It is difficult to know how much larger or smaller to make areas of the body that are in perspective.
A fairly simple way to check your drawing is to use perspective lines to make estimations.In my example image I've drawn a boy kicking his foot into the air towards the camera, making his kicking foot appear larger in frame.
Note, the horizon line should be placed early on in the sketch, and adding some perspective lines will help.
If we want to know how much bigger to draw the kicking foot, first make sure there are perspective lines running along either side of the grounded foot. Then we can rough in an area on the ground, where we think the kicking foot would be if dropped vertically to the floor. It might help to sketch a view from the side, as my example shows. Then we can draw vertical parallel lines to tell us how wide the foot is if placed somewhere along that plotted point.