Isometric soleus contraction in long sitting (Soleus strengthening isometric, feet against wall, sitting)

Sit upright on the floor with your legs in front of you and the balls of your feet flat against a wall.
Your knees should be bent.
Keeping your knees bent, push your toes into the wall as if trying to move away from the wall.
Counterbalance the force of your toes by fixing through your arms to prevent yourself sliding away from the wall.
Hold this position.