Panoramic ultrasound: a novel and valid tool for monitoring change in muscle mass

Peripheral quantitative computed tomography is a valid imaging technique for tracking changes in skeletal muscle cross-sectional area

Peripheral quantitative computed tomography (pQCT) has recently expanded to quantifying skeletal muscle, however its validity to determine muscle cross-sectional area (mCSA) compared to magnetic resonance imaging (MRI) is unknown. Eleven male participants (age: 22 ± 3 y) underwent pQCT and MRI dual-leg mid-thigh imaging before (PRE) and after (POST) 6 weeks of resistance training for quantification of mid-thigh mCSA and change in mCSA. mCSA agreement at both time points and absolute change in mCSA across time was assessed using Bland-Altman plots for mean bias and 95% limits of agreement (LOA), as well as Lin's concordance correlation coefficients (CCC). Both pQCT and MRI mCSA increased following 6 weeks of resistance training (∆mCSApQCT: 6.7 ± 5.4 cm2, p < 0.001; ∆mCSAMRI: 6.0 ± 6.4 cm2, p < 0.001). Importantly, the change in mCSA was not different between methods (p = 0.39). Bland-Altman analysis revealed a small mean bias (1.10 cm2, LOA: -6.09, 8.29 cm2) where pQCT tended to overestimate mCSA relative to MRI when comparing images at a single time point. Concordance between pQCT and MRI mCSA at PRE and POST was excellent yielding a CCC of 0.982. For detecting changes in mCSA, Bland-Altman analysis revealed excellent agreement between pQCT and MRI (mean bias: -0.73 cm2, LOA: -8.37, 6.91 cm2). Finally, there was excellent concordance between pQCT and MRI mCSA change scores (CCC = 0.779). Relative to MRI, pQCT imaging is a valid technique for measuring both mid-thigh mCSA at a single time point and mCSA changes following a resistance training intervention.

Exploring the utility of ultrasound to assess disuse atrophy in different muscles of the lower leg

BACKGROUND

Skeletal muscle is a highly plastic tissue crucial for many functions associated with whole-body health across the life course. Magnetic resonance imaging (MRI) is the current gold standard for measuring skeletal muscle size. However, MRI is expensive, and access to facilities is often limited. B-mode ultrasonography (U/S) has been proposed as a potential alternative to MRI for the assessment of muscle size. However, to date, no work has explored the utility of U/S to assess disuse muscle atrophy (DMA) across muscles with different atrophy susceptibility profiles, an omission which may limit the clinical application of previous work.

METHODS

To address this significant knowledge gap, 10 young men (22 ±  years, 24.1 ± 2.3 kg/m2) underwent 15-day unilateral leg immobilization using a knee-brace and air boot. Cross-sectional area (CSA) and muscle thickness (MT) of the tibialis anterior (TA) and medial gastrocnemius (MG) were assessed via U/S before and after immobilization, with CSA and muscle volume assessed via MRI.

RESULTS

With both muscles combined, there were good correlations between each U/S and MRI measure, both before (e.g., CSAMRI vs. MTU/S and CSAU/S: r = 0.88 and 0.94, respectively, both P < 0.0001) and after (e.g., VOLMRI vs. MTU/S and CSAU/S: r = 0.90 and 0.96, respectively, both P < 0.0001) immobilization. The relationship between the methods was notably stronger for MG than TA at each time-point (e.g., CSAMRI vs. MTU/S: MG, r = 0.70, P = 0.0006; TA, r = 0.37, P = 0.10). There was no relationship between the degree of DMA determined by the two methods in either muscle (e.g., TA pre- vs. post-immobilization, VOLMRI: 136 ± 6 vs. 133 ± 5, P = 0.08; CSAU/S: 6.05 ± 0.3 vs. 5.92 ± 0.4, P = 0.70; relationship between methods: r = 0.12, P = 0.75).

CONCLUSIONS

Both MTU/S and CSAU/S provide comparable static measures of lower leg muscle size compared with MRI, albeit with weaker agreement in TA compared to MG. Although both MTU/S and CSAU/S can discern differences in DMA susceptibility between muscles, neither can reliably assess degree of DMA. Based on the growing recognition of heterogeneous atrophy profiles between muscles, and the topical importance of less commonly studied muscles (i.e., TA for falls prevention in older adults), future research should aim to optimize accessible methods to determine muscle losses across the body.

Skeletal muscle estimation: A review of techniques and their applications

Quantifying skeletal muscle size is necessary to identify those at risk for conditions that increase frailty, morbidity, and mortality, as well as decrease quality of life. Although muscle strength, muscle quality, and physical performance have been suggested as important assessments in the screening, prevention, and management of sarcopenic and cachexic individuals, skeletal muscle size is still a critical objective marker. Several techniques exist for estimating skeletal muscle size; however, each technique presents with unique characteristics regarding simplicity/complexity, cost, radiation dose, accessibility, and portability that are important factors for assessors to consider before applying these modalities in practice. This narrative review presents a discussion centred on the theory and applications of current non-invasive techniques for estimating skeletal muscle size in diverse populations. Common instruments for skeletal muscle assessment include imaging techniques such as computed tomography, magnetic resonance imaging, peripheral quantitative computed tomography, dual-energy X-ray absorptiometry, and Brightness-mode ultrasound, and non-imaging techniques like bioelectrical impedance analysis and anthropometry. Skeletal muscle size can be acquired from these methods using whole-body and/or regional assessments, as well as prediction equations. Notable concerns when conducting assessments include the absence of standardised image acquisition/processing protocols and the variation in cut-off thresholds used to define low skeletal muscle size by clinicians and researchers, which could affect the accuracy and prevalence of diagnoses. Given the importance of evaluating skeletal muscle size, it is imperative practitioners are informed of each technique and their respective strengths and weaknesses.

Thigh muscle mass evaluated by point-of-care ultrasound is associated with short-term mortality in patients with sepsis in the emergency department

Muscle mass depletion is associated with mortality and morbidity in various conditions including sepsis. However, few studies have evaluated muscle mass using point-of-care ultrasound in patients with sepsis. This study aimed to evaluate the association between thigh muscle mass, evaluated using point-of-care ultrasound with panoramic view in patients with sepsis in the emergency department, and mortality. From March 2021 to October 2022, this prospective observational study used sepsis registry. Adult patients who were diagnosed with sepsis at the emergency department and who underwent point-of-care ultrasounds for lower extremities were included. The thigh muscle mass was evaluated by the cross-sectional area of the quadriceps femoris (CSA-QF) on point-of-care ultrasound using panoramic view. The primary outcome was 28 day mortality. Multivariable Cox proportional hazard model was performed. Of 112 included patients with sepsis, mean CSA-QF was significantly lower in the non-surviving group than surviving group (49.6 [34.3-56.5] vs. 63.2 [46.9-79.6] cm2, p = 0.002). Each cm2 increase of mean CSA-QF was independently associated with decreased 28 day mortality (adjusted hazard ratio 0.961, 95% CI 0.928-0.995, p = 0.026) after adjustment for potential confounders. The result of other measurements of CSA-QF were similar. The muscle mass of the quadriceps femoris evaluated using point-of-care ultrasound with panoramic view was associated with mortality in patients with sepsis. It might be a promising tool for determining risk factors for mortality in sepsis patients in the early stages of emergency department.

Blood flow restriction therapy with exercise are no better than exercise alone in improving athletic performance, muscle strength, and hypertrophy: a systematic review and meta-analysis

BACKGROUND

The benefits of Blood Flow Restriction Therapy (BFRT) have gained attention in recent times.

OBJECTIVE

This review aimed to evaluate the immediate (up to 24 hours), intermediate (up to 6 weeks), and long term (6-10 weeks) effects of BFRT plus exercises (EX) compared to EX only on athletic performance (sprint and jump performance), muscle strength, and hypertrophy in athletes and physically active population.

METHODS

A literature search was conducted to select randomized controlled trials across four electronic databases from inception till April 2021. The search yielded twenty-seven studies in total.

RESULTS

Based on eligibility criteria, twenty-one studies were analyzed. No differences were found between both groups for immediate (standardized mean difference [SMD] -0.02, 95% confidence interval [CI] -0.31, 0.27) and long-term effects (SMD -0.30, 95%CI -0.90, 0.30) on sprint performance. For jump performance, no significant effect was observed immediately (SMD -0.02 (95% CI -1.06, 1.02) and long term (SMD -0.40 (95% CI -1.46, 0.67). Similarly, muscle torque at intermediate (SMD 0.90 (95% CI -1.01, 2.81) and long term (SMD -0.54 (95% CI -1.19, 0.12), muscle strength at intermediate (SMD 1.12 (95% CI 0.20, 2.04), and long term (SMD -0.07 (95% CI -0.56, 0.42) also showed non-significant effects. Muscle hypertrophy at intermediate (SMD 0.16 (95% CI -0.31, 0.63) and long term (SMD -0.20 (95% CI -0.90, 0.50) were not statistically significant.

CONCLUSIONS

There was no significant difference observed in BFRT plus EX group compared to the EX-group on athletic performance, muscle strength, and muscle hypertrophy.

Acute muscle loss assessed using panoramic ultrasound in critically ill adults: a prospective observational study

PURPOSE

Panoramic ultrasound is one of the recently introduced ultrasound evaluation techniques. We herein examined the relationship between the cross-sectional area of the rectus femoris muscle on panoramic ultrasound and its volume based on the gold standard computed tomography (CT) evaluation.

METHODS

This was a single-center prospective observational study. A panoramic ultrasound assessment of the cross-sectional area of the rectus femoris muscle and a simple CT evaluation of its volume were performed on days 1 and 7 of hospitalization. Physical functions were assessed at discharge.

RESULTS

Twenty patients were examined. The rate of change in the cross-sectional area of the rectus femoris muscle on panoramic ultrasound correlated with that in its volume on CT (correlation coefficient 0.59, p = 0.0061). In addition, a correlation was observed between the absolute value for the rectus femoris muscle cross-sectional area on panoramic ultrasound and physical functions at discharge. Rectus femoris muscle distances did not correlate with either.

CONCLUSION

In the acute phase of critical illness, the cross-sectional area of the rectus femoris muscle on panoramic images correlated with its volume on CT and, thus, it is a valid method for assessing muscle mass.

Reliability of Panoramic Ultrasound in Assessing Rectus Femoris Size, Shape, and Brightness: An Inter-Examiner Study

Extended field-of-view ultrasound (US) imaging, also known as panoramic US, represents a technical advance that allows for complete visualization of large musculoskeletal structures, which are often limited in conventional 2D US images. Currently, there is no evidence examining whether the experience of examiners influences muscle shape deformations that may arise during the glide of the transducer in panoramic US acquisition. As no studies using panoramic US have analyzed whether two examiners with differing levels of experience might obtain varying scores in size, shape, or brightness during the US assessment of the rectus femoris muscle, our aim was to analyze the inter-examiner reliability of panoramic US imaging acquisition in determining muscle size, shape, and brightness between two examiners. Additionally, we sought to investigate whether the examiners' experience plays a significant role in muscle deformations during imaging acquisition by assessing score differences. Shape (circularity, aspect ratio, and roundness), size (cross-sectional area and perimeter), and brightness (mean echo intensity) were analyzed in 39 volunteers. Intraclass correlation coefficients (ICCs), standard error of measurements (SEM), minimal detectable changes (MDC), and coefficient of absolute errors (CAE%) were calculated. All parameters evaluated showed no significant differences between the two examiners (p > 0.05). Panoramic US proved to be reliable, regardless of examiner experience, as no deformations were observed. Further research is needed to corroborate the validity of panoramic US by comparing this method with gold standard techniques.

Physiological and clinical effects of low-intensity blood-flow restricted resistance exercise compared to standard rehabilitation in adults with knee osteoarthritis-Protocol for a randomized controlled trial

INTRODUCTION

Osteoarthritis (OA) is a common disease with high socioeconomical costs. In Denmark, standard rehabilitation (SR) consists of a combination of patient education and supervised physical exercise involving a standardized neuromuscular training program. As an evidence-based alternative, high-load (>70% 1RM) resistance training (HIRT) has shown positive rehabilitation effects in knee-OA but may not be tolerated in all patients (~25%) due to knee joint pain. However, low-load resistance training (20-40% 1RM) with concurrent partial blood-flow restriction (BFR) appears to produce effects similar to HIRT yet involving reduced joint pain during and after exercise. The aim is to examine the effect of low-load BFR training compared to SR on pain, thigh muscle mass and muscle function in adults with knee-OA. We hypothesize that 12 weeks of BFR will lead to superior improvements in pain, muscle mass and mechanical muscle function compared to SR.

METHODS AND ANALYSIS

90 participants diagnosed with radiographic knee-OA will be randomized to either BFR or SR twice a week for 12 weeks. BFR will consist of two selected lower limb strength exercises performed with an inflated pneumatic occlusion cuff. Intervention procedures in SR consist of a full 8 weeks GLA:D course followed by 4 weeks of team group training. Primary outcome variable is the change in KOOS-Pain subscale from baseline to 12 weeks. Secondary outcome variables are changes in pain sensitivity, functional performance, muscle mass and mechanical muscle function. Intention-to-treat and per-protocol analyses will be conducted. One-way analysis of variance will be performed to evaluate between-group changes. Pre-to-post intervention comparisons will be analyzed using a mixed linear model. Regression analysis will be performed to evaluate potential associations between selected outcome variables.

Value of conventional ultrasound and shear wave elastography in the assessment of muscle mass and function in elderly people with type 2 diabetes

OBJECTIVES

We assessed muscle mass and function using ultrasound (US) and shear wave elastography (SWE) for sarcopenia in elderly patients with type 2 diabetes.

METHODS

There were 84 patients with type 2 diabetes enrolled in this study; of these, 30 had sarcopenia and 54 did not. We measured appendicular skeletal muscle mass index (ASMI), handgrip strength, calf circumference, 6-m walking speed, and 5-time chair stand test. All patients were in the supine position with their knees in straight and bent poses in turn. The US-derived thickness (Tstraight, Tbent), cross-sectional area (CSAstraight, CSAbent), and SWE (SWEstraight, SWEbent) of the rectus femoris muscle (RFM) were measured and the differences (ΔT, ΔCSA, ΔSWE) were calculated. We assessed the correlations of clinical indicators with US and SWE features. We then compared the clinical indicators and US and SWE features between patients with and without sarcopenia to determine independent predictors. Diagnostic models were established based on these independent predictors.

RESULTS

The ASMI was correlated with Tbent (r = 0.57, p < 0.001) and CSAbent (r = 0.50, p < 0.001). Handgrip strength was correlated with Tbent (r = 0.53, p < 0.001) and CSAbent (r = 0.51, p < 0.001). Between patients with and without sarcopenia, the indicators of age, ΔCSA, and ΔSWE were statically different (all p ≤ 0.001). Based on these results, a diagnostic model for sarcopenia was established with 83.3% sensitivity, 83.3% specificity, and 83.3% accuracy.

CONCLUSIONS

In elderly people with type 2 diabetes, sarcopenia patients had smaller muscle CSA and less stiffness than non-sarcopenia patients. US and SWE might be useful to screen them.

KEY POINTS

• Sarcopenia is common in elderly people with type 2 diabetes. • Ultrasound and shear wave elastography might be useful methods for quantitatively assessing muscle mass and strength. • Ultrasound and shear wave elastography might be useful methods for screening sarcopenia in elderly patients with type 2 diabetes.

Panoramic ultrasound imaging does not produce muscle morphology deformation during imaging acquisition: A validity study

PURPOSE

Despite panoramic ultrasound imaging (US) is a promising advance for the morphological and histological assessment of large musculature which cannot be entirely assessed using B-mode, there is no evidence assessing if this technology produces muscle deformation during imaging acquisition. We aimed to analyze differences in size, shape and brightness descriptors between B-mode and panoramic US images and to assess the concordance between both methods. Methods We analyzed size (cross-sectional area and perimeter), shape (circularity, aspect ratio and roundness) and brightness (mean echo-intensity) features of cervical multifidus (CM) and short rotators (SR) in 46 healthy volunteers. Images were acquired in B-mode and extended field-of-view mode. For validity analysis, mean differences between methods were calculated. For agreement analysis, intraclass correlation coefficients (ICCs), standard error of measurements (SEM), minimal detectable changes (MDC) and coefficient of variation (CV%) were calculated.

RESULTS

All parameters showed no significant differences between both methods for either CM or SR (P > 0.05). Panoramic US showed excellent concordance with B-mode for assessing all CM parameters (all ICCs > 0.9), while for SR the agreement ranged from good-to-excellent (ICC from 0.861 to 0.978).

CONCLUSION

Panoramic US seems to be a valid tool for assessment of muscle size, shape and brightness as no deformation in comparison with B-mode images was seen. Further research is needed to corroborate these findings comparing panoramic US imaging with Gold Standard methods.

Ultrasound assessment of degenerative muscle sarcopenia: the University of Barcelona ultrasound scoring system for sarcopenia

AIM

This study aimed to (1) determine the intraobserver and interobserver reliability of ultrasonographic measurement of muscle thickness (MT) and cross-sectional area (CSA) of the rectus femoris and biceps brachii, correlating these values with manual measurements on dissected cadavers and (2) develop the first semiquantitative musculoskeletal ultrasound (MSUS) scoring system of muscle morphology in sarcopenia and assess its intraobserver and interobserver reliability. In addition, the MSUS morphology score was compared with the corresponding histological images to verify concurrent validity.

METHODS

Ten cryopreserved limbs of 10 cadavers aged 68-91 years were evaluated. The MSUS scoring system was based on the severity of muscle degeneration on a 3-point qualitative scale: grade 1 (normal), grade 2 (moderate changes) and grade 3 (severe changes). Reliability was assessed with intraclass correlation coefficient (ICC) for the MT and CSA and with Cohen's kappa coefficients (κ) for the MSUS scoring system. Concurrent validity was analysed with ICC.

RESULTS

The results showed excellent intraobserver and interobserver reliability for both the MSUS evaluation of MT and CSA (ICC ≥0.93). The MSUS scoring system showed excellent intraobserver reliability (κ=1.0) and very good interobserver reliability (κ=0.85). There was also a high intra- and inter-observer reliability for the histological scorings (ĸ ≥0.85 and mean ĸ=0.70, respectively), as well as high reliability between the histology and MSUS scoring systems (ICC=0.92). All results were statistically significant (p≤0.001).

CONCLUSION

MSUS measures of MT and CSA and the novel MSUS scoring system for degenerative muscle changes in sarcopenia was found to be reliable and strongly associated with histological findings.

Linking muscle architecture and function in vivo: conceptual or methodological limitations?

Background

Despite the clear theoretical link between sarcomere arrangement and force production, the relationship between muscle architecture and function remain ambiguous in vivo.

Methods

We used two frequently used ultrasound-based approaches to assess the relationships between vastus lateralis architecture parameters obtained in three common conditions of muscle lengths and contractile states, and the mechanical output of the muscle in twenty-one healthy subjects. The relationship between outcomes obtained in different conditions were also examined. Muscle architecture was analysed in panoramic ultrasound scans at rest with the knee fully extended and in regular scans at an angle close to maximum force (60°), at rest and under maximum contraction. Isokinetic and isometric strength tests were used to estimate muscle force production at various fascicle velocities.

Results

Measurements of fascicle length, pennation angle and thickness obtained under different experimental conditions correlated moderately with each other (r = 0.40-.74). Fascicle length measured at 60° at rest correlated with force during high-velocity knee extension (r = 0.46 at 400° s^-1) and joint work during isokinetic knee extension (r = 0.44 at 200° s^-1 and r = 0.57 at 100° s^-1). Muscle thickness was related to maximum force for all measurement methods (r = 0.44-0.73). However, we found no significant correlations between fascicle length or pennation angle and any measures of muscle force or work. Most correlations between architecture and force were stronger when architecture was measured at rest close to optimal length.

Conclusion

These findings reflect methodological limitations of current approaches to measure fascicle length and pennation angle in vivo. They also highlight the limited value of static architecture measurements when reported in isolation or without direct experimental context.

Acute changes in motor unit discharge property after concentric versus eccentric contraction exercise in knee extensor

This study aimed to investigate the motor unit firing property immediately after concentric or eccentric contraction exercise. Eighteen healthy men performed repetitive maximal isokinetic knee extension exercises with only concentric or eccentric contraction until they exerted less than 80% of the baseline strength. Before and after the fatiguing exercise, high-density surface electromyography of the vastus lateralis was recorded during submaximal ramp-up isometric contraction and individual motor units were identified. Only motor units that could be tracked before and after exercise were analyzed. Muscle cross-sectional area of the vastus lateralis was measured using ultrasound, and electrically evoked torque was recorded before and after the exercise. Sixty-five and fifty-three motor units were analyzed before and after the concentric and eccentric contractions, respectively. The results showed that motor units with moderate to high recruitment thresholds significantly decreased recruitment thresholds under both conditions, and the motor unit discharge rates significantly increased after concentric contraction compared to eccentric contraction. A greater muscle cross-sectional area was observed with concentric contraction. The evoked torque was significantly decreased under both conditions, but no difference between the conditions. These results suggest that fatiguing exercise with concentric contraction contributes to greater neural input to muscles and metabolic responses than eccentric contraction.

Motor unit dysregulation following 15 days of unilateral lower limb immobilisation

Disuse atrophy, caused by situations of unloading such as limb immobilisation, causes a rapid yet diverging reduction in skeletal muscle function when compared to muscle mass. While mechanistic insight into the loss of mass is well studied, deterioration of muscle function with a focus towards the neural input to muscle remains underexplored. This study aimed to determine the role of motor unit adaptation in disuse-induced neuromuscular deficits. Ten young, healthy male volunteers underwent 15 days of unilateral lower limb immobilisation with intramuscular electromyography (iEMG) bilaterally recorded from the vastus lateralis (VL) during knee extensor contractions normalised to maximal voluntary contraction (MVC), pre and post disuse. Muscle cross-sectional area was determined by ultrasound. Individual MUs were sampled and analysed for changes in motor unit (MU) discharge and MU potential (MUP) characteristics. VL CSA was reduced by approximately 15% which was exceeded by a two-fold decrease of 31% in muscle strength in the immobilised limb, with no change in either parameter in the non-immobilised limb. Parameters of MUP size were reduced by 11% to 24% with immobilisation, while neuromuscular junction (NMJ) transmission instability remained unchanged, and MU firing rate decreased by 8% to 11% at several contraction levels. All adaptations were observed in the immobilised limb only. These findings highlight impaired neural input following immobilisation reflected by suppressed MU firing rate which may underpin the disproportionate reductions of strength relative to muscle size. KEY POINTS: Muscle mass and function decline rapidly in situations of disuse such as bed rest and limb immobilisation. The reduction in muscle function commonly exceeds that of muscle mass, which may be associated with the dysregulation of neural input to muscle. We have used intramuscular electromyography to sample individual motor unit and near fibre potentials from the vastus lateralis following 15 days of unilateral limb immobilisation. Following disuse, the disproportionate loss of muscle strength when compared to size coincided with suppressed motor unit firing rate. These motor unit adaptations were observed at multiple contraction levels and in the immobilised limb only. Our findings demonstrate neural dysregulation as a key component of functional loss following muscle disuse in humans.

Agreement and reliability of lower limb muscle architecture measurements using a portable ultrasound device

High end ultrasonography devices lack in portability and are expensive. We investigated the agreement and reliability of a handheld and portable ultrasound system for human lower limb muscle architecture measurements. We captured ultrasound images of the rectus femoris (RF), vastus lateralis (VL) and gastrocnemius medialis (GM) in 36 active healthy participants (15 female, 21 male) at 50% of muscle length using the handheld Lumify (L12-4, linear-array 37 mm, Philips Healthcare, Amsterdam, Netherlands) and a high-end laboratory device (ACUSON Juniper, linear-array 54 mm, 12L3, SIEMENS Healthineers, Erlangen, Germany). We compared measurements of muscle fascicle length, pennation angle and thickness. To assess inter-session reliability of the Lumify system, participants were measured twice within 1 week. Comparing RF architecture measurements of both devices resulted in intra-class correlations (ICCs) ranging from 0.46–0.82 and standardized mean difference (SMDs) ranging from −0.45–0.05. For VL, ICCs ranged from 0.60–0.89 and SMDs ranged from −0.11–0.13. ICCs and SMDs for the GM ranged from 0.82–0.86 and −0.07–0.07. Calculating inter-session reliability for RF resulted in ICCs ranging from 0.44–0.76 and SMDs ranging from −0.38–0.15. For VL, ICCs and SMDs ranged from 0.57–0.75 and −0.13–0.02. ICCs for GM ranged from 0.75–0.92 and SMDs ranged from −0.15–0.16. Measurement of muscle thickness demonstrated the highest agreement (ICC ≥0.82) and reliability (ICC ≥0.75) across all muscles. The Lumify system was comparable to a high-end device and reliable for GM measurements. However, agreement and reliability were lower for the RF and VL. Of all evaluated architectural parameters, muscle thickness exhibited highest agreement and reliability.

Influence of Subcutaneous Adipose Tissue and Skeletal Muscle Thickness on Rectus Femoris Echo Intensity in Younger and Older Males and Females

OBJECTIVES

Ultrasound measurements of muscle echo intensity are commonly used surrogates of muscle composition (eg, intramuscular adipose tissue). However, given that soundwaves are increasingly attenuated with tissue depth, the interpretation of echo intensity may be confounded by adipose and skeletal muscle thickness. Our objectives are to compare the associations between adipose or muscle tissue thickness and rectus femoris echo intensity in younger and older males and females.

METHODS

Participants included in this analysis were derived from 3 previously published cohorts of younger (<45 years) and older (≥60 years) males and females. Ultrasound images of the rectus femoris were evaluated for muscle thickness, echo intensity, and subcutaneous adipose tissue thickness.

RESULTS

Older adults (n: 49 males, 19 females) had a higher body mass index (P = .001) compared with younger adults (n: 37 males, 49 females). Muscle thickness was negatively associated with echo intensity in older males (r = -0.59) and females (r = -0.53), whereas no associations were observed in younger males (r = 0.00) or females (r = -0.11). Subcutaneous adipose tissue thickness displayed no associations with echo intensity in any group.

CONCLUSIONS

Despite the known influence of subcutaneous adipose tissue thickness on beam attenuation, we observed no association with muscle echo intensity, indicating that adipose tissue correction may be required to better understand muscle echo intensity across differences in adiposity. The negative associations between muscle thickness and echo intensity in older, but not younger adults, suggests these associations may be related to the co-occurrence of skeletal muscle atrophy and intramuscular adipose tissue infiltration with advancing age.

Effect of Set-Structure on Upper-Body Muscular Hypertrophy and Performance in Recreationally-Trained Male and Female

ABSTRACT

Davies, TB, Halaki, M, Orr, R, Mitchell, L, Helms, ER, Clarke, J, and Hackett, DA. Effect of set structure on upper-body muscular hypertrophy and performance in recreationally trained men and women. J Strength Cond Res 36(8): 2176-2185, 2022-This study explored the effect of volume-equated traditional-set and cluster-set structures on muscular hypertrophy and performance after high-load resistance training manipulating the bench press exercise. Twenty-one recreationally trained subjects (12 men and 9 women) performed a 3-week familiarization phase and were then randomized into one of two 8-week upper-body and lower-body split programs occurring over 3 and then progressing to 4 sessions per week. Subjects performed 4 sets of 5 repetitions at 85% one repetition maximum (1RM) using a traditional-set structure (TRAD, n = 10), which involved 5 minutes of interset rest only, or a cluster-set structure, which included 30-second inter-repetition rest and 3 minutes of interset rest (CLUS, n = 11). A 1RM bench press, repetitions to failure at 70% 1RM, regional muscle thickness, and dual-energy x-ray absorptiometry were used to estimate changes in muscular strength, local muscular endurance, regional muscular hypertrophy, and body composition, respectively. Velocity loss was assessed using a linear position transducer at the intervention midpoint. TRAD demonstrated a significantly greater velocity loss magnitude (g = 1.50) and muscle thickness of the proximal pectoralis major (g = -0.34) compared with CLUS. There were no significant differences between groups for the remaining outcomes, although a small effect size favoring TRAD was observed for the middle region of the pectoralis major (g = -0.25). It seems that the greater velocity losses during sets observed in traditional-set compared with cluster-set structures may promote superior muscular hypertrophy within specific regions of the pectoralis major in recreationally trained subjects.

Comparisons between skeletal muscle imaging techniques and histology in tracking midthigh hypertrophic adaptations following 10 weeks of resistance training

This study had two aims. AIM1 was to determine the agreement between mid-thigh vastus lateralis (VL) cross-sectional area measured by ultrasound (mCSA_US) versus magnetic resonance imaging (mCSA_MRI) at a single time point, and the ability of each to detect hypertrophic changes. AIM2 was to assess the relationships between pre-to-post training changes in thigh lean mass determined by DXA, VL mCSA_US, ultrasound-determined VL thickness (VL_Thick), and VL mean myofiber cross-sectional area (fCSA) with changes in VL mCSA_MRI. Twelve untrained males (Age: 20±1 y, BMI: 26.9±5.4 kg/m²; n=12) engaged in a 10-week resistance training program (2x/week) where right mid-thigh images and VL biopsies were obtained prior to and 72-hours following the last training bout. Participants' VL mCSA_MRI (p=0.005), DXA thigh lean mass (p=0.015), and VL_Thick (p=0.001) increased following training, whereas VL mCSA_US and fCSA did not. For AIM1, mCSA_US demonstrated excellent concordance (CCC = 0.830) with mCSA_MRI, albeit mCSA_US values were systematically lower compared to mCSA_MRI (mean bias: -2.29 cm²). Additionally, PRE-to-POST VL mCSA changes between techniques exhibited good agreement (CCC = 0.700; mean bias: -1.08 cm²). For AIM2, moderate, positive correlations existed for PRE-to-POST changes in VL mCSA_MRI and DXA thigh lean mass (r=0.580, p=0.048), mCSA_US (r=0.622, p=0.031), and VL_Thick (r=0.520, p=0.080). A moderate, negative correlation existed between mCSA_MRI and fCSA (r=-0.569, p=0.054). Our findings have multiple implications: i) resistance training-induced hypertrophy was dependent on the quantification method, ii) ultrasound-determined mCSA shows good agreement with MRI, and iii) tissue-level changes poorly agreed with mean fCSA changes and this requires further research.

Skeletal muscle analysis of panoramic ultrasound is reliable across multiple raters

Ultrasound devices are common in muscle physiology laboratories due to their ease of use and validity to assess skeletal muscle characteristics. The current study assessed the reliability of ultrasound skeletal muscle image analysis across multiple raters with limited experience. Vastus lateralis (VL), rectus femoris (RF), and first dorsal interosseus (FDI) images were separately analyzed by three novice raters to determine muscle thickness (MT), cross-sectional area (CSA), and echo-intensity (EI). Separate analyses of variance (ANOVA) assessed statistical differences between and within raters. Intra-class correlation coefficients (ICC) between (inter-rater) and within (intra-rater) raters, the standard error of the measurement (SEM) and minimal difference needed to be considered real were calculated. Inter-rater reliability was high for the VL and RF (ICC: 0.984–0.999), while the FDI was lower (0.614–0.962). Further, intra-rater reliability was greater than 0.961 for each rater. SEM values calculated for inter-rater reliability expressed as a percentage of the mean ranged from 0.4–5.8% across variables. Similarly, SEM values for intra-rater reliability were between 0.8–5.8%, 0.6–3.6%, and 0.4–3.2% for Raters 1, 2 and 3, respectively. Despite this, significant differences (p<0.05) between raters were observed for RF MT and EI, VL CSA and EI, and FDI MT, suggesting that potentially more measurement trials or greater practice time may be necessary to reduce systematic error among multiple raters. Post-image acquisition processing is reliable among and within raters as determined through ICCs and SEMs. This study provided consistent results among three separate novice raters given the same training, a unique yet realistic setting in muscle physiology laboratories.

Human skeletal muscle size with ultrasound imaging: a comprehensive review

Skeletal muscle size is an important factor in assessing adaptation to exercise training and detraining, athletic performance, age-associated atrophy and mobility decline, clinical conditions associated with cachexia, and overall skeletal muscle health. Magnetic resonance (MR) imaging and computed tomography (CT) are widely accepted as the gold standard methods for skeletal muscle size quantification. However, it is not always feasible to use these methods (e.g., field studies, bedside studies, large cohort studies). Ultrasound has been available for skeletal muscle examination for more than 50 years and the development, utility, and validity of ultrasound imaging are underappreciated. It is now possible to use ultrasound in situations where MR and CT imaging are not suitable. This review provides a comprehensive summary of ultrasound imaging and human skeletal muscle size assessment. Since the first study in 1968, more than 600 articles have used ultrasound to examine the cross-sectional area and/or volume of 107 different skeletal muscles in more than 27,500 subjects of various ages, health status, and fitness conditions. Data from these studies, supported by decades of technological developments, collectively show that ultrasonography is a valid tool for skeletal muscle size quantification. Considering the wide-ranging connections between human health and function and skeletal muscle mass, the utility of ultrasound imaging will allow it to be employed in research investigations and clinical practice in ways not previously appreciated or considered.

Internal and External Oblique Muscle Asymmetry in Sprint Hurdlers and Sprinters: A Cross-Sectional Study

The abdominal muscles are vital in providing core stability for functional movements during most activities. There is a correlation between side asymmetry of these muscles and dysfunction. Thus, the purpose of this study was to evaluate and compare trunk muscle morphology and trunk rotational strength between sprint hurdlers, an asymmetrical sport, and sprinters, a symmetrical sport. Twenty-one trained collegiate sprint hurdlers and sprinters were recruited for the study (Hurdlers: 4M, 7F; Sprinters: 8M, 2F), average age (years) hurdlers: 20 ± 1.2; sprinters: 20.4 ± 1.9, height (cm) hurdlers: 172.6 ± 10.2; sprinters: 181.7 ± 4.5, and weight (kg) hurdlers: 67.6 ± 12.0; sprinters: 73.9 ± 5.6. Using real-time ultrasound, panoramic images of the internal oblique (IO) and external oblique (EO) were obtained at rest and contracted (flexion and rotation) in a seated position for both right and left sides of the trunk. While wearing a specially crafted shoulder harness, participants performed three maximal voluntary trunk rotational contractions (MVC). The three attempts were then averaged to obtain an overall MVC score for trunk rotation strength. Average MVC trunk rotational strength to the right was greater among all participants, p < 0.001. The IO showed greater and significant thickness changes from resting to contracted state than the EO, this was observed in all participants. The IO side asymmetry was significantly different between groups p < 0.01. Hurdlers, involved in a unilaterally demanding sport, exhibited the expected asymmetry in muscle morphology and in trunk rotational strength. Interestingly, sprinters, although involved in a seemingly symmetrical sport, also exhibited asymmetrical trunk morphology and trunk rotational strength.

Muscle Thickness and Echogenicity Measured by Ultrasound Could Detect Local Sarcopenia and Malnutrition in Older Patients Hospitalized for Hip Fracture

BACKGROUND

The aim of this work was to assess whether the muscle thickness and echogenicity were associated with dysphagia, malnutrition, sarcopenia, and functional capacity in acute hospital admission for a hip fracture.

METHODS

Observational study that assessed nutritional status by Global Leadership Initiative on Malnutrition, risk of dysphagia and sarcopenia by European Working Group on Sarcopenia in Older People and Barthel functional index. We measured muscle thickness and echogenicity of masseter, bicipital, and quadriceps rectus femoris (RF) and vastus intermedius (VI) by ultrasound.

RESULTS

One hundred and one patients were included in the study (29.7% sarcopenia and 43.8% malnutrition). Logistic regression models adjusted for age, sex, and body mass index showed an inverse association of the masseter thickness with both sarcopenia (OR: 0.56) and malnutrition (OR: 0.38) and quadriceps with sarcopenia (OR: 0.74). In addition, patients at high risk of dysphagia had lower masseter thickness (p: 0.0001) while patients able to self-feeding had thicker biceps (p: 0.002) and individuals with mobility on level surfaces higher thickness of biceps (p: 0.008) and quadriceps (p: 0.04).

CONCLUSION

Thickness of the masseter was associated with risk of dysphagia, biceps with the ability to self-feed, and that of the quadriceps RF-VI with mobility.

Skeletal Muscle and Childhood Cancer: Where are we now and where we go from here

Skeletal muscle (muscle) is essential for physical health and for metabolic integrity, with sarcopenia (progressive muscle mass loss and weakness), a pre-curser of aging and chronic disease. Loss of lean mass and muscle quality (force generation per unit of muscle) in the general population are associated with fatigue, weakness, and slowed walking speed, eventually interfering with the ability to maintain physical independence, and impacting participation in social roles and quality of life. Muscle mass and strength impairments are also documented during childhood cancer treatment, which often persist into adult survivorship, and contribute to an aging phenotype in this vulnerable population. Although several treatment exposures appear to confer increased risk for loss of mass and strength that persists after therapy, the pathophysiology responsible for poor muscle quantity and quality is not well understood in the childhood cancer survivor population. This is partly due to limited access to both pediatric and adult survivor muscle tissue samples, and to difficulties surrounding non-invasive investigative approaches for muscle assessment. Because muscle accounts for just under half of the body's mass, and is essential for movement, metabolism and metabolic health, understanding mechanisms of injury responsible for both initial and persistent dysfunction is important, and will provide a foundation for intervention. The purpose of this review is to provide an overview of the available evidence describing associations between childhood cancer, its treatment, and muscle outcomes, identifying gaps in current knowledge.

Teleguided self-ultrasound scanning for longitudinal monitoring of muscle mass during spaceflight

Loss of muscle mass is a major concern for long duration spaceflight. However, due to the need for specialized equipment, muscle size has only been assessed before and after spaceflight where ~20% loss is observed. Here, we demonstrate the utility of teleguided self-ultrasound scanning (Tele-SUS) to accurately monitor leg muscle size in astronauts during spaceflight. Over an average of 168 ± 57 days of spaceflight, 74 Tele-SUS sessions were performed. There were no significant differences between panoramic ultrasound images obtained by astronauts seven days prior to landing and expert sonographer after flight or between change in muscle size assessed by ultrasound and magnetic resonance imaging. These findings extend the current capabilities of ultrasound imaging to allow self-monitoring of muscle size with remote guidance.

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We examined teleguided self-ultrasound to monitor leg muscle size on the ISS

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Muscle thickness ultrasound does not detect change in muscle size during spaceflight

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Panoramic ultrasound accurately monitors change in muscle size compared to MRI

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Teleguided self-ultrasound reveals upper and lower leg muscle loss during spaceflight

Extended field-of-view ultrasound imaging is reliable for measuring Transversus Abdominis muscle size at rest and during contraction

Background

The strength and size of core muscles, including the abdominal muscles, are crucial to proper function in most activities. Therefore, it is important to reliably assess these characteristics. Our primary objective was to determine if the length, thickness and cross-sectional area of the transversus abdominis (TrA) can be visualized independently from the internal and external abdominal oblique muscles using extended field of view ultrasound imaging at rest and with contraction and to establish its intra- and inter-tester reliability.

Methods

Twenty-six individuals were recruited to participate in the study (20 F, 6 M), average age 24.0 years (SD 9.4), height 170.7 cm (SD 8.6) and weight 63.9 kg (SD 9.0). From this total number of participants, two groups of 16 randomly selected participants were assessed to determine intra- and inter-tester reliability respectively. Extended field of view ultrasound images were obtained at three vertebral levels during rest and contraction in the side lying position for both the right and left sides of the trunk.

Results

Excellent intra-tester and inter-tester reliability was seen (ICC range of 0.972 to 0.984). The overall average percent standard error of the measurement for all measurements and locations was approximately 4%. The overall average minimal difference for the thickness measurement for the resting and contraction conditions combined were as follows: intratester 0.056 (0.014) cm and intertester 0.054 (0.017) cm, for area intratester 0.287 (0.086) cm² and intertester 0.289 (0.101) cm² and for length intratester 0.519 (0.097) cm and intertester 0.507 (0.085) cm.

Conclusions

Extended field of view ultrasound imaging is an effective method of reliably capturing clear images of the TrA during rest and contraction. It provides an efficient mechanism for the analysis of muscle morphology by being able to measure the cross-sectional area, thickness, and length on one image. This methodology is recommended for studies investigating TrA function and training.

Measures Derived from Panoramic Ultrasonography and Animal-Based Protein Intake Are Related to Muscular Performance in Middle-Aged Adults

Ultrasonography advantageously measures skeletal muscle size and quality, but some muscles may be too large to capture with standardized brightness mode (B-mode) imaging. Panoramic ultrasonography can capture more complete images and may more accurately measure muscle size. We investigated measurements made using panoramic compared to B-mode ultrasonography images of the rectus femoris with muscular performance. Concurrently, protein intake plays an important role in preventing sarcopenia; therefore, we also sought to investigate the association between animal-based protein intake (ABPI) and muscular performance. Ninety-one middle-aged adults were recruited. Muscle cross-sectional area (CSA) and thickness were obtained using B-mode and panoramic ultrasound and analyzed with Image J software. Muscular performance was assessed using isokinetic dynamometry, a 30-s chair test, and handgrip strength. Three-day food diaries estimated dietary intakes. Linear regression models determined relationships between measures from ultrasonography and muscular performance. Mixed linear models were used to evaluate the association between ABPI and muscular performance. Muscle CSA from panoramic ultrasonography and ABPI were positively associated with lower-body strength (β ± S.E.; CSA, 42.622 ± 20.024, p = 0.005; ABPI, 65.874 ± 19.855, p = 0.001), lower-body endurance (β ± S.E.; CSA, 595 ± 200.221, p = 0.001; ABPI, 549.944 ± 232.478, p = 0.020), and handgrip strength (β ± S.E.; CSA, 6.966 ± 3.328, p = 0.004; ABPI, 0.349 ± 0.171, p = 0.045). Panoramic ultrasound shows promise as a method for assessing sarcopenia. ABPI is related to better muscular performance.

Are muscle fibres of body builders intrinsically weaker? A comparison with single fibres of aged-matched controls

AIM

Skeletal muscles of Body Builders (BB) represent an interesting model to study muscle mass gains in response to high volume resistance training. It is debated whether muscle contractile performance improves in proportion to mass. Here, we aim to assess whether muscle hypertrophy does not occur at the expense of performance.

METHODS

Six BB and Six untrained controls (CTRL) were recruited. Cross-sectional area (CSA) and maximum voluntary contraction (MVC) of quadriceps femoris muscle (QF) and CSA and architecture of vastus lateralis (VL) were determined. Moreover, a biopsy was taken from VL mid-portion and single fibres were analysed.

RESULTS

QF CSA and MVC were 32% (n.s., P = .052) and 58% (P = .009) higher in BB than in CTRL, respectively. VL CSA was 37% higher in BB (P = .030). Fast 2A fibres CSA was 24% (P = .048) greater in BB than in CTRL, when determined in immunostained sections of biopsy samples. Single permeabilized fast fibres CSA was 37% (n.s., P = .052) higher in BB than in CTRL, and their force was slightly higher in BB (n.s.), while specific tension (P₀ ) was 19% (P = .024) lower. The lower P₀ was not explained either by lower myosin content or by impaired calcium diffusion. Conversely, the swelling caused by skinning-induced permeabilization was different and, when used to correct P₀ , differences between populations disappeared.

CONCLUSIONS

The results show that high degree of muscle hypertrophy is not detrimental for force generation capacity, as increases in fibre size and force are strictly proportional once the differential swelling response is accounted for.

Reliability and Validity of Panoramic Ultrasound Imaging for Evaluating Muscular Quality and Morphology: A Systematic Review

Panoramic ultrasound (US) is a novel method used to assess linear dimensions, cross-sectional area, fatty infiltrate and echo-intensity features of muscles that cannot be measured with B-mode US. However, a structured overview of its validity and reliability is lacking. MEDLINE, PubMed, SCOPUS and Web of Science databases were systematically searched for studies evaluating reliability or validity data on panoramic US imaging to determine the muscular morphology and/or quality of skeletal muscles. Most studies had acceptable methodological quality. Seventeen studies analyzing reliability (n = 16) or validity (n = 5) were included. Twelve studies assessed cross-sectional area, seven studies assessed echo-intensity, five assessed linear dimensions (fascicle/tendon length, muscle/subcutaneous adipose thickness or between-structure distance) and one assessed intramuscular fat. Panoramic US seems to be a reliable and valid tool for the assessment of muscle morphology and quality in healthy populations at specific locations, particularly the lower extremities. Studies including scanning procedures are needed to confirm these findings in locations not included in this revision and in both clinical and healthy populations.

Methodological considerations for and validation of the ultrasonographic determination of human skeletal muscle hypertrophy and atrophy

Magnetic resonance imaging (MRI) is the current gold standard for measuring changes in muscle size (cross-sectional area [CSA] and volume) but can be cost-prohibitive and resource-intensive. We evaluated the validity of B-mode ultrasonography (US) as a low-cost alternative to MRI for measuring muscle hypertrophy and atrophy in response to resistance training and immobilization, respectively. Fourteen young men performed 10wk of unilateral resistance training (RT) to induce muscle hypertrophy. In the final two weeks of the 10wk, the subjects' contralateral leg was immobilized (IMB). The cross-sectional area of the vastus lateralis (VLCSA) was measured at the mid-thigh before and after each intervention using MRI (VLCSA_MRI ) and US (VLCSA_US ). The relationship and agreement between methods were assessed. Reliability of US measurements ranged from good to excellent in all comparisons (ICC >0.67). VLCSA significantly increased after 10 weeks of RT (VLCSA_US : 7.9 ± 3.8%; VLCSA_MRI : 7.8 ± 4.5%) and decreased after 2 weeks of IMB (VLCSA_US : -8.2%±5.8%; VLCSA_MRI : -8.7 ± 6.1%). Significant correlations were identified between MRI and US at each time point measured (all r > 0.85) and, importantly, between MRI- and US-derived changes in VLCSA. Bland-Altman analysis revealed minimal bias in US measurements relative to the MRI (-0.5 ± 3.0%) and all measurements were within the upper and lower limits of agreement. Our data suggest that B-mode ultrasonography can be a suitable alternative to MRI for measuring changes in muscle size in response to increased and decreased muscle loading in young men.

Muscle Assessment by Ultrasonography: Agreement with Dual-Energy X-Ray Absorptiometry (DXA) and Relationship with Physical Performance

BACKGROUND

Different methods have been proposed to study skeletal muscle mass in sarcopenia diagnosis, although all have inherent drawbacks. The aim of this study was to evaluate the utility of muscle ultrasound in muscle assessment by studying its correlation with dual-energy x-ray absorptiometry (DXA) and calf circumference (CC), cut-off values for ultrasound-based detection of low muscle mass, and the correlation with muscle performance.

METHODS

Fifty-seven participants older than 70 years, underwent a muscle ultrasound study, DXA, calf circumference (CC) and functional assessment. Ultrasound measurements were taken in the femoral quadriceps (transverse plane) and in the medial gastrocnemius (transverse and longitudinal planes). Muscle function was assessed by gait speed, Short Physical Performance Battery (SPPB) and grip strength.

RESULTS

Median age was 78.9 years (IQR 74.9 - 81.9), and 33 were women (57.9%). We found good correlation between muscle thickness of gastrocnemius muscle in transverse and longitudinal plane and appendicular lean mass measured by DXA (r=0.546 and r=0.689 respectively) and good correlations between muscle thickness of gastrocnemius in transverse and longitudinal plane with CC (r=0.651 and r=0.447 respectively). The thickness of gastrocnemius medialis optimal cut-off points for low muscle mass were 18,5mm in the transverse plane (Sensitivity: 77,8%, Specificity: 77,1%), and 17.3mm in the longitudinal plane (Sensitivity: 100%,Specificity: 68.8%). Muscle thickness was also significantly correlated with gait speed, SPPB and grip strength.

CONCLUSIONS

Measures of gastrocnemius medialis thickness obtained by ultrasound are reliable and correlate well with DXA and CC values and muscle performance.

Minimizing sedentary behavior (without increasing medium-to-vigorous exercise) associated functional improvement in older women is somewhat dependent on a measurable increase in muscle size

The optimal pattern of sedentarism displacement and mechanisms underlying its health effects are poorly understood. Therefore, the aim of this study was to quantify muscle-tendon adaptation in response to two different sedentarism displacement interventions and relate any adaptations to functional outcomes. Thirty-four older women (73±5yrs) underwent skeletal muscle-tendon size and functional assessments. Participants were randomly allocated to: Sedentary behavior fragmentation (SBF), Light intensity physical activity (LIPA), or Control groups. Measures were taken at weeks 0 and 8. Gait speed significantly increased (p=0.003), in both experimental groups (SBF: 0.06 ± 0.08m/s, 6±10%, LIPA: 0.06 ± 0.07m/s, 6±6%), but not control (-0.02 ± 0.12m/s, -2±9%). Accordingly, the relative change in Vastus Lateralis muscle volume, accounted for 30% (p=0.027), and 45% (p=0.0006) of the explained variance in the relative change in gait speed, for SBF and LIPA respectively. Gastrocnemius Medialis fascicle length changes were positively associated with gait speed changes, following LIPA exclusively (R²= 0.50, p=0.009). This is the first study to show SBF and LIPA are adequate loading in older women, with related muscle adaptation and clinically relevant gait speed improvements. Such adaptations appear similar irrespective of whether sedentarism displacement is prescribed in a single bout (LIPA) or in frequent micro-bouts (SBF).

Disuse-Induced Muscle Loss and Rehabilitation: The National Aeronautics and Space Administration Bed Rest Study

Objectives

The time course and magnitude of atrophic remodeling and the effects of an acute rehabilitation program on muscle atrophy are unclear. We sought to characterize bed rest-induced leg muscle atrophy and evaluate the safety and efficacy of an acute rehabilitation program.

Design

Prespecified analysis of a randomized controlled trial.

Setting

Single-center urban hospital.

Patients

Adults (24-55 yr) randomized to 70 days of sedentary bed rest.

Interventions

The 11-day post-bed rest rehabilitation program consisted of low intensity exercise and progressed to increased aerobic exercise duration, plyometric exercises, and higher intensity resistance exercise.

Measurements and Main Results

Upper (rectus femoris, vastus lateralis, quadriceps, hamstrings, adductors) and lower leg (medial gastrocnemius, lateral gastrocnemius, and soleus) MRI scans were obtained once before, nine times during, and three times after bed rest to assess muscle cross-sectional area. The magnitude and rate of muscle atrophy and recovery were determined for each muscle. Nine participants completed 70 days of sedentary bed rest and an 11-day rehabilitation program. A total of 11,588 muscle cross-sectional area images were quantified. Across all muscles except the rectus femoris (no change), there was a linear decline during bed rest, with the highest atrophic rate occurring in the soleus (-0.33%/d). Following rehabilitation, there was rapid recovery in all muscles; however, the quadriceps (-3.74 cm²; 95% CI, -7.36 to -0.12; p = 0.04), hamstrings (-2.30 cm²; 95% CI, -4.07 to -0.54; p = 0.01), medial gastrocnemius (-0.62 cm²; 95% CI, -1.10 to -0.14; p = 0.01), and soleus (-1.85 cm²; 95% CI, -2.90 to -0.81; p < 0.01) remained significantly lower than baseline.

Conclusions

Bed rest results in upper and lower leg muscle atrophy in a linear pattern, and an 11-day rehabilitation program was safe and effective in initiating a rapid trajectory of muscle recovery. These findings provide important information regarding the design and refinement of rehabilitation programs following bed rest.

Evaluation of the Lower Trapezius Muscle Using Ultrasound Panoramic View (a Novel Approach): An Intra- and Inter-Rater Reliability Study

The panoramic view ultrasound remains uncommon in clinical practice, probably because of its difficulty, high-cost, and lack of research. Morphological changes in muscles have been demonstrated to be related to symptomatology and provide data of interest for clinical assessment. Thus, the aim of this study was to evaluate the measurement reliability of the length of the lower trapezius muscle with the panoramic view ultrasound using a novel tool, SIG_VIP^®. Twenty healthy volunteers were measured by two expert sonographers using the SIG_VIP^® tool with a novel approach. Statistical analyses were performed with the R software. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimal detectable change (MDC), and Bland-Altman plots were calculated. All the results indicated good intra-rater reliability (ICC_3,1, 0.92 to 0.96; SEM, 0.59 to 0.85; MDC, 1.64 to 2.35) and inter-rater reliability (ICC_3,2, 0.84 to 0.89; SEM, 1.22 to 1.53; MDC, 3.39 to 4.25). The novel system used with the described methodology can reliably measure the length of the inferior fibers of the trapezius muscle. Further research must be conducted to evaluate the reliability in patients and how pathology is related to the length of the lower trapezius muscle.

Panoramic Ultrasound Examination of Posterior Neck Extensors in Healthy Subjects: Intra-Examiner Reliability Study

Previous studies analyzing morphometry of posterior cervical muscles with ultrasound (US) imaging have mainly used Brightness mode (B-mode). Our aim was to investigate the intra-examiner reliability of panoramic US imaging for assessing posterior-lateral cervical muscle layers. Panoramic US images of the neck at C4/C5 level were acquired in 25 asymptomatic subjects (40% women; mean age: 24 years) by an experienced assessor. The cross-sectional area (CSA) of the upper trapezius, splenius, semispinalis, multifidi, rotators, and levator scapulae was measured from panoramic US scans on two separate days. Intra-class correlation coefficients (ICC3,1), standard error of measurement (SEM), minimal detectable change (MDC) and mean, absolute and percent errors were calculated. In general, intra-examiner reliability was excellent with ICC3,1 ranging from 0.978 (trapezius) to 0.993 (semispinalis). The SEM ranged from 0.02 (multifidus) to 0.07 (semispinalis/levator), whereas the MDC ranged from 0.05 (cervical multifidus) to 0.19 (levator/semispinalis). Absolute error was lower than 0.11 cm² (levator/semispinalis). No differences between males and females were found. This study found that intra-examiner/rater reliability of panoramic US imaging was excellent for assessing the CSA of the posterior-lateral neck extensor muscles in asymptomatic subjects. The current findings suggest that panoramic US may be a reliable technique for examining the size of the cervical extensor muscles in both males and females.

Effects of Whole-Body Vibration Training and Blood Flow Restriction on Muscle Adaptations in Women: A Randomized Controlled Trial

Centner, C, Ritzmann, R, Gollhofer, A, and König, D. Effects of whole-body vibration training and blood flow restriction on muscle adaptations in women: a randomized controlled trial. J Strength Cond Res 34(3): 603-608, 2020-The purpose of the present randomized controlled trial was to investigate potential synergistic effects of whole-body vibration (WBV) training combined with blood flow restriction (BFR) on muscle mass and strength, and jump performance. Fifty healthy women (26.1 ± 4.6 years) were randomly allocated to one of the following experimental groups: WBV training combined with BFR (WBV + BFR) or WBV only. Before and after the 10-week training intervention, muscle cross-sectional area (CSA) of the vastus lateralis (VL) and gastrocnemius medialis (GM) was evaluated. Additionally, changes in muscle strength and jump performance were assessed before and after the intervention. The level of significance was set to p < 0.05. Vastus lateralis muscle CSA increased in both groups (p < 0.05). The increase in CSA was less pronounced after WBV than WBV + BFR, although the difference was not significant (p = 0.30). Likewise, GM CSA demonstrated comparable increases in both groups with a significant main effect of time (p < 0.05) but no interaction effect (p = 0.89). Assessment of muscular strength (p = 0.70) and jump performance (p = 0.40) did not reveal significant differences between the groups. The results of the present study indicate that the combination of WBV training with BFR shows a noticeable trend toward higher increases in muscle CSA compared with WBV alone. Despite the lack of significance, the results imply clinical relevance particularly in populations showing contraindications toward high training loads. This, however, needs to be confirmed in future research.

Panoramic ultrasound vs. MRI for the assessment of hamstrings cross-sectional area and volume in a large athletic cohort

We investigated the validity of panoramic ultrasound (US) compared to magnetic resonance imaging (MRI) for the assessment of hamstrings cross-sectional area (CSA) and volume. Hamstrings CSA were acquired with US (by an expert operator) at four different sites of femur length (FL) in 85 youth competitive alpine skiers (14.8 ± 0.5 years), and successively compared to corresponding scans obtained by MRI, analyzed by a trained vs. a novice rater. The agreement between techniques was assessed by Bland–Altman analyses. Statistical analysis was carried out using Pearson’s product moment correlation coefficient (r). US-derived CSA showed a very good agreement compared to MRI-based ones. The best sites were 40% FL (0 = mid patellar point) for biceps femoris long head (r = 0.9), 50% for semitendinosus (r = 0.9), and 30% for semimembranosus (r = 0.86) and biceps femoris short head (BFsh, r = 0.8). US-based vs. MRI-based hamstrings volume showed an r of 0.96. Poorer r values were observed for the novice compared to the trained rater, with the biggest difference observed for BFsh at 50% (r = 0.001 vs. r = 0.50, respectively) and semimembranosus at 60% (r = 0.23 vs. r = 0.42, respectively). Panoramic US provides valid CSA values and volume estimations compared to MRI. To ensure optimal US-vs.-MRI agreement, raters should preferably possess previous experience in imaging-based analyses.

Increased tumour burden alters skeletal muscle properties in the KPC mouse model of pancreatic cancer

BACKGROUND

Cancer cachexia is a multifactorial wasting syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force generating capacity. We address these issues in a novel transgenic mouse model Kras, Trp53 and Pdx-1-Cre (KPC) of pancreatic ductal adenocarcinoma (PDA) using multi-parametric magnetic resonance (mp-MR) measures.

METHODS

KPC mice (n = 10) were divided equally into two groups (n = 5/group) depending on the size of the tumor i.e. tumor size <250 mm³ and >250 mm³. Using mp-MR measures, we demonstrated the changes in the gastrocnemius muscle at the microstructural level. In addition, we evaluated skeletal muscle contractile function in KPC mice using an in vivo approach.

RESULTS

Increase in tumor size resulted in decrease in gastrocnemius maximum cross sectional area, decrease in T₂ relaxation time, increase in magnetization transfer ratio, decrease in mean diffusivity, and decrease in radial diffusivity of water across the muscle fibers. Finally, we detected significant decrease in absolute and specific force production of gastrocnemius muscle with increase in tumor size.

CONCLUSIONS

Our findings indicate that increase in tumor size may cause alterations in structural and functional parameters of skeletal muscles and that MR parameters may be used as sensitive biomarkers to noninvasively detect structural changes in cachectic muscles.

Feasibility of eccentric overloading and neuromuscular electrical stimulation to improve muscle strength and muscle mass after treatment for head and neck cancer

PURPOSE

Treatment of head and neck cancer (HNC) results in severe weight loss, mainly due to the loss of lean body mass. Consequently, decreases in muscular strength and health-related quality of life (HRQL) occur. This study investigated the feasibility of a 12-week novel strength training (NST) and conventional strength training (CST) intervention delivered after HNC treatment.

METHODS

Participants were randomized to a NST group (n = 11) involving eccentric overloaded strength training and neuromuscular electrical stimulation (NMES), or a CST group (n = 11) involving dynamic resistance exercises matched for training volume. Feasibility outcomes included recruitment, completion, adherence, and evidence of progression. A neuromuscular assessment involving maximal isometric voluntary contractions (MIVCs) in the knee extensors was evaluated prior to and during incremental cycling to volitional exhaustion at baseline and after the interventions. Anthropometrics and patient-reported outcomes (PROs) were also assessed.

RESULTS

Although recruitment was challenging, completion was 100% in NST and 82% in CST. Adherence was 92% in NST and 81% in CST. Overall, MIVC increased by 19 ± 23%, muscle cross-sectional area improved 18 ± 22%, cycling exercise time improved by 18 ± 13%, and improvements in HRQL and fatigue were clinically relevant.

CONCLUSIONS

Both interventions were found to be feasible for HNC patients after treatment. Strength training significantly improved maximal muscle strength, muscle cross-sectional area, and PROs after HNC treatment. Future research should include fully powered trials and consider the use of eccentric overloading and NMES during HNC treatment.

IMPLICATIONS FOR CANCER SURVIVORS

Eccentric- and NMES-emphasized strength training may be useful alternatives to conventional strength training after HNC treatment.

Neuromuscular function and fatigability in people diagnosed with head and neck cancer before versus after treatment

PURPOSE

Treatment for head and neck cancer is associated with multiple side effects, including loss of body mass, impaired physical function and reduced health-related quality of life. This study aimed to investigate the impact of treatment (radiation therapy ± concurrent chemotherapy) on (i) muscle strength, muscle cross-sectional area and patient-reported outcomes, and (ii) central and peripheral alterations during a whole-body exercise task.

METHODS

Ten people with head and neck cancer (4 female; 50 ± 9 years) completed a lab visit before and after (56 ± 30 days) completion of treatment. Participants performed a neuromuscular assessment (involving maximal isometric voluntary contractions in the knee extensors and electrical stimulation of the femoral nerve) before and during intermittent cycling to volitional exhaustion. Anthropometrics and patient-reported outcomes were also assessed.

RESULTS

From before to after treatment, maximal isometric muscle strength was reduced (P = 0.002, d = 0.73), as was potentiated twitch force (P < 0.001, d = 0.62), and muscle cross-sectional area (e.g., vastus lateralis: P = 0.010, d = 0.64). Exercise time was reduced (P = 0.008, d = 0.62) and peripheral processes contributed to a reduction in maximal force due to cycling. After treatment, the severity of self-reported fatigue increased (P = 0.041, r = - 0.65) and health-related quality of life decreased (P = 0.012, r = - 0.79).

CONCLUSION

Neuromuscular function was impaired in patients with head and neck cancer after treatment. Whole-body exercise tolerance was reduced and resulted in predominantly peripheral, rather than central, disturbances to the neuromuscular system. Future research should evaluate strength training after treatment for head and neck cancer, with the overall aim of reducing fatigue and improving health-related quality of life.

Blood Flow Restriction Training Applied With High-Intensity Exercise Does Not Improve Quadriceps Muscle Function After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

BACKGROUND

A major goal of rehabilitation after anterior cruciate ligament reconstruction (ACLR) is restoring quadriceps muscle strength. Unfortunately, current rehabilitation paradigms fall short of this goal, such that substantial quadriceps muscle strength deficits can limit return to play and increase the risk of recurrent injuries. Blood flow restriction training (BFRT) involves the obstruction of venous return to working muscles during exercise and may lead to better recovery of quadriceps muscle strength after ACLR.

PURPOSE

To examine the efficacy of BFRT with high-intensity exercise on the recovery of quadriceps muscle function in patients undergoing ACLR.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 34 patients (19 female, 15 male; mean age, 16.5 ± 2.7 years; mean height, 169.0 ± 19.7 cm; mean weight, 73.2 ± 17.7 kg) scheduled to undergo ACLR were randomly assigned to 1 of 4 groups: concentric (n = 8), eccentric (n = 8), concentric with BFRT (n = 9), and eccentric with BFRT (n = 9). The exercise component of the intervention consisted of patients performing a single-leg isokinetic leg press, at an intensity of 70% of the patients' 1-repetition maximum during either the concentric or eccentric action, for 4 sets of 10 repetitions 2 times per week for 8 weeks beginning at 10 weeks postoperatively. Patients randomized to the BFRT groups performed the leg-press exercise with a cuff applied to the thigh, set to a limb occlusion pressure of 80%. Isometric and isokinetic (60 deg/s) quadriceps peak torque, quadriceps muscle activation, and rectus femoris muscle volume were assessed before ACLR, after BFRT, and at the time that patients returned to activity and were converted to the change in values from baseline for analysis. Also, 1-way analyses of covariance were used to compare the change in values for each dependent variable between groups after BFRT and at return to activity (P ≤ .05).

RESULTS

No significant differences were found between groups for any outcome measures at either time point (P > .05).

CONCLUSION

An 8-week BFRT plus high-intensity exercise intervention did not significantly improve quadriceps muscle strength, activation, or volume. On the basis of our findings, the use of BFRT in conjunction with high-intensity resistance exercise in patients undergoing ACLR to improve quadriceps muscle function may not be warranted.

REGISTRATION

NCT03141801 ( ClinicalTrials.gov identifier).

Longitudinal Assessment of Quadriceps Muscle Morphology Before and After Anterior Cruciate Ligament Reconstruction and Its Associations With Patient-Reported Outcomes

BACKGROUND

Reductions in muscle size are common after anterior cruciate ligament reconstruction (ACLR) and may contribute to suboptimal patient outcomes. However, few studies have quantified postoperative alterations in muscle quality and evaluated its associations with patient-reported function.

HYPOTHESES

Rectus femoris cross-sectional area (CSA) will decrease postoperatively but improve at return to activity (RTA), rectus femoris muscle quality (percentage fat [PF]) will increase postoperatively and be greater at RTA compared with preoperative values, and rectus femoris CSA and PF will be associated with International Knee Documentation Committee (IKDC) scores at both postoperative time points.

STUDY DESIGN

Case series.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 26 individuals who sustained an ACL injury and underwent reconstructive surgery were evaluated preoperatively (T₀), 9 weeks post-ACLR (T₁), and at RTA. Rectus femoris CSA and PF were evaluated bilaterally via ultrasound imaging, and patient-reported function was assessed using the IKDC score.

RESULTS

Bilateral reductions in rectus femoris CSA were noted from T₀ to T₁ (P < 0.01). Only the uninvolved limb returned to preoperative CSA (P = 0.80), as the involved limb failed to return to preoperative levels at RTA (P = 0.04). No significant changes in rectus femoris PF were observed across time points (P > 0.05). Lesser PF (P < 0.01) but not CSA (P = 0.75) was associated with higher IKDC score at T₁. Lesser PF (P = 0.04) and greater CSA (P = 0.05) was associated with higher IKDC score at RTA.

CONCLUSION

Substantial atrophy occurs bilaterally after ACLR, and the involved limb does not return to preoperative muscle size despite the patient completing rehabilitation. Quadriceps muscle morphology is associated with patient-reported function and may be an important rehabilitation target after ACLR.

CLINICAL RELEVANCE

Quadriceps atrophy and poor muscle quality may contribute to suboptimal patient functioning and quadriceps dysfunction and may be important in RTA decision making. Assessing muscle morphology using ultrasound may be a feasible and clinically beneficial tool in patients after ACLR.

Ultrasound for Measuring the Cross-Sectional Area of Biceps Brachii Muscle in Sarcopenia

Background: Ultrasound is emerging as an effective method for measuring muscle mass in elderly people. It has been applied in numerous studies to obtain measurement of lower limbs. The study aims to explore the relationship between sarcopenia and ultrasound measurements of biceps brachii. Methods: Participants (n=179) aged over 60 years were enrolled from the first affiliated hospital of Zhejiang University. The muscle thickness (MT), cross-sectional area (CSA) and fat thickness (FT) of these participants were recorded. Spearman test and partial correlation test was used to determine the correlation between indicators. Mann-Whitney U test was performed to compare ultrasonic parameters between sarcopenia group and non-sarcopenia group. The binary logistic regression analysis was employed to detect the potential indicators and prediction equation of sarcopenia. Receiver operating characteristic (ROC) curve analysis was performed for the accuracy of equation. Results: The prevalence of sarcopenia were 16.3% and 10.8% respectively in men and women. CSA was significantly lower in sarcopenia group than non-sarcopenia group in women (P<0.05). CSA was positively correlated with skeletal muscle mass index (SMI) and grip strength (men: r=0.460, 0.433; women: r=0.267, 0.392). After controlling of age and BMI, these correlations disappeared. Binary logistic regression analysis showed that age (OR=1.149, 95%CI: 1.060-1.246; P=0.001) and CSA (OR=0.465, 95%CI: 0.225-0.963; P=0.039) was significant indicators associated with sarcopenia. Area Under Curve was 0.822 (95%CI: 0.725-0.919, P<0.001) for the prediction equation composed of age, gender and CSA for sarcopenia. Conclusion: CSA of the biceps brachii measured with ultrasound is an important indicator associated with sarcopenia.

Cardiac cachexia

Cachexia is a multifactorial disease characterized by a pathologic shift of metabolism towards a more catabolic state. It frequently occurs in patients with chronic diseases such as chronic heart failure and is especially common in the elderly. In patients at risk, cardiac cachexia is found in about 10% of heart failure patients. The negative impact of cardiac cachexia on mortality, morbidity, and quality of life demonstrates the urgent need to find new effective therapies against cardiac cachexia. Furthermore, exercise training and nutritional support can help patients with cardiac cachexia. Despite ongoing efforts to find new therapies for cachexia treatment, also new preventive strategies are needed.

Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training

Low-load blood flow restriction (LL-BFR) training has gained increasing interest in the scientific community by demonstrating that increases in muscle mass and strength are comparable to conventional high-load (HL) resistance training. Although adaptations on the muscular level are well documented, there is little evidence on how LL-BFR training affects human myotendinous properties. Therefore, the aim of the present study was to investigate morphological and mechanical Achilles tendon adaptations after 14 wk of strength training. Fifty-five male volunteers (27.9 ± 5.1 yr) were randomly allocated into the following three groups: LL-BFR [20-35% of one-repetition maximum (1RM)], HL (70-85% 1RM), or a nonexercising control (CON) group. The LL-BFR and HL groups completed a resistance training program for 14 wk, and tendon morphology, mechanical as well as material properties, and muscle cross-sectional area (CSA) and isometric strength were assessed before and after the intervention. Both HL (+40.7%) and LL-BFR (+36.1%) training induced significant increases in tendon stiffness (P < 0.05) as well as tendon CSA (HL: +4.6%, LL-BFR: +7.8%, P < 0.001). These changes were comparable between groups without significant changes in Young's modulus. Furthermore, gastrocnemius medialis muscle CSA and plantar flexor strength significantly increased in both training groups (P < 0.05), whereas the CON group did not show significant changes in any of the evaluated parameters. In conclusion, the adaptive change in Achilles tendon properties following low-load resistance training with partial vascular occlusion appears comparable to that evoked by high-load resistance training.NEW & NOTEWORTHY Low-load blood flow restriction (LL-BFR) training has been shown to induce beneficial adaptations at the muscular level. However, studies examining the effects on human tendon properties are rare. The findings provide first evidence that LL-BFR can increase Achilles tendon mechanical and morphological properties to a similar extent as conventional high-load resistance training. This is of particular importance for individuals who may not tolerate heavy training loads but still aim for improvements in myotendinous function.

Effect of Time on Human Muscle Outcomes During Simulated Microgravity Exposure Without Countermeasures-Systematic Review

Background: Space Agencies are planning human missions beyond Low Earth Orbit. Consideration of how physiological system adaptation with microgravity (μG) will be managed during these mission scenarios is required. Exercise countermeasures (CM) could be used more sparingly to decrease limited resource costs, including periods of no exercise. This study provides a complete overview of the current evidence, making recommendations on the length of time humans exposed to simulated μG might safely perform no exercise considering muscles only. Methods: Electronic databases were searched for astronaut or space simulation bed rest studies, as the most valid terrestrial simulation, from start of records to July 2017. Studies were assessed with the Quality in Prognostic Studies and bed rest analog studies assessed for transferability to astronauts using the Aerospace Medicine Systematic Review Group Tool for Assessing Bed Rest Methods. Effect sizes, based on no CM groups, were used to assess muscle outcomes over time. Outcomes included were contractile work capacity, muscle cross sectional area, muscle activity, muscle thickness, muscle volume, maximal voluntary contraction force during one repetition maximum, peak power, performance based outcomes, power, and torque/strength. Results: Seventy-five bed rest μG simulation studies were included, many with high risk of confounding factors and participation bias. Most muscle outcomes deteriorated over time with no countermeasures. Moderate effects were apparent by 7-15 days and large by 28-56 days. Moderate effects (>0.6) became apparent in the following order, power and MVC during one repetition maximum (7 days), followed by volume, cross sectional area, torques and strengths, contractile work capacity, thickness and endurance (14 days), then muscle activity (15 days). Large effects (>1.2) became apparent in the following order, volume, cross sectional area (28 days) torques and strengths, thickness (35 days) and peak power (56 days). Conclusions: Moderate effects on a range of muscle parameters may occur within 7-14 days of unloading, with large effects within 35 days. Combined with muscle performance requirements for mission tasks, these data, may support the design of CM programmes to maximize efficiency without compromising crew safety and mission success when incorporated with data from additional physiological systems that also need consideration.

Ultrasound assessment of muscle mass in response to exercise training in chronic kidney disease: a comparison with MRI

BACKGROUND

Chronic kidney disease (CKD) is a catabolic condition associated with muscle wasting and dysfunction, which associates with morbidity and mortality. There is a need for simple techniques capable of monitoring changes in muscle size with disease progression and in response to interventions aiming to increase muscle mass and function. Ultrasound is one such technique; however, it is unknown how well changes in muscle cross-sectional area (CSA) measured using ultrasound relate to changes in whole muscle volume measured using magnetic resonance imaging. We tested whether rectus femoris CSA (RF-CSA) could be used as a valid indication of changes in quadriceps muscle volume as a single measure of muscle size and following a 12 week exercise intervention that resulted in muscle hypertrophy.

METHODS

Secondary analysis of data was collected from the ExTra CKD study (ISRCTN 36489137). Quadriceps muscle size was assessed from 36 patients with non-dialysis CKD before and after 12 weeks of supervised exercise that resulted in muscle hypertrophy.

RESULTS

Strong positive correlations were observed between RF-CSA and quadriceps volume at baseline (r² = 0.815, CI 0.661 to 0.903; P < 0.001) and following 12 week exercise (r² = 0.845, CI 0.700 to 0.923; P < 0.001). A moderate positive association was also observed between changes in RF-CSA and quadriceps following exercise training (rho = 0.441, CI 0.085 to 0.697; P = 0.015). Bland-Altman analysis revealed a small bias (bias 0.6% ± 12.5) between the mean percentage changes in RF-CSA and quadriceps volume but wide limits of agreement from -24 to 25.

CONCLUSIONS

Rectus femoris CSA appears to be a reliable index of total quadriceps volume as a simple measure of muscle size, both as a single observation and in response to exercise training in non-dialysis CKD patients.

Ultrasound imaging for sarcopenia, spasticity and painful muscle syndromes

PURPOSE OF REVIEW

On the basis of its various advantages and the relevant awareness of physicians, ultrasound imaging has overwhelmingly taken its place in the scientific arena. This is true both from the side of daily clinical applications and also from the side of research. Yet, ultrasound provides real-time (diagnostic) imaging and (interventional) guidance for a wide spectrum of muscle disorders. In this regard, this review aims to discuss the potential/actual utility of ultrasound imaging in particular muscle disorders, that is, sarcopenia, spasticity and fibromyalgia/myofascial pain syndrome.

RECENT FINDINGS

Due to the aging population worldwide and the importance of functionality in the older population, mounting interest has been given to the diagnosis and management of sarcopenia in the recent literature. Likewise, several articles started to report that ultrasound imaging can be used conveniently and effectively in the early diagnosis and quantification of sarcopenia.For spasticity, aside from ultrasound-guided botulinum toxin injections, intriguing attention has been paid to sonographic evaluation of muscle architecture, echogenicity and elasticity in the follow-up of these chronic conditions.As regards painful muscle syndromes, quantitative ultrasound techniques have been shown to detect statistically significant differences between healthy controls and patients with myofascial pain syndrome.

SUMMARY

Ultrasound imaging seems to be a promising tool that indisputably deserves further research in the management of a wide range of muscle disorders. VIDEO ABSTRACT: http://links.lww.com/COSPC/A17.

A Critical Evaluation of the Biological Construct Skeletal Muscle Hypertrophy: Size Matters but So Does the Measurement

Skeletal muscle is highly adaptable and has consistently been shown to morphologically respond to exercise training. Skeletal muscle growth during periods of resistance training has traditionally been referred to as skeletal muscle hypertrophy, and this manifests as increases in muscle mass, muscle thickness, muscle area, muscle volume, and muscle fiber cross-sectional area (fCSA). Delicate electron microscopy and biochemical techniques have also been used to demonstrate that resistance exercise promotes ultrastructural adaptations within muscle fibers. Decades of research in this area of exercise physiology have promulgated a widespread hypothetical model of training-induced skeletal muscle hypertrophy; specifically, fCSA increases are accompanied by proportional increases in myofibrillar protein, leading to an expansion in the number of sarcomeres in parallel and/or an increase in myofibril number. However, there is ample evidence to suggest that myofibrillar protein concentration may be diluted through sarcoplasmic expansion as fCSA increases occur. Furthermore, and perhaps more problematic, are numerous investigations reporting that pre-to-post training change scores in macroscopic, microscopic, and molecular variables supporting this model are often poorly associated with one another. The current review first provides a brief description of skeletal muscle composition and structure. We then provide a historical overview of muscle hypertrophy assessment. Next, current-day methods commonly used to assess skeletal muscle hypertrophy at the biochemical, ultramicroscopic, microscopic, macroscopic, and whole-body levels in response to training are examined. Data from our laboratory, and others, demonstrating correlations (or the lack thereof) between these variables are also presented, and reasons for comparative discrepancies are discussed with particular attention directed to studies reporting ultrastructural and muscle protein concentration alterations. Finally, we critically evaluate the biological construct of skeletal muscle hypertrophy, propose potential operational definitions, and provide suggestions for consideration in hopes of guiding future research in this area.