Stand tall with a neutral spine and your feet slightly wider than shouder width apart. Hold a barbell in your hands with an underhand grip and hands the same width as your feet. The barbell should be resting at your thighs. This is your start position. Keeping your elbows and upper arms still, bend at the elbows and drive the barbell up towards your chest. Exhale as you do this and squeeze your biceps. Reverse the movement to return with control to the start positon, inhaling as you do so. Repeat for the required number of reps (or time).