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Biomechanics and Motor Development PSE4U Faulhafer Every movable bone in the human body, acting alone or in concert with others, is part of a lever system that facilitates movement. List the 4 purposes of levers: 1. __________________________________________________________________ 2. __________________________________________________________________ 3. __________________________________________________________________ 4. __________________________________________________________________ Every lever is composed of 3 parts: 1. ___________________________________ 2. ___________________________________ 3. ___________________________________ Use page 230 in your textbook to complete a chart summarizing the three types of levers. Type of Lever Description Diagram Example For each of the following exercises, state what class of lever it is, what joint acts as the fulcrum, and what muscle(s) act(s) as the force. Exercise Bicep curl Calf raises Shoulder raises Crunches Overhead triceps extension Fulcrum (joint) Force Lever Lever and Torque Problems Just like we worked with the conservation of momentum principle dealing with moving bodies (ie hockey players colliding and figure skaters spinning) we can also use this principle when dealing with force/torque produced by muscles in the body, to compensate for added weight on the body. Example 1 How much force must be produced by the biceps brachii, attaching at 90 degrees to the radius at 3 cm from the centre of rotation at the elbow joint, to support a weight of 70 N held in the hand at a distance of 30 cm from the elbow joint? Example 2 Calculate the force passing through the Achilles tendon, in body weights, when the heel is raised 5.5 cm. The tendon is 6.5 cm from the ankle joint centre and pulls vertically. A ground reaction force from the individuals’ body weight of 785 N is applied 12.5 cm from the ankle joint centre. Example 3 Calculate the muscle force required to hold a briefcase without motion, given that the briefcase weighs 2 kg, the distance from the elbow to the handle is 27 cm, the forearm and hand are 2.25% of the total body weight acting at 15 cm from the elbow, the muscle pulls at an angle of 75 degrees toward the body and inserts 3 cm from the elbow. The individual is 68 kg.
