Answer
$\vec{F_1}=\vec{F_2}=6,400 N$
Work Step by Step
If the force reaches 10 times their body weight, then the overall downward force is given by:
$ F = 10*9.8 m/s^2*55 kg$
We know that the force is evenly split between the two muscles. Since the forces are equal to each other, we will find only $\vec{F_1}$.
$2\vec{F_1}sin(25^{\circ})= 10*9.8 m/s^2*55 kg$
Finally, we obtain:
$\vec{F_1}=\vec{F_2}=6,400 N$
