Question

Imagine that you do 10 pull-ups in 10 seconds. What is the average power supplied by your arm muscles when moving your body?

Answer 1

The work done against the force of gravity (when going up or down) is $mg\Delta y$. Therefore, the work done for a complete repetition is $2mg\Delta y$. Let's suppose that the mass of the person is 80 kg and the distance $\Delta y$ equals 60 cm. Also, let suppose that the arms comprise 10% of the body mass and are not included in the moving mass. Then, we can calculate the average power supplied by the arm muscles when moving the person's body:

$$P_{avg}=\dfrac{W}{t},$$ $$P_{avg}=\dfrac{10\cdot2\cdot(1-0.1)\cdot80\ kg\cdot9.8\ \dfrac{m}{s^2}\cdot0.6\ m}{10\ s}=847\ W.$$