Yep. The push ups were bad.

Ever play that game at a slumber parties called “Light as a feather, stiff as a board”? One person lays on a table. Someone tells a ghost story and then five or six people chant “light as a feather stiff as a board” while “levitating” the person with their forefingers? The theory for why it works is that by telling the scary story and chanting those words the person becomes flat and rigid and thus easier to lift than a person who is relaxed. Same reason protesters go limp when authorities try to drag them away. It is harder to lift up a limp body. If I practice push ups using all the muscles in my whole body to stay flat, tight, and totally straight in the end it will be much less work for my poor tired arms. Not being straight and rigid makes my arms have to do way more work than they should have to. So stronger arms will help. But in the end better push ups will help more.