As a personal trainer in London I get a lot of clients asking me how they can get bigger chest and shoulder muscles. And I always tell them to make sure they guard against rotator cuff injuries. If you try to build the major muscles of the chest and shoulders without strengthening your rotator cuff, you’re asking for injury.
The four muscles of the rotator cuff originate in the scapula (shoulder blades) and insert into the upper region of the humerus (the bone of the upper arm). The rotator cuff muscles keep the head of the humerus stabilised in the ball and socket joint of the shoulder (the glenohumeral joint. They prevent the head (ball) of the humerus from grinding against the glenoid (socket) of the scapula, and also prevent dislocation of the shoulder joint by the larger muscles during movement. In short, the rotator cuff muscles stabilise the shoulder joint.
These are the four rotator cuff muscles:
The supraspinatus assists the deltoid in abduction of the arm (raising the arm out to the side) and prevents the humerus grinding up against the acromion process of the scapula.
This rotator cuff muscle assists external rotation of the shoulder, and resists posterior dislocation of the shoulder by pulling the humerus towards the glenoid fossa (socket).
3. Teres minor
The teres minor also assists external rotation in the same way as the infraspinatus does, except that the teres minor is a smaller thinner muscle with a much smaller point of origin than the infraspinatus.
This rotator cuff muscle enables medial (ie- internal) rotation of the arm, and stabilises the ball and socket joint. It’s the most important internal rotator of the upper arm.
Rotator cuff injuries
If you don’t specifically train these four muscles, they will be liable to tendon tears when you exercise the major muscles of the shoulder and chest. Around 75% of all shoulder pain is due to a partial or full tear of the supraspinatus.
Over-emphasis on chest training (such as heavy bench-pressing) can restrict the flexibility of the shoulder joint and weaken the rear delts/external rotators. This can be overcome by a more balanced training regime which pays equal attention to exercising the rear delt muscles and upper back muscles.
Other exercises in the gym which carry increased risk of rotator cuff injuries include tricep dips, standing barbell row, barbell shoulder press behind neck, lat pulldown behind neck (lat pulldown machine), and dumbell lateral raises which over-emphasise the ‘thumbs down’ rotation during the movement.
The subscapularis is vulnerable to injury among sports-people who perform a lot of throwing actions such as tennis (serve and smash), baseball, and javelin throwers.
Partial tears of the rotator cuff can heal themselves over time with a regime of ice compressions, rest, stretching, and rehab exercises. Full tears usually require surgery, followed by progressive rehab exercise.
Exercises for the rotator cuff
Using a light dumbbell (anything from 2kg to 5kg), perform a series of external rotations and internal rotations, one arm at a time. Keep the movements slow and smooth, and pay close attention to good form. Never jerk or force the movements. And keep the reps high, around 15. And a thorough stretching session after each workout will ensure that the muscles of the shoulder joint don’t get too tight.
Look out for exercise videos for the rotator cuff on ‘This week’s exercise’ page of Fitness4London.com.
Dominic Londesborough is a personal trainer in London with 11 years experience.