What Is Happening During a Biceps Curl?

A biceps curl is a basic weightlifting exercise that helps to sculpt the major muscle in the upper front portion of your arm. But there’s more to the curl than flexing your biceps: A biceps curl involves accessory muscles, mechanics and force used to complete the exercise. Before starting your weight-training plan, check with your physician to ensure you do not have any injuries or medical conditions that could keep you from safely exercising.

A biceps curl often is performed with dumbbells, a weighted bar or resistance bands to increase the workload. Take one weight in each hand, turn your palms in toward your hips and stand with your feet shoulder-width apart. Slowly lift your hands or one hand in toward your chest, twisting the weight as you lift it to bring your palm facing your chest. You should feel your biceps working. Slowly lower the weight to return to your starting position. Repeat until you have completed 10 to 12 repetitions on each arm. Rest and repeat for two additional sets.

The biceps curl is a pulling exercise. This means lifting the weight toward your shoulder and chest pulls on the biceps muscle, which makes it stronger with time. When you lift your arm toward your chest, you are initiating arm flexion. Holding weights for resistance also increases the pulling force your bicep must complete, which can help your muscles grow stronger, faster.

While the biceps muscle is working during a curl, other muscles are working in opposition. Your triceps on the back of your upper arm are a biceps muscle antagonist and are longest when you complete the exercise and your arm is once again straight.

Your biceps and triceps are not the only muscles moving and working during the biceps curl. Other muscles act as synergists that help your biceps lift the weight. These include the brachialis and brachioradialis muscles in the front of the arm. Other muscles act as stabilizers, which means they keep your arm from shaking and control the muscle as you lift the weights up and down. Examples of stabilizer muscles include the front of your shoulders, upper and middle trapezius, wrist flexors and levator scapulae in your shoulder blades.