Why Shoulder Endurance Testing Matters in the Overhead Athlete

Strength Alone Doesn’t Tell the Full Story

In overhead sports, athletes rarely struggle when they are fresh.

Problems often emerge later in games, practices, tournaments, or throwing sessions — when fatigue begins to influence force production, scapular control, timing, and movement efficiency.

For baseball players, volleyball athletes, tennis players, quarterbacks, swimmers, and CrossFit athletes, the shoulder must repeatedly tolerate and transfer high levels of force at high velocity.

That’s why shoulder endurance testing is becoming increasingly important in modern sports physical therapy and return-to-sport decision making.

At Praxis Physical Therapy, we utilize objective testing strategies to better understand how an athlete’s shoulder performs under repeated load — not just how strong it is during a single repetition.

Why Endurance Matters for the Shoulder

Traditional shoulder strength testing can provide useful information, but maximal strength alone may not fully capture the demands of overhead sport.

The shoulder functions as a dynamic stabilizer during throwing, serving, hitting, climbing, and overhead lifting. Throughout competition, the rotator cuff and scapular musculature must repeatedly:

• Produce force

• Transfer energy

• Stabilize the humeral head

• Absorb deceleration forces

• Maintain efficient mechanics under fatigue

  
  

As fatigue accumulates, athletes may experience:

• Reduced force production

• Changes in throwing or serving mechanics

• Decreased scapular control

• Reduced velocity or accuracy

• Increased movement variability

  
  

In many cases, endurance deficits may exist even when isolated strength testing appears “normal.”

The Posterior Shoulder Endurance Test

The posterior shoulder plays a critical role in deceleration and force absorption during overhead movement.

After ball release or contact, the posterior rotator cuff and scapular stabilizers work aggressively to slow the arm down and control movement.

The Posterior Shoulder Endurance Test helps assess:

• Posterior cuff endurance

• Scapular stabilizer capacity

• Fatigue tolerance

• Long-lever force control

This can be especially valuable in:

• Baseball pitchers

• Volleyball athletes

• Tennis players

• Quarterbacks

• Overhead strength athletes

Athletes who demonstrate endurance deficits may struggle to maintain efficient mechanics late in competition or during high-volume training.

The Anterior Shoulder Endurance Test

The anterior shoulder contributes heavily to force transfer, stabilization, and dynamic control during overhead loading.

The Anterior Shoulder Endurance Test challenges the athlete’s ability to maintain force production and positional stability in long-lever positions that resemble sport demands.

This testing can provide insight into:

• Anterior shoulder stability

• Long-lever force tolerance

• Dynamic shoulder control

• Repeated overhead loading capacity

For overhead athletes, these qualities are critical for:

• Throwing velocity

• Serving power

• Force transfer efficiency

• Maintaining performance throughout competition

  
  

The Athletic Shoulder (ASH) Test

One increasingly recognized method of shoulder force assessment is the Athletic Shoulder (ASH) Test developed by Ben Ashworth and colleagues.

The ASH Test uses long-lever isometric testing positions — commonly referred to as the:

• I position

• Y position

• T position

I POSITION

Y POSITION

T POSITION

These positions help assess shoulder force production in sport-relevant positions while also identifying asymmetries between sides.

Research has demonstrated excellent reliability of the ASH Test in athletic populations, making it a valuable tool for:

• Return-to-sport testing

• Performance monitoring

• Fatigue assessment

• Shoulder rehabilitation progression

Emerging evidence also suggests that rate of force development and endurance qualities may provide important information beyond traditional maximal strength testing alone.

Objective Testing Improves Return-to-Sport Decisions

One of the biggest challenges in sports rehabilitation is determining when an athlete is truly prepared to return to full competition.

Pain alone is not enough.

Range of motion alone is not enough.

Even isolated strength testing may not fully reflect the demands of high-level sport.

Objective testing allows clinicians to better evaluate:

• Force production

• Endurance capacity

• Symmetry

• Fatigue response

• Sport-specific tolerance

This helps bridge the gap between rehabilitation and performance.

How To Use These Clinically:

For the Anterior Shoulder Endurance Test (ASET) and Posterior Shoulder Endurance Test (PSET) that Ben Ashworth and the Athletic Shoulder group have been discussing more recently, the commonly used parameters are:

Posterior Shoulder Endurance Test (PSET)

• Position: Prone horizontal abduction ("T" position) or modified "Y" position depending on sport.

• Load: 2% of body weight

• Hold Time Goal: 90 seconds

• Pass Criteria:

  • Maintain position without compensation

  • No significant scapular winging

  • No loss of humeral position

  • No pain reproduction

  • Complete full 90-second hold

Anterior Shoulder Endurance Test (ASET)

• Position: Long-lever shoulder flexion/scaption position (typically supine or standing depending on protocol)

• Load: 2% of body weight

• Hold Time Goal: 90 seconds

• Similar criteria:

  • No loss of position

  • No compensatory trunk movement

  • Good scapular control

  • No pain reproduction

Quick Clinical Examples

Athlete Weight	2% BW Load
60 kg (132 lb)	1.2 kg (2.6 lb)
70 kg (154 lb)	1.4 kg (3.1 lb)
80 kg (176 lb)	1.6 kg (3.5 lb)
90 kg (198 lb)	1.8 kg (4.0 lb)
100 kg (220 lb)	2.0 kg (4.4 lb)

How I Use It Clinically

For overhead athletes at Praxis, I would consider:

• <60 sec = significant endurance deficit

• 60–89 sec = improving but not ideal

• ≥90 sec = acceptable baseline endurance capacity

• Compare side-to-side and monitor symptom response

The key point is that these tests are intended to assess rotator cuff and scapular endurance, not maximal strength. An athlete may pass dynamometry or the ASH test but still fail endurance testing, which is often where late-game shoulder fatigue, velocity loss, and symptom recurrence show up. This is one reason these tests pair nicely with the ASH Test (I-Y-T positions) and VALD dynamometry when building a comprehensive return-to-sport battery.

For baseball, volleyball, tennis, and rugby athletes, I often use:

1. ASH Test (peak force + RFD)

2. ER/IR dynamometry

3. Anterior Shoulder Endurance Test (90 sec @ 2% BW)

4. Posterior Shoulder Endurance Test (90 sec @ 2% BW)

5. CKCUEST or Upper Quarter Y-Balance

6. Sport-specific power testing

That combination gives a much better picture of shoulder readiness than strength testing alone.

Modern Sports Physical Therapy Goes Beyond Basic Rehab

At Praxis Physical Therapy, we believe overhead athletes deserve more than generic rehab exercises.

Our approach integrates:

• Objective testing

• Sports performance principles

• Strength and conditioning

• Movement analysis

• Return-to-sport progression

• Individualized programming

Whether you are recovering from injury or trying to optimize performance, understanding how the shoulder tolerates repeated load can be an important piece of the puzzle.

Final Thoughts

Overhead athletes do not simply need strong shoulders.

They need shoulders capable of repeatedly producing and absorbing force under fatigue.

As sports physical therapy continues to evolve, endurance testing and long-lever force assessments are becoming increasingly valuable tools for understanding athletic readiness and improving return-to-sport decision making.

The goal is not just returning athletes to participation.

The goal is preparing them to perform.

Praxis Physical Therapy

Bellingham, Washington

Performance Rehabilitation | Return to Sport | Sports Physical Therapy | Strength & Conditioning Integration

References

Ashworth B, et al. The Athletic Shoulder (ASH) Test: Reliability of a Novel Isometric Strength Test in Elite Rugby Players.

McFarland EG, et al. Clinical and biomechanical considerations in overhead athletes.

Cools AM, et al. Rehabilitation of scapular dyskinesis in overhead athletes.

Wilk KE, et al. Current concepts in the rehabilitation of the overhead throwing athlete.