This narrative review provides an overview of the current knowledge of B-mode ultrasound-derived echo intensity (EI) as an indicator of skeletal muscle quality. PubMed and Google Scholar were used to search the literature. Advanced search functions were used to find original studies with the terms ‘echo intensity’ and/or ‘muscle quality’ in the title and/or abstract. Publications that conceptually described muscle quality but did not include measurement of EI were not a focus of the review. Importantly, the foundational premise of EI remains unclear. While it is likely that EI reflects intramuscular adiposity, data suggesting that these measurements are influenced by fibrous tissue is limited to diseased muscle and animal models. EI appears to show particular promise in studying muscular aging. Studies have consistently reported an association between EI and muscle function, though not all chronic interventions have demonstrated improvements. Based on the existing literature, it is unclear if EI can be used as a marker of muscle glycogen following exercise and nutritional interventions, or if EI is influenced by hydration status. Inconsistent methodological approaches used across laboratories have made comparing EI studies challenging. Image depth, rest duration, participant positioning, probe tilt, and the decision to correct for subcutaneous adipose tissue thickness are all critical considerations when interpreting the literature and planning studies. While some areas show conflicting evidence, EI shows promise as a novel tool for studying muscle quality. Collaborative efforts focused on methodology are necessary to enhance the consistency and quality of the EI literature.

Echo intensity as an indicator of skeletal muscle quality: applications, methodology, and future directions.

Muscle quality (MQ), defined as the amount of strength and/or power per unit of muscle mass, is a novel index of functional capacity that is increasingly relied upon as a critical biomarker of muscle health in low functioning aging and pathophysiological adult populations. Understanding the phenotypical attributes of MQ and how to use it as an assessment tool to explore the efficacy of resistance exercise training interventions that prioritize functional enhancement over increases in muscle size may have implications for populations beyond compromised adults, including healthy young adults who routinely perform physically demanding tasks for competitive or occupational purposes. However, MQ has received far less attention in healthy young populations than it has in compromised adults. Researchers and practitioners continue to rely upon static measures of lean mass or isolated measures of strength and power, rather than using MQ, to assess integrated functional responses to resistance exercise training and physical stress. Therefore, this review will critically examine MQ and the evidence base to establish this metric as a practical and important biomarker for functional capacity and performance in healthy, young populations. Interventions that enhance MQ, such as high-intensity stretch shortening contraction resistance exercise training, will be highlighted. Finally, we will explore the potential to leverage MQ as a practical assessment tool to evaluate function and enhance performance in young populations in non-traditional research settings.

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Skeletal Muscle Quality: A Biomarker for Assessing Physical Performance Capabilities in Young Populations.

Quantifying echo intensity (EI), a proposed measure of muscle quality, is becoming increasingly popular. Additionally, much attention has been paid to regional differences in other ultrasonically e...

/pdf/variability-of-regional-quadriceps-echo-intensity-in-active-31p1xs7pgj.pdf

Variability of regional quadriceps echo intensity in active young men with and without subcutaneous fat correction

BackgroundUltrasonography is used to evaluate muscle quality (i.e. echo intensity [EI]), but an attenuation of ultrasound waves occurs in deeper tissues, potentially affecting these measures.Purpos...

Influence of muscle depth and thickness on ultrasound echo intensity of the vastus lateralis.

The length–tension relationship affects knee extension performance; however, whether anatomical variations in different quadriceps regions affect this relationship is unknown. Regional (proximal, m...

The effect of regional quadriceps anatomical parameters on angle-specific isometric torque expression

Ultrasonography of the lower body typically encompasses supine rest due to fluid shifts affecting tissue size and composition. However, vastus lateralis (VL) examination is completed in the lateral recumbent position, and this positional change may influence morphology and its ability to predict function. This study aimed to examine the effect of position on VL morphology and its relationship with lower-body performance. Cross-sectional area (CSA), muscle thickness (MT), pennation angle (PA), echo intensity (UnCorEI), subcutaneous adipose tissue thickness (SFT), and echo intensity corrected for SFT (CorEI) were assessed in 31 resistance-trained males (23.0 ± 2.1 yrs; 1.79 ± 0.08 m; 87.4 ± 11.7 kg) immediately after transitioning from standing to supine (IP), after 15 min of standing (ST), and after 15 min of rest in three recumbent positions: supine (SUP), dominant lateral recumbent (DLR), non-dominant lateral recumbent (NDLR). Participants also completed unilateral vertical jumps, isometric/isokinetic tests, and a one-repetition maximum leg press. CSA, MT, PA, and SFT were greater in ST compared to NDLR, DLR, and SUP (p < 0.05). CSA, UnCorEI, and CorEI were different between recumbent positions; however no differences were observed for MT, PA, and SFT. Different magnitudes of relationships were observed between muscle morphological characteristics measured after rest in different positions and performance variables. Muscle morphology in IP generally appears to be the best predictor of performance for most variables, although utilizing the NDLR and DLR positions may provide comparable results, whereas morphology measured in ST and SUP provide weaker relationships with physical performance. IP also requires less time and fewer requirements on the technician and subject, thus researchers should consider this positioning for VL examination.

https://www.mdpi.com/2411-5142/4/3/64/pdf

Effects of Rest Position on Morphology of the Vastus Lateralis and Its Relationship with Lower-Body Strength and Power.

CONTEXT The Dynavision D2™ Mode A test (ModeA) is a 1-minute reaction time (RT) test commonly used in sports science research and clinical rehabilitation. However, there is limited data regarding the effect of repeated testing (ie, training) or subsequent periods of no testing (ie, detraining) on test-retest reliability and RT performance. Therefore, the purpose of this study was to examine the test-retest reliability, training, and detraining effects associated with the D2™ ModeA test. DESIGN Repeated measures/reliability. METHODS Twenty-four recreationally active men and women completed 15 training sessions consisting of 2 ModeA tests per session (30 tests). The participants were then randomized to either 1 or 2 weeks of detraining prior to completing 15 retraining sessions (30 tests). The training and retraining periods were separated into 10 blocks for analysis (3 tests per block). The number of hits (hits) and the average RT per hit (AvgRT) within each block were used to determine RT performance. Intraclass correlation coefficients, SEM, and minimum difference were used to determine reliability. Repeated-measures analysis of variance/analysis of covariance were used to determine training and detraining effects, respectively. RESULTS The ModeA variables demonstrated excellent test-retest reliability (intraclass correlation coefficient2,3 > .93). Significant improvements in hits and AvgRT were noted within training blocks 1 to 5 (P < .05). No further improvements in RT performance were noted between training blocks 6 through 10. There was no effect of detraining period on RT. The RT performance was not different between blocks during retraining. CONCLUSIONS It appears that 15 tests are necessary to overcome the training effect and establish reliable baseline performance for the ModeA test. Detraining for 1 to 2 weeks did not impact RT performance. The authors recommend that investigators and clinicians utilize the average of 3 tests when assessing RT performance using the D2 ModeA test.

Test-Retest Reliability, Training, and Detraining Effects Associated With the Dynavision D2™ Mode A Visuomotor Reaction Time Test.

Objective:Recumbent rest elicits a decrease in muscle size of the lower extremity, but the extent of decrease may be related to differences in muscle quality. This could have implications for ultra...

Muscle Quality, Measured by Ultrasound-Derived Corrected Echo Intensity, Does not Affect Changes in Cross-sectional Area of the Vastus Lateralis Following Recumbent Rest:

Bri-Ana D I Johnson

Papers

Influence of muscle depth and thickness on ultrasound echo intensity of the vastus lateralis.

Effects of Rest Position on Morphology of the Vastus Lateralis and Its Relationship with Lower-Body Strength and Power.

Test-Retest Reliability, Training, and Detraining Effects Associated With the Dynavision D2™ Mode A Visuomotor Reaction Time Test.

Muscle Quality, Measured by Ultrasound-Derived Corrected Echo Intensity, Does not Affect Changes in Cross-sectional Area of the Vastus Lateralis Following Recumbent Rest: