SETUP: Attach a straight-bar to a low pulley and take an overhand-grip. Make sure to wrap your thumbs around the bar, too.
REP: Curl the bar by squeezing your biceps. You will feel your forearms engage a lot here, particularly in the bottom third of each repetition. Keep your elbows to your sides throughout.
TIP: Stay close to the pulley. The further we move away, the more likely our elbows will pop out, disengaging the target muscles.