One way to do more work with less power is to use levers. A lever is a device that increases work power or range of motion. The joints are the levers in the human body. They act as levers that increase the power of muscle or increase the distance through which the muscle can move a bone. If you raise yourself on your toes, you are making use of one kind of lever. The muscles that form the calves of your legs have to do the work of lifting your whole body. You would need to have much larger calf muscles if they had to undergo the strain of lifting your body by a direct pull. Yet you easily raise yourself on your toes, because your foot acts as a lever.
In the act of raising yourself on your toes, your weight bears straight down on the point where the bone below your knee rests on your ankle bone. The muscles of your calf pull upward on your heel bone, and your foot pivots upward on the fulcrum (the point around which the lever moves) which is formed by the bones that make up the ball of your foot. Although we say that we raise ourselves on our toes, we actually raise ourselves on the balls of our feet and steady ourselves with our toes.
If you reach down and grasp the back of your foot just above your heel, you can feel the strong tendon- called the Achilles tendon - that connects the muscles of your calf to your heel bone. If, now, you raise your self on the ball of your foot, you can feel the calf muscles tighten and bulge as they contract and pull upward on your heel.
