The Effect of Unstable Loads on Scapular Kinematics and Muscle Activation During Overhead Press in Overhead Athletes With Subacromial Pain Syndrome

The research aims to compare the differences between stable and unstable load conditions during shoulder pressing in overhead athletes with SAPS and to compare the differences between SAPS and healthy athletes with stable and unstable load conditions.

Study Overview

• Status: Recruiting
• Conditions: Subacromial Pain Syndrome
• Intervention / Treatment: Behavioral: stable load shoulder press; Behavioral: Unstable load shoulder press

• Study Type: Observational
• Enrollment (Estimated): 27

Contacts and Locations

• Study Contact: Name: Yi Chung Tsai, Master; Phone Number: (886)972877917; Email: sc969183@gmail.com

Study Locations

• Taiwan
  • Taipei, Taiwan
    • Recruiting
    • National Yang Ming Chiao Tung University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Probability Sample

Study Population

Participants were recruited from sports-related venues.

Description

The inclusion criteria for both the experimental and control groups were as follows: (1) amateur or recreational overhead athletes aged 18-40 years (e.g., volleyball, tennis, baseball); (2) sport participation history of more than 3 years; (3) weekly overhead sport participation of more than 4 hours; (4) ability to meet the minimum loading requirements of the equipment for both stable and unstable conditions, defined as a 15-repetition maximum (15RM) for stable shoulder press of ≥10 kg and unstable shoulder press of ≥8 kg.

The individual inclusion criteria for the experimental group were: (1) diagnosis of subacromial pain syndrome, defined as at least 3 positive findings out of 5 clinical tests (Painful Arc test, Neer impingement test, Empty Can test, Hawkins-Kennedy impingement test, and Resisted External Rotation test); (2) Visual Analogue Scale (VAS) score of ≤3 during shoulder press performance; (3) symptoms present on the dominant side.

The individual inclusion criteria for the control group were: absence of shoulder pain within the past 6 months, including no pain at the glenohumeral joint, acromioclavicular joint, sternoclavicular joint, scapulothoracic joint, or cervical spine.

The exclusion criteria were as follows: (1) history of surgical intervention for fracture or dislocation of the shoulder or elbow joint within the past 6 months; (2) direct trauma to the cervical spine or upper extremity within the past 1 month; (3) shoulder pain or neurological symptoms of cervical origin; (4) any condition preventing the completion of the experimental protocol; (5) bilateral shoulder pain.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Control group	Behavioral: stable load shoulder press; Participants performed a shoulder press using a barbell loaded at their individual 15-repetition maximum; Behavioral: Unstable load shoulder press; Participants performed a shoulder press using a unstable loaded at their individual 15-repetition maximum
Experimental group	Behavioral: stable load shoulder press; Participants performed a shoulder press using a barbell loaded at their individual 15-repetition maximum; Behavioral: Unstable load shoulder press; Participants performed a shoulder press using a unstable loaded at their individual 15-repetition maximum

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Scapular kinematics (degrees) during shoulder elevation measured by VIPER™ system	Scapular upward rotation, posterior tilt, and external rotation angles (in degrees) were recorded during shoulder press using the VIPER™ electromagnetic tracking system. Data were collected at 30°, 60°, 90°, and 120° of humeral elevation, and reported as mean values for each angle.	Immediately after the single session
Surface electromyography (TeleMyo2400T G2, Noraxon USA Inc., Scottsdale, AZ, USA)	Muscle activation of upper trapezius, lower trapezius, serratus anterior, anterior deltoid, biceps brachii, triceps brachii, rectus abdominis, erector spinae during shoulder press	Immediately after the single session
Barbell trajectory (measured with camera)	The trajectory was captured by attaching reflective markers to the end of the barbell and recording kinematic data at a sampling frequency of 60 Hz using a camera.	Immediately after the single session

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Shoulder average pain intensity	Pain is measured with Visual Analogue scale (VAS) Score range from 0 to 10. Scoring of 0 represents no pain and scoring of 10 represents pain as bad as it could possibly be.	Immediately after the single session

Collaborators and Investigators

• Sponsor: National Yang Ming Chiao Tung University

Study record dates

Study Major Dates

• Study Start (Actual): September 26, 2024
• Primary Completion (Estimated): June 30, 2026
• Study Completion (Estimated): June 30, 2026

Study Registration Dates

• First Submitted: June 9, 2026
• First Submitted That Met QC Criteria: June 9, 2026
• First Posted (Actual): June 15, 2026

Study Record Updates

• Last Update Posted (Actual): June 15, 2026
• Last Update Submitted That Met QC Criteria: June 9, 2026
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: NYCU113008AF

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

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