Take a light resistance band and wrap it around each hand. Adjust the disance between your hands to making it easier or more challenging.
Create tension in the band, actively pulling it apart, and begin rotating your arms upward.
Squeeze your glutes, and keep your ribcage down, as you elevate your scapula (Shrug your shoulders) and allow the band to pass over your head.
Continue until the band touches your back.
Then reverse the motion and return to the start. Repeat for repetitions.
Over time aim to tighten your shoulder circles by adopting a closer grip or upgrading to a stronger resistance band.
Conversely, take a wider grip to make the movement easier, and ensure you keep your arms straight throughout the movement.