You need to decrease the angles in both your hips, and knees as much as possible. Keep you knees slightly bent to help circulation both ways though. Also loosen your belt a little around you hips and maybe lean the seat back more than normal. Maybe even loosen up your shoes a little as well. This will all help with circulation to your lower body. Stretching before hand goes a long way too for me.
I am Rhino68W, and I approve of this message.