Effects of different exercise rehabilitation programs on shoulder joint function recovery in male racket sport club members

Background: Shoulder dysfunction is prevalent among recreational racket-sport participants due to high mechanical demands and insufficient proximal control. Contemporary rehabilitation emphasizes kinetic-chain coordination and dynamical-systems principles, suggesting recovery reflects reorganization of neuromuscular synergies, rather than isolated joint correction. However, evidence on sequencing effects in coordination-based rehabilitation remains limited. This study compared two exercise sequences: pelvic–lumbar coordination followed by shoulder stabilization (LS) versus the reverse order (SL). Methods: Thirty-two adult male participants with shoulder discomfort were randomly assigned to LS (n = 16) or SL (n = 16). Each group completed two 20-minute programs in opposite orders, with assessments at pre-test, post-test 1, and post-test 2. Shoulder abduction tasks (discrete and continuous) were recorded at 240 fps and analyzed using MediaPipe Pose. Joint-angle data were processed in Python and MATLAB. Principal component analysis defined dynamical degrees of freedom (DDOF), and biomechanical degrees of freedom (BDOF). Range of motion (ROM) was analyzed using two-way Analysis of Variance (ANOVA), and DDOF/BDOF using nonparametric tests (α = 0.05). Results: In discrete tasks, the LS group showed greater dominant shoulder ROM and higher DDOF at both post-tests compared with SL (p < 0.05), with no group differences in BDOF. In continuous tasks, LS demonstrated progressive increases in ROM across sessions (pre-test < post-test 1 < post-test 2), outperforming SL, while both groups showed time-related increases in BDOF. Conclusions: Prioritizing pelvic–lumbar coordination before shoulder stabilization led to superior improvements in shoulder function. Effects were task-specific: discrete tasks enhanced DDOF, whereas continuous tasks promoted earlier BDOF expansion. These findings support coordination reorganization as a key mechanism in rehabilitation. Clinical Trial Registration: ISRCTN15911792 (retrospectively registered, 30 March 2026).

Shoulder joint; Exercise rehabilitation; Racket sport; Core stabilization and adjustment training (CSAT)

[1] Dupuy A, Sorg M, Morel C, Rudewicz A, Colin E, Blazevich AJ, et al. Shoulder overuse injury history is associated with imbalanced strength functional ratio and bilateral asymmetry in overhead male para athletes in resting and fatigued conditions. American Journal of Physical Medicine & Rehabilitation. 2025; 104: 1028–1035.

[2] McMullen J, Uhl TL. A kinetic chain approach for shoulder rehabilitation. Journal of Athletic Training. 2000; 35: 329–337.

[3] Kibler WB, McMullen J, Uhl T. Shoulder rehabilitation strategies, guidelines, and practice. Operative Techniques in Sports Medicine. 2000; 8: 258–267.

[4] Sciascia A, Cromwell R. Kinetic chain rehabilitation: a theoretical framework. Rehabilitation Research and Practice. 2012; 2012: 853037.

[5] Kibler BW, Sciascia A, Wilkes T. Scapular dyskinesis and its relation to shoulder injury. Journal of the American Academy of Orthopaedic Surgeons. 2012; 20: 364–372.

[6] Jie LJ, Kleynen M, Rothuizen G, Kal E, Rothgangel A, Braun S. Overview of effects of motor learning strategies in neurologic and geriatric populations: a systematic mapping review. Archives of Rehabilitation Research and Clinical Translation. 2024; 6: 100379.

[7] O’Reilly D, Delis I. Dissecting muscle synergies in the task space. eLife. 2024; 12: RP87651.

[8] Vernooij CA, Rao G, Perdikis D, Huys R, Jirsa VK, Temprado JJ. Functional coordination of muscles underlying changes in behavioural dynamics. Scientific Reports. 2016; 6: 27759.

[9] Campos FM, Calado JM. Approaches to human arm movement control—a review. Annual Reviews in Control. 2009; 33: 69–77.

[10] Pregnolato G, Severini G, Maistrello L, Rimini D, Lencioni T, Carpinella I, et al. Muscle synergy analysis for clinical characterization of upper limb motor recovery after stroke. Archives of Physical Medicine and Rehabilitation. 2026; 107: 261–269.

[11] Braun Janzen T, Thompson WF, Ammirante P, Ranvaud R. Timing skills and expertise: discrete and continuous timed movements among musicians and athletes. Frontiers in Psychology. 2014; 5: 1482.

[12] Takahashi M, Mutsuzaki H, Iwamoto K, Monma M, Nejishima M, Ono T, et al. Association between shoulder morphological changes and glenohumeral maximum external rotation during late cocking phase. Orthopaedic Journal of Sports Medicine. 2025; 13: 23259671251343232.

[13] Wörner EA, Safran MR. Racquet sports: tennis, badminton, racquetball, squash. In DeLee JC, Drez D III, Miller MD (eds.) Specific sports-related injuries (pp. 431–446). 5th edn. Elsevier: Philadelphia. 2022.

[14] Jacquier-Bret J, Gorce P. Kinematics of the tennis serve using an optoelectronic motion capture system: are there correlations between joint angles and racket velocity? Sensors. 2024; 24: 3292.

[15] Akalu Y, Tallent J, Frazer AK, Siddique U, Rostami M, Howatson G, et al. Determining the cortical, corticospinal, and reticulospinal responses to metronome-paced and self-paced strength training. European Journal of Applied Physiology. 2026; 126: 1333–1356.

[16] Sheikhhoseini R, Abdollahi S, Salsali M, Anbarian M, Guess TM. Coordination and variability of muscular activation in male athletes with and without subacromial impingement syndrome: a case-control study. PLOS ONE. 2025; 20: e0319048.

[17] Uchida T, Matsuo T, Ogasawara I, Konda S, Tanaka H, Nakata K. Inter-joint coordination of shoulder joint complex during two different arm elevation speeds. Journal of Bodywork and Movement Therapies. 2025; 42: 589–595.

[18] Dubois O, Roby-Brami A, Parry R, Jarrassé N. JcvPCA and JsvCRP: a set of metrics to evaluate changes in joint coordination strategies. PLOS ONE. 2025; 20: e0325792.

[19] Daffertshofer A, Lamoth CJ, Meijer OG, Beek PJ. PCA in studying coordination and variability: a tutorial. Clinical Biomechanics. 2004; 19: 415–428.

[20] Ting LH, Chvatal SA. Decomposing muscle activity in motor tasks: methods and interpretation. In Danion F, Latash ML (eds.) Motor control: theories, experiments, and applications (pp. 102–138). Oxford University Press: New York. 2010.

[21] Onitsuka K, Kubota K, Yokoyama M, Miyazawa T, Hamaguchi T, Taniguchi H, et al. Clinical utility of markerless motion capture for kinematic evaluation of sit-to-stand during 30 s-CST at one year post total knee arthroplasty: a retrospective study. BMC Musculoskeletal Disorders. 2023; 24: 254.

[22] Choi H, Kwon O, Choi WJ, You JSH. Effects of isolated shoulder versus core-shoulder chain exercises on motor control and isokinetic torque in baseball pitchers with shoulder impingement syndrome: a single-blinded randomized controlled trial. Journal of Sports Sciences. 2024; 42: 1331–1340.

[23] Lin YC, Lin HT, Lu CC, Chou PP, Su FC. Is early trunk rotation really hazardous for shoulder biomechanics in baseball throwing? Journal of Shoulder and Elbow Surgery. 2022; 31: 1282–1293.

[24] Sheikhhoseini R, Abdollahi S, Salsali M, Anbarian M. Biomechanical coordination and variability alters following repetitive movement fatigue in overhead athletes with painful shoulder. Scientific Reports. 2025; 15: 718.

[25] Krajewski KT, Rogers N, Lundin MA, Rogers A, Kanai S, Moore L, et al. Examining muscle synergy composition and segmental coordination during overground walking in individuals with a rotationplasty about the knee. Scientific Reports. 2025; 15: 26891.

[26] Hafkamp MSJ, Casanova R, Bootsma RJ. Freezing and freeing of degrees of freedom in joint action learning. Frontiers in Psychology. 2023; 14: 1287148.

[27] Lu TW, Lu SH, Yu CH, Wu KW, Kuan YC. A multi-objective optimal control approach to motor strategy changes in older people with mild cognitive impairment during obstacle crossing. Journal of NeuroEngineering and Rehabilitation. 2024; 21: 200.

[28] Díaz MA, Mohamadi PHA, De Bock S, Langlois K, De Winter J, Verstraten T, et al. A muscle synergy-based method to improve robot-assisted movements. Scientific Reports. 2025; 15: 11627.