The Effect of Cross Training on Clinical and Functional Outcomes in Frozen Shoulder Rehabilitation

This randomized controlled, single-blind, quasi-experimental study primarily aims to investigate the effects of unilateral resistance exercise applied without directly loading the affected shoulder on muscle strength and upper extremity function in individuals with frozen shoulder. Additionally, the study seeks to examine the effects on joint range of motion, quality of life, and activities of daily living. The study will be conducted among individuals diagnosed with frozen shoulder at the Physiotherapy and Rehabilitation Outpatient Clinic of Malatya Battalgazi State Hospital. The data collection process is planned to be completed between February 2026 and December 2026.

Participants will be selected from the relevant population using a non-probability convenience sampling method. Individuals meeting the inclusion criteria will be enrolled after providing written informed consent. The study will be carried out in accordance with the principles of the Declaration of Helsinki. Participants will be randomly assigned to either the control or intervention group.

The study will include individuals aged 18-65 years with a diagnosis of unilateral primary or secondary frozen shoulder, presenting with more than 50% restriction in at least one of the following shoulder movements compared to the unaffected side: external rotation, abduction, or flexion, and with more than 30% limitation in joint range of motion in at least two movement planes.

Individuals with concomitant shoulder trauma (e.g., rotator cuff injury), bilateral shoulder involvement, acromioclavicular joint osteoarthritis, prior treatment for frozen shoulder, psychiatric disorders that may affect compliance with medical or physical therapy interventions, concomitant neurological conditions, or a Mini-Mental State Examination (MMSE) score below 24 will be excluded from the study.

Study Overview

• Status: Not yet recruiting
• Conditions: Frozen Shoulder
• Intervention / Treatment: Other: Cross-Education Group; Other: Standard Physical Therapy Group

Detailed Description

Frozen shoulder (FS) is a clinical condition characterized by progressive shoulder pain and marked restriction in joint range of motion, substantially affecting individuals' activities of daily living and overall quality of life. The lifetime prevalence of frozen shoulder in the general population has been reported to range between 2% and 5%. The condition most commonly occurs in the fifth and sixth decades of life and may lead to significant functional limitations throughout its clinical course. Additionally, involvement of the contralateral shoulder has been observed in a considerable proportion of individuals diagnosed with frozen shoulder.

The clinical course of frozen shoulder is typically described in three stages: the inflammatory stage, during which pain and inflammation predominate; the frozen stage, characterized by pronounced joint stiffness; and the thawing stage, during which gradual improvements in shoulder mobility are observed. Pain, often more severe at night, is a dominant feature in the early stage, whereas pain may decrease in later stages despite persistent movement restrictions. During the thawing stage, pain generally becomes minimal while range of motion progressively improves.

The diagnosis of frozen shoulder primarily relies on clinical evaluation and is defined by the presence of shoulder pain accompanied by significant limitations in both active and passive glenohumeral joint range of motion. Although frozen shoulder has historically been considered a self-limiting condition, contemporary evidence suggests that spontaneous and complete recovery may not occur in all individuals, and long-term functional impairments may persist in some cases.

The shoulder joint, owing to its extensive range of motion, depends heavily on the coordinated and balanced activation of surrounding musculature for stability and function. Pain, weakness, or impaired coordination within these muscle groups may disrupt shoulder biomechanics, resulting in notable functional deficits. In frozen shoulder, pain-related protective muscle activation and movement avoidance behaviors may contribute to progressive deterioration of periarticular muscle function.

Pain and restricted mobility in frozen shoulder are not limited to local mechanical factors but may also induce central nervous system mechanisms that suppress motor output. Pain-related inhibition has been associated with reductions in maximal voluntary muscle force, altered motor unit recruitment, and decreased muscle endurance. Furthermore, reduced use of the affected upper extremity and protective immobilization behaviors may exacerbate neuromuscular dysfunction.

The primary goals in frozen shoulder management are pain reduction and restoration of shoulder joint mobility. In clinical practice, analgesic interventions, physiotherapy, and manual mobilization techniques are commonly employed and have been shown to contribute to functional improvements. However, during phases in which pain is prominent and direct mechanical loading of the affected shoulder is poorly tolerated, the applicability of conventional exercise approaches may be limited. These challenges highlight the need for alternative rehabilitation strategies aimed at preserving neuromuscular function when direct exercise of the affected extremity is not feasible.

Cross-education refers to the phenomenon whereby unilateral resistance training leads to strength gains in the homologous muscles of the contralateral, untrained limb. This effect has been extensively investigated in conditions involving unilateral immobilization, orthopedic injuries, and movement restrictions, where maintaining muscle function in the non-exercised extremity is clinically desirable. Unilateral exercise interventions have been shown to enhance contralateral strength output, with evidence suggesting that these effects are predominantly mediated by neural mechanisms rather than peripheral muscular adaptations.

The mechanisms underlying cross-education are widely considered to originate from central nervous system adaptations. Unilateral resistance training has been associated with increased excitability of contralateral motor cortical regions and modifications within motor networks responsible for movement planning and execution. These neural adaptations may facilitate improved motor output in the untrained limb independent of muscle hypertrophy. Cross-education has therefore been conceptually linked to motor learning processes involving central reinforcement of efficient muscle activation patterns.

More recently, the potential contribution of visual-motor networks, including mechanisms associated with the mirror neuron system, has been proposed. Activation of shared neural substrates during both movement execution and observation may modulate motor cortical excitability, suggesting that visually mediated strategies could influence cross-education effects.

Frozen shoulder presents a unique clinical scenario characterized by pain, restricted mobility, and central inhibition mechanisms. These factors complicate efforts to maintain muscle strength and neuromuscular function during periods when direct loading of the affected shoulder is limited. Given that cross-education enables strength-related neural adaptations without imposing mechanical stress on the affected extremity, it represents a conceptually relevant approach for this population. Consequently, cross-education may offer a promising rehabilitation strategy for preserving shoulder function and supporting recovery in individuals with frozen shoulder.

• Study Type: Observational
• Enrollment (Estimated): 38

Contacts and Locations

• Study Contact: Name: Melisa İlhan; Phone Number: +905539712295; Email: melisailhan09@gmail.com
• Study Contact Backup: Name: Zeynal YASACI; Phone Number: +905075409791; Email: zeynal.yasaci@inonu.edu.tr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study will include patients aged 18-65 years with a diagnosis of unilateral primary or secondary frozen shoulder. Participants will be randomly assigned to either the control or intervention group.

Description

Inclusion Criteria:

• Having a diagnosis of unilateral primary or secondary frozen shoulder.
• Range of motion in external rotation, abduction, or flexion reduced by less than 50% in at least one of these directions compared to the unaffected shoulder.
• Loss of joint range of motion exceeding 30% in at least two movement planes compared to the unaffected shoulder.
• Aged between 18 and 65 years.

Exclusion Criteria:

• Presence of a concomitant shoulder injury (e.g., rotator cuff tear).
• Osteoarthritis in both shoulders or in the acromioclavicular joint.
• Previous treatment for frozen shoulder.
• Psychiatric disorders that may interfere with adherence to medical or physical therapy.
• Presence of other neurological disorders.
• A score below 24 on the Mini-Mental State Examination (MMSE).

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
cross training group; Participants diagnosed with frozen shoulder will receive 20 minutes of standard physiotherapy followed by 20 minutes of cross-education intervention.	Other: Cross-Education Group; In the experimental group, each session will last 40 minutes, comprising 20 minutes of standard physical therapy and 20 minutes of cross-education. The standard physical therapy content will be identical to that of the control group. The cross-education program will aim to increase the internal rotation, external rotation, flexion, and abduction strength of the unaffected shoulder during immobilization. Resistance exercises will be performed at 70-80% of the one-repetition maximum (1RM) of the unaffected extremity, with loads progressively adjusted according to individual tolerance. Strengthening exercises targeting the internal rotators, external rotators, flexors, and abductors will be performed using dumbbells and therabands. Each contraction will last 3 seconds, with repetitions performed at 10-second intervals.
standard physical therapy group; A 40-minute standard physiotherapy program will be administered to participants diagnosed with frozen shoulder	Other: Standard Physical Therapy Group; The program will be applied to both groups twice weekly for eight weeks, with the experimental group additionally receiving cross-education. The control group will undergo a 40-minute standard physical therapy protocol per session, progressively structured to reduce pain and improve shoulder range of motion. During weeks 0-3, passive and active-assisted range of motion exercises, scapular mobilization, stretching, and joint mobilizations with distraction will be performed within pain limits. Between weeks 3-5, active-assisted and active exercises, stretching, joint mobilizations, and scapulothoracic strengthening will continue. During weeks 6-8, active range of motion and strengthening exercises targeting the rotator cuff and scapulothoracic muscles will be implemented within pain limits.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Shoulder Pain and Functional Disability	Participants' shoulder pain and functional disability will be assessed using the Shoulder Pain and Disability Index (SPADI). The SPADI is a 13-item self-reported questionnaire designed to evaluate pain and functional impairment associated with shoulder dysfunction. Each item is rated on a numeric scale ranging from 0 ('no pain/no difficulty') to 10 ('worst imaginable pain/extreme difficulty requiring assistance'). The total SPADI score ranges from 0 to 100, with higher scores indicating greater pain and functional disability. The SPADI has been demonstrated to be a valid and reliable outcome measure for the assessment of individuals with frozen shoulder.	Baseline and post-intervention (8 weeks later )

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Numeric Pain Rating Scale (NPRS)	Pain at rest, during activity, and at night will be assessed. Activity-related pain intensity will be evaluated using the Numeric Pain Rating Scale (NPRS). The NPRS is an 11-point scale ranging from 0 to 10, where 0 indicates 'no pain' and 10 represents 'the worst pain imaginable.	Baseline and post-intervention (8 weeks later )
Muscle Strength	The isometric muscle strength of the shoulder flexor, extensor, abductor, adductor, and internal and external rotator muscle groups will be assessed using a handheld dynamometer. During the measurements, participants will be tested in a seated position on a standard chair. Participants will be instructed to generate a maximal voluntary isometric contraction against the dynamometer for approximately 3 seconds. Three trials will be performed for each muscle group, with a 1-minute rest interval between trials. The highest value obtained from the three trials will be recorded as the isometric muscle strength	Baseline and post-intervention (8 weeks later )
Joint Range of Motion Assessment	Shoulder joint range of motion will be assessed using goniometric measurements. Shoulder flexion will be evaluated in the supine position, with the scapula stabilized laterally, while participants are instructed to actively and passively elevate the arm. Shoulder abduction will be assessed in the same position by instructing participants to actively and passively raise the arm laterally. Shoulder internal and external rotation range of motion will be measured with the shoulder stabilized and the elbow positioned at 90° of flexion, while participants are instructed to rotate the forearm inward and outward, respectively, under both active and passive conditions. Active total elevation will be measured in the seated position using a goniometer. Active shoulder internal rotation will be evaluated by measuring the distance between the tip of the thumb and the spinous process of the T5 vertebra while the hand is positioned behind the back	Baseline and post-intervention (8 weeks later )
Upper Extremity Function	Subjective assessment of upper extremity function and symptoms will be performed using the Quick Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH), which consists of 11 items. The QuickDASH score ranges from 0 to 100, with higher scores indicating greater functional disability.	Baseline and post-intervention (8 weeks later )
Quality of Life (QoL)	To assess participants' health-related quality of life, the Short Form-12, Version 2 (SF-12v2), a 12-item abbreviated form of the SF-36 Health Survey, will be used. The SF-12v2 encompasses two main components: physical health and mental health. Scores range from 0 to 100, with higher scores indicating better quality of life.	Baseline and post-intervention (8 weeks later )
Activities of Daily Living (ADL)	The Canadian Occupational Performance Measure (COPM) is a semi-structured interview tool used to assess participants' engagement in meaningful daily activities. Participants will be asked to identify four activities, which will then be evaluated using a 10-point Likert scale. Perceived performance will be rated from 1 (cannot do) to 10 (able to do extremely well), and satisfaction with performance will be rated from 1 (not at all satisfied) to 10 (extremely satisfied). Final performance and satisfaction scores will be determined by calculating the mean of the scores for the four selected activities.	Baseline and post-intervention (8 weeks later )
Reaction Time Measurement	Participants will be assessed in a standardized seated position (feet fully in contact with the floor, shoulders in neutral alignment, elbows approximately 90° flexion). For reaction time measurements and related procedures, LED-based cue modules will be positioned on the table at fixed intervals, and the hand-to-cue distance will be standardized.	Baseline and post-intervention (8 weeks later )

Collaborators and Investigators

• Sponsor: Inonu University
• Investigators: Principal Investigator: Zeynal YASACI, inonu universitesi

Publications and helpful links

General Publications

• Saldıran T, Tanhan A, Çelikel R, Dinçer E. Reliability of a Visual-Cognitive Technology in Measuring Reaction Times: Associations with Age, Activity Level, and Grip Strength. J Manipulative Physiol Ther. 2025;48(6-9):789-99.
• Loubani K, Kizony R, Milman U, Schreuer N. Hybrid Tele and In-Clinic Occupation Based Intervention to Improve Women's Daily Participation after Breast Cancer: A Pilot Randomized Controlled Trial. Int J Environ Res Public Health. 2021;18(11).
• Mena-del Horno S, Balasch-Bernat M, Louw A, Luque-Suarez A, Rodríguez-Brazzarola P, Navarro-Ledesma S, et al. Is there any benefit of adding a central nervous system–focused intervention to a manual therapy and home stretching program for people with frozen shoulder? A randomized controlled trial. Journal of Shoulder and Elbow Surgery. 2023;32(7):1401-11.
• Duzgun I, Turgut E, Eraslan L, Elbasan B, Oskay D, Atay OA. Which method for frozen shoulder mobilization: manual posterior capsule stretching or scapular mobilization? J Musculoskelet Neuronal Interact. 2019;19(3):311-6.
• Yasaci Z, Celik D. Does Integration of Graded Motor Imagery Training Augment the Efficacy of a Multimodal Physiotherapy Program for Patients With Frozen Shoulder? A Randomized Controlled Trial. Clinical Orthopaedics and Related Research®. 2025;483(4):707-16.
• Lluch-Girbés E, Dueñas L, Mena-Del Horno S, Luque-Suarez A, Navarro-Ledesma S, Louw A. A central nervous system-focused treatment approach for people with frozen shoulder: protocol for a randomized clinical trial. Trials. 2019;20(1):498.
• Hendy A, Lamon S. The Cross-Education Phenomenon: Brain and Beyond. Frontiers in Physiology. 2017;8.
• Lee M, Carroll T. Cross Education. Sports Medicine. 2007;37:1-14.
• Paillard T. Cross-Education Related to the Ipsilateral Limb Activity on Monopedal Postural Control of the Contralateral Limb: A Review. Front Physiol. 2020;11:496.
• Mortezanejad M, Roostayi MM, Daryabor A, Salemi P. The Effect of Contraction Type and Training Volume in Unilateral Exercises on Cross-Education: A Narrative Review Study. Muscle Ligaments and Tendons Journal. 2023.
• Mirto M, Esposito F, Iaia FM, Codella R. Cross-Education of Strength: From Theory to Practice in Contemporary Sports Rehabilitation-A Narrative Review and Clinical Implications. Sports Med Open. 2025;11(1):129.
• Frazer AK, Pearce AJ, Howatson G, Thomas K, Goodall S, Kidgell DJ. Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength. Eur J Appl Physiol. 2018;118(9):1751-72.
• Sokk J, Gapeyeva H, Ereline J, Merila M, Pääsuke M. Shoulder muscle function in frozen shoulder syndrome patients following manipulation under anesthesia: A 6-month follow-up study. Orthopaedics & Traumatology: Surgery & Research. 2013;99(6):699-705.
• de la Serna D, Navarro-Ledesma S, Alayón F, López E, Pruimboom L. A Comprehensive View of Frozen Shoulder: A Mystery Syndrome. Front Med (Lausanne). 2021;8:663703.
• Vita F, Pederiva D, Tedeschi R, Spinnato P, Origlio F, Faldini C, et al. Adhesive capsulitis: the importance of early diagnosis and treatment. J Ultrasound. 2024;27(3):579-87.
• Mertens M, Meeus M, Girbes EL, Dueñas L, Twickler M, Verborgt O, et al. Differences in biomechanical and metabolic factors between patients with frozen shoulder and asymptomatic individuals. A cross-sectional study. Musculoskeletal science & practice. 2024;72:102980.
• Rawat P, Eapen C, Seema KP. Effect of rotator cuff strengthening as an adjunct to standard care in subjects with adhesive capsulitis: A randomized controlled trial. Journal of Hand Therapy. 2017;30(3):235-41.e8.
• Griesser MJ, Harris JD, Campbell JE, Jones GL. Adhesive Capsulitis of the Shoulder: A Systematic Review of the Effectiveness of Intra-Articular Corticosteroid Injections. JBJS. 2011;93(18):1727-33.
• Kim W-M, Seo Y-G, Park Y-J, Cho H-S, Lee S-A, Jeon S-J, et al. Effects of Different Types of Contraction Exercises on Shoulder Function and Muscle Strength in Patients with Adhesive Capsulitis. International Journal of Environmental Research and Public Health. 2021;18(24):13078.
• Millar N, Meakins A, Struyf F, Willmore E, Campbell A, Kirwan P, et al. Frozen shoulder. Nature Reviews Disease Primers. 2022;8.

Study record dates

Study Major Dates

• Study Start (Estimated): March 15, 2026
• Primary Completion (Estimated): December 25, 2026
• Study Completion (Estimated): December 25, 2026

Study Registration Dates

• First Submitted: March 2, 2026
• First Submitted That Met QC Criteria: March 30, 2026
• First Posted (Actual): April 3, 2026

Study Record Updates

• Last Update Posted (Actual): April 3, 2026
• Last Update Submitted That Met QC Criteria: March 30, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Function; Muscle strength; Frozen shoulder; Cross training
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Joint Diseases; Bursitis
• Other Study ID Numbers: 1004

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Participant data will be securely stored by the investigators and may be shared with authorized personnel if deemed necessary, in accordance with applicable privacy regulations.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No