According to classical mechanics for a force to  lift a mass it should be slightly greater than its weight . My hypothesis  is that a human body can lift itself  by a force far less than its weight . It is obvious phenomenon that when lifting an object  of 60 kg up , it would be extremely hard than lifting one's body " 60 kg" .while standing. This applied to many phenomenon  .A body will seem to have inertia far less than its actual mass inertia , moving and walking effortlessly ,