Biomechanics of the Pull-Up
Biomechanics of the Pull-Up:
Pull-ups are a core training exercise for most climbers, and are used in many other sports. The grip position used in a pull-up has a significant impact on which muscles are being used and therefore being strengthened. Understanding the anatomy and biomechanics of the different variations of the pull-up can help you more specifically target your strength training for specific muscle groups and movement patterns. This is particularly important for athletes with shoulder and/or elbow pain to ensure you are loading the different structures of the arm and shoulder appropriately.
The three main grip variations that will be covered in this blog post are the standard grip, reverse grip, and wide grip pull-ups. In general, the muscle activation for each of these pull-up variations follows the same basic pattern:
Initial pull: Inferior trapezius, pectoralis major, infraspinatus, brachialis
Mid-range of the pull-up: Latissimus dorsi, teres major, biceps brachii
End-range/top of pull-up: Subscapularis, triceps brachii
During the eccentric or lowering phase of the movement, the deltoid muscle elevates the head of the humerus within the acromioclavicular joint of the shoulder. This is notable because this motion increases abrasive effects and physiological impingement of the tendons of the shoulder joint which could play a role in shoulder pain during the pull-up, especially when fatigue is a factor.
While the biomechanics is similar across the different pull-up variations, each type has subtle differences and biases different muscles making it unique and best suited for different situations and training goals.
Standard Grip Pull-Ups:
The standard grip pull-up utilizes a highly functional shoulder and hand position for climbing and has a very balanced distribution of force among muscle groups when performed correctly making it an effective and safe default exercise for climbers.
From the dead hang position, the brachialis muscle helps to initiate elbow flexion while the lower traps will stabilize the scapula. The lats are very active during the pull-up and act to pull the humerus down towards the body throughout the entire movement.
In the mid-range of the pull-up, the biceps become more active to increase elbow flexion. While the rhomboid major and middle traps take over the role of scapular stabilization. Two of our shoulder internal rotators (teres major and subscapularis) help to set the body position so that we can pull our chest towards the bar and the infraspinatus (an external rotator) balances out these forces.
At the top phase of the pull-up since our elbows are fully flexed, the biceps have a diminished role, and instead, the triceps help to push our chin up and over the bar.
The standard pull-up position places a significant load on the brachialis and biceps brachii so if you’ve had an injury to either of these regions you may need to reduce the volume or intensity at which you perform this exercise.
Reverse Grip Pull-Ups (Chin-Ups):
The reverse grip pull-up (aka the chin-up) is performed with the forearms supinated (palms facing towards you). The movement is initiated by the brachialis and biceps and pec major (an internal rotator) plays an active part in balancing the high degree of shoulder external rotation that occurs in this position as well as assisting in with shoulder extension as we pull our body up towards the bar.
In the middle range of this exercise, the supraspinatus stabilizes the shoulder joint, and the infraspinatus keeps the shoulder in a safe adducted position.
At the end of the movement activation of the deltoids increases to add further stability and the triceps are activated for the final push to the top of the range of movement.
The reverse grip pull-up places the shoulder in extreme external rotation demanding greater activation of the rotator cuff so it may not be the ideal choice for someone with a history of shoulder instability, supraspinatus issues, or an injury to the long head of biceps.
Wide Grip Pull-Ups:
Again, beginning in the dead hang position, but this time with the hands much wider than shoulder width, the brachialis and biceps help to initiate the pull however because our arms are placed at a mechanically disadvantaged position in the wide grip pull-up, we will be relying much more heavily on our lats to pull us up rather than elbow flexion. Our traps and rhomboids will also have increased stabilization demands since our scapulae are set much further apart.
Once in the middle range of this pull-up, the rhomboid major will have an increased role as it continues drawing our shoulder blades together.
Like the other pull-up variations, at the very end of the motion, the triceps will activate to assist the lats in pulling your chest up to the bar.
The wide grip position reduces subacromial space which could increase the risk of physiological shoulder impingement, however, this risk can be reduced by paying attention to your form. The most common compensations that may occur during this exercise are elevation (rising) of the shoulder blades, shoulder protraction (rolling forwards), and significant asymmetry in movement or tempo between sides. If you notice any of these poor mechanics occurring in your wide grip pull-ups try reducing the load when practicing this movement by using a band, pulley system, or spot for assistance and focus on proper form.
Key Takeaways:
The grip position of a pull-up changes the activation of and load on the various muscles and tendons of the upper arm and back and exercise selection should be appropriate to train specific muscle groups and rehabilitate specific injuries
The standard grip pull-up biases the muscles of the anterior elbow (biceps and brachialis) and may be problematic for individuals with anterior elbow or anterior shoulder pain
The wide grip pull-up biases the muscles of the upper back (lats and rhomboids) and when done with poor form may increase impingement of the shoulder structures
The reverse grip pull-up biases the rotator cuff and deltoid and may be problematic for those with rotator cuff tendon pathologies
Our physiotherapists at Elios Health are keen to help you develop the strengths and stability you need for your goals. Visit us on Main Street in Vancouver, at the intersection of King Edward and Main Streets. We offer RMT massage, manual physiotherapy, naturopathic medicine, acupuncture, and nutritional counselling.
Original Article by Rachel Rubin Sarganis
Photo by Vitolda Klein