Inter-Rater Reliability of Ultra Sound Based Rectus Abdominis Thickness Following Blood Flow Restriction Training

August 5, 2026 updated by: Riphah International University

Inter-Rater Reliability of Ultra Sound Based Rectus Abdominis Thickness Following Blood Flow Restriction Training : A Retrospective Analysis.

Accurate assessment of skeletal muscle morphology is important in sports physiotherapy, exercise rehabilitation, and research. B-mode ultrasonography is a non-invasive and accessible method for assessing muscle thickness; however, ultrasound-based measurements may be influenced by image acquisition, anatomical landmark identification, and operator-dependent measurement procedures. Establishing inter-rater reliability is therefore essential to determine whether different assessors can obtain consistent measurements of muscle thickness from the same ultrasound images. The rectus abdominis is an important component of the abdominal musculature and contributes to trunk stabilization and functional performance during exercise. Blood flow restriction (BFR) training has gained increasing attention as a low-load exercise strategy for promoting muscular adaptations, although research has predominantly focused on peripheral limb muscles. Therefore, this study aims to evaluate the inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurements following a standardized BFR training protocol using ImageJ software. Establishing reliable measurement of rectus abdominis thickness will provide a methodological basis for future research investigating abdominal muscle morphology and adaptations in sports physiotherapy, exercise rehabilitation, and BFR-based training.

Study Overview

Status

Recruiting

Conditions

Detailed Description

A retrospective methodological reliability study design will be employed to evaluate the inter-rater reliability of ultrasound-based measurements of rectus abdominis muscle thickness following a standardized blood flow restriction (BFR) training protocol. The study will utilize previously collected B-mode ultrasound images obtained from healthy young adult male participants who completed the original BFR training protocol. The existing dataset will be reviewed according to predefined eligibility criteria, and only ultrasound images of sufficient quality for identification and measurement of the rectus abdominis muscle will be included in the analysis.

The original BFR training protocol involved low-load resistance exercise performed under blood flow restriction. During the intervention, pneumatic cuffs were applied to the limbs, and participants performed a standardized squat exercise protocol at a low percentage of one-repetition maximum with prescribed repetitions and rest intervals. Ultrasound images of the rectus abdominis obtained according to the standardized imaging protocol will be analyzed retrospectively. The rectus abdominis was selected because it is a superficial abdominal muscle that can be visualized using B-mode ultrasonography and has relatively well-defined anatomical boundaries, allowing its thickness to be assessed using a standardized measurement procedure. Furthermore, the rectus abdominis contributes to trunk stabilization during functional and resistance exercises.

Ultrasound images will be analyzed using ImageJ software. Two independent raters will perform the measurements of rectus abdominis muscle thickness using the same standardized measurement protocol. The raters will independently identify the anatomical boundaries of the rectus abdominis and obtain linear thickness measurements from the ultrasound images. The use of a single standardized image-analysis platform and identical measurement procedures for both raters will minimize variability related to software and measurement techniques. The primary outcome will be the rectus abdominis muscle thickness measured in millimeters (mm).

Inter-rater reliability will be assessed using the Intraclass Correlation Coefficient (ICC) with a two-way random-effects model for absolute agreement and single measurements [ICC (2,1)], reported with the corresponding 95% confidence interval. ICC values below 0.50 will be interpreted as poor reliability, values from 0.50 to 0.75 as moderate reliability, values from 0.75 to 0.90 as good reliability, and values above 0.90 as excellent reliability. Absolute reliability and measurement error will additionally be assessed using the Standard Error of Measurement (SEM) and Minimal Detectable Change at the 95% confidence level (MDC95), where appropriate. Bland-Altman analysis will be performed to evaluate systematic differences and limits of agreement between the two raters. All statistical analyses will be conducted using SPSS, with the level of statistical significance set at p < 0.05.

If the ultrasound-based rectus abdominis thickness measurement demonstrates good to excellent inter-rater reliability, the findings will support the reproducibility of the standardized measurement protocol and its application in future research involving abdominal muscle morphology. The study may provide a methodological foundation for future investigations examining changes in abdominal muscle morphology following BFR and other exercise interventions, with potential relevance to sports physiotherapy, rehabilitation, and exercise science.

Study Type

Observational

Enrollment (Estimated)

50

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

  • Name: Dr Saad Rauf, PhD
  • Phone Number: 03325957732

Study Locations

  • Pakistan
      • Islamabad, Pakistan, 44000
        • Recruiting
        • Faculty of Rehabilitation for Data Collection and Research Work
        • Contact:
          • Muhammad Haris
          • Phone Number: 03437181808

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Non Athletes

Description

Inclusion Criteria:

  • Recreationally Active

Exclusion Criteria:

  • Known Musculoskeletal injury

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Retrospective BFR Cohort
Healthy active male participants who underwent a short-duration blood flow restriction (BFR) training protocol. Pre- and post-training ultrasound images of the rectus abdominis muscle were retrospectively analyzed to assess inter-rater reliability of ultrasound-based muscle thickness measurements.
Group 1
Healthy active male participants assessed before the BFR training program. Baseline B-mode ultrasound images of the rectus abdominis muscle were obtained and used for measurement of muscle thickness.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurement
Time Frame: Baseline (pre-training) and post-training ultrasound images obtained at the completion of the two-week BFR training protocol.
Inter-rater reliability between two independent raters in measuring rectus abdominis muscle thickness from B-mode ultrasound images using ImageJ software.
Baseline (pre-training) and post-training ultrasound images obtained at the completion of the two-week BFR training protocol.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurement
Time Frame: Pre-training and immediately post-training.
Rectus abdominis muscle thickness
Pre-training and immediately post-training.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Riphah International University

Investigators

  • Principal Investigator: Saad Rauf, PhD, Riphah International University, Isra University, Islamabad

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

August 4, 2026

Primary Completion (Estimated)

September 6, 2026

Study Completion (Estimated)

September 20, 2026

Study Registration Dates

First Submitted

August 5, 2026

First Submitted That Met QC Criteria

August 5, 2026

First Posted (Actual)

August 10, 2026

Study Record Updates

Last Update Posted (Actual)

August 10, 2026

Last Update Submitted That Met QC Criteria

August 5, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

  • REC/MS-PT/02569

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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