Doppler Ultrasound-Based Leg Blood Flow Assessment During Single-Leg Knee-Extensor Exercise in an Uncontrolled Setting

Summary

This test-retest study evaluated leg blood flow measured by the Doppler ultrasound technique during single-leg knee-extensor exercise. The within-day, between-day, and inter-rater reliability of the method was investigated. The approach demonstrated high within-day and acceptable between-day reliability. However, the inter-rater reliability was unacceptably low during rest and at low workloads.

Abstract

Doppler ultrasound has revolutionized the assessment of organ blood flow and is widely used in research and clinical settings. While Doppler ultrasound-based assessment of contracting leg muscle blood flow is common in human studies, the reliability of this method requires further investigation. Therefore, this study aimed to investigate the within-day test-retest, between-day test-retest, and inter-rater reliability of Doppler ultrasound for assessing leg blood flow during rest and graded single-leg knee-extensions (0 W, 6 W, 12 W, and 18 W), with the ultrasound probe being removed between measurements. The study included thirty healthy subjects (age: 33 ± 9.3, male/female: 14/16) who visited the laboratory on two different experimental days separated by 10 days. The study did not control for major confounders such as nutritional state, time of day, or hormonal status. Across different exercise intensities, the results demonstrated high within-day reliability with a coefficient of variation (CV) ranging from 4.0% to 4.3%, acceptable between-day reliability with a CV ranging from 10.1% to 20.2%, and inter-rater reliability with a CV ranging from 17.9% to 26.8%. Therefore, in a real-life clinical scenario where controlling various environmental factors is challenging, Doppler ultrasound can be used to determine leg blood flow during submaximal single-leg knee-extensor exercise with high within-day reliability and acceptable between-day reliability when performed by the same sonographer.

Introduction

Doppler ultrasound, introduced in the 1980s, has been extensively used to determine contracting muscle blood flow, particularly in the single-leg knee-extensor model, allowing measurement of blood flow in the common femoral artery (CFA) during small muscle mass activation^1,2,3,4,5,6. Doppler ultrasound-based blood flow technology has provided valuable insights into vascular regulation in various populations, including healthy adults^7,

Protocol

The study was evaluated by the Regional Ethical Committee of the Capital Region of Denmark (file no. H-21054272), who determined that this was a quality study. In accordance with Danish legislation, the study was thus approved locally by the internal Research and Quality Improvement Board at the Department of Clinical Physiology and Nuclear Medicine, Rigshospitalet (file no. KF-509-22). The study was performed according to the guidelines of the Declaration of Helsinki. All subjects provided oral and written informed cons.......

Discussion

This study assessed the reliability of Doppler ultrasound methodology for evaluating leg blood flow (LBF) during submaximal single-leg knee-extensor exercise in healthy participants. The results indicated high within-day reliability and acceptable between-day reliability, while inter-rater reliability was found to be unacceptable at rest and at 0 W.

Although probe removal between measurements appeared to have little impact, the difference in reliability between within-day and between-day measu.......

Materials

Name	Company	Catalog Number	Comments
EKO GEL	EKKOMED A7S	DK-7500 Holstebro
RStudio, version 1.4.1717	R Project for Statistical Computing
Saltin Chair			This was built from an ergometer bike and a carseat owned by Professor Bengt Saltin. The steelconstruction was built from a specialist who custommade it.
Ultrasound apparatus equipped with a linear probe (9 MHz, Logic E9)	GE Healthcare	Unknown	GE Healthcare, Milwaukee, WI, USA
			Ultrasound gel