Yes, weightlifting can be understood by physical laws, just like any other everyday phenomenon. However, not in the way that you seem to think. Working against the force created by the mass of something doesn’t magically give you more mass as some counter-force. Rather, you have to exert energy to work against the force of gravity, and once your muscles start to exhaust, they develop microscopic rips and tears. When you eat to regain energy, those rips and tears are repaired, except they grow back stronger and larger, ie you’ve gained mass. So it’s a biological process, and I’d ask any follow-up questions you have in a biology subreddit.