The infraspinatus (L. infra, below ; spinus, spine [of scapula]) is a thick rotator cuff muscle covering the majority of the posterior surface of the shoulder blade below the scapular spine.
It is a prime mover in shoulder external rotation and plays important roles in shoulder stability. Most notably, it prevents excessive anterior and posterior migration of the humeral head.
The infraspinatus is very similar to the teres minor, in terms of function and location. They can be hard to tell apart due to their proximity and similar fiber direction, and are sometimes actually fused together.
Classified as a scapulohumeral (intrinsic shoulder) muscle, the infraspinatus is situated medial to the rhomboids, inferior to the supraspinatus and superior to the teres minor.
The medial portion of the muscle is visible from the surface of the physique, while the rest of it lies deep to the posterior deltoid.
The infraspinatus arises from the infraspinous fossa, passes over the humeral head and inserts on the greater tubercle of the humerus.
The fibers run obliquely between multiple tendinous septa, forming a multipennate muscle architecture.
Middle facet of the greater tubercle of the humerus
Shoulder external rotation
Shoulder horizontal abduction
Anterior shoulder stability
Posterior shoulder stability
Subscapular nerve (C4-C6)
Note #1: The table below only includes exercises that train the infraspinatus directly by focusing on its main of external rotation. Other exercises that train the infraspinatus indirectly include many posterior deltoid exercises and some Olympic-style lifts (i.e. all clean, snatch and pull variations).
Note #2: The word “upright” in the context of an “upright shoulder external rotation” exercise, refers to the upper arm being abducted to 90° (i.e. arm is up and out to the side, parallel to the floor).
Inhibited/Excessively Lengthened Infraspinatus: The infraspinatus tends to become inhibited and excessively lengthened in those with upper crossed syndrome (UCS). The shoulder internal rotation associated with UCS facilitates the internal rotators, which in turn reciprocally inhibit and stretch out the infraspinatus and other external rotators. Often, this chronically internally rotated position is brought on by: overuse of the internal rotators due to poor postural habits (i.e. hunching over, lots of sitting, using on a computer, etc.); a disproportionate focus on push and vertical pull exercises relative to horizontal pull exercises, and exercises involving internal rotation rather than external rotation.
Overactive/Short Infraspinatus: An overactive and short infraspinatus is less common a weak and lengthened one. However, overactivity/shortening of the muscle is prevalent among overhead throwing athletes (e.g. pitchers, quarterbacks), who are constantly going into external rotation due to the nature of their sport. This can cause overuse of the infraspinatus, making it and the other external rotators overactive and short. This, in turn, can reciprocally inhibit the subscapularis, leading to poor internal rotator strength and range of motion. Overuse beyond a certain point can lead to injuries, such as a infraspinatus tear.
Weakness from Infraspinatus Tear: The infraspinatus is the second most commonly torn rotator cuff muscle (supraspinatus tears are most common). Overuse of the infraspinatus can eventually result in a tear, since the muscle is continually enduring microtrauma. Thus, it’s more likely to tear under intense exertion. However, a tear can also be the result of damage from subacromial impingement. In this case, the supraspinatus tears first since it is first to be impinged. But eventually, the tear can expand to the infraspinatus.
If your infraspinatus is inhibited and excessively lengthened, consider the following:
As mentioned earlier, this problem may be a symptom of upper crossed syndrome. If this is the case, you need to address that for a complete solution. Read how to fix upper crossed syndrome (article coming soon).
If your infraspinatus is overactive and short (especially if you’re an overhead throwing athlete), consider the following:
Release and stretch the infraspinatus, teres minor and rear deltoid. Do this on a daily basis, including before exercises involving an internally rotated position (i.e. most upper body exercises; anything from DB internal rotations to bench to rows to pull ups). This will help improve internal rotator muscle activation and range of motion.
Increase training volume on the subscapularis exercises. The larger internal rotator muscles – such as the pec major, lats and front delt – may not actually need any additional training (in fact, they may be overactive/short and synergistically inhibiting the subscap).
Try to avoid exercises involving extending the arm behind the torso (e.g. dips) and overhead exercises (e.g. overhead press), especially if you are an overhead/throwing athlete. If you refuse to avoid these exercises, at least minimize training volume use low training intensity when doing them.
If you have excessive kyphosis, do thoracic mobility exercises to improve thoracic extension and thoracic rotation. This should reduce your kyphotic curvature and allow your scapulae to sit properly against the ribcage. Not only can this increase shoulder external rotation range of motion, but it can also improve increase shoulder internal rotation range of motion, which overhead throwers often lack (see this article).
The correct approach for overhead throwing athletes ultimately depends on a number of individual factors. For more detailed information on this, I recommend reading this, this and this to start with.
For general infraspinatus training guidelines and exercise technique tips, see below:
It’s easy to accidentally train the wrong muscles when doing certain infraspinatus exercises. When starting out, avoid the technically difficult exercises in favor of easier ones:
Easier: Any supported upright shoulder external rotation variation (90° abduction) or any dumbbell lying shoulder external rotation variation (0° shoulder abduction). Choose just one or two of these when starting out.
Harder: Any non-supported upright shoulder external rotation variation (90° abduction) and any cable shoulder external rotation variation (0° shoulder abduction). Don’t do these until you’ve learned how to activate the infraspinatus properly and have strengthened it noticeably with the easier exercises.
Use light weight for medium to high reps (8-15+) on direct infraspinatus exercises. Never go to failure. After all, the infraspinatus is a small muscle, and part of a delicate structure. Using more weight than you can reasonably handle is ineffective at best, and dangerous at worst.
Do 2-4 sets of infraspinatus exercises, 1-3 times per week. This does not include any sets you may do to warm up before upper body training workouts (see next bullet point).
Do a couple very light sets of any one infraspinatus exercise before workouts involving compound upper body exercises. It’s essential to avoid fatigue on these sets. You should use even lighter weight than on your normal working sets (see previous bullet point).
On any dumbbell lying shoulder external rotation variation, place a small rolled-up towel between your elbow and torso. This improves your form by keeping your upper arm in the correct position.