(1) Calculate the reactive force and reactive muscle moment at the knee for a seated leg extension, with a weight of 35, 45, and 55 lbs. Assume that the leg is held at an angle ????.

(2) Read the accompanying article on squat technique. Calculate and compare the joint reactive forces (Rj) and reactive moments (Mj) at the hip, knee, and ankle for the two squat forms illustrated. Assume the subject is lifting an unloaded bar (45 lbs), and his posture is symmetric.

(5) Determine the vertical ground reaction forces acting on a man at the feet (FF) and at the hands (FH) while performing push-ups. The man weights 71 kg and has a height of 1.76 m. At this instant, the angle his body makes with the horizontal plane is 20°, and the angular velocity, and angular acceleration are measured as 4 rad/s and 7 rad/s2, respectively. The distance from the bottom of his feet to his center of gravity is 1.02 m. The distance between his head and shoulders is 0.32 m.

Model assumptions:

(i) The body is kept straight, and rotates about the toe/floor contact point.

(ii) The arms can be modeled as weightless rods, hinged at the middle.

(iii) The arms transmit vertical forces only.

Answer rating: 100% (QA)

There are two reactive forces which act on the knee from hip to knee which is downward while other is canter of gravity in upward direction These two ... View the full answer