What's Causing Shoulder Pain in Overhead Athletes: Rotator Cuff Function + Scapular Control + Training Load

Shoulder pain is the most common complaint among overhead athletes — but pain alone doesn't tell you what's wrong or what to do about it. Three variables — rotator cuff function, scapular control, and training load — drive most of these injuries. Understanding how they interact is what separates effective treatment from guesswork.

The scope of the problem

Shoulder pain affects between 18% and 90% of overhead athletes depending on the sport and level of competition. In collegiate baseball, softball, swimming, and tennis, rotator cuff tendinopathy and subacromial impingement account for more than half of all shoulder injuries. In Major League Baseball, the shoulder is the most injured area in the entire body — particularly for pitchers.

These numbers are not surprising when you consider what overhead sports actually ask of the shoulder. A baseball pitch, tennis serve, or volleyball spike places the shoulder at extreme external rotation, then demands powerful eccentric braking as the arm decelerates. That sequence — explosive load followed by rapid deceleration — is where tissue damage accumulates over time.

The more important question is not how common shoulder pain is. It is why it develops, and which factors are actually changeable.

Factor 1: Rotator cuff function

The rotator cuff is a group of four muscles — supraspinatus, infraspinatus, teres minor, and subscapularis — that wrap around the ball of the shoulder joint. Their job is not primarily to move the arm. Their job is to compress the ball into the socket and keep it centered during motion.

When the rotator cuff is working correctly, the shoulder can absorb high loads efficiently. When it isn't — due to weakness, fatigue, or poor timing — the ball of the joint shifts subtly out of position during overhead movement. That small shift is enough to pinch soft tissue, increase stress on the tendons, and start a cycle of irritation that eventually becomes pain.

Research consistently identifies rotator cuff weakness as a primary modifiable risk factor for shoulder injuries in overhead athletes. Specifically, the ratio between external rotation (ER) and internal rotation (IR) strength matters. An ER/IR isometric strength ratio below 0.75 is the most prevalent risk factor for overuse shoulder injuries found in studies of overhead athletes — more prevalent than any single range of motion measure.

In practical terms: most overhead athletes have strong internal rotators from throwing, serving, and spiking. External rotators — the muscles that control deceleration — are almost always undertrained by comparison. That imbalance builds over an entire season.

Factor 2: Scapular control

The scapula is the foundation of the shoulder. Every overhead movement depends on the scapula rotating upward and tilting correctly to keep the socket in the right position. When that movement is off — a condition called scapular dyskinesis — the mechanics of the entire shoulder chain are compromised.

Scapular dyskinesis refers to abnormal or altered movement of the shoulder blade during arm elevation. It is found in a significant percentage of overhead athletes with shoulder pain, and is linked to rotator cuff tendon stress, impingement, and labral pathology. A 2025 study in young overhead athletes confirmed that scapular dyskinesis is directly associated with rotator cuff muscle weakness — the two conditions reinforce each other.

The mechanism is straightforward: if the scapula does not rotate properly, the space under the acromion narrows during arm elevation. Tendons get compressed in that narrowed space repeatedly over thousands of repetitions. At the same time, poor scapular positioning changes the length-tension relationship of the rotator cuff muscles, making them mechanically less effective at every point in the motion.

From a training standpoint, scapular control depends on the strength and timing of the serratus anterior, lower trapezius, and mid trapezius. These muscles are consistently underloaded in standard upper-body training programs. Athletes often come in with well-developed deltoids and pectorals, and visibly weak posterior scapular stabilizers.

There is also a kinetic chain component that is easy to overlook. Research shows that a 20% reduction in trunk energy production increases the load on the shoulder by up to 34% to maintain the same throwing or striking velocity. Thoracic mobility, hip rotation, and core stability all feed into how much the shoulder has to compensate. Shoulder pain in an overhead athlete is almost never a shoulder-only problem.

Factor 3: Training load

Training load — the total volume and intensity of overhead work across a given period — is the third major driver of shoulder injuries. It is also the most frequently mismanaged.

Shoulder injuries in overhead athletes tend to cluster around two patterns. The first is a rapid spike in workload: a preseason ramp-up that is too aggressive, a jump in practice volume after a rest period, or a position change that introduces a new overhead demand. The second is accumulated fatigue over a long competitive season, where tissue stress slowly exceeds recovery capacity without any single obvious trigger.

Both patterns point to the same root cause: the rate of load increase outpaces the rate of tissue adaptation. Tendons, in particular, adapt slowly compared to muscle. An athlete can feel physically ready to increase volume long before their tendons have actually caught up. That gap is where most overuse injuries develop.

Extrinsic load factors including position, training conditions, and time of season also have documented influence on shoulder injury rates. Athletes who train more than 16 hours per week show significantly higher rates of shoulder pain. In-season shoulder injuries are more common than pre-season injuries, reflecting cumulative fatigue rather than inadequate conditioning.

How the three factors interact

Rotator cuff weakness, scapular dyskinesis, and training load spikes rarely operate in isolation. They amplify each other.

An athlete with a weak ER/IR ratio enters a heavy training block. As volume increases, the fatigued external rotators become less able to control deceleration. The scapula begins compensating for the rotator cuff instability, and over time its own stabilizers fatigue as well. Joint mechanics deteriorate subtly. Tendon stress accumulates. Eventually, a threshold is crossed — and what looked like a sudden onset of shoulder pain was actually months in the making.

This is why isolated treatments often produce incomplete results. Strengthening the rotator cuff without addressing scapular mechanics leaves a mechanical gap. Correcting scapular movement without modifying training load returns the athlete to the same tissue stress that caused the problem. Reducing volume without addressing the underlying strength deficits leaves the shoulder vulnerable the next time load increases.

Effective management addresses all three variables simultaneously.

What this means for assessment and treatment

Clinical assessment of shoulder pain in an overhead athlete should evaluate all three domains:

• Rotator cuff strength: Rotator cuff strength — particularly ER/IR ratio and eccentric capacity at end range

• Scapular kinematics: Scapular kinematics — movement quality during elevation, signs of dyskinesis, posterior stabilizer strength and timing

• Training load history: Training load history — recent changes in volume, intensity, position, or competitive schedule

• Kinetic chain screening: Kinetic chain screening — thoracic mobility, hip rotation, core stability, and how trunk deficits may be increasing shoulder demand

Treatment that addresses only the local shoulder tissue without evaluating the full picture is likely to produce temporary results. The shoulder is a high-demand structure in a chain of structures. Its capacity to handle load depends on everything beneath and behind it.

Closing takeaway

Shoulder pain in overhead athletes is rarely caused by a single structural failure. It is most often the result of a rotator cuff that cannot adequately control deceleration, a scapula that is not providing a stable platform for movement, and a training load that has exceeded the system's capacity to recover. Identifying which of these factors is dominant — and addressing all three in the correct order — is what drives durable outcomes for athletes who need to return to full overhead performance.

References & Further Reading

Tooth C, et al. Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review. Sports Health. 2020;12(5):478-487.

Yu IY, Ma R, Kim TG. The relationship between scapular dyskinesis and rotator cuff strength in adolescent baseball players. J IES. 2025.

Patel et al. Rehabilitative and Preventive Effects of the Thrower's Ten Program in Overhead Athletes. Cureus. 2025;17(10):e95081.

Relationship between Shoulder Pain, Trunk and Lower Limb Pain in Overhead Athletes. Int J Sports Phys Ther. 2024.

Wu D, et al. Specific Modes of Exercise to Improve Rotator Cuff-Related Shoulder Pain. Front Bioeng Biotechnol. 2025;13:1560597.

JOSPT Clinical Practice Guideline: Rotator Cuff Tendinopathy. J Orthop Sports Phys Ther. 2025;55(4):235-274.

Is Strength the Main Risk Factor of Overuse Shoulder Injuries? PMC. 2024.