Shoulder external rotation across a table - forearm supported (Wheelchair)

Sit in your wheelchair with your feet resting on the footrests with a solid object such as a table to your side.
Ensure the brakes are applied.
Place your forearm on the table to your side whilst keeping your elbow bent and tucked into your side.
When ready, sweep your forearm across the table away from you keeping your elbow still.
Return to the start position, and repeat.