Sometimes. it has to do with the bands create a greater stretch reflex ,because it accelerates you down faster than gravity normally would.,which causes the muscles to contract harder. So when you have all the band tension at the top say 200lbs. and only 100 at the bottom , you body still thinks that it has the 200 at the bottom and therefor will fire in an effort to lift that much. But having less weight allows for a greater acceleration because the body is contracting with the idea of moving 200 extra lbs when in all actuallity is only moving 100. Something along those lines.