Latissimus Dorsi Activation During Shoulder Extension Exercises

NCT ID: NCT07297758

Last Updated: 2025-12-29

Basic Information

• Recruitment Status: RECRUITING
• Total Enrollment: 30 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2025-10-14
• Study Completion Date: 2026-03-01

Brief Summary

This observational, cross-sectional laboratory study at Hacettepe University will examine surface EMG activation of the latissimus dorsi during resisted, dynamic shoulder extension performed at three shoulder flexion angles (30°,60°, 90°, 120°). The primary objective is to quantify latissimus dorsi activation and to determine how elevation angle influences activation; secondary analyses compare synergists.

Detailed Description

During shoulder abduction or flexion, narrowing of the subacromial space can lead to subacromial pain syndrome. Weakness or poor coordination of the scapulothoracic and scapulohumeral muscles is among the main causes of subacromial narrowing in individuals with symptomatic rotator cuff tendinopathy. More specifically, insufficient scapular upward rotation and posterior tilt, together with an inadequate ability of the rotator cuff to counter the deltoid's superior pull on the humeral head, may cause impingement of the subacromial soft tissues during overhead dynamic tasks. In young, healthy shoulders, the cranially directed forces that occur during abduction are balanced by co-contraction of the rotator cuff, which prevents superior translation of the humeral head and protects subacromial tissues. When this stabilizing role of the rotator cuff diminishes, the deltoid attempts to compensate; however, this compensation produces a more cranially oriented force, increasing superior migration of the humeral head and the likelihood of subacromial pain.

The latissimus dorsi (LD) originates from the spinous processes of the lower thoracic vertebrae, the thoracolumbar fascia, and the iliac crest, and-together with the teres major-attaches to the medial lip of the intertubercular groove of the humerus. It contributes to shoulder adduction, internal rotation, and extension, and is an important muscle directly linking the upper limb to the trunk. In addition to the rotator cuff, the glenohumeral adductors (pectoralis major and latissimus dorsi) also help limit superior translation of the humeral head; owing to the medio-inferior direction of their tendon force vectors, they act as humeral head depressors. Osteokinematically, the LD can pull the humeral head inferiorly over the glenoid fossa, potentially helping to prevent subacromial impingement.

Various exercises have been recommended for LD rehabilitation, and surface electromyography (sEMG) studies have examined LD activity during movements such as pulldown and pullover. Numerous studies have also sought to determine maximal voluntary isometric contraction (MVIC) of the LD. Prior EMG research indicates that the highest LD MVIC levels are obtained during maximal isometric shoulder extension. A recent study using both surface and fine-wire electrodes also recorded higher LD activation during shoulder extension compared with trunk tasks. Although shoulder extension exercises are widely used at different elevation angles in clinical practice, the effects of performing extension at different angles-particularly on LD activation-have not been clearly delineated. Despite various recommendations for LD rehabilitation, it remains unclear whether different implementations produce different activation profiles, and LD activation during dynamic application of this exercise has not yet been investigated. Therefore, it is important to examine how the highest LD activity obtained during maximal isometric shoulder extension changes when the exercise is performed dynamically. Defining the LD activation profile in dynamic exercise may inform appropriate exercise selection in clinical rehabilitation and help reduce the risk of subacromial impingement.

Aim. To address this gap by examining the level of LD activation during dynamic shoulder extension relative to the reference activity determined by maximal isometric shoulder extension. The study has two specific aims: (1) to determine the EMG activation level of the latissimus dorsi during a shoulder extension exercise, and (2) to investigate the effects of performing shoulder extension at different elevation angles on latissimus dorsi activation.

Conditions

Muscle Activation

Keywords

Shoulder; Latissimus Dorsi; Exercise

Study Design

• Observational Model Type: OTHER
• Study Time Perspective: CROSS_SECTIONAL

Study Groups

Healthy Active Adults

Ages 18-40; Tegner ≥5; no GH restriction; no shoulder/cervical/lumbar complaints in last 6 months; no systemic/neurologic disease; BMI ≤25 kg/m².

Exercise

Intervention Type: BEHAVIORAL

Standing with the shoulder in \~30° abduction and external rotation and the elbow extended, participants elevate the arm to three preset flexion angles (30°,60°, 90°, 120°; measured by goniometer) and then perform shoulder extension past the trunk against color-coded elastic bands. Bands are anchored overhead and pulled diagonally downward; the band angle is adjusted to match each shoulder-flexion condition. Tempo is metronome-paced: 3 s concentric, 3 s isometric (at peak), 3 s eccentric. Resistance is individualized using the OMNI Perceived Exertion Scale and titrated until 6-8/10 is reached prior to data capture. Each condition is recorded for 3 repetitions with \~5 s between reps; \~2 min rest is provided between conditions. A brief familiarization (\~3 min per condition) is given, and the order of MVICs and exercise conditions is randomized.

Interventions

Exercise

Standing with the shoulder in \~30° abduction and external rotation and the elbow extended, participants elevate the arm to three preset flexion angles (30°,60°, 90°, 120°; measured by goniometer) and then perform shoulder extension past the trunk against color-coded elastic bands. Bands are anchored overhead and pulled diagonally downward; the band angle is adjusted to match each shoulder-flexion condition. Tempo is metronome-paced: 3 s concentric, 3 s isometric (at peak), 3 s eccentric. Resistance is individualized using the OMNI Perceived Exertion Scale and titrated until 6-8/10 is reached prior to data capture. Each condition is recorded for 3 repetitions with \~5 s between reps; \~2 min rest is provided between conditions. A brief familiarization (\~3 min per condition) is given, and the order of MVICs and exercise conditions is randomized.

Intervention Type: BEHAVIORAL

Eligibility Criteria

Inclusion Criteria

• Age between 18 and 40,
• No restriction of the glenohumeral joint,
• No complaints related to the shoulder, cervical, or lumbar region in the last 6 months,
• No systemic or neurological disease,
• Agreeing to participate in the study,
• A Tegner Activity Score of 5 or higher,

Exclusion Criteria

• A body mass index greater than 25 kg/m2

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 40 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Hacettepe University

OTHER

Sponsor Role: lead

Responsible Party

Irem Duzgun

Professor, Department of Physiotherapy and Rehabilitation

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Irem Duzgun, PhD, Professor

Role: PRINCIPAL_INVESTIGATOR

Hacettepe University

Locations

Hacettepe University

Ankara, Samandag, Turkey (Türkiye)

Site Status: RECRUITING

Countries

Turkey (Türkiye)

Central Contacts

Irem Duzgun, Professor, PhD

Role: CONTACT

Phone: 312-305 15 76

Email: iremduzgun@hacettepe.edu.tr

Kubra Caylan Gurses, MSc

Role: CONTACT

Phone: 312 305 25 25-186

Email: kubracaylan@hacettepe.edu.tr

Facility Contacts

Irem Duzgun, PhD, Professor

Role: primary

Other Identifiers

Shoulder-EX-EMG

Identifier Type: -

Identifier Source: org_study_id