You are helping a patient to strengthen their hip flexors. Your patient is perfo

Question

You are helping a patient to strengthen their hip flexors. Your patient is performing a hip flexion exercise as illustrated below (assume knee in full extension). While he was standing, you measured the distance from the hipjointtothecenterofmassofthethigh,shankandfoottobe0.34,0.72,and1.08m.Themassesofhisthigh, shank, and foot are 16.2, 11.5, and 3.3kg. Calculate the amount of hip flexor muscle torque required to holdthe leg isometrically at 47°. If the patient were to add a 2.5kg mass to their ankle (0.95m from the hip joint), what would the new flexor muscle torquebe?

Explanation / Answer

Solution:-

Distance from the hip joint to the center of mass of the thigh, shank & foot to be 0.34, 0.72 & 1.08 m.

The masses of his thigh, shank, and foot are 16.2, 11.5, and 3.3kg

Total mass = 16.2+11.5+3.3 = 31 kg

Force = 31*9.8 = 303.8

So Torque of hip flexor muscle required to holdthe leg isometrically at 47° = Force * distance = 303.8 * 2.14* Cos 47

= 303.8 * 2.14* 0.68 = 442. 09 Nm

If the patient were to add a 2.5kg mass to their ankle (0.95m from the hip joint), what would the new flexor muscle torque be

= (31+2.5)*9.8*(2.14+0.95)*0.68 = 689.8 Nm

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