Shoulder Biomechanics
Our shoulders have greater mobility than any other joint in our body due to their complex anatomic structure. The shoulder girdle is made up of three bones including the proximal humerus, scapula and clavicle. There are four articular surfaces including the glenohumeral, sternoclavicular
The main articulation happens at the glenohumeral joint which is housed within a capsule and surrounded by muscles and ligaments. One key to the shoulder’s incredible mobility is the glenoid’s shallow depth. There is limited contact between the humeral head and glenoid or socket. Only about 25% of the humeral head makes any contact. For climbers this is a double edge sword. We are rewarded with amazing mobility at the cost of compromised structure.
Stability is supplemented by the fibrocartilaginous ring called the labrum which is attached to the outer rim of the glenoid. The shoulder joint relies on extrinsic or outside support from a handful of muscles and ligaments. Supporting ligaments include the superior, middle, and inferior glenohumeral ligaments. For dynamic activity the shoulder relies on support from the rotator cuff which is composed of four muscles including the supraspinatus, infraspinatus, teres minor, and subscapularis.
The rotator cuffs main function is to hold the humeral head within the glenoid. Most of us are familiar with the rotator cuff as shoulder discomfort is usually a result of acute or chronic injury to it. Often the supraspinatus (muscle or tendon) is damaged. The supraspinatus is susceptible because it passes through a narrow space between the humeral head and acromion process and when the shoulder is abducted impingement can occur. Furthermore repeated abduction with impingement can cause repetitive use injury to the muscle or tendon and even eventual ischemia (or lack of blood flow) to structures. Many of the motions required to rock climb put our shoulders at risk of acute and chronic shoulder injury.
Common Shoulder Injuries
Common Shoulder Injuries: Although the supraspinatus is vulnerable there are many other common sources of shoulder pain and discomfort. This is a limited list of some of the more common shoulder ailments. It is by no means comprehensive.
Rotator Cuff Tears (RCT): In general individuals with RCTs will report trouble with overhead activity, be unable to hold the affected extremity in an elevated position and may report pain that awakes them from sleep. In other folks the tear (lesion) may be asymptomatic. As we learned above 4 muscles make up the rotator cuff. The supraspinatus is the most common damaged and torn. RCTs are not a good injury to sit on as progression of the tear can cause atrophy of the rotator cuff and make repair extremely difficult. In young healthy athletes an orthopedist should evaluate a full tear as soon as possible for the best chances of a favorable outcome, (i.e. eventual return to climbing). With RCTs your provider should also rule out subacromial spurring and calcified tendinopathy.
Multidirectional Instability of the Shoulder (MDI): Arises from shoulder joint laxity, sometimes congenital or developed slowly over time. Often individuals have a history of overhead sports that repetitively strain and stretch the glenohumeral joint. Extreme motion leads to ligaments being stretched, micro tears of the labrum and rotator cuff and potentially dislocation or subluxation.
Glenohumeral Osteoarthritis: Results from damage to the cartilage that covers the bones of the glenohumeral joint. Bone on bone contact leads to bone spurs of (Osteophytes) and compromises smooth articulation and leads to eventual reduced motion.
Impingement Syndrome: Tendons of the rotator cuff and subacromial bursa are pinched in the narrow space beneath the acromion leading to inflammation and swelling. Symptoms are worse with the affected arm raised. As we get older arthritis, bone spurs and calcifications can make the impingement worse.
Labral Tears: Abnormal movement of the humerus (fall, blow, and crash), repetitive trauma of the greater tuberosity, rotator cuff on the posterior labrum can cause soft tissue pinching or impingement as a result of repetitive overhead activity. One common labral injury is called a Superior Labral Anterior to Posterior Tear or SLAP tear. As the name suggest it’s a labral tear on the top of the labrum compromising the attachment of the biceps tendon to the glenoid and can even lead to biceps rupture.
Shoulder Bursitis: Most joints have fluid filled pads that help “cushion” the joint. The pads or bursae can become inflamed. Acromioclavicular Joint Injuries: Usually associated with sport injuries, direct trauma and occur often in young adults. Typically the result of a fall with an upper extremity in the adducted position which pushes the acromion medially and inferiorly from the clavicle. Can have accompanying neurovascular injury, sternoclavicular dislocation and brachial plexus injury.
Clavicle Fractures: Usually results from a fall onto the top of the shoulder. Clavicle protects the great vessels, brachial plexus and lungs so can have serious complications. Be sure to assess neurovascular status of the affected limb.
Glenohumeral Dislocation: Associated with high impact trauma. Usually the individual will hold the affected arm in the contra lateral hand, will have pain with motion, and a palpable humeral head in the axilla or a dimple inferior to the acromion laterally. Most dislocations are anterior (90%) from abduction, extension and external rotations forces. Posterior dislocations often happen as a result of a fall from a seizure or electric shock. In both cases be sure to assess for nerve injury.
Proximal Humerus Fractures: Often seen in the elderly with low energy falls. When seen in younger individuals usually the result of a motor vehicle crash or sports injury.
Frozen Shoulder (adhesive Capsulitis): Most folks will complain of stiffness and pain. Can have a gradual onset and spontaneous resolution. Treatment usually includes range of motion exercise and sometimes corticosteroid joint injections. Arthroscopy is rarely used.
Shoulders and Rock Climbing
I always thought we were built for climbing. Our close animal ancestors the great apes, (chimpanzees) were well adapted tree climbers and in my mind this meant humans must be meant to climb as well.
It turns out the shoulder design of our tree dwelling ancestors and homo sapiens are a little different. While chimpanzees were hanging in trees our hominoid kin walking the earth needed a shoulder layout that would allow them to hunt, throw spears and use tools. I am not sure that natural selection had sport climbing or bouldering in mind as our shoulders evolved. Especially with modern climber’s obsessions with increasing steep climbs and boulder problems our shoulders are under tremendous and repetitive workloads. Sport climbing specifically is harsh on the shoulders as we often attempt to hang on, pivoting our body around a locked off shoulder. Often for a little longer then we should, putting the fatigued joint at risk of injury as our form dwindles and stabilizing structures get tired. Along with the typical climber hunch back posture and compromised shoulder mechanics that follow climbers are primed for shoulder injury as instability insidiously develops from endless lock off, gastons and hang dogging on our favorite rock climbs.
Don’t always climb overhangs, vary things up. Sometimes throwing in a day of slab climbing of crack climbing in to give your shoulders a little rest.
Stabilize antagonist muscles. A big back and underdeveloped chest muscles is a recipe for disaster. Throw in some “push” type exercise.
Give your shoulders some rest, along with the rest of your body from time to time.
Don’t always climb to full fatigue especially when climbing at your limit. In many sports as intensity increases so do injuries.
Focus on smooth movement in everything you do. Have light weight days at the gym where you focus on form. Precision of movement is everything on a hard climb. If you train sloppy you will climb sloppy and expose your shoulder to injurious forces.
Spend some time with a movement specialist, or guru of form. Poor movement over and over will lead to injury. Abolish old unhealthy movement patterns that lead to injury.
Diversify your training. Take the dog for a Nordic ski, chop wood, go for a skate ski or to a kick boxing class.
Train smart. Obsessive training has diminishing returns and will lead to injury. Find a mentor or coach.
Climbing hard more than a few days a week will eventually lead to injury. Devote a day to active rest and mental training. Work on your positive self-talk.
Avoid obsessive stretching. Stretching is important but don’t go nuts.
Commit to technique. Keep your feet on the wall. Professional athletes letting their feet rip may look good in a picture but will only get you hurt.
Using large muscles puts less strain on the small ones. Train to push through your legs, not just pull with your arms.
Most of us do a good job training our Deltoids in the gym but many of us lack specific training for the all-important rotator cuff. Deltoid training without rotator cuff exercise, specifically external rotations movements, can still leave our shoulders vulnerable to injury while climbing.
All trainers and exercise efficienatos have their favorite external shoulder rotations exercise. Below is a list just to get you started on the path to more stable shoulders. Remember these exercises need to be done with light weight and more of a focus on form then repetition.
I sprinkle rotator cuff exercises into my work out every couple days. Again light weight. Perfect from!
Standing or Lying Dumbbell External Rotation
Rubber Band External Rotation
Scapular Plan Elevation
Cuban press
Face Pull
External Rotation at 90 Degrees Abduction
Front Lateral Raise/Cross Body raise/Y
Scapular Wall Slides
Plank Plus
Lat pull down without bending elbows.
References
Chang CY, Torriani M, Huang AJ. (2016). Rock climbing injuries: acute and chronic repetitive trauma. Curr Probl in Diagn Radiol. 45(3)205-14.
Modarresi S, Motamedi D, Jude CM. (2011). Superior labral anteroposterior lesions of the shoulder: part 1, anatomy and anatomic variants. Am J Roentgen. 197(3):596–603.
Kibler WB. (2006). Scapular involvement in impingement: signs and symptoms. Instr Course Lect. 55:35–43.
Roach NT, Venkadesan M, Rainbow MJ, Lieberman DE. (2013). Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo. Nature. 498(7455):483-6.
Quillen DM, Wuchner M, Hatch RL. (2004). Acute shoulder injuries. Am Fam Physician. 70(10).
Reinold MM, Escamilla RF, Wilk KE. (2009). Current concepts in the scientific and clinical rationale behind exercises for glenohumeral and scapulothoracic musculature. J Orthop Sports Phys Ther, 39:105.
Martinoli C, Bianchi S, Prato N, et al. (2003). US of the shoulder: non-rotator cuff disorders. Radiographics, 23:381.
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