The Shoulder Dysfunction & Load-Intolerance Cycle
Hypotheses & open questionsHow might mechanics, fatigue, symptoms, and exposure interact?
This proposed framework connects pressing mechanics, fatigue, movement responses, symptoms and training exposure to help identify what to adjust and monitor.
Key Takeaways
Understanding the Shoulder Dysfunction Cycle
The model organizes eight interacting states, with several possible entry and exit points.
Scapular dyskinesis is common in asymptomatic athletes; it is a finding, not a diagnosis.
Fatigue and pain can change movement, but the response may be protective, neutral or costly depending on context.
Modeled joint loading, EMG, bar kinematics, symptoms and injury are different endpoints.
Technique, recovery, load management, clinical care and support conditions can enter at multiple stages.
Published Launch Pad studies report changes in acute pressing mechanics and training performance under specific support conditions and programs.
How to read the framework
Eight states, two-way transitions, many entry and exit points
Complex-systems injury models examine how interacting constraints create patterns over time [1]. This proposed framework applies that approach to repetitive pressing by organizing relationships that can be tested separately.
Altered scapular motion is common without pain. Across 12 studies and 1,401 athletes, Burn and colleagues reported dyskinesis in 61% of overhead and 33% of nonoverhead athletes [2]. In five prospective cohorts involving 419 athletes, Hickey and colleagues found a 43% higher future shoulder-pain risk with baseline dyskinesis (RR 1.43, 95% CI 1.05–1.93) [3]. The Scapular Summit consensus recommends interpreting this movement finding within a clinical examination [4].
AMM Research · Visual 59 · prevalence and prospective association
Scapular dyskinesis: prevalence and later pain risk
Two evidence layers answer different questions. Prevalence describes how often dyskinesis was observed; the prospective synthesis reports association with later shoulder pain.
Reported dyskinesis prevalence
Systematic review · heterogeneous athlete samples
Future shoulder-pain incidence
Asymptomatic athletes followed for 9–24 months
Relative risk with 95% confidence interval
Point estimate 1.43 · 95% CI 1.05–1.93 · vertical dashed line = no association (RR 1.0)
AMM Research · Visual 58 · proposed feedback model
The Shoulder Dysfunction & Load-Intolerance Cycle
The figure places the eight-state framework in the context of pressing and shoulder mechanics.
Every adjacent state can influence its neighbor in either direction; Stage 08 reconnects with Stage 01. Athletes may enter, stabilize, or exit at any stage.
Evidence behind the links
How Mechanics, Fatigue, and Symptoms Interact
Task constraints change mechanics
In experienced lifters, grip width, scapular pose and shoulder-abduction targets changed modeled glenohumeral and acromioclavicular forces [5]. Lateral barbell forces also materially affect calculated net joint moments [6].
Measured mechanics and modeled forcesMechanics inform demand, with model limits
Motion and external-force measurements feed models that estimate muscle and joint demand under stated anatomical and optimization assumptions.
Mechanistic inferenceDemand and fatigue interact
Duffey and Challis recruited 18 recreational lifters (10 men and 8 women) for sets to failure at 75% 1RM and found systematic changes in bar kinematics as repetitions accumulated [7]. A 2024 narrative review examines proposed links between fatigue and shoulder biomechanics [8].
Direct kinematics · narrative risk synthesisRecruitment is direction-specific
Wattanaprakornkul and colleagues used EMG to show direction-specific rotator-cuff recruitment during bench press and row [9]. These recruitment patterns describe how the muscles coordinate the task.
EMG recruitment studyMovement can adapt without “failure”
A slower or altered bar path may preserve performance, redistribute load or signal that the rep has left its intended standard. The direction is athlete- and task-dependent; the model should record the adaptation before assigning it a value.
Direct observation · interpretation requiredPain changes movement variably
Hodges and Tucker propose that pain alters motor behavior by redistributing activity within and between muscles. The response can protect a threatened region in the short term while creating other costs if it persists [10].
General pain-adaptation theorySymptoms and tolerance are not interchangeable
Pain can reduce willingness or ability to repeat a task, while low tolerance can raise the chance that a dose provokes symptoms. Neither proves structural damage. Clinical examination is the appropriate route when symptoms persist, recur or follow trauma.
Proposed state transitionExposure meets the athlete’s current state
The same session can be tolerable in one state and excessive in another. Injury-surveillance reviews describe the problems reported in strength sports [11].
Proposed exposure relationshipAMM Research · Visual 60 · Mausehund et al. (2022)
Lateral hand force changes the mechanical record
Mean lateral-to-vertical barbell-force ratio across four bench-press techniques. Positive values are lateral; the small negative value is medial.
Practical use
Addressing the Cycle and Monitoring the Response
Use the model as a measurement plan: identify an observable state, change one defensible input and track the intended outcome and downstream response.
Standardize. Record grip, range, contacts, support, load and fatigue endpoint. Use video or velocity only if the measurement changes a decision.
Decide what it means. A changed bar path may be an acceptable solution or an invalid repetition. Apply the rule specified before the set.
Adjust exposure. Reduce dose, proximity to failure, range or frequency; then observe whether tolerance returns rather than assuming one mechanical cause.
Escalate appropriately. Clinical assessment can identify diagnoses, red flags and individualized constraints that this training framework cannot.
The relationship is bidirectional. Better capacity can expand tolerable exposure; an appropriate exposure can build capacity. Pain reduction may permit cleaner practice, and cleaner practice may improve confidence. Conversely, rest alone may reduce symptoms without restoring tolerance for the original task.
Where the support interface belongs
A changed surface enters at the task-constraint stage
The Launch Pad studies show how a complete support condition can change acute repetition mechanics and training performance under specific programs. In this framework, support enters as one task constraint.
Acute crossover · n = 10 resistance-trained men
The surface changed measured repetition outputs
Right/left pectoralis sEMG, mean/peak velocity, vertical bar displacement and power.
The Launch Pad condition produced 24.4% and 27.1% higher pectoralis sEMG, 17.5% and 15.8% higher mean/peak velocity and 15.8% greater vertical bar displacement. The 8.8% power difference was not significant after correction (p = .071) [12].
AMM Research · Visual 61 · Kidwell et al. (2026)
Six outcomes from the acute crossover
Condition means from 10 trained men performing five repetitions at 70% 1RM. Each chart uses its own zero-origin unit scale; SD is printed rather than implied by bar length.
Right pectoralis sEMG
Zero-origin scale to 120% MVC. Mean ± SD: 70.2 ± 24.8 vs 87.3 ± 20.1; p < .001.
Left pectoralis sEMG
Zero-origin scale to 120% MVC. Mean ± SD: 68.3 ± 23.4 vs 86.8 ± 20.0; p < .001.
Mean bar velocity
Zero-origin scale to 0.8 m/s. Mean ± SD: 0.40 ± 0.09 vs 0.47 ± 0.09; p < .001.
Peak bar velocity
Zero-origin scale to 0.8 m/s. Mean ± SD: 0.57 ± 0.11 vs 0.66 ± 0.09; p < .001.
Vertical displacement
Zero-origin scale to 60 cm. Mean ± SD: 38 ± 7 vs 44 ± 4; p = .005.
Concentric power
Zero-origin scale to 400 W. Mean ± SD: 249 ± 103 vs 271 ± 93; p = .071, not significant.
In a four-week trial of 42 intermediate-trained men, the same supervised eccentric-overload program produced an average 1-RM gain of 18.4 kg (40.6 lb) with the Launch Pad versus 11.1 kg (24.5 lb) conventionally: a 7.3 kg (16.1 lb) difference, about 66% greater average improvement (p < .001) [13].
Mean bench-press 1RM gain
Four weeks · 12 supervised sessions
Same AEL program.
Different support.
The 42 intermediate-trained men were randomized to two support conditions within the same supervised eccentric-overload program.
In a separate eight-week trial, 30 collegiate football players completed matched periodized programs for 24 supervised sessions. The Launch Pad group improved more in 1-RM, NFL-225 repetitions and seated medicine-ball throw distance; all reported between-group comparisons were p < .001 [14]. These findings concern strength, repetition performance and seated-throw distance under the tested training program.
Research agenda
Testing How the Cycle Develops
A strong longitudinal design would standardize grip, range, support and load; repeatedly capture three-dimensional motion, vertical and lateral external forces, bar kinematics, muscle activity, symptoms, next-day function and exposure; and define in advance what counts as a meaningful state transition.
AMM Research · Visual 64 · proposed study design
Testing the Proposed Sequence
The proposed study sequence separates task standardization, motion measurement and clinical outcomes.
| Question | Minimum evidence |
|---|---|
| Does a constraint change mechanics? | Randomized, familiarized condition comparison with direct motion and force data. |
| Does the mediator change tolerance? | Repeated exposure with temporal ordering and symptom/function measures. |
| Does an intervention interrupt the loop? | Prospective comparison showing the targeted link changes before downstream outcomes. |
| Does the result generalize? | Replication across sexes, body dimensions, training ages and clinical states. |
Use the cycle to ask a better next question
Identify the observable link, choose a reversible input and measure whether the intended state actually changed.
Medical notice: This proposed framework is educational and is not a diagnostic or treatment algorithm. Persistent, traumatic, postoperative or neurologic symptoms require individualized evaluation by an appropriately qualified clinician.
References
- Bittencourt NFN, Meeuwisse WH, Mendonça LD, Nettel-Aguirre A, Ocarino JM, Fonseca ST. (2016). Complex systems approach for sports injuries: Moving from risk factor identification to injury pattern recognition—narrative review and new concept. British Journal of Sports Medicine, 50(21), 1309–1314. doi:10.1136/bjsports-2015-095850. ↩
- Burn MB, McCulloch PC, Lintner DM, Liberman SR, Harris JD. (2016). Prevalence of scapular dyskinesis in overhead and nonoverhead athletes: A systematic review. Orthopaedic Journal of Sports Medicine, 4(2), 2325967115627608. doi:10.1177/2325967115627608. ↩
- Hickey D, Solvig V, Cavalheri V, Harrold M, McKenna L. (2018). Scapular dyskinesis increases the risk of future shoulder pain by 43% in asymptomatic athletes: A systematic review and meta-analysis. British Journal of Sports Medicine, 52(2), 102–110. doi:10.1136/bjsports-2017-097559. ↩
- Kibler WB, Ludewig PM, McClure PW, Michener LA, Bak K, Sciascia AD. (2013). Clinical implications of scapular dyskinesis in shoulder injury: The 2013 consensus statement from the Scapular Summit. British Journal of Sports Medicine, 47(14), 877–885. doi:10.1136/bjsports-2013-092425. ↩
- Noteboom L, Belli I, Hoozemans MJM, Seth A, Veeger HEJ, van der Helm FCT. (2024). Effects of bench press technique variations on musculoskeletal shoulder loads and potential injury risk. Frontiers in Physiology, 15, 1393235. doi:10.3389/fphys.2024.1393235. ↩
- Mausehund L, Werkhausen A, Bartsch J, Krosshaug T. (2022). Understanding bench press biomechanics—the necessity of measuring lateral barbell forces. Journal of Strength and Conditioning Research, 36(10), 2685–2695. doi:10.1519/JSC.0000000000003948. ↩
- Duffey MJ, Challis JH. (2007). Fatigue effects on bar kinematics during the bench press. Journal of Strength and Conditioning Research, 21(2), 556–560. doi:10.1519/R-19885.1. ↩
- Motlagh JG, Lipps DB. (2024). The contribution of muscular fatigue and shoulder biomechanics to shoulder injury incidence during the bench press exercise: A narrative review. Journal of Strength and Conditioning Research, 38(12), 2147–2163. doi:10.1519/JSC.0000000000004973. ↩
- Wattanaprakornkul D, Halaki M, Cathers I, Ginn KA. (2011). Direction-specific recruitment of rotator cuff muscles during bench press and row. Journal of Electromyography and Kinesiology, 21(6), 1041–1049. doi:10.1016/j.jelekin.2011.09.002. ↩
- Hodges PW, Tucker K. (2011). Moving differently in pain: A new theory to explain the adaptation to pain. Pain, 152(3 Suppl), S90–S98. doi:10.1016/j.pain.2010.10.020. ↩
- Tung MJY, Lantz GA, Lopes AD, Berglund L. (2024). Injuries in weightlifting and powerlifting: An updated systematic review. BMJ Open Sport & Exercise Medicine, 10(4), e001884. doi:10.1136/bmjsem-2023-001884. ↩
- Kidwell JA, Yamamoto T, Hetherton KJ, Truneh N, Bright JJ, Blatney AE, et al. (2026). Acute effects of thoracic-spinal elevation via a novel bench press pad on sEMG and barbell kinetics in resistance-trained males. International Journal of Exercise Science, 19(1), 1003. doi:10.70252/IJES2026103. ↩
- Goldman P, Taylor J, Yamamoto T, Blatney AE, Sahni TK, Lechner RJ, et al. (2025). Eccentrically overloaded bench press training: Augmenting strength gains via a novel bench press pad. Scientific Journal of Sport and Performance, 4(4), 480–490. doi:10.55860/JCDL3612. ↩
- Blatney AE, Kidwell JA, Yamamoto T, Goldman P, Hetherton KJ, Dolezal BA. (2026). Effects of an eight week training regimen with a novel bench press pad compared to a traditional bench on upper body strength and performance in collegiate American football players. Scientific Journal of Sport and Performance, 5(1), 10–21. doi:10.55860/RNUB8627. ↩