Question

1)     Calculate the muscular force needed for the back to adopt Position B.

2)     Calculate the size of the reaction force on the L5 vertebra in Position B.

3)     Compare the muscular forces and the reaction forces in the L5 vertebra for positions A and B.

In light of your results, do you now believe that one position is safer than the other?

Image transcriptions

1a_B-5-DYN_Watch_your_Back_S (Protected View) - Word (Unlicensed Product) A Khalil Sheikh File Home Insert Design Layout References Mailings Review View Help Tell me what you want to do Share Situations to analyse The two diagrams below illustrate a person lifting a weight using two different methods. For this problem, assume it is a woman 1.65 m tall who weighs 55 kg and who is lifting a 10 kg load. The mass of the entire upper body (torso, head and arms) corresponds to approximately 65% of a person's total mass. The body's centre of gravity is located about 0.50 m from the hips (see figures below). The horizontal distance between the load lifted and the hips is shown in the diagrams. For each situation, calculate: The size of the muscular force exerted on lumbar vertebra L5, at the hip level The size of the reaction force on the L5 vertebra -0.50 m - CM ! 25 0.50 m - 0.30 m - - 0.55 m - Fig. 3- Position A: back bent forward Fig. 4- Position B: knees bent, back straight. Source: Mathieu Riopel Source: Mathieu Riopel Simplifying hypotheses and anatomical clarifications Assume that the movement is carried out slowly so the conditions of static equilibrium apply. In other words, do the approximation as if there is no acceleration. Even though the back contains a great many muscles and tendons, we combine the action of these muscles into a single force directed parallel to the vertebral column, acting on the spinous process of the vertebra (Figure 5 below provides some information about the L5 vertebra). Spinous 6.5 cm process Muscular Pivot force Fig. 5 Source : Mathieu Riopel . Assume that L5, which is at the hip level, pivots around the axis of rotation shown here and is inclined in the same direction as the back for the positions illustrated. Page 3 of 7 1070 words -+ 100% Hi | Links a Amazon.com - Online Shopping 9 W 8:54 PM Search for anything 11/23/2020