Alright, so I was creating an anti-gravity device (handwaved) in a new world, that counteracts certain amounts of weight. I was wondering what would happen if the device counteracted just enough of the weight of a human that while they would not be able to float through the air, like in zero g, but only feel MINIMAL weight holding them down. Items held also experience the weight change, but because only a set amount of weight can be counteracted, the weight is spread evenly throughout the item and the human. The mass is not lost, but the weight is (mostly) counteracted. What would that be like, side-effects-wise?
Ah, it meddles with the gravitational constant, so that two bodies are attracted by a smaller factor.
Short term use would require careful motion, as when the astronauts were on the moon, because reflexes are set for normal weight, and motions are likely to be excessive. Practice would be indicated. Gym classes revolving about it from grade school level onward.
Longer term use would mean acquiring more skill in motion, but would mean the whole host of issues from lack of gravity. Muscle would atrophy. Bones would weaken. Even circulation is affected, not merely because the heart is a muscle that would atrophy (and grow more spherical), but because the system is set up on the assumption that gravity is affecting it, and it is, for instance, more difficult to pull up blood from the feet than pull it from the hands. As a consequence more fluid builds up in the body and the kidneys remove it from the body as excess, and the number of red blood cells goes down as there are too many for the new volume of blood.
Intermittent use would therefore be wiser, but there would no doubt be cases where the person has to use it constantly for medical issues, and fools who would use it excessively for ease.