Goals of this article
The goal of this article will be to cover the basic anatomy of the bicep muscle. The biceps is the largest muscle group in the upper arm. It also has multiple attachment points and is fairly complicated since it acts at two joint (the shoulder and the elbow). Knowing the anatomy will help you better target this muscle to increase power output and produce large, powerful looking arms.
This article marks the first in a series that will focus on body weight and barbell only exercises that target the biceps. The biceps are key part of the physique and instantly noticeable. Therefore they are a priority for many starting their workout journey.
With that said, not everyone has access to extensive gym equipment. Therefore, my goal here is to give you the tools to train with minimal equipment for the best possible results.
The figure above highlights the position of the biceps with each of the two heads shown and labelled. The long head of the biceps is located on the outside. And the short head on the inside of the upper arm.
Muscles of the upper arm
The forward-facing part of the upper arm (also known as the anterior aspect) contains three muscles. These are the: coracobrachialis, the brachialis, and the biceps brachii. The Biceps is the largest of these 3. The brachialis, when well developed pushes up on the biceps from underneath and can help accentuate the biceps peak.
The coracobrachialis, also forms part of the upper arm but only crosses the shoulder joint. Its major role is in shoulder joint flexion, adduction of the arm, and inward rotation. We will focus to a greater extent on the other two muscles here.
Attachments of the biceps
The bicep brachii has 2 heads. Each head starts from its own “origin” and crosses the shoulder joint to connect to the main belly of the biceps muscle (see figure below). Both heads of the bicep attach to the scapula. The short head attaches to the coracoid process of the scapula. The long head attaches just above the humerus to the supraglenoid tubercle (a bony ridge on the scapula).
The humerus and the scapula are the two bones which make up the shoulder joint. The heads of the biceps cross the shoulder joint to attach to the scapula. In about 10% of the population, a third head also exits next to the short head!
In the figure above, the insertion point of the biceps tendon is shown on the radius. The lateral (outside facing bone) in the forearm. The radius is on the same side as the thumb when the palms are facing forward. For a small but significant minority, there are two tendons next to each other that attach to the radius.
The muscle belly then attaches through the biceps tendon to the radius (a bone in the forearm). The attachment point is called the radial tuberosity (a rough attachment point on a bone). For the majority of the population there is one tendon.
Function of the muscles
Knowing these insertion points sets us up nicely for understanding the function of the biceps. Muscles cause movements by shortening and bringing closer together the two bones that they link on each end.
Movements at the elbow joint
The biceps causes flexion at the elbow joint and supination of the radioulnar joint. The biceps also crosses the shoulder, so it plays a role at this joint. It assists with flexion of the shoulder joint (done primarily through the activity of the anterior deltoid and the upper pectoralis major muscle groups). Assist is code for dynamic stability. This means that the bicep stabilizes the joint when these movements are done. This is done more so early in the range of motion (about the first 30 degrees of shoulder joint flexion).
Studies have shown that the long head of the biceps is key for shoulder stability.
Appearance of the muscle
The outward appearance of the muscle is largely due to genetics. Those with shorter stature (and shorter arms) will be able to achieve greater muscle peak. While those with longer arms will have lesser peaks but fuller looking arms. The long head makes up the peak of the biceps and the short head makes the width.
Training the biceps in a targeted manner will allow you to achieve the desired, so without further ado, lets get into some key ideas you can apply to your bicep workouts.
Bicep workout tips
The main function of the biceps is to cause flexion at the elbow joint. To do this, the biceps shortens concentrically while producing force. Of course, the alternative to this is an eccentric contraction, where the biceps produces force while lengthening.
Recently, some have provided evidence that this type of contraction can cause tissue damage and subsequent recovery leading to larger muscles.
Here we will provide general recommendations to increase biceps mass. These can be applied while varying the weight, number of reps, and total volume as desired to fit into your weekly exercise routine.
1 – Altering your grip to target each head of the muscle
Narrowing your grip when doing bar curls will enforce long head activation. In contrast, wider grip will enhance short head activation.
Bar curls shown below with narrow grip:
The long head will be preferentially activated when using a narrow grip. The long head is on the outside of the arm and can be targeted to enhance the appearance of the bicep peak.
Wider grip is shown here:
Short head is preferentially recruited when using a wider grip in performing bar curls. Focusing on the short head will help increase the width of the muscle. A well developed short head of the biceps gives the appearance of a fuller looking muscle in general.
2 – Elbow placement during the curls is key
Keeping your elbows slightly in front of your body during the curls will maximize activation of the biceps short head. The bar curl is shown from the side view going from the starting to the final position:
Keeping your elbows in line with your body will maximize activation of the long head. Once again, the exercise is shown from the starting to the final position below, note the alignment of the upper arm with the body:
3 – Range of motion
Studies have shown that the short head is more active in the latter part of the curl. In contrast, the long head is more active early in the range of motion.
Therefore, the activity can be adjusted to target each. By carrying out partial curls as shown below, either the short, or the long head can be selectively strengthened. You can use partial reps to finish your sets.
For example, you can complete a full set and complete it with 6-8 partial curls to target each head on different days or in separate sets.
Curling up to only 90 degrees will allow you to focus on the long head. These curls can be performed at the end of a set of full range of motion to selectively target the long head. Alternatively, the upper part of the range of motion can be performed at the end of a set to focus on the short head.
4 – The amount of supination
Both supination and pronation are movements that happen at the radio-ulnar joint, a fibrous joint made up of the radius and the ulna in the forearm. The range of motion in this joint is limited and the movement happens as the lower part of the radius flips over the ulna and back.
First let’s cover what supination is. As shown in the pictures below, supination is the palm forward facing position. Movement that makes the palm face backwards is termed pronation.
As shown by this study the amount of supination can variably activate heads of the biceps.
From a neutral or pronated position – the short head of the biceps is the more efficient supinator.
When the forarm is already supinated – the long head of the biceps is the more efficient supinator.
Therefore, performing curls from a neutral or pronated position (thumb facing forward) will target the short head. Performing curls with the dumbbell in your hand and staying in the supinated (palm facing up position) throughout the range of motion will target the long head of the biceps.
5 – Behind every great bicep there is a great brachialis
This muscle is located under the main muscle belly of the biceps and may be thought to be part of and the same thing. While the brachialist is anatomically distinct from the bicep, the location makes it a prime candidate for targeted exercises.
The brachialis originates at lower half of the anterior surface of the humerus and inserts on the ulnar tuberosity. Given that the brachialis only crosses the elbow joint and inserts onto the ulna, its only function is elbow joint flexion.
Strengthening the brachialis through hypertrophy can help create the appearance of fuller, more powerful looking biceps as well.
As shown by this paper flexing the arm with a neutral or pronated position in the forearms will minimize biceps involvement and stress the brachialis.
Performing reverse or hammer curls can be used to target the brachialis. Sets of these curls can be performed in addition to your normal routine throughout the week to target this muscle group.
This article has provided some detail on the anatomy of the biceps muscle group as well as brief summary on the brachialis and coracobrachialis which make up the upper arm. The next articles in this series will provide more specific details and exercises to help you train and enhance the appearance of your bicep muscle with minimal equipment.
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