Impact of Neuromuscular Control With and Without Electrical Stimulation and Long-term Effect of Kinetic Chain Exercises in Multidirectional Shoulder Instability Patients

Summary

Background: Shoulder instability is commonly observed in adolescents and young females, ranging from asymptomatic multidirectional instability (MDI) to symptomatic conditions. Patients with MDI often experience shoulder pain, muscle tension, and episodes of subluxation. This condition is associated with hypermobility spectrum disorder (HSD) and hypermobile Ehlers-Danlos syndrome (hEDS), both characterized by generalized joint laxity and recurrent joint dislocations, significantly affecting daily activities and athletic performance. Current literature lacks clarity on the actual humeral head displacement, shoulder joint kinetics, and muscle activity characteristics during movement in patients with MDI accompanied by HSD or hEDS. Additionally, the effects of electrical stimulation on different shoulder muscles and its impact on humeral head displacement in MDI patients remain to be validated.

Objective: The purposes of this study are to (1) examine whether patients with hEDS/HSD and MDI have increased humeral head translation compared to healthy controls during three isometric contraction ; (2) investigate the relationship between humeral head translation and associated muscle activity during three isometric exercises ; (3) examine the effect of NMES and NMCT to humerus/scapula muscles on humeral head translations in MDI patients with hEDS/HSD Outcome measurements: The primary outcomes include changes in acromiohumeral distance (AHD) or humeroglenoid distance (HGD) under four conditions (no stimulation, NMCT, BLH/Infraspinatus/MD stimulation, and SA stimulation) during three isometric contractions (shoulder flexion, horizontal adduction, and fully extended elbow holding weight).

The secondary outcomes assess muscle activation differences in BLH, infraspinatus, MD, UT, LT, and SA before and after NMCT.

Conditions

• Multidirectional Instability
• Hypermobility Spectrum Disorder
• Electrical Stimulation
• Neuromuscular Control
• Humeral Head Translation

Interventions

BEHAVIORAL

neuromuscular eletrical stimulation

The GM300TE COMBO NMES (Gemore Technology Co., Ltd., New Taipei City, Taiwan), a portable machine with dual controllable channels and a manual switch, will be applied to the biceps long head, infraspinatus, middle deltoid, LT and SA. Muscle force generation is modulated by stimulated frequency, pulse width, and intensity \[Bdaiwi et al., 2015\]. It linearly increases with stimulated amplitude and pulse duration. The electronics of the unit creates the electrical impulses with an output frequency of 50 Hz and a pulse width of 300 microseconds. The synchronous (S) mode and asymmetrical rectangular wave-pulse will be used throughout the experiment following protocol from previous research (Bdaiwi, et al., 2015). The amplitude will be settled as muscle motor-level contraction with self-perception of maximal tolerable intensity. The time of tetanic stimulation is 7 seconds with 20-second intervals between stimulations to avoid muscle fatigue. The two circular electrodes are used on each muscl

BEHAVIORAL

neuromuscular control training

To ensure that the humeral head remains centered during the three specific isometric tasks, the examiner positioned the shoulder according to the direction of instability (anterior, inferior, or posterior) by placing the arm in 20° of shoulder flexion, 0° (neutral), or 10° of extension, respectively. In each position, the examiner gently applied a downward force on the upper arm in a horizontal direction, and the participant was instructed to gently resist the force. The goal was to guide the humeral head gradually toward the center of the glenoid, without excessive scapular movement. This training was directly supervised by a physical therapist, who provided verbal and tactile feedback to ensure correct movement execution (Figure 1). The physical therapist was also responsible for conducting the USG assessment. After a 5-minute familiarization session, participants performed the designated instability-specific isometric task for 3 repetitions.

Sponsors & Collaborators

• National Taiwan University Hospital

  lead OTHER

Study Design

Allocation

NON_RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

20 Years

Max Age

50 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-11-09

Primary Completion

2026-06-15

Completion

2026-07-30

Countries

• Taiwan

Study Locations