I am currently carrying out a study that deals with this topic among other muscles also. It seems most research studies I review come from researchers that do not have much of a weight training or bodybuilding background which is unfortunate because when I look for evidence of something proven to scientifically work, oftentimes I do not find the procedures of the study to follow that of a typical bodybuilding workout, exercises, nutrtiion, supplementation, etc.Bascially I Mean we I can't relate how it can be applied to a bodybuilder's routine when they are performiong the study on someone who has little to know experience weight training. However, during some preliminary trials we were using EMG analysis on the outer long head, inner short head of the biceps, and the brachialis during a lot of different variations of curls. While both heads are active during any type of curl the, long head is most activated when the upper arm falls behind the plane of the body. Incline dumbbell curls (both with a supinated grip and neutral grip work the long head, Incline cable curls, and cable curls where you are facing away from the stack and the cable comes up between your legs, and single arm cable curls with a D-handle and a rope facing away form the rack work the biceps long head the most relative to the short head. Also, its not just the type of exercise but the way you do the exercise that counts. One example I found is the when performing both standing barbell curls the long head was deactivated somewhat when the person brought their elbows forward, but iof their elbows were kept by the side throughout the curl, the long head remained active. One other interesting point, during machine preacher curls, the long head was not extremely active during the begiinning of the curl but became active during the peak contracvtion part of the movement. The machine version has resistance form beginning to end unlike the barbell version. The key to activating the long head is to keep the long head biceps tendon in a somewhat stretched to stretched position so their is tension on the long head biceps. Bring the arm forward somewhat shortens the tendon which means the long head of the biceps cant produce tension until it shortens along with the short head until the long head tendon takes up the slack. Hope I didn't lose anyone.
