Simulation of Back and Arms I

Objectives: 1.Understand the centers of gravity on different parts of a body;   2.Use digital measurement tools to find lever arms for forces;   3.Apply the conditions of equilibrium to determine the amount of force that is exerted by the person's erector spinae muscle when the person is bending over to support a load;   4.Find out how the force on the person's erector spinae muscle depends on his/her weight and the weight of a load.

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Instruction:

K represents the lower end of the spinal column. We consider it as the pivot, the person is balanced with the weight of the Trunk, Head and Neck (THN), the weight of the Arms and Hands (AH), the weight of the Load (L) and the force on the Erector Spinae muscle (ES). WTNH and WAH are located on the centers of gravity of the respective body parts.

Download the photo(Click to download the image) and find the lever arm values by using a digital measurement tool. (Information of the image: the load is 30 cm high. Please use this information for calibration.)

Weight of the person WP= N.
  Force   Lever arm
  TNH   WTNH= 54.5% of weight(W)= N.   LATNH= m
  AH   WAH= 10.7% of weight(W)=N.   LAAH= m
  Load   WL= N.   LAL= m
  ES   The FES = N.   LAES= m

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