Draw some more basic shapes for his legs and his tummy.
Now draw more basic shapes for the lower legs and feet.
Draw a bunch of ovals in the arms.
Draw the outline of the arms by using the ovals from the last step.
Draw the top and bottom of two ovals for the chest muscles, then draw the curves on the tummy with a line through it for the abs. Start tracing the outline of the basic shapes that you drew.
Outline more of the legs and draw the muscle lines.