SETUP: Take an underhand-grip on a barbell, hands placed about shoulder-width apart. I like to perform this exercise sitting down, resting elbows on thighs. You can also perform it while resting your forearms across a bench.
REP: Extend your wrists to let the bar move down – but don’t let the bar hang in your fingertips! – then curl the barby flexing your wrists up towards your elbows.
TIP: Don’t perform these standing up, you’ll fatigue your biceps long before your forearms have taken necessary punishment.