Acromioclavicular Joint Dislocation, Acromioclavicular Joint Injury
Conditions
Keywords
Cross-Education, Contralateral Training, Eccentric Exercise, Concentric Exercise, Resistance Training, Immobilization, Shoulder Rehabilitation, Acromioclavicular Joint Injury, Neuromuscular Function, Muscle Strength, Transcranial Magnetic Stimulation, Electromyography, Upper Limb Function, Physical Therapy, Rehabilitation
Brief summary
This randomized controlled trial aims to compare the effects of contralateral eccentric and concentric resistance training performed during the immobilization period following acromioclavicular joint injury. Immobilization is commonly prescribed after injury but may lead to reductions in muscle mass, neuromuscular function, force production, and upper-limb functionality. Contralateral resistance training, also known as cross-education training, involves exercising the non-injured limb to induce beneficial adaptations in the immobilized limb through neural mechanisms. While both eccentric and concentric exercise may produce contralateral effects, their relative effectiveness in a clinical population remains unclear. Participants with acute acromioclavicular joint injury requiring sling immobilization will be randomly assigned to either a contralateral eccentric training group or a contralateral concentric training group. During immobilization, participants will perform supervised resistance training with the non-injured upper limb. Following immobilization, all participants will receive the same standardized rehabilitation program. Neuromuscular function, muscle morphology, force production, upper-limb function, and quality of life will be assessed before immobilization, after immobilization, and following rehabilitation. The findings may contribute to the development of more effective rehabilitation strategies for patients recovering from upper-limb injuries requiring temporary immobilization.
Detailed description
Acromioclavicular joint injury is one of the most common shoulder injuries in physically active individuals. Temporary immobilization using a sling is frequently prescribed during the acute phase of recovery; however, immobilization can result in rapid declines in muscle strength, muscle mass, neuromuscular function, and upper-limb performance. Cross-education is a neurophysiological phenomenon whereby unilateral resistance training induces adaptations in the contralateral untrained limb. Previous experimental studies have demonstrated that resistance exercise performed with the non-immobilized limb may attenuate strength loss and neuromuscular impairments in an immobilized limb. However, the relative effectiveness of different muscle contraction modes during cross-education training in clinical populations remains poorly understood. The purpose of this randomized controlled trial is to compare the effectiveness of contralateral eccentric versus contralateral concentric resistance training performed during the immobilization period in patients with acromioclavicular joint injury. Participants will be randomly allocated to one of two intervention groups: (1) contralateral eccentric resistance training or (2) contralateral concentric resistance training. Both interventions will be performed using the non-injured upper limb during the period of prescribed sling immobilization. Participants will undergo comprehensive assessments before immobilization, immediately after immobilization, and after completion of a standardized rehabilitation program. Outcomes will include measures of neuromuscular function obtained through peripheral nerve stimulation, transcranial magnetic stimulation, electromyography, and voluntary force assessments. Muscle morphology will be evaluated using ultrasound imaging, while upper-limb function and quality of life will be assessed using validated clinical questionnaires. Following immobilization, all participants will receive the same rehabilitation program focused on restoring shoulder stability, muscle strength, and functional capacity. The primary objective is to determine whether eccentric or concentric contralateral resistance training more effectively preserves neuromuscular function and facilitates recovery following immobilization. The results of this study may provide evidence to optimize rehabilitation strategies for patients with acromioclavicular joint injuries and other musculoskeletal conditions requiring temporary upper-limb immobilization.
Interventions
BEHAVIORALContralateral Eccentric Resistance Training
Supervised unilateral eccentric elbow flexor training performed with the non-injured limb during sling immobilization (2-4 weeks). Training is performed 3 times/week, 5 sets of 8-12 repetitions at 60-90% 1RM, with 4-second contractions and 3-minute rest intervals between sets.
BEHAVIORALContralateral Concentric Resistance Training
Supervised unilateral concentric elbow flexor training performed with the non-injured limb during sling immobilization (2-4 weeks). Training is performed 3 times/week, 5 sets of 8-12 repetitions at 60-90% 1RM, with 4-second contractions and 3-minute rest intervals between sets.
Sponsors
Universidad Nacional Andres Bello
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
SINGLE (Outcomes Assessor)
Masking description
Outcome assessors and data analysts will be blinded to group allocation throughout data collection and statistical analysis.
Intervention model description
Participants with acute acromioclavicular joint injury requiring a period of upper-limb immobilization with a sling, either following conservative management or surgical repair, will be randomly assigned to one of two parallel intervention groups: contralateral concentric resistance training or contralateral eccentric resistance training. Both interventions will be performed with the non-injured upper limb during the immobilization period. Following immobilization, all participants will receive the same standardized rehabilitation program. Outcomes will be assessed at baseline, after immobilization, and after completion of rehabilitation.
Eligibility
Sex/Gender
ALL
Age
18 Years to 36 Years
Healthy volunteers
No
Inclusion criteria
* Men and women aged 18 to 36 years. * Diagnosis of acute acromioclavicular joint injury confirmed by an orthopedic surgeon. * Physician-prescribed upper-limb immobilization using a sling for approximately 2 to 4 weeks, with or without surgical repair. * Ability to understand study procedures and provide written informed consent. * Medical clearance to participate in the rehabilitation and resistance training program.
Exclusion criteria
* Previous surgery or severe musculoskeletal injury affecting either upper limb within the previous 12 months. * Neurological disorders affecting motor function or neuromuscular performance. * Contraindications to transcranial magnetic stimulation according to established safety guidelines. * Current participation in another clinical trial or structured upper-limb rehabilitation program. * Cognitive impairment or inability to comply with study procedures. * Pregnancy. * Any medical condition that, in the opinion of the investigators, may compromise participant safety or study participation.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Maximal Voluntary Isometric Contraction | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Maximal voluntary isometric force of the injured upper limb assessed using a calibrated dynamometer. Force values will be recorded during standardized maximal isometric contractions and used to evaluate changes in muscle performance throughout immobilization and rehabilitation. Unit: Newtons (N) |
| Rate of Force Development | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Rate of force development (RFD) of the injured upper limb assessed during maximal voluntary isometric contractions using a calibrated dynamometer. RFD will be calculated from the force-time curve and used as an indicator of explosive force production and neuromuscular performance. Unit: N·s-¹ (N/s) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Elbow Flexors Voluntary Activation | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Voluntary activation of the elbow flexors assessed using the interpolated twitch technique during maximal voluntary isometric contractions. Values will be expressed as a percentage of voluntary neural drive to the muscle. Unit: % |
| Biceps Brachii Motor Supramaximal Response Amplitude | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Peak-to-peak amplitude of the motor supramaximal response (MSUP) evoked by peripheral nerve stimulation during submaximal contractions as an indicator of motor pathway excitability. Unit: mV |
| Biceps Brachii Motor Evoked Potential Amplitude | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Motor evoked potential (MEP) amplitude elicited by transcranial magnetic stimulation and normalized to peripheral responses to assess corticospinal excitability. Unit: mV |
| Biceps Brachii Silent Period Duration | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Duration of the electromyographic silent period following transcranial magnetic stimulation during voluntary contractions as an indicator of cortical inhibition. Unit: ms |
| Biceps Brachii Short-Interval Intracortical Inhibition | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Short-interval intracortical inhibition assessed using paired-pulse transcranial magnetic stimulation as an index of intracortical inhibitory function. Unit: mV |
| Biceps Brachii Cervicomedullary Motor Evoked Potential Amplitude | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Motor unit discharge characteristics assessed using high-density surface electromyography, including discharge rate, recruitment thresholds, and estimates of intrinsic motoneuron properties. Unit: mV |
| Biceps Brachii Motor Unit Behavior | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Motor unit discharge characteristics assessed using high-density surface electromyography, including discharge rate, recruitment thresholds, and estimates of intrinsic motoneuron properties. Unit: pulses/s (pps) |
| Biceps Brachii MMAX Amplitude | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Peak-to-peak amplitude of the maximal compound muscle action potential (MMAX) evoked by peripheral nerve stimulation as an indicator of peripheral excitability. Unit: mV |
| Biceps Brachii Peripheral Contractile Properties | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Evoked twitch and doublet force responses obtained using peripheral nerve stimulation to assess muscle contractile function. Unit: N |
| Biceps Brachii Muscle Thickness | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Muscle thickness assessed by B-mode ultrasonography as an indicator of muscle morphology and preservation during immobilization and rehabilitation. Unit: mm |
| Upper Limb Function (QuickDASH) | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Upper-limb disability and functional status assessed using the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire. Unit: 0-100 points |
| Health-Related Quality of Life (SF-36) | Baseline, post-immobilization (2-4 weeks), and post-rehabilitation (6-8 weeks) | Health-related quality of life assessed using the 36-Item Short Form Health Survey (SF-36). Unit: 0-100 points |
Countries
Chile
Contacts
CONTACTOmar E Valdés Tapia, PT, MSc, PhD(c)
STUDY_DIRECTORClaudio Chamorro Lange, PhD
Universidad Nacional Andres Bello
STUDY_DIRECTORLuis Peñailillo Escaráte, PhD
Universidad Nacional Andres Bello
Outcome results
None listed