a joint)

The effort – the force applied (muscle contraction)

The load – the resistance to be moved (body weight or external force)

There are three classes of levers, each defined by the relative position of the fulcrum, effort, and load.

First-class levers have the fulcrum between the effort and the load, like a seesaw. In the body, an example is found at the neck during nodding, where the atlanto-occipital joint acts as the fulcrum, the neck muscles provide the effort, and the head is the load. These levers can provide both speed and force, depending on the position of the components.

Second-class levers have the load between the fulcrum and the effort. An example in the body is standing on tiptoe: the ball of the foot is the fulcrum, the body weight is the load, and the effort comes from the calf muscles. This type of lever is efficient for producing force but sacrifices speed and range of motion.

Third-class levers are the most common in the human body. In these levers, the effort is between the fulcrum and the load. A classic example is elbow flexion during a bicep curl—the elbow joint is the fulcrum, the biceps muscle provides the effort, and the weight in the hand is the load. Third-class levers favour speed and range of movement over mechanical advantage, allowing rapid and controlled motion in sport and daily activities.

Levers outside the body are also critical in sport. Tools and equipment such as hockey sticks, tennis racquets, oars, and golf clubs act as external levers that extend the reach and power of the athlete. The principles of lever mechanics still apply: adjusting the length of the lever or the position of the force can significantly affect control, speed, and force output. For example, gripping a bat closer to the end increases swing speed (longer resistance arm), while choking up on the handle increases control.

Understanding levers helps athletes, coaches, and therapists refine technique, select appropriate equipment, and reduce injury risk. It also highlights how the body balances power, speed, and efficiency to perform complex movements through simple mechanical principles.