A generalised challenge, for anyone that would like to participate this month, post up your results, experiences of it in this thread.
Using one hand only, hold a barbell out vertically, away from the body.
Twist the barbell to horizontal (palm facing down) and then back to vertical.
Twist it back to horizontal etc.
Use a lighter barbell, if required. How many reps can you manage? Please join in, for fun and for the personal satisfaction.