The Centre for Physical Activity Research (CFAS) is supported by TrygFonden (grants ID 101390 and ID 20045. JPH was supported by grants from Helsefonden and Rigshospitalet. During this work, RMGB was supported by a post.doc. grant from Rigshospitalet.

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...

Assessing Leg Blood Flow in Training Workloads

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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...

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 activation1,2,3,4,5,6. Doppler ultrasound-based blood flow technology has provided valuable insights into vascular regulation in various populations, including healthy adults7,8, individuals with diabetes9, hypertension10, COPD11,12, and heart failure13,14.
One advantage of Doppler ultrasound is its non-invasiveness compared to other blood flow determination methods like thermodilution, and it can be combined with arterial and venous catheterization if necessary3,4,6,15. It also enables beat-to-beat blood flow velocity measurement, allowing for the detection of rapid changes16. However, Doppler ultrasound-based blood measurements have limitations, including difficulties in obtaining stable recordings during excessive limb movement at near-maximal exercise intensities and the requirement for ultrasound accessibility to the targeted blood vessel, excluding evaluations during ergometer bicycling15. Hence, the single-leg knee-extensor model is well-suited for LBF evaluation using Doppler ultrasound during dynamic exercise at submaximal intensities17, minimizing the influence of exercise-related heart and lung limitations and facilitating comparisons between healthy subjects and patients with cardio-pulmonary diseases11.
Despite being widely used, the between-day reliability of the single-leg knee-extensor model using Doppler ultrasound has not been investigated on a larger scale in recent decades, with prior studies involving small populations (n = 2)3,18,19,20.
This study aimed to investigate (1) the within-day test-retest reliability, (2) the between-day test-retest reliability, and (3) the inter-rater reliability of Doppler ultrasound for LBF evaluation during single-leg knee-extensor exercise at 0 W, 6 W, 12 W, and 18 W. The measurements were conducted in a clinically realistic scenario where the probe was removed between measurements. It is important to note that several intrinsic and extrinsic environmental factors known to influence LBF were not controlled during the measurements, which could introduce variability and affect reliability. Considering advancements in Doppler ultrasound technology and blood flow analysis software, we hypothesized that, even in an uncontrolled setting, acceptable within- and between-day reliability of LBF measurements could be achieved at all intensities when performed by the same sonographer.

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			<td>EKO GEL</td>
			<td>EKKOMED A7S</td>
			<td>DK-7500 Holstebro</td>
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			<td>RStudio, version 1.4.1717</td>
			<td>R Project for Statistical Computing</td>
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			<td>Saltin Chair</td>
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			<td>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.</td>
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			<td>Ultrasound apparatus equipped with a linear probe (9 MHz, Logic E9)</td>
			<td>GE Healthcare</td>
			<td>Unknown</td>
			<td>GE Healthcare, Milwaukee, WI, USA</td>
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			<td>&#160; &#160;</td>
			<td>&#160; &#160;</td>
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			<td>Ultrasound gel</td>
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doppler ultrasound-based leg blood flow assessment during single-leg knee-extensor exercise in an uncontrolled setting

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 &#177; 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.

Author Spotlight: Assessing the Reliability of Doppler Ultrasound in Measuring Leg Blood Flow 

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

This method is widely recognized and applied in numerous clinical and research settings. The primary objective of this study was to assist the reproducibility of the method, thereby providing valuable insights into the measurement error. By doing so, we can say what is genuine physiological change and what is due to measurement error.Ultimately, this will enhance our understanding of this method. The primary obstacle lies in exploring physiological changes during various activities in everyday life, as conducting such investigation is feasible only under specific experimental setups. t has been over two decades since the last reliability study was conducted during single leg knee extensor exercise.Over this period, technology has significantly evolved, making it imperative to revisit this research area to gain valuable insight into the measurement era associated with the current method. Doppler ultrasound is non-invasive compared to other blood flow determination methods like Thermodilution, and it can be combined with arterial and venous catheterization if necessary. It also enables beat to beat blood flow velocity measurements so we could detect rapid changes.In the future, our main goal is to investigate the regulation of blood flow to contracting skeletal muscle in patients with chronic obstructive pulmonary disease.

Participants 
From May 2022 to October 2022, a total of thirty healthy men and women were recruited to participate in the study. All participants had no history of cardiovascular, metabolic, or neurological diseases. They were not instructed to make any changes to their usual habits, including caffeine, alcohol, nicotine, vigorous exercise, or any other factors that could potentially impact vascular function.
Experimental procedures 
Participants rep...

Watch this Scientific Journal Video about Assessing the Reliability of Doppler Ultrasound in Measuring Leg Blood Flow at JoVE.com

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.

Doppler ultrasound has revolutionized the assessment of organ blood flow and is widely used in research and clinical settings. While Doppler ...

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1.5K Görüntüleme.  Copenhagen University Hospital. Bu yöntem çok sayıda klinik ve araştırma ortamında yaygın olarak tanınmakta ve uygulanmaktadır. Bu çalışmanın temel amacı, yöntemin tekrarlanabilirliğine yardımcı olmak ve böylece ölçüm hatası hakkında değerli bilgiler sağlamaktı. Bunu yaparak, neyin gerçek fizyolojik değişim olduğunu ve neyin ölçüm hatasından kaynaklandığını söyleyebiliriz.Sonuç olarak, bu, bu yöntem hakkındaki anlayışımızı geliştirecektir. Birincil engel, günlük yaş...