An intense isometric contraction is terrific for muscle growth for two reasons. First, it quickly recruits the largest motor units because it's a maximum voluntary contraction. Second, isometrics increase the neural drive between the motor cortex in your brain and the trained muscle.

Gymnasts use a lot of isometric contractions when training on the rings. The single-arm hang simulates the effects in a commercial gym-friendly manner.

1. Hang from a pull-up bar with an underhand grip with the pinky fingers touching each other.
2. Pull yourself up so the elbows are at 90 degrees.
3. Quickly grab your left wrist with your right hand so the left hand is the only one gripping the bar. Maintain the 90-degree left elbow angle as your forearms, biceps, and upper-back fire to maintain your body position. Try to hold for about 10 seconds.
4. Switch sides and repeat with the right hand gripping the bar.