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The Influence of Moment Arms on Torque
Perform the following movements while sitting or standing.
- Use of a long moment arm. Hold your dance bag or another heavy object at shoulder height with
your elbows extended. Think about the distance your bag is from your shoulder, that is, the moment arm
of the resistance, and the large torque that this bag would exert. Note the amount of muscular effort that
is required to hold the bag in place. - Shortening the moment arm. Bend your elbows, bringing your bag close to your chest at shoulder
height. Notice the change in the moment arm of the resistance. Why does your bag feel lighter, and why
is less muscular effort required to hold it at shoulder height? - Application to other dance movements. Now consider the weight of your leg as the resistance.
How would bending your knee for a développé versus lifting the leg with your knee straight make it easier
to lift the leg higher?
ConCept Demonstration 2.2
RAl = moment arm of leg
RAf = moment arm of foot
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