Exercise #3: Half Circle Arm Rotations.
Those arm circles you had to do in gym class are surprisingly good at building upper body strength, but the repetitive motion makes it easy to zone out and abandon quality circles. Half-circle rotations are a more active move that works deep into your arm muscles.
To do them, stand with your feet hip-width apart and hold your arms out parallel to the floor. With your palms facing forward, cup both hands as if you’re holding a tennis ball in each hand. Rotate your whole arm forward in a half circle so that the cupped hand goes from facing forward to facing behind you. Keep your elbows locked to maximize muscle engagement. Then, rotate back into your original position. Rotate back and forth as fast as you can.
Tip: Think of the motion as a slap forward and a slap back