The rate of velocity development associates with muscle echo intensity, but not muscle cross-sectional area in older men

Reliability and Validity of Muscle Size and Quality Analysis Techniques

OBJECTIVE

This study investigated reliability and validity of muscle cross-sectional area and echo intensity using an automatic image analysis program.

METHODS

Twenty-two participants completed two data collection trials consisting of ultrasound imaging of the vastus lateralis (VL) at 10 and 12 MHz. Images were analyzed manually and with Deep Anatomical Cross-Sectional Area (DeepACSA). Reliability statistics (i.e., intraclass correlation coefficient [ICC] model 2,1, standard error of measure expressed as a percentage of the mean [SEM%], minimal differences [MD] values needed to be considered real) and validity statistics (i.e., constant error [CE], total error [TE], standard error of the estimate [SEE]) were calculated.

RESULTS

Automatic analyses of ACSA and EI demonstrated good reliability (10 MHz: ICC2,1 = 0.83 - 0.90; 12 MHz: ICC2,1 = 0.87-0.88), while manual analyses demonstrated moderate to excellent reliability (10 MHz: ICC2,1 = 0.82-0.99; 12 MHz: ICC2,1 = 0.73-0.99). Automatic analyses of ACSA presented greater error at 10 (CE = -0.76 cm2, TE = 4.94 cm2, SEE = 3.65 cm2) than 12 MHz (CE = 0.17 cm2, TE = 3.44 cm2, SEE = 3.11 cm2). Analyses of EI presented greater error at 10 (CE = 3.35 a.u., TE = 2.70 a.u., SEE = 2.58 a.u.) than at 12 MHz (CE = 3.21 a.u., TE = 2.61 a.u., SEE = 2.34 a.u.).

CONCLUSION

The results suggest the DeepACSA program may be less reliable compared to manual analysis for VL ACSA but displayed similar reliability for EI. In addition, the results demonstrated the automatic program had low error for 10 and 12 MHz.

Effects of High-Velocity Versus Low-Velocity Resistance Training on Muscle Echo Intensity in Healthy Young Women: A Randomized Controlled Trial

BACKGROUND

Improving muscle quality to prevent and treat muscle dysfunction is critical. However, effective measures to improve muscle quality remain poorly understood. We investigated the effects of high- and low-velocity resistance training (RT) on muscle quality, mass, and function before and after an 8-week intervention.

HYPOTHESIS

High-velocity RT would improve muscle quality more effectively than low-velocity RT.

STUDY DESIGN

Randomized controlled trial.

LEVEL OF EVIDENCE

Level 1.

METHODS

A total of 33 healthy young women (23.1 ± 2.2 years) were assigned randomly to high-velocity (n = 16) or low-velocity (n = 17) groups. Both groups underwent concentric knee extension RT with a 60% 1-repetition maximum (1RM) load, performing 10 repetitions of 4 sets, 3 times per week for 8 weeks. The high-velocity group was instructed to complete each repetition as quickly as possible (mean repetition duration of 0.5 seconds), while the low-velocity group was required to execute each repetition in 3 seconds. Before and after the 8-week intervention, quadriceps femoris echo intensity (EI), muscle thickness (MT), isokinetic peak torque (60 and 300 deg/s), rate of velocity development (RVD) at 300 deg/s, and 1RM were assessed. Split-plot factorial design analysis of variance was used to compare the group × time interaction.

RESULTS

A group×time interaction was observed for EI (P < 0.01). Only the high-velocity group showed a significant reduction in EI after the intervention. MT revealed a main effect of time (P < 0.01), with both groups significantly increasing MT. RVD showed a group × time interaction (P < 0.05), with significant increase only in the high-velocity group. Isokinetic peak torque and 1RM showed main effects of time (P < 0.01), with significant increases in both groups.

CONCLUSION

High-velocity RT may be superior to low-velocity RT in enhancing muscle quality and RVD.

CLINICAL RELEVANCE

These results emphasize the importance of RT velocity for muscle quality improvement.

Exploring the associations between skeletal muscle echogenicity and physical function in aging adults: A systematic review with meta-analyses

BACKGROUND

Assessment and quantification of skeletal muscle within the aging population is vital for diagnosis, treatment, and injury/disease prevention. The clinical availability of assessing muscle quality through diagnostic ultrasound presents an opportunity to be utilized as a screening tool for function-limiting diseases. However, relationships between muscle echogenicity and clinical functional assessments require authoritative analysis. Thus, we aimed to (a) synthesize the literature to assess the relationships between skeletal muscle echogenicity and physical function in older adults (≥60 years), (b) perform pooled analyses of relationships between skeletal muscle echogenicity and physical function, and (c) perform sub-analyses to determine between-muscle relationships.

METHODS

CINAHL, Embase, MEDLINE, PubMed, and Web of Science databases were systematically searched to identify articles relating skeletal muscle echogenicity to physical function in older adults. Risk-of-bias assessments were conducted along with funnel plot examination. Meta-analyses with and without sub-analyses for individual muscles were performed utilizing Fisher's Z transformation for the most common measures of physical function. Fisher's Z was back-transformed to Pearson's r for interpretation.

RESULTS

Fifty-one articles (n = 5095, female = ∼2759, male = ∼2301, 72.5 ± 5.8 years, mean ± SD (1 study did not provide sex descriptors)) were extracted for review, with previously unpublished data obtained from the authors of 13 studies. The rectus femoris (n = 34) and isometric knee extension strength (n = 22) were the most accessed muscle and physical qualities, respectively. The relationship between quadriceps echogenicity and knee extensor strength was moderate (n = 2924, r = -0.36 (95% confidence interval: -0.38 to -0.32), p < 0.001), with all other meta-analyses (grip strength, walking speed, sit-to-stand, timed up-and-go) resulting in slightly weaker correlations (r:  -0.34 to -0.23, all p < 0.001). Sub-analyses determined minimal differences in predictive ability between muscle groups, although combining muscles (e.g., rectus femoris + vastus lateralis) often resulted in stronger correlations with maximal strength.

CONCLUSION

While correlations were modest, the affordable, portable, and noninvasive ultrasonic assessment of muscle quality was a consistent predictor of physical function in older adults. Minimal between-muscle differences suggest that echogenicity estimates of muscle quality are systemic. Therefore, practitioners may be able to scan a single muscle to estimate full-body skeletal muscle quality/composition, while researchers should consider combining multiple muscles to strengthen the model.

Can segmental bioelectrical impedance be used as a measure of muscle quality?

Recent works have shown bioelectrical impedance spectroscopy (BIS) may assess tissue quality. The purpose of this project was to examine associations between ultrasound echo intensity (EI) of quadriceps muscles (vastus lateralis [VL], vastus medialis [VM], vastus intermedius [VI], rectus femoris [RF]) and BIS parameters (R0, R1, C, α, fp), and if the associations are specific to individual muscles or associated with a representation of the entire quadriceps. Twenty-two participants (age: 22 ± 4 years; BMI: 25.47 ± 3.26 kg/m2) participated in all study activities. Participants had transverse ultrasound scans of each individual quadriceps muscle taken at 25, 50, and 75 % of the muscle length to generate an average EI for the VL, VM, VI, and RF, which were further averaged to generate an EI for the entire quadriceps. For BIS, participants were seated with electrodes placed on the thigh to measure the segmental quadriceps. The Cole-impedance model parameters that best fit the BIS data for each participant was used for all analyses. Pearson's correlation coefficient (r) were calculated to determine associations between muscles' EI and BIS parameters. The results suggest averaged EI of individual VL, VM, VI, RF muscles and the average EI of the segmental quadriceps were significantly related to the R0, C, α metrics of the Cole-impedance model representing quadriceps segmental tissues. This supports that segmental BIS may be an appropriate technique for rapid evaluation of segmental muscle quality.

Effects of plyometric- and cycle-based high-intensity interval training on body composition, aerobic capacity, and muscle function in young females: a field-based group fitness assessment

High-intensity interval training (HIIT) is an effective alternative to moderate intensity continuous training for improvements in body composition and aerobic capacity; however, there is little work comparing different modalities of HIIT. The purpose of this study was to compare the effects of plyometric- (PLYO) and cycle-oriented (CYC) HIIT on body composition, aerobic capacity, and skeletal muscle size, quality, and function in recreationally trained females. Young (21.7 ± 3.1 yrs), recreationally active females were quasi-randomized (1:1 ratio) to 8 weeks of twice weekly PLYO (n = 15) or CYC (n = 15) HIIT. Body composition (four-compartment model), VO2peak, countermovement jump performance, muscle size, and echo intensity (muscle quality), as well as strength and power of the knee extensors and plantar flexors were measured before and after training. Both groups showed a similar decrease in body fat percentage (p < 0.001;η p 2   = 0.409) and echo intensity (p < 0.001;η p 2 = 0.558), and an increase in fat-free mass (p < 0.001;η p 2   = 0.367) and VO2peak (p = 0.001;η p 2 = 0.318). Muscle size was unaffected (p > 0.05), whereas peak torque was reduced similarly in both groups (p = 0.017;η p 2 = 0.188) and rapid torque capacity was diminished only for the knee extensors after CYC (p = 0.022; d = -0.67). These results suggest that PLYO and CYC HIIT are similarly effective for improving body composition, aerobic capacity, and muscle quality, whereas muscle function may express moderate decrements in recreationally active females. ClinicalTrials.gov (NCT05821504).

Usefulness of muscle echo intensity for evaluating functional performance in the older population: A scoping review

Muscle echo intensity, as measured by ultrasonography, could be used as a new marker of functional performance in older populations. This scoping review aimed to present evidence on the utility of muscle echo intensity as determined by ultrasonography for assessing functional performance in older adults. The eligibility criterion included observational studies that investigated the associations between muscle echo intensity and functional performance in older adults. Terms, such as "echo intensity" and "older adults", were searched for in databases, such as PubMed, Web of Science, the Cochrane database of systematic reviews, and the Cumulative Index of Nursing and Allied Health Literature, in April 2021. Two independent reviewers screened and extracted the data; 46 papers, of which almost one-third were Japanese, were subsequently identified for inclusion. The representative functional performances included in this review were muscle strength, gait speed, sit-to-stand test results, and timed up-and-go test results. Poor to moderate associations were found between muscle echo intensity and functional performance; however, heterogeneities were observed in the characteristics of study participants. Moreover, the accurate effect size and causal inferences between muscle echo intensity and functional performance remained unclear. Further longitudinal studies are needed to determine these causal inferences.

Ultrasonographic findings in long COVID: A cross-sectional study of 312 patients

Background

Fatigue and muscle weakness are common complaints in COVID-19 survivors. However, little is still known about the skeletal muscle qualitative and quantitative characteristics after hospitalization due to moderate and severe COVID-19.

Objectives

To assess rectus femoris and vastus intermedius muscle thickness (MT) and rectus femoris echo intensity (EI) and to establish its association with demographic, clinical, functional, and inflammatory parameters in long COVID patients after hospital discharge.

Methods

Cross-sectional study with 312 COVID-19 patients (53.53% male; age: 54.59 ± 13.50 years), with a laboratory-confirmed diagnosis of COVID-19. Patients were assessed 3-11 months after hospital discharge. We evaluated MT of the right rectus femoris and vastus intermedius and EI of the right rectus femoris using a portable ultrasound system, 6-13 MHz, broadband linear transducer. We corrected EI using the subcutaneous fat thickness. Ultrasonographic parameters were tested in association with demographic (sex and age); functional (Handgrip strength measurement, Timed Up and Go, 1 min Sit-to-Stand test, EuroQoL-5 Dimensions-5 Levels, World Health Organization Disability Assessment Schedule (WHODAS 2.0), Post-COVID-19 Functional Status, Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT), Medical Research Council (MRC) sum score, Borg Dyspnea Scale, MRC Dyspnea score, Visual Analogue Scale (VAS), Epworth Sleepiness Scale, Insomnia Severity Index, Functional Independence Measurement (FIM), and Functional Oral Intake Scale); clinical (length of hospital stay, intubation, and presence of comorbidities such as systemic hypertension, diabetes, obesity, chronic obstructive pulmonary disease, asthma), and inflammatory data assessed by the C-reactive protein and D-dimer serum concentrations.

Results

Rectus femoris MT was associated with age, handgrip strength, Epworth Sleepiness Scale, and subcutaneous fat thickness (r² = 27.51%; p < 0.0001). Vastus intermedius MT was associated with age, pain intensity, handgrip strength, Epworth Sleepiness scale, FIM, and time since hospital discharge (r² = 21.12%; p < 0.0001). Rectus femoris EI was significantly associated with the male sex, TUG, Epworth Sleepiness Scale, and C-Reactive Protein levels (r² = 44.39%; p < 0.0001). Mean MT of rectus femoris and vastus intermedius are significantly different (p < 0.001).

Conclusion

After hospital discharge, long COVID patients present qualitative and quantitative skeletal muscle characteristics associated with a combination of demographic, clinical, and functional parameters.

Muscle quality indices separately associate with joint-level power-related measures of the knee extensors in older males

PURPOSE

The purpose of this study was to investigate associations of muscle quality indices with joint-level power-related measures in the knee extensors of thirty-two older males (65-88 years).

METHODS

Muscle quality indices included: echo intensity, ratio of intracellular- to total water content (ICW/TW), and specific muscle strength. Echo intensity was acquired from the rectus femoris (EI_RF) and vastus lateralis (EI_VL) by ultrasonography. ICW/TW was computed from electrical resistance of the right thigh obtained by bioelectrical impedance spectroscopy. Specific muscle strength was determined as the normalized maximal voluntary isometric knee extension (MVIC) torque to estimated knee extensor volume. Isotonic maximal effort knee extensions with a load set to 20% MVIC torque were performed to obtain the knee extension power-related measures (peak power, rate of power development [RPD], and rate of velocity development [RVD]). Power and RPD were normalized to MVIC.

RESULTS

There were no significant correlations between muscle quality indices except between EI_RF and EI_VL (|r|≤ 0.253, P ≥ 0.162). EI_RF was negatively correlated with normalized RPD and RVD (r ≤  - 0.361, P ≤ 0.050). ICW/TW was positively correlated with normalized peak power (r = 0.421, P = 0.020). Specific muscle strength was positively correlated with absolute peak power and RPD (r ≥ 0.452, P ≤ 0.012).

CONCLUSION

Knee extension power-related measures were lower in participants with higher EI, lower ICW/TW, and lower specific muscle strength, but the muscle quality indices may be determined by independent physiological characteristics.

The relationship between quantitative magnetic resonance imaging of the ankle plantar flexors, muscle function during walking and maximal strength in people with neuromuscular diseases

BACKGROUND

Progression of plantar flexor weakness in neuromuscular diseases is usually monitored by muscle strength measurements, although they poorly relate to muscle function during walking. Pathophysiological changes such as intramuscular adipose tissue affect dynamic muscle function independent from isometric strength. Diffusion tensor imaging and T2 imaging are quantitative MRI measures reflecting muscular pathophysiological changes, and are therefore potential biomarkers to monitor plantar flexor functioning during walking in people with neuromuscular diseases.

METHODS

In fourteen individuals with plantar flexor weakness diffusion tensor imaging and T2 scans of the plantar flexors were obtained, and the diffusion indices fractional anisotropy and mean diffusivity calculated. With a dynamometer, maximal isometric plantar flexor strength was measured. 3D gait analysis was used to assess maximal ankle moment and power during walking.

FINDINGS

Fractional anisotropy, mean diffusivity and T2 relaxation time all moderately correlated with maximal plantar flexor strength (r > 0.512). Fractional anisotropy and mean diffusivity were not related with ankle moment or power (r < 0.288). T2 relaxation time was strongly related to ankle moment (r = -0.789) and ankle power (r = -0.798), and moderately related to maximal plantar flexor strength (r < 0.600).

INTERPRETATION

In conclusion, T2 relaxation time, indicative of multiple pathophysiological changes, was strongly related to plantar flexor function during walking, while fractional anisotropy and mean diffusivity, indicative of fiber size, only related to maximal plantar flexor strength. This indicates that these measures may be suitable to monitor muscle function and gain insights into the pathophysiological changes underlying a poor plantar flexor functioning during gait in people with neuromuscular diseases.

The impact of skeletal muscle disuse on distinct echo intensity bands: A retrospective analysis

Echo intensity (EI) is a novel tool for assessing muscle quality. EI has traditionally been reported as the mean of the pixel histogram, with 0 and 255 arbitrary units (A.U.) representing excellent and poor muscle quality, respectively. Recent work conducted in youth and younger and older adults suggested that analyzing specific EI bands, rather than the mean, may provide unique insights into the effectiveness of exercise and rehabilitation interventions. As our previous work showed deterioration of muscle quality after knee joint immobilization, we sought to investigate whether the increase in EI following disuse was limited to specific EI bands. Thirteen females (age = 21 yrs) underwent two weeks of left knee immobilization and ambulated via crutches. B-mode ultrasonography was utilized to obtain images of the immobilized vastus lateralis. The percentage of the total number of pixels within bands of 0–50, 51–100, 101–150, 151–200, and 201–255 A.U. was examined before and after immobilization. We also sought to determine if further subdividing the histogram into 25 A.U. bands (i.e., 0–25, 26–50, etc.) would be a more sensitive methodological approach. Immobilization resulted in a decrease in the percentage of pixels within the 0–50 A.U. band (-3.11 ± 3.98%), but an increase in the 101–150 A.U. (2.94 ± 2.64%) and 151–200 A.U. (0.93 ± 1.42%) bands. Analyses of variance on the change scores indicated that these differences were large and significant (%EI0-50 vs. %EI101-150: p < .001, d = 1.243); %EI0-50 vs. %EI151-200: p = .043, d = 0.831). The effect size for the %EI51-100 versus %EI101-150 comparison was medium/large (d = 0.762), but not statistically significant (p = .085). Further analysis of the 25 A.U. bands indicated that the percentage of pixels within the 25–50 A.U. band decreased (-2.97 ± 3.64%), whereas the 101–125 (1.62 ± 1.47%) and 126–150 A.U. (1.18 ± 1.07%) bands increased. Comparison of the 50 A.U. and 25 A.U. band methods found that 25 A.U. bands offer little additional insight. Though studies are needed to ascertain the factors that may influence specific bands, changes in EI during muscle disuse are not homogeneous across the pixel histogram. We encourage investigators to think critically about the robustness of data obtained from EI histograms, rather than simply reporting the EImean value, in muscle quality research.

Ultrasound imaging of quadriceps muscle in patients with knee osteoarthritis: The test-retest and inter-rater reliability and concurrent validity of echo intensity measurement

BACKGROUND

Echo intensity(EI) on ultrasonography images of skeletal muscle reflects muscle composition.

OBJECTIVES

The primary aim of the study was to investigate the inter-rater and test-retest reliability of EI using grayscale histogram analysis of the cross-sectional area of quadriceps femoris(QF) muscle in patients with knee osteoarthritis(KOA). The secondary aim of the study was to determine the concurrent validity of the Free Hand Tool(FHT) when compared to Rectangular Marquee Tool(RMT) for calculating the region of interest(ROI) in ImageJ.

METHODS

This study included thirty patients with KOA. Echogenicity of the QF muscle were performed by two different raters. The reliability analysis was applied using intraclass correlation coefficient(ICC), standard error of measurement(SEM) and coefficient of variation(CV). Spearman rank correlation coefficients were calculated for assessing concurrent validity of the FHT to RMT. The Bland-Altman plots was used to show disagreement between tools. Wilcoxon signed-rank test was used for differences in assessments between test/retest sessions, raters, tools.

RESULTS

The inter-rater and test-retest reliability of the EI using FHT and RMT was found to be excellent (ICC_FHT = 0.91-0.95, 0.98-0.99, ICC_RMT = 0.91-0.98, 0.91-0.99,respectively). Bland-Altman analysis demonstrated a slight bias when region ROI calculations were collected from RMT or FHT (bias ranging from 2.75 to-2.40 a. u). There were no significant differences between test/retest sessions, raters and tools(p > 0.05). Spearman correlation coefficient showed excellent correlation between tools used for echogenicity assessment of QF muscle(p < 0.001).

CONCLUSION

EI assessment using ultrasonography in the QF muscle showed excellent reliability. Evaluating muscle echogenicity using both FHT and RMT appears to be reliable and validity for monitoring muscle changes due to KOA.

Rate of Force Development Is Related to Maximal Force and Sit-to-Stand Performance in Men With Stages 3b and 4 Chronic Kidney Disease

Introduction: The primary aims of the present study were to assess the relationships of early (0–50 ms) and late (100–200 ms) knee extensor rate of force development (RFD) with maximal voluntary force (MVF) and sit-to-stand (STS) performance in participants with chronic kidney disease (CKD) not requiring dialysis.

Methods: Thirteen men with CKD (eGFR = 35.17 ±.5 ml/min per 1.73 m², age = 70.56 ±.4 years) and 12 non-CKD men (REF) (eGFR = 80.31 ± 4.8 ml/min per 1.73 m², age = 70.22 ±.9 years) performed maximal voluntary isometric contractions to determine MVF and RFD of the knee extensors. RFD was measured at time intervals 0–50 ms (RFD₀₋₅₀) and 100–200 ms (RFD_100−200). STS was measured as the time to complete five repetitions. Measures of rectus femoris grayscale (RF GSL) and muscle thickness (RF MT) were obtained via ultrasonography in the CKD group only. Standardized mean differences (SMD) were used to examine differences between groups. Bivariate relationships were assessed by Pearson's product moment correlation.

Results: Knee extensor MVF adjusted for body weight (CKD=17.14 ±.1 N·kg^0.67, REF=21.55 ±.3 N·kg^0.67, SMD = 0.79) and STS time (CKD = 15.93 ±.4 s, REF = 12.23 ±.7 s, SMD = 1.03) were lower in the CKD group than the REF group. Absolute RFD_100−200 was significantly directly related to adjusted MVF in CKD (r = 0.56, p = 0.049) and REF (r = 0.70, p = 0.012), respectively. STS time was significantly inversely related to absolute (r = −0.75, p = 0.008) and relative RFD₀₋₅₀ (r = −0.65, p = 0.030) in CKD but not REF (r = 0.08, p = 0.797; r = 0.004, p = 0.991). Significant inverse relationships between RF GSL adjusted for adipose tissue thickness and absolute RFD_100−200 (r =−0.59, p = 0.042) in CKD were observed.

Conclusion: The results of the current study highlight the declines in strength and physical function that occur in older men with CKD stages 3b and 4 not requiring dialysis. Moreover, early RFD was associated with STS time in CKD while late RFD was associated MVF in both CKD and REF.

Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT03160326 and NCT02277236.

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

BACKGROUND

Ultrasonography 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.

PURPOSE

To determine whether muscle thickness (MT) affects EI and if EI varies between the superficial and deep portions of the muscle.

MATERIALS AND METHODS

MT, EI, subcutaneous adipose tissue thickness (SAT), tissue depth (DIS_DEEP), and EI of the overall (EI_FULL) as well as deep (EI_DEEP) and superficial (EI_SUPF) portions of the vastus lateralis (VL) were assessed in 33 resistance-trained males using ultrasonography. The difference (EI_DIFF) between EI_SUPF and EI_DEEP was calculated. Mean differences between EI_FULL, EI_SUPF, and EI_DEEP were analyzed using a repeated-measures analysis of variance (ANOVA). Relationships between measures of muscle depth/ thickness and EI were examined using Pearson's r.

RESULTS

EI_SUPF was greater than EI_DEEP (P < 0.001) and EI_FULL (P < 0.001). MT was negatively correlated with EI_FULL (P < 0.001) and positively correlated with EI_DIFF (P < 0.001). SAT was not correlated with any EI measure, but DIS_DEEP was positively correlated with EI_DIFF (P < 0.001).

CONCLUSION

EI of the VL is heterogeneous, as the deeper portion produces lower values than the superficial portion. Thicker muscles present lower EI but have greater discrepancies in EI between the superficial and deep portions. Although SAT was not correlated with EI, DIS_DEEP was related to EI_DIFF, demonstrating that the combination of MT and SAT should be considered when evaluating muscle quality. Future research is necessary to determine if changes in EI following resistance training are driven by increases in MT.

Echo intensity is weakly associated with muscular strength and endurance in young, healthy adults

The purpose of this study was to evaluate the relationships between echo intensity (EI) and muscular strength (maximal voluntary isometric contraction [MVIC]) and endurance (time-to task-failure [TTF]) in young adults. Ultrasonography was used to examine the dominant vastus lateralis of 15 young men and 15 young women. The participants completed an MVIC to assess muscular strength and sustained a bilateral, leg extension at 45% MVIC to assess muscular endurance. There was a significant (r = -0.354, p = 0.028) correlation between EI and normalized MVIC force for the combined sample (n = 30). There was also a significant (r = -0.520, p = 0.002) correlation between EI and absolute MVIC force for the combined sample. The correlation between EI and TTE was significant for the men (r = -0.449, p = 0.047) and the combined sample (r = -0.477, p = 0.004). Overall, muscle quality as assessed by EI does not appear to be strongly related to muscular strength, but there may be a modest correlation with muscular endurance.

Evaluating the relationship between quadriceps muscle quality captured using ultrasound with clinical severity in women with knee osteoarthritis

BACKGROUND

Infiltration of muscle with non-lean tissue, such as fat, reduces muscle quality. Ultrasound captures muscle quality through measurement of echogenicity. Given the potential implications of quadriceps muscle quality on physical function, particularly in knee osteoarthritis, the purpose of this study was to investigate the relationship between echogenicity, muscle thickness and subcutaneous fat thickness with the clinical severity of osteoarthritis.

METHODS

Thirty-one women with clinical knee osteoarthritis participated. Rectus femoris and vastus lateralis echogenicity, muscle thickness and subcutaneous fat thickness were measured from ultrasound images of the most symptomatic knee. Clinical severity of osteoarthritis was characterized with pain, self-reported function, six-minute walk test, and knee extensor strength. Correlation coefficients were calculated between muscle and fat architecture outcomes (muscle quality, muscle and fat thicknesses) and osteoarthritis clinical severity outcomes.

FINDINGS

Data from 25 women were of sufficient quality for analysis. Echogenicity (muscle quality) related to the six-minute walk test for both rectus femoris (r = -0.52, p = 0.02) and vastus lateralis (r = -0.74, p = 0.004), with poorer muscle quality related to lower mobility. Subcutaneous fat thickness was related to the six-minute walk test (rectus femoris, r = -0.61, p = 0.0012; vastus lateralis, r = -0.73, p = 0.003) and strength (rectus femoris, r = -0.46, p = 0.02; vastus lateralis, r = -0.59, p = 0.03). Muscle thickness was not related to any severity outcomes.

INTERPRETATION

Muscle quality, rather than thickness, is associated with mobility performance in women with knee osteoarthritis. Thus, interventions for osteoarthritis that specifically target muscle quality, rather than size, should be explored.

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

PURPOSE

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.

METHOD

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.

RESULT

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.

CONCLUSION

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.

Effects of age on vertical jump performance and muscle morphology characteristics in females

BACKGROUND

Declines in muscle morphology and function are commonly reported as a consequence of aging. However, few studies have investigated the influence of age on a comprehensive set of muscle function-related measures (i.e., reactive strength, power, etc.) that focuses on a dynamic performance task such as the vertical jump across the adult life span. This study aimed to examine the effects of age on muscle morphology characteristics (muscle cross-sectional area [CSA] and echo intensity [EI]) and vertical jump height, power, and reactive strength index (RSI) in females.

METHODS

Twenty-six young (22±2 years), 30 middle-aged (36±5 years), and 23 older (71±5 years) females participated in this study. Muscle CSA and EI were determined from ultrasound scans of the vastus lateralis. Countermovement jumps were used to assess jump height, RSI, movement time, and peak power (Pmax).

RESULTS

Muscle CSA, jump height, and Pmax were higher for the young compared to the old and middle-aged (P≤0.027) and for the middle-aged compared to the old (P<0.001). Movement time and EI values were lower (P≤0.004) and RSI values were higher (P<0.001) for the young and middle-aged compared to the old; however, no differences were observed between the young and middle-aged (P=0.367-0.620).

CONCLUSIONS

Of all the variables assessed in this study, RSI exhibited the greatest decline (76%) between the young and old females. Such findings highlight the importance of reactive strength when assessing age-related changes in neuromuscular performance.

Effects of an 8-week resistance training intervention on plantar flexor muscle quality and functional capacity in older women: A randomised controlled trial

The present study examined 8 weeks of resistance training and its effects on muscle quality measures, plantar flexor muscle strength, muscle thickness and functional capacity in older women. Moreover, we tested if changes in muscle quality were associated with functional capacity. Twenty-four older women (66.3 ± 5.8 years; 69.0 ± 3.0 kg; 25.3 ± 1.4 kg·m^-2) were recruited to the study. After completion of the baseline assessment, participants were randomly assigned to either the resistance training (RET, n = 12) or an active control group (CTR, n = 12). Muscle quality was evaluated through muscle echo intensity (MQ_EI) and specific tension (MQ_ST). Muscle thickness, unilateral plantar flexor muscle strength and functional tests were evaluated at baseline and after the training period. After 8 weeks, both MQ_EI and MQ_ST did not respond to the intervention. Furthermore, significant changes in stair climb performance (P < 0.05) were not associated with plantar flexor-derived muscle quality (P > 0.05). Finally, significant gains in muscle hypertrophy were observed in the RET group (P < 0.01), while muscle strength failed to change significantly (P > 0.05). In conclusion, a resistance training program provided significant benefits in the stair climb test, unrelated to plantar flexor-derived muscle quality measures as previously demonstrated in quadriceps femoris.

Age-, sex-, and region-specific differences in skeletal muscle size and quality

Ultrasonography-derived cross-sectional area (CSA) and echo intensity (EI) are increasingly utilized by investigators to study muscle size and quality, respectively. We sought to examine age, sex, and region (proximal, middle, distal) differences in vastus lateralis and rectus femoris CSA and EI, and determine whether correction for subcutaneous fat thickness influences the magnitude of EI differences. Fifteen younger men (mean age = 23 years), 15 younger women (aged 21 years), 11 older men (aged 74 years), and 15 older women (aged 70 years) participated. Clear differences were observed among age, sex, and region for vastus lateralis CSA (p ≤ 0.013, d = 0.38-0.73), whereas rectus femoris CSA was only different between younger and older participants at the proximal region (p = 0.017, d = 0.65). Uncorrected EI was greatest at the distal region of both muscles (p < 0.001, d = 0.59-1.38), with only the younger men having significantly lower EI values than the other groups (p ≤ 0.043, d = 0.37-0.63). Subcutaneous fat correction resulted in a marked increase in the magnitude of sex-specific EI differences (p ≤ 0.032, d ≥ 0.42). Additionally, subcutaneous fat correction increased the uniformity of EI throughout the thigh. These findings highlight considerable region-specific differences in muscle size and quality among younger and older men and women and highlight the need to correct for subcutaneous fat thickness when examining EI. Novelty Rectus femoris CSA is similar between younger and older adults except at the most proximal site evaluated. Age- and sex-specific differences in uncorrected EI are nonuniform across the thigh. Correction for subcutaneous fat thickness substantially increased EI in women, resulting in greater sex differences.

Neuromuscular function of the plantar flexors and predictors of peak power in middle-aged and older males

Little evidence exists regarding the contribution of torque and velocity to the age-related decrease in peak power (PP) for the plantar flexors (PFs). A comprehensive assessment of PF neuromuscular function is necessary to elucidate age-related changes, especially between middle-aged and older adults, in order to identify early, age-related decrements. Thus, the purpose of this study was to examine neuromuscular function of the PFs in middle-aged and older males, and identify predictors of PP. Twenty-eight healthy, middle-aged (n = 13; 45.1 ± 2.7 yrs) and older (n = 15; 65.3 ± 3.2 yrs) males performed concentric isotonic PF contractions ranging in intensity from 20% to 70% isometric strength using a dynamometer. PP in addition to velocity and torque at the moment in time PP occurred, as well as the rate of velocity, torque (RTD), and power (RPD) development were recorded. The rate of electromyography rise (RER) was derived from the linear slope of the normalized electromyography signal. Isometric and concentric dynamic strength were assessed, as well as cross-sectional area and muscle quality (i.e., echo intensity) of the PFs via panoramic ultrasonography. The relationship between serum c-terminal agrin levels and select variables was examined to explore the potential role of neuromuscular junction deterioration. Appendicular lean mass and physical activity level were similar between groups (p > 0.05), and only PP (p = 0.046; d = 0.79), RPD (p = 0.026; d = 0.90), RTD (p = 0.022; d = 0.91), and RER (p = 0.010; d = 1.04) were lower in older males. When groups were collapsed, RTD was the only significant predictor of PP, while c-terminal agrin levels were not associated with any variables. Our findings indicate that PP and time-dependent parameters of muscle activation and contractile function of the PFs are dramatically diminished in older adults compared to middle-aged adults. PP is produced at the same velocity and relative intensity in middle-aged and older males, and RTD is most influential for PP. The inability of the PFs to be rapidly activated appeared to be influential for the age-related impairment in PP and time-dependent contractile parameters.

Ultrasonography Monitoring of Trauma-Induced Heterotopic Ossification: Guidance for Rehabilitation Procedures

Traumatic injury is one of varying causes of heterotopic ossification (HO). After HO occurrence, rehabilitation training need alterations to avoid the aggravation of HO. Therefore, monitoring of HO development plays an important role in the rehabilitation procedure. The aims of this study are to evaluate the post-traumatic HO occurring at various joints, to describe the features of HO development in ultrasound images, and to provide a guidance for the orthopedist to make individualized rehabilitation therapy. Eight subjects with the post-traumatic HO were recruited in this study. The joints on the injured side was examined by plain radiography. The joints on the injured side and the corresponding sites on the uninjured sides were scanned by ultrsonography. The HO tissues were segmented automatically using a semi-supervised segmentation algorithm. Then the HO tissues were evaluated in comparison with the corresponding region of the uninjured side. During the development stage of immature HO, ultrasonography was sensitive to observe the involved soft tissue and the calcification of HO. The characteristics of HO tissues in ultrasound image included the hyperechoic mass occasionally accompanied with acoustic shadow and the irregular muscular architecture. It was found that the mean grayscale value of HO was significantly higher (p < 0.001) than that of the uninjured side at the middle and late stages. During the development period of HO, the HO grayscale value gradually increased and the mean grayscale of value of mature HO was significantly higher (p < 0.05) than that of immature HO. According to the information of HO provided by ultrasound, the orthopedist properly adjusted the rehabilitation treatment. The results demonstrated that the visualization of HO using ultrasonography revealed the development of HO in the muscle tissues around the injured joints and thus provide a guidance for the orthopedist to make individualized rehabilitation therapy. Ultrasound could be a useful imaging modality for quantitative evaluation of HO during the rehabilitation of traumatic injury.