Lie back on a flat bench with a dumbbell in each hand held near the top of your thighs.
Bring the dumbbells to the torso sides with the arms extended and slightly bent at the elbows. Palms are facing upwards.
Keep your elbows and arms close to your torso. Slowly lower your arms to the floor as low, as only you can. When you feel the muscle stretch, stop and lock your arms. This will be your starting position.
Exhaling, slowly curl the weights up contracting the biceps as you simultaneously rotate your wrists so that the palms face up at the end of the movement. Hold the upper arm (from elbow to shoulder) stationary. Only the forearms should move. Continue curling the weight until your biceps are fully contracted. Make a brief pause as you squeeze your muscles.
Inhaling, return the dumbbells back to the starting position very slowly.