The short head of the biceps is the shorter and medial of the two muscle parts that form the biceps in the anterior part of the upper arm. Like the long head, the short head is a flexor of the elbow joint and supinator of the forearm. In addition, at the shoulder joint, the short head aids in the adduction of the humerus.
As with any particular muscle group, complete isolation of the short head is impossible. Nevertheless, some exercises provide better engagement of the short head to achieve that prominent upper arm bulge. These exercises include wide-grip EZ bar curls, wide-grip spider curls, and Preacher wide-grip cable bar curls, among others.
During elbow flexion, like a biceps pose, the long head gives the biceps the height or the “peak” as bodybuilders commonly call it. However, the short head is responsible for the upper arm's width and thickness, creating the biceps' round and bulging look.
The biceps, also known by its Latin name as biceps brachii (meaning "two-headed muscle of the arm"), is a large, thick muscle on the ventral portion of the arm. This muscle group is composed of a short and long head, each with its own origin from the scapula.
The short head originates from the apex of the coracoid process, and the long head from the supraglenoid tubercle of the scapula. However, they converge as one muscle belly along the upper arm before tapering and inserting into the same area at the anterior aspect of the elbow.
The main functions of these two heads of the biceps are to move the forearm towards your body (elbow flexion) and rotate the forearm outward (supination).
The biceps primarily is a strong forearm supinator. A study by Jarrett, et al. states "In the neutral and pronated forearm, the short head is the relatively more efficient supinator. The long head becomes more efficient at supination in the supinated forearm."
The biceps are weak elbow flexors. Contrary to popular belief, the biceps is not the most powerful muscle in the upper arm responsible for lifting or lowering the forearm, especially in the absence of supination.
The biceps' most essential function during elbow flexion is stabilizing and supporting the stronger brachialis muscle, which lies under the biceps. However, with supination and flexion, the brachialis' mechanical momentum is at a disadvantage over the bicep muscles.
A study by Moon, et al. has demonstrated that the biceps exhibited the most significant resultant force at a shoulder flexion angle of 75°. Therefore, they concluded that when performing the biceps curl exercise using a cable machine, one should flex the shoulder at a 75° angle to maximize the movement's focus on the biceps.
These results are helpful from the perspective of exercise design as they highlight the differences in the biceps muscle activation with a postural change of the shoulder.
An exercise to take advantage of the effects of shoulder flexion on biceps' muscle activation could be designed around an adjustable angle preacher bench in combination with a wide-grip cable bar to activate the short head of the biceps better.
The EZ bar is an excellent option for lifting heavier weights when used with a slightly-supinated wide grip. It puts less strain on the wrist than a supinated grip on a straight bar. In addition, with the wide grip on the bar, a small degree of rotation on the shoulder emphasizes the short head better.
In a study by Marcolin et al., they examined differences in muscle activation of the biceps and brachioradialis while performing three forearm variants of curls (dumbbell, EZ bar, and straight bar) in resistance-trained individuals. They found differences in activation between all three exercises, with the EZ bar producing the most significant muscle activation on the biceps even though the glenohumeral joint angle was unchanged (0 degrees) between the three forearm variants.
To perform this exercise, stand with feet shoulder-width apart while holding an EZ bar with a slightly supinated wide grip. Let the bar sit on the thighs and position the elbows on the sides of the body. Lift the bar towards the shoulder, hold for a second, and squeeze the biceps. Lower the bar slowly to the thighs and repeat until a set is completed.
Another great exercise to target the short head biceps and one that also takes advantage of the effects of shoulder flexion for greater recruitment of the biceps resulting in a more significant resultant force is the wide-grip spider curls.
Set the incline bench at a 45° angle. Lie face-down on the inclined bench with the chest and stomach pressed against the bench, and the head placed higher than the top of the backrest. Hold the bar using a wide supinated grip, slightly more than shoulder width. Slowly curl the bar up, pause at the top of the movement for a second or two, and squeeze the biceps. Then slowly lower the bar at the starting position and repeat the action.
Anyone can add a routine or two from this exercise by switching the barbell for dumbbells or an EZ bar. Use a wide, slightly supinated grip for the EZ bar and do the same movement above. However, use an underhand grip for dumbbells and add supination at the top of the action.
Cable machines provide constant tension throughout the movement of any exercise resulting in more significant strength gains and muscle growth as it fatigues muscles faster and better compared to using free weights.
An adjustable angle preacher bench would be great for this exercise to benefit from greater biceps activation at 75° shoulder flexion.
Adjust the preacher bench so that the shoulder flexion would be at a 75° angle. Attach a wide-grip cable bar to the cable machine. With a wide supinated grip, slowly pull the bar towards the shoulder, hold for a second and squeeze the biceps. Then, slowly reverse the action to the starting point and repeat the movement until a set is completed.
If access to an adjustable angle preacher bench is not an option, a flat bench can also be utilized as an alternative. A flat bench wide-grip cable bar curl can be performed by positioning the bench perpendicularly to the cable machine. Using the top pulley, attach a wide grip cable bar.
Sit on the bench facing the machine, grab the cable bar with a wide supinated grip and lie with the back firmly positioned on the bench. If need be, adjust the distance of the bench from the machine so that the shoulder is at 75° flexion.
Start pulling the cable towards the shoulder while maintaining the elbow position. Hold and squeeze the biceps, then extend the elbow back to the starting position and repeat for the desired number of repetitions to complete a set.
The standard dumbbell concentration curls position the back of the elbow to the inner side of the thighs and lift the forearm with an underhand grip towards the body's midline.
However, this variation targets the short head better due to grip position, a greater degree of shoulder flexion, outward rotation of the shoulder, the direction of the lift, and supination at the top of the motion. But as a word of caution, do not overdo outward shoulder rotation (lateral rotation) to prevent discomfort and joint flexibility issues.
Sit on a bench with feet firmly planted on the ground more than shoulder-width apart. Grab a dumbbell with the right hand using a slightly supinated grip. With a degree of outward shoulder rotation, lean forward and let the right arm hang almost perpendicular to the floor until the outer side of the elbow touches the inner side of the right knee.
The dumbbell should rest at the bottom straight to the body's midline and the forearm's position should be that when lifted is going towards the side of the shoulder. Place the left elbow on top of the left thigh and the left palm firmly planted on the right thigh directly behind the right elbow to provide better stability for the right arm doing the lift.
In comparison to the standard dumbbell concentration curls, this position eliminates any possibility of using swaying motions to gain lifting momentum. Lift the right forearm towards the side of the shoulder while slowly supinating through the motion. At the top of the movement, the pinky should rest higher than the thumb.
Hold for a second and squeeze the biceps. Then, reverse the action to the starting point and repeat. Do the same exercise and number of repetitions for the other arm.
Choosing the most effective isolation exercises for the short head and proper form execution produces faster results and more significant muscle gains. However, isolation exercises are not the be-all and end-all of a particular muscle group's development and prominent-looking physical appearance. The growth of surrounding muscle groups also helps accentuate the short head biceps.
So, in this case, don't forget the brachialis. Giving the brachialis a good exercise, like pronated grip chin-ups, can be an excellent way to add volume to those bulging biceps. Focusing on this muscle group increases the peak and girth of the upper arm as it pushes up the short and long head. Utilize various exercises to change routines and shock those muscles even more.
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