The Shoulder Dysfunction & Load-Intolerance Cycle: A Proposed Framework for Repetitive Pressing
Hypotheses & open questionsHow might mechanics, fatigue, symptoms, and exposure interact?
This proposed model organizes possible relationships among pressing mechanics, fatigue, movement responses, symptoms, and training exposure. Its links need to be tested separately. The diagram is not an inevitable progression or a diagnosis.
Key Takeaways
A cycle is useful only if it preserves uncertainty and reversibility.
The model organizes eight interacting states that can be observed and tested separately rather than assumed to form one inevitable chain.
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.
The published Launch Pad research changes the surface-mechanics/performance question; it does not validate a pain or injury pathway.
How to read the framework
Eight states, two-way transitions, many entry and exit points
Complex-systems injury models reject the idea that one isolated “risk factor” produces a predictable outcome. They ask how interacting constraints create a pattern over time [1]. This article applies that logic to repetitive pressing, but the cycle is a proposal: it is a map of testable links, not a validated natural history.
That distinction is essential because altered scapular motion is common without pain. Burn and colleagues synthesized 12 studies involving 1,401 athletes and reported dyskinesis in 61% of overhead athletes and 33% of nonoverhead athletes [2]. Hickey and colleagues pooled five prospective cohorts (419 athletes) and found a 43% higher future shoulder-pain risk when dyskinesis was present at baseline (RR 1.43, 95% CI 1.05–1.93) [3]. Prevalence and prospective association can coexist: a common sign may shift risk without identifying cause, diagnosis or destiny. The Scapular Summit consensus likewise treats dyskinesis as an impairment that must be interpreted inside a clinical examination, not as a diagnosis by itself [4].
AMM Research · Visual 59 · prevalence and prospective association
A common movement finding can shift risk without becoming a diagnosis
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 realistic scene orients the reader to the training, mechanical, symptom, and clinical contexts. The exact eight-state model remains native text below.
Orientation layer only · the image does not encode links, probability, timing, or a mandatory order.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
What is measured, what is associated and what remains proposed
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].
Direct mechanics + modeling · not symptomsMechanics inform demand, with model limits
Motion and external force help estimate muscle and joint demand, but the estimates depend on anatomical and optimization assumptions. A lower modeled component is not proof of lower tissue damage or clinical risk.
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 integrates fatigue and shoulder-biomechanics hypotheses, but it does not provide a prospective injury threshold [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]. Recruitment describes a motor strategy; it does not identify a damaged structure.
Direct EMG · no injury endpointMovement 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 theory · not bench-specificSymptoms 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 where problems are reported in strength sports, but heterogeneous methods cannot supply this model’s transition probabilities [11].
Exposure logic · no causal sequenceAMM 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
Intervene at the earliest observable link—then verify the response
The model is not a checklist for locating one root cause. It is a measurement plan: identify the state that can be observed, change one defensible input and watch both 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 provide direct evidence that one complete support condition changed acute repetition mechanics/performance and longitudinal performance under specific programs. They do not validate the full cycle or establish a clinical interruption.
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 displacement. Power was 8.8% higher but nonsignificant after correction (p = .071) [12]. No pain or injury outcome was measured.
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]. That is an interface comparison under AEL, not an AEL-versus-conventional-training comparison.
Mean bench-press 1RM gain
Four weeks · 12 supervised sessions
Same AEL program.
Different support.
42 intermediate-trained men were randomized to the same supervised eccentric-overload program. The comparison estimates the effect of the tested equipment-and-program combination; it is not AEL versus conventional training.
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]. Those are performance outcomes. They do not show that the interface prevented injury, treated pain or changed any specific transition in this cycle.
Research agenda
Test links in sequence instead of validating the picture by impression
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 · study-design boundary
A plausible sequence is not a validated causal pathway
The illustration separates three activities that are often collapsed in prose: standardizing the task, measuring motion, and assessing a clinical outcome.
| Question | Minimum evidence | Null result that still matters |
|---|---|---|
| Does a constraint change mechanics? | Randomized, familiarized condition comparison with direct motion and force data. | The configuration changes perceived support but not the preregistered mechanical mediator. |
| Does the mediator change tolerance? | Repeated exposure with temporal ordering and symptom/function measures. | Mechanics change without a later tolerance difference. |
| Does an intervention interrupt the loop? | Prospective comparison showing the targeted link changes before downstream outcomes. | Symptoms improve equally while the proposed mediator remains unchanged. |
| Does the result generalize? | Replication across sexes, body dimensions, training ages and clinical states. | A response appears only in one subgroup or configuration. |
Bench constraints can change acute mechanics and performance; fatigue can change bar kinematics; pain-related motor adaptation is variable; a support condition can change acute and longitudinal performance outcomes.
The direction and strength of most transitions, whether the complete loop occurs in pressing athletes, and whether any equipment configuration changes pain, injury or rehabilitation outcomes.
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. ↩