1,000 Health and Fitness Tips #0016: The Incline Dumbbell Curl
One Great Exercise For Biceps Growth--Plus An Interesting Caveat
Though the bicep is most well-known for flexing the elbow, it also contributes to shoulder flexion (i.e. the motion of lifting your upper arm over your head).
For this reason, putting your upper arm into shoulder extension, or behind your body, increases the stretch on your bicep.
Since some research suggests that increasing the stretch on the target muscle during your repetitions leads to greater muscle growth (I, II, III, IV, V, VI, VII), I think this makes bicep exercises that extend your shoulder a great option for growing your biceps.
One such example is the seated incline dumbbell curl where you tilt the bench backwards a few notches so that your shoulders are more extended at the bottom of the curl.
Notably, the more you tilt the bench back, the more stretched the bicep will be at the part of the curl where your forearm is parallel to the floor—and parallel to the direction of gravity as a result. This is useful to recognize because this is the part of the movement where the force you are resisting is greatest.
Also worth noting is that I usually only complete the first half of the curl because–again due to the relationship of the angle of your arm/bicep relative to the direction of gravity–there is less and less tension on the bicep as you move past the part of the curl where your forearm is parallel with the floor.
CAVEAT: One notable exception to the idea that an exercise that induces a greater stretch on the target muscle is superior to an exercise that induces less of a stretch is the preacher curl. Though the preacher curl—where the shoulder is in flexion— stretches the long head of the bicep less than an incline curl, I am aware of one study that showed greater biceps growth in the preacher curl vs. the incline dumbbell curl. (VIII) One explanation for this is that the biceps are under more tension in the stretched portion of the preacher curl (i.e. when the elbow is straight) than they are in the stretched portion of an incline curl—Dr. Milo Wolf, an expert in how range-of-motion impacts muscle growth, briefly explains this concept in this video about the preacher curl. Nonetheless, I still think that the incline curl is a great option for growing the biceps, and likely a better option than a normal curl. Notably, I think the preacher curl is also a great option for biceps growth—potentially a superior option to the incline dumbbell curl.