Investigation of Latissimus Dorsi Muscle Activation During Different Exercises
Overview
- Phase
- Not Applicable
- Status
- Recruiting
- Sponsor
- Hacettepe University
- Enrollment
- 30
- Locations
- 1
- Primary Endpoint
- Electromyography
Overview
Brief Summary
This single-visit, laboratory study will quantify latissimus dorsi activation during standardized band/body-weight exercises commonly used in rehabilitation (e.g., standing bent-over row, inferior glide, seated press-up, body-lifting). Healthy, physically active adults (18-40 y; Tegner ≥5) will perform three repetitions per exercise with metronome-paced phases (≈3 s concentric, 3 s isometric, 3 s eccentric), 5-s rest between repetitions and 2-min between exercises; load will be individualized to reach OMNI RPE 6-8. Surface EMG (TeleMyo DTS; Noraxon) will be recorded from the latissimus dorsi (medial and lateral) and selected synergists (teres major, infraspinatus, posterior deltoid, triceps); electrode placement will follow SENIAM recommendations. Signals will be band-pass filtered (20-500 Hz), rectified, RMS-smoothed with a 100-ms window, and normalized to %MVIC using standardized MVC tests; exercise/MVC order will be randomized to limit bias. The primary outcome is mean normalized EMG amplitude per exercise; secondary outcomes include peak amplitude and categorical activation levels (low ≤20% MVIC, moderate 21-40%, high 41-60%, very high >60%). The study involves minimal risk (possible mild skin irritation under electrodes and transient post-exercise fatigue).
Detailed Description
The latissimus dorsi (LD) originates from the spinous processes of the lower six thoracic vertebrae and the thoracolumbar fascia/iliac crest, and-together with the teres major-attaches to the medial lip of the intertubercular groove of the humerus. Functionally, LD contributes to shoulder adduction, internal rotation, and extension, linking the upper limb to the trunk. Alongside the rotator cuff, prevention of superior translation of the humeral head may be provided by the glenohumeral adductors (pectoralis major and LD) acting as humeral head depressors via a medio-inferior vector created by their tendon orientation. From an osteokinematic perspective, LD may protect against subacromial pain by facilitating inferior glide of the humeral head on the glenoid.
Selecting an appropriate strengthening exercise is critical to restore muscle performance and functional arm elevation in patients with shoulder injury or dysfunction. The literature emphasizes exercises targeting activation of the rotator cuff and scapulothoracic muscles that contribute to functional elevation. Surface electromyography (sEMG) is commonly used to guide exercise selection and progression by quantifying a muscle's contribution across different exercises, thereby enabling evidence-based advancement in strengthening programs.
However, much of the existing LD literature centers on lateral pull-down variations, with limited data for rehabilitation-relevant tasks such as low row, inferior glide, bent-over row (with trunk flexion), seated press-up, and body-lifting. Focusing on a single exercise limits clinical decision-making for shoulder rehabilitation (exercise selection and progression). Therefore, to support a scientific, evidence-based progression for LD strengthening in rehabilitation, this study was planned to obtain comprehensive sEMG data across multiple exercises.
Aim: To examine LD EMG activation levels during different exercises and determine between-exercise differences.
Study Design
- Study Type
- Observational
- Observational Model
- Other
- Time Perspective
- Cross Sectional
Eligibility Criteria
- Ages
- 18 Years to 40 Years (Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Age 18-40 years
- •No range-of-motion restriction at the glenohumeral joint
- •No shoulder, cervical, or lumbar region complaints/injury within the past 6 months
- •No systemic or neurological disease
- •Competent to consent and provides written informed consent
- •Tegner Activity Scale ≥ 5
Exclusion Criteria
- •Body mass index (BMI) \> 25 kg/m²
Outcomes
Primary Outcomes
Electromyography
Time Frame: Baseline (Day 1)
Surface EMG from the latissimus dorsi (medial and lateral sites) will be recorded with an 8-channel system (TeleMyo DTS; Noraxon). Skin will be shaved and cleaned with 70% isopropyl alcohol; bipolar Ag/AgCl electrodes will be placed per SENIAM with a 2 cm inter-electrode distance (MLD \~lateral to T9; LLD \~4 cm inferior to the scapular inferior angle, midway between the spine and lateral trunk). A synchronized video (Logitech C920) will mark movement onset/offset and will be deleted after analysis (no copies kept). Signals will be normalized to %MVIC using three 5-s MVIC trials (30-s rest between trials; \~2-min between muscles) performed in standardized positions with verbal encouragement. The outcome is the mean %MVIC during the steady phase of each exercise.
Secondary Outcomes
- Electromyography-Other muscles(Baseline (Day 1))
- Activity Level(Baseline (Day 1))
Investigators
Irem Duzgun
Professor, Department of Physiotherapy and Rehabilitation
Hacettepe University