Grip the weights at each end of a single dumbbell and let it hang arms’ length. Curl the weight up while gripping tightly, then lower under control to the starting position.
 
Purpose
The hammerhead curl is a simple exercise for the forearms and biceps, and to help strengthen and stabilize the elbow. The neutral grip places more emphasis on the forearms, and holding the weights allows for hand and grip training. It’s also a simple way to training both arms together when you only have access to a single dumbbell, or weights beyond what you can use in a single arm.
 
Programming
Generally sets of 10-30 reps are appropriate.