Intra- and intermuscular variation in human quadriceps femoris architecture assessed in vivo

The relationship between muscle thickness and pennation angle is mediated by fascicle length in the muscles of the lower extremities

Muscle morphological architecture, a crucial determinant of muscle function, has fascinated researchers since the Renaissance. Imaging techniques enable the assessment of parameters such as muscle thickness (MT), pennation angle (PA), and fascicle length (FL), which may vary with growth, sex, and physical activity. Despite known interrelationships, robust mathematical models like causal mediation analysis have not been extensively applied to large population samples. We recruited 109 males and females, measuring knee flexor and extensor, and plantar flexor MT, PA, and FL using real-time ultrasound imaging at rest. A mixed-effects model explored sex, leg (dominant vs. non-dominant), and muscle region differences. Males exhibited greater MT in all muscles (0.1 to 2.1 cm, p < 0.01), with no sex differences in FL. Dominant legs showed greater rectus femoris (RF) MT (0.1 cm, p = 0.01) and PA (1.5°, p = 0.01), while vastus lateralis (VL) had greater FL (1.2 cm, p < 0.001) and PA (0.6°, p = 0.02). Regional differences were observed in VL, RF, and biceps femoris long head (BFlh). Causal mediation analyses highlighted MT's influence on PA, mediated by FL. Moderated mediation occurred in BFlh, with FL differences. Gastrocnemius medialis and lateralis exhibited FL-mediated MT and PA relationships. This study unveils the intricate interplay of MT, FL, and PA in muscle architecture.

Constitutional thinness might be characterized by physiologically adapted and not impaired muscle function and architecture: new results from the NUTRILEAN study

PURPOSE

While muscle mass and skeletal muscle fibers phenotype have been shown atypical in constitutional thinness (CT), force production capacities and its architectural determinants have never been explored. The present study compared muscle functionality and architecture between participants with CT and their normal-weight (NW) counterparts.

METHODS

Anthropometry, body composition (Dual-X-ray Absorptiometry), physical activity/sedentary behavior (ActiGraph wGT3X-BT), ultrasound recording of the Vastus Lateralis (2D-ultrasound system), and functional capacities at maximal isometric and isokinetic voluntary contractions (MVCISO and MVCCON) during knee extension (isokinetic dynamometer chair Biodex) have been measured in 18 women with CT (body mass index < 17.5 kg/m2) and 17 NW women.

RESULTS

A lower fat-free mass (ES: -1.94, 95%CI: -2.76 to -1.11, p < 0.001), a higher sedentary time, and a trend for a lower time spent at low-intensity physical activity, were observed in CT vs NW participants. While absolute MVCISO, MVCCON, rate of torque development (RTD), and torque work were all markedly lower in CT, these differences disappeared when normalized to body or muscle mass. Muscle thickness and fascicle length were found lower in CT (ES: -1.29, 95%CI: -2.03 to -0.52, p < 0.001; and ES: -0.87, 95%CI: -1.58 to -0.15, p = 0.02, respectively), while pennation angle was found similar.

CONCLUSION

Despite lower absolute strength capacities observed in CT, present findings support the hypothesis of physiological adaptations to the low body and muscle mass than to some intrinsic contractile impairments. These results call for further studies exploring hypertrophy-targeted strategies in the management of CT.

Autoregulation Does Not Provide Additional Benefits to a Mixed Session Periodized Resistance Training Program in Trained Men

ABSTRACT

Bartolomei, S, Francesco, L, Latini, D, and Hoffman, JR. Autoregulation does not provide additional benefits to a mixed session periodized resistance training program in trained men. J Strength Cond Res XX(X): 000-000, 2024-The aim of this investigation was to study how autoregulation impacted training volume, performance, and muscle size on a 10-week mixed session periodized (MSP) resistance training program, characterized by the inclusion of different training foci in each session. Twenty-four resistance trained men were assigned to an autoregulated mixed session periodized (AMSP group; n = 13; age = 26.2 ± 4.9 y; body mass = 82.0 ± 8.7 kg; height = 176.8 ± 6.0 cm) or into an MSP (n = 11; age = 24.0 ± 2.6; body mass = 81.3 ± 10.5 kg; height = 174.0 ± 5.4 cm) group. Subjects in both groups trained 5 days per week for 10 weeks and performed the same exercises. The difference between the groups consisted in the use of a perceived recovery-based scale to adjust the individual training volume in the AMSP program. Maximal strength (bench press and squat 1 repetition maximum), power (bench press throw and countermovement jump), and muscle architecture (muscle thickness [MT] of biceps brachii, trapezius, vastus lateralis and vastus medialis) were collected before and after the 10-week training period. In addition, training volume and session load were calculated for each training session. A higher total training volume (p < 0.001) was seen in AMSP program compared with MSP program, but no differences (p > 0.05) were noted in the average session load. No significant differences between the groups were detected for MT of both upper-body and lower-body muscles (p's > 0.05) and lean body mass (p = 0.681). No significant differences between the groups were detected for any strength or power measurements. Results of this study indicate that a perceived recovery-based AMSP training program was not more effective than an MSP training program for increasing muscle size and performance in resistance trained men.

Effect of applied cadence in repeated sprint cycling on muscle characteristics

PURPOSE

This study aimed to investigate physiological responses, muscle-tendon unit properties of the quadriceps muscle, and mechanical performance after repeated sprint cycling at optimal and 70% of optimal cadence.

METHODS

Twenty recreational cyclists performed as first sprint performance cycling test and during subsequent sessions two repeated sprint cycling protocols at optimal and 70% of optimal cadence, in random order. The muscle-tendon unit outcome measures on the dominant leg included muscle thickness, fascicle length (Lf), pennation angle (θp), and stiffness for the rectus femoris (RF), vastus lateralis (VL), and vastus medialis muscle (VM) at baseline, immediately after repeated sprint cycling, and 1-h post-exercise.

RESULTS

The results showed an increase in muscle thickness and θp in RF, VL, and VM for both cadences from baseline to immediately after exercise. The Lf decreased in RF (both cadences), while stiffness decreased in RF, VL, and VM at optimal cadence, and in VL at 70% of optimal cadence from baseline to immediately after exercise.

CONCLUSION

The present study revealed that the alterations in muscle characteristics were more marked after repeated sprint cycling at optimal cadence compared with a lower cadence most likely as a result of higher load on the muscle-tendon unit at optimal cadence.

Skeletal muscle architecture and aging: A comparison of ultrasound techniques and an assessment of intrarater reliability

OBJECTIVE

To assess intrarater reliability of ultrasound-determined measurements of skeletal muscle characteristics across different measurement outcomes, imaging techniques, and age groups.

METHODS

2D ultrasound images (B-mode) of the quadriceps were obtained from young (26 ± 4 year, n = 8 M, 8 F) and older (70 ± 7 year, n = 7 M, 5 F) adults on two occasions, separated by 6 ± 3 days. With participants in both standing and supine postures, images were collected from five anatomical sites along the anterior (two sites) and lateral (three sites) compartments of the thigh corresponding to 56%, 39%, and 22% (lateral only) of femur length. Images were analysed for muscle thickness, pennation angle, and echogenicity. Intraclass correlation coefficients (ICC) were used to assess reliability.

RESULTS

Muscle thickness values were higher (p < 0.05) on images collected in the stand versus supine posture only for muscles of the anterior compartment, independent of age. Echogenicity values were higher (p < 0.05) in the vastus intermedius on images collected in the supine versus stand posture only in older adults. Pennation angle values were not impacted by imaging posture (p > 0.05). ICC values for thickness, echogenicity, and pennation angle were generally higher for analyses conducted on images collected in the supine versus stand posture. Imaging posture generated a greater difference in ICC values in the lateral versus anterior muscles and in older versus younger participants.

CONCLUSION

Our findings suggest that participant posture during imaging impacts the absolute values and intrarater reliability of ultrasound-determined muscle characteristics in a muscle-specific fashion, and this effect is greater in older compared to younger individuals.

Exploring the Relationship between Ultrasonographic Measures of the Quadriceps and Knee Extensor Muscle Fitness in Endurance-Trained Individuals

Background

B-mode ultrasonography is an accessible and cost-effective method to assess muscle size and quality through muscle thickness (MT) and echo intensity (EI), respectively. Muscle thickness and EI have demonstrated relationships with maximal strength and local muscle endurance, providing a noninvasive and efficient modality to examine muscle fitness. However, these relationships have not been quantified in the individual quadriceps muscles of habitually endurance-trained populations, which may provide information to practitioners regarding rehabilitation and performance.

Methods

Twenty-three participants (males: N = 10; females: N = 13) underwent B-mode ultrasonography to assess MT, EI, and adipose tissue thickness-corrected echo intensity (cEI) in the vastus intermedius (VI), vastus lateralis (VL), and rectus femoris (RF). Muscle fitness was evaluated through maximal strength (1RM) and local muscle endurance (4 sets to failure at 50% 1RM) during dynamic knee extension. Relationships between ultrasonography outcomes and muscle fitness were examined through stepwise multiple linear regression.

Results

The results indicate that VI cEI is the strongest predictor of 1RM strength (r = -0.643), while no ultrasonography-derived measures significantly predicted local muscle endurance.

Conclusion

The study demonstrates that ultrasonography, specifically measures of cEI in the VI, has the greatest association with maximal strength in endurance-trained individuals. These findings suggest monitoring VI muscle size and quality may benefit practitioners who aim to improve knee extension strength for performance or following injury. In addition, the findings support the use of EI examinations in trained populations.

Multimodal and conventional resistance training interventions improve muscle function in older adults: Findings from the Training IMCT study

Age-associated remodeling processes affect the intramuscular connective tissue (IMCT) network, which may significantly impair muscle function. Thus, we aimed to test whether including exercises shown to efficiently target the IMCT to a conventional resistance exercise intervention (CONV) would result in greater functional gains as compared to CONV alone. Fifty-three men and women (66.2 ± 3.3 years) were assigned to either CONV (n = 15), multimodal training (MULTI; n = 17) or a control (CTRL; n = 21) group. All subjects were tested at baseline, and those assigned to CONV or MULTI underwent a 16-week training intervention. The CONV group followed a progressive resistance training program, in which the number of weekly training sessions gradually increased from 1 to 3. In the MULTI group, one of these sessions was replaced with plyometric training, followed by self-myofascial release. Testing included maximal strength and power, imaging-based muscle volume, architecture, and functional performance. The intervention effects were analyzed using two- or three-way repeated measures ANOVA models (α = 0.05). Briefly, the maximal knee extension isometric contraction, one-repetition maximum, and isokinetic peak torque increased in all groups (p < 0.05), albeit to a lesser extent in CTRL. On the other hand, quadriceps femoris muscle volume (p = 0.019) and vastus lateralis pennation angle (p < 0.001) increased only in the MULTI group. Handgrip strength did not change in response to the intervention (p = 0.312), whereas Sit-to-Stand performance improved in all groups after the first 8-wks, but only in MULTI and CONV after 16-wks (all p < 0.001). In conclusion, we found that a resistance training intervention in which one weekly training session is replaced by plyometric training is feasible and as effective as a program consisting solely of conventional strength training sessions for inducing gains in muscle strength and function in older adults. Muscle size and architecture improved only in the MULTI group. German Clinical Trials: DRKS00015750.

The Effect of Eccentric or Isometric Training on Strength, Architecture, and Sprinting across an Australian Football Season

PURPOSE

This study aimed to investigate the effect of an isometric (ISO) or Nordic hamstring exercise (NHE) intervention, alongside a sprint training program on hamstring strength, architecture, and sprinting performance in Australian footballers.

METHODS

Twenty-five male athletes undertook NHE ( n = 13) or ISO ( n = 12) training across a 38-wk period (including preseason and in season). Biceps femoris long head (BFlh) architecture, ISO, and eccentric knee flexor strength were assessed at baseline, at the end of preseason (14 wk), and at the conclusion of the intervention. Sprint times and force-velocity profiles were determined at baseline and at the end of preseason.

RESULTS

After the intervention, both groups had significant improvements in BFlh fascicle length (NHE: 1.16 cm, 95% CI = 0.68 to 1.63 cm, d = 1.88, P < 0.001; ISO: 0.82 cm, 95% CI = 0.57 to 1.06 cm, d = 1.70, P < 0.001), muscle thickness (NHE: 0.11 cm, 95% CI = 0.01 to 0.21 cm, d = 0.51, P = 0.032; ISO: 0.21 cm, 95% CI = 0.10 to 0.32 cm, d = 0.86, P = 0.002), and eccentric strength (NHE: 83 N, 95% CI = 53 to 114 N, d = 1.79, P < 0.001; ISO: 83 N, 95% CI = 17 to 151 N, d = 1.17, P = 0.018). Both groups also finished the intervention weaker isometrically than they started (NHE: -45 N, 95% CI = -81 to -8 N, d = -1.03, P = 0.022; ISO: -80 N, 95% CI = -104 to -56 N, d = -3.35, P < 0.001). At the end of preseason, the NHE group had improved their 5-m sprint time by 3.3% ± 2.0%), and their maximum horizontal velocity was 3% ± 2.1% greater than the ISO group who saw no changes.

CONCLUSIONS

Both ISO and NHE training with a periodized sprinting program can increase BFlh fascicle length, thickness, and eccentric strength in Australian footballers. NHE training also improves 5-m sprint time and maximum velocity. However, both interventions reduced ISO strength. These findings provide unique, contextually relevant insights into the adaptations possible in semiprofessional athletes.

Fully Automated Analysis of Muscle Architecture from B-Mode Ultrasound Images with DL_Track_US

OBJECTIVE

B-mode ultrasound can be used to image musculoskeletal tissues, but one major bottleneck is analyses of muscle architectural parameters (i.e., muscle thickness, pennation angle and fascicle length), which are most often performed manually.

METHODS

In this study we trained two different neural networks (classic U-Net and U-Net with VGG16 pre-trained encoder) to detect muscle fascicles and aponeuroses using a set of labeled musculoskeletal ultrasound images. We determined the best-performing model based on intersection over union and loss metrics. We then compared neural network predictions on an unseen test set with those obtained via manual analysis and two existing semi/automated analysis approaches (simple muscle architecture analysis [SMA] and UltraTrack). DL_Track_US detects the locations of the superficial and deep aponeuroses, as well as multiple fascicle fragments per image.

RESULTS

For single images, DL_Track_US yielded results similar to those produced by a non-trainable automated method (SMA; mean difference in fascicle length: 5.1 mm) and human manual analysis (mean difference: -2.4 mm). Between-method differences in pennation angle were within 1.5°, and mean differences in muscle thickness were less than 1 mm. Similarly, for videos, there was overlap between the results produced with UltraTrack and DL_Track_US, with intraclass correlations ranging between 0.19 and 0.88.

CONCLUSION

DL_Track_US is fully automated and open source and can estimate fascicle length, pennation angle and muscle thickness from single images or videos, as well as from multiple superficial muscles. We also provide a user interface and all necessary code and training data for custom model development.

Validation of bioimpedance phase angle in lower extremity of male patients with chronic spinal cord injury

[Purpose] This study aimed to evaluate the relationship between lower extremity phase angle and muscle thickness/echo intensity in males with chronic spinal cord injury. It also compared bioelectrical impedance analysis measurements to investigate skeletal muscle degeneration between individuals with spinal cord injury and healthy controls. [Participants and Methods] This cross-sectional study included 12 male patients with chronic spinal cord injury and 14 healthy male controls. We used bioelectrical impedance analysis and ultrasonography to measure the lower extremity phase angle and muscle thickness/echo intensity of the rectus femoris muscle, respectively. We also compared the bioelectrical impedance analysis measurements between individuals with spinal cord injury and healthy controls. [Results] Lower extremity phase angle was strongly correlated with muscle thickness and echo intensity of the rectus femoris muscle in individuals with spinal cord injury. All measures differed significantly between individuals with spinal cord injury and healthy controls. [Conclusion] These findings suggest that lower extremity phase angle is a valuable skeletal muscle indicator in spinal cord injury. Furthermore, bioelectrical impedance analysis revealed degeneration of the lower extremity skeletal muscles in individuals with chronic spinal cord injury.

Three-dimensional mapping of ultrasound-derived skeletal muscle shear wave velocity

Introduction: The mechanical properties of skeletal muscle are indicative of its capacity to perform physical work, state of disease, or risk of injury. Ultrasound shear wave elastography conducts a quantitative analysis of a tissue's shear stiffness, but current implementations only provide two-dimensional measurements with limited spatial extent. We propose and assess a framework to overcome this inherent limitation by acquiring numerous and contiguous measurements while tracking the probe position to create a volumetric scan of the muscle. This volume reconstruction is then mapped into a parameterized representation in reference to geometric and anatomical properties of the muscle. Such an approach allows to quantify regional differences in muscle stiffness to be identified across the entire muscle volume assessed, which could be linked to functional implications. Methods: We performed shear wave elastography measurements on the vastus lateralis (VL) and the biceps femoris long head (BFlh) muscle of 16 healthy volunteers. We assessed test-retest reliability, explored the potential of the proposed framework in aggregating measurements of multiple subjects, and studied the acute effects of muscular contraction on the regional shear wave velocity post-measured at rest. Results: The proposed approach yielded moderate to good reliability (ICC between 0.578 and 0.801). Aggregation of multiple subject measurements revealed considerable but consistent regional variations in shear wave velocity. As a result of muscle contraction, the shear wave velocity was elevated in various regions of the muscle; showing pre-to-post regional differences for the radial assessement of VL and longitudinally for BFlh. Post-contraction shear wave velocity was associated with maximum eccentric hamstring strength produced during six Nordic hamstring exercise repetitions. Discussion and Conclusion: The presented approach provides reliable, spatially resolved representations of skeletal muscle shear wave velocity and is capable of detecting changes in three-dimensional shear wave velocity patterns, such as those induced by muscle contraction. The observed systematic inter-subject variations in shear wave velocity throughout skeletal muscle additionally underline the necessity of accurate spatial referencing of measurements. Short high-effort exercise bouts increase muscle shear wave velocity. Further studies should investigate the potential of shear wave elastography in predicting the muscle's capacity to perform work.

Strength and passive stiffness of the quadriceps are associated with patellar alignment in older adults with knee pain

BACKGROUND

Maintaining normal patellar alignment is important for knee health. Altered activation of individual quadriceps muscles have been found related to patellar alignment. However, the relationships between strength and passive stiffness of the quadriceps and patellar alignment remains unexplored.

METHODS

Participants aged between 60 and 80 years with activity-induced knee pain were recruited. Knee pain was quantified using an 11-point numeric rating scale. Quadriceps strength was assessed using a Cybex dynamometer and passive stiffness of rectus femoris, vastus lateralis, and vastus medialis were measured by shear-wave ultrasound elastography. Patellar alignments were assessed using MR imaging. Linear regression was used to examine relationships between quadriceps properties and patellar alignments with and without controlling for potential covariates.

FINDINGS

Ninety-two eligible participants were assessed (71.7% females, age: 65.6 ± 3.8 years; pain scale: 4.6 ± 2.0), most of whom had knee pain during stair climbing (85.9%). We found that 17% of patellar lateral tilt angle could be explained by lower quadriceps strength (adjusted R2 = 0.117; P < 0.001), especially in females (R2 = 0.281; P < 0.001; adjusted R2 = 0.211; P < 0.001). In addition, a higher stiffness ratio of vastus lateralis/medialis accounted for 12% of patellar lateral displacement (adjusted R2 = 0.112; P = 0.008).

INTERPRETATION

Quadriceps strength and relative stiffness of lateral to medial heads are associated with patellar alignment in older adults with knee pain. It suggests that quadriceps weakness and relatively stiffer lateral quadriceps may be risk factors related to patellar malalignments in the elderly.

Effect of knee joint angle on vastus medialis and vastus lateralis rigidity during isometric submaximal voluntary knee extensions

The use of shear wave elastography during voluntary contraction has enabled the non-invasive assessment of load sharing strategies between agonist muscles. However, the change in joint angle and voluntary contraction intensity can modify contribution between muscles. The aim of this study was to investigate the effect of knee joint angle on the local mechanical properties of the vastus medialis (VM) and the vastus lateralis (VL) during isometric submaximal voluntary contractions from shear wave elastography mapping. The VM and VL Young's modulus at rest and during constant isometric submaximal voluntary contractions (i.e., 25%, 50% and 75% of maximal voluntary contraction [MVC]) were assessed for two knee angles (50° and 100° | knee fully extended = 0°) in twelve participants. No significant difference was found in the VM Young's modulus among all torque levels and knee angles (p > 0.05). VL Young's modulus was significantly higher at 25% MVC for a knee angle of 100° than at 75% MVC for the same knee angle and was greater at 25% MVC for a knee angle of 100° than for 50° (p < 0.05). In contrast to the VM, the contribution of the VL to the knee joint torque production during isometric voluntary contraction appears to depend on the muscle length and the relative knee extension torque level.

FES-rowing: a well-tolerated and highly beneficial exercise for a patient with Brown-Sequard syndrome

CONTEXT

Brown-Séquard Syndrome (BSS) is a rare neurological condition associated with Spinal Cord Injury (SCI). Hemisection of the spinal cord causes paralysis of the homolateral side, and thermoalgesic dysfunction on the opposite side. Cardiopulmonary and metabolic alterations have been reported. For all these patients, regular physical activity is highly recommended and functional electrical stimulation (FES) may be a good option, especially for those with paraplegia. However, to our knowledge, the effects of FES have primarily been studied in those with complete SCI and data regarding application and effects in patients with incomplete lesions (with sensory feedback) is lacking. The present case report therefore evaluated the feasibility and effectiveness of a 3-month FES-rowing program in a patient with BSS.

METHODS

Knee extensor muscle strength and thickness, walking and rowing capacities as well as quality of life were evaluated before and after 3 months of FES-rowing (two sessions per week) in a 54 year old patient with BSS.

RESULTS

The individual had excellent tolerance and adherence to the training protocol. All measured parameters were greatly improved after 3 months: on average, + 30% rowing capacity, + 26% walking capacity, + 24.5% isometric strength, + 21.9% quadriceps muscle thickness, + 34.5% quality of life.

CONCLUSION

FES-rowing appears to be well tolerated and highly beneficial for a patient with incomplete SCI and could therefore be considered as an appealing exercise option for these patients.

Architectural anatomy of the human tibialis anterior presents morphological asymmetries between superficial and deep unipennate regions

The tibialis anterior muscle plays a critical role in human ambulation and contributes to maintaining the upright posture. However, little is known about its muscle architecture in males and females. One hundred and nine physically active males and females were recruited. Tibialis anterior muscle thickness, pennation angle, and fascicle length were measured at rest in both unipennate regions of both legs using real-time ultrasound imaging. A linear mixed model was used with muscle thickness, pennation angle, or fascicle length as the dependent variables. All models were carried out with and without total leg lean mass and shank length as covariates. Causal mediation analysis was computed to explore the effect of muscle thickness on the relationship between fascicle length and pennation angle. There were no significant differences between dominant and nondominant legs regarding muscle architecture. Muscle thickness and pennation angle were greater in the deep than the superficial unipennate region in males (1.9 mm and 1.1°, p < 0.001) and women (3.4 mm and 2.2°, p < 0.001). However, the fascicle length was similar in both regions for both sexes. The differences remained significant after accounting for differences in leg lean mass and shank length. In both regions, muscle thickness was 1-3 mm greater in males and superficial pennation angle 2° smaller in females (both, p < 0.001). After accounting for leg lean mass and shank length, sex differences remained for muscle thickness (1.6 mm, p < 0.05) and pennation angle (3.4°, p < 0.001) but only in the superficial region. In both regions, leg lean mass and shank-adjusted fascicle length were 1.4 mm longer in females than males (p < 0.05). The causal mediation analysis revealed that the estimation of fascicle length was positive, suggesting that a 10% increase in muscle thickness would augment the fascicle length, allowing a 0.38° pennation angle decrease. Moreover, the pennation angle increases in total by 0.54° due to the suppressive effect of the increase in fascicle length. The estimated mediation, direct, and total effects were all significantly different from zero (p < 0.001). Overall, our results indicate that the architectural anatomy of the tibialis anterior shows sexual dimorphism in humans. Tibialis anterior presents morphological asymmetries between superficial and deep unipennate regions in both sexes. Lastly, our causal mediation model identified a suppressive effect of fascicle length on the pennation angle, suggesting that increments in muscle thickness are not always aligned with increments in fascicle length or the pennation angle.

Regional muscle features and their association with knee extensors force production at a single joint angle

This study aimed (i) to investigate the role of regional characteristics of the knee extensors muscles (vastus lateralis: VL, vastus intermedius: VI and rectus femoris: RF) in determining maximum-voluntary force (MVF); and (ii) to understand which regional parameter of muscle structure would best predict MVF. Muscle architecture (e.g., pennation angle and fascicle length), muscle volume (Vol), anatomical (ACSA) and physiological cross-sectional-area (PCSA) were measured in the proximal (0-33% of the muscle length), middle (33-66% of the muscle length) and distal (66-100% of the muscle length) portions of each muscle in fifteen healthy males using ultrasound and Magnetic Resonance Imaging (MRI). Knee extensors force was calculated in isometric condition at a single knee joint angle of 90 degrees. Regional ACSA, Vol and PCSA were correlated with MVF production. Regional muscle geometry showed no significant correlations with MVF. Among regions, the middle portion of each muscle was largely correlated with MVF compared to all the other regions (distal and proximal). To understand which regional structural parameter best predicted MVF, a stepwise multiple linear regression was performed. This model showed a significant explanatory power (P < 0.001, R2 = 0.76, adjusted R2  = 0.71), including muscle Vol collected in the mid portions of VL and RF. Even if no significant differences were reported between Vol, PCSA and ACSA in determining MVF, our results showed that the RF and VL volume collected in the middle portion of the muscle length are strong determinants of MVF produced by the knee extensors at 90 degrees joint angle.

Diffusion tensor imaging: Influence of segmentation on fiber tracking in the supraspinatus muscle-An inter-operator reliability analysis

The ability of muscle to generate force depends on its architecture and health condition. MR-based diffusion tensor imaging of muscle (mDTI) is an innovative approach for showing the fiber arrangement for the whole muscle volume. For accurate calculations of fiber metrics, muscle segmentation prior to tractography is regarded as necessary. Since segmentation is known to be operator dependent, it is important to understand how segmentation affects tractography. The aim of this study was to compare the results of deterministic fiber tracking based on muscle models generated by two independent operators. In addition, this study compares the results with a segmentation-free approach. Fifteen subjects underwent mDTI of the right shoulder. The results showed that mDTI can be successfully applied to complex joints such as the human shoulder. Furthermore, operator segmentation did not influence the results of fiber tracking and fascicle length (FL), fiber volume (FV), fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) showed excellent intraclass correlation estimates (≥ 0.975). As an exploratory approach, the segmentation-free fiber tracking showed significant differences in terms of mean fascicle length. Based on these findings, we conclude that tractography is not sensitive to small deviations in muscle segmentation. Furthermore, it implies that mDTI and automatic segmentation approaches or even a segmentation-free analysis can be considered for evaluation of muscle architecture.

Neuromuscular disorders in women and men with spinal cord injury are associated with changes in muscle and tendon architecture

OBJECTIVE

The present study aimed to determine the association between neuromuscular function, motor function impairment, and muscle and tendon structures in individuals with spinal cord injury (SCI) compared to a control (non-disabled) population.

DESIGN

A cross-sectional study with a control group.

SETTING

Center of Adapted Sports Training and Special Physical Education.

PARTICIPANTS

Fifteen individuals with SCI and motor function impairments participated in the study. A paired non-disabled group was recruited for comparison.

INTERVENTIONS

Not applicable.

OUTCOME MEASURES

Muscle (biceps brachii, rectus femoris, vastus lateralis, vastus medialis, and tibialis anterior) and tendon (quadriceps and patellar tendons) structures were assessed by ultrasound imaging (thickness, pennation angle, fascicle length, and echogenicity). Neuromuscular electrophysiological disorders were also assessed using electrodiagnosis techniques (stimulus non-responsivity and chronaxie) in the same muscles.

RESULTS

Except for the biceps brachii muscle, muscle thickness, pennation angle, and fascicle length were lower (p < 0.01) while echogenicity and chronaxie were greater (p < 0.01) in SCI participants. The SCI participants had a higher prevalence of neuromuscular electrophysiological disorders for all muscles, except the biceps brachii.

CONCLUSION

Neuromuscular disorders occur in association with muscle and tendon maladaptation in individuals with chronic SCI. A higher prevalence of electrophysiological disorders suggests an acquired polyneuromyopathy for muscles with motor function impairment even though the muscle was innerved, in addition to widespread muscle atrophy.

Influence of ultrasound machine settings on quantitative measures derived from spatial frequency analysis of muscle tissue

BACKGROUND

Ultrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle.

METHODS

Longitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter.

RESULTS

PSFR was affected by modifications in focus location only (p < 0.001) with differences noted between all locations. Mmax% was influenced by the interaction of gain and focus location (p < 0.001) but was also independently affected by increasing window depth (p < 0.001). Both Mmax and Sum parameters were sensitive to small changes in machine settings with the interaction of focus location and window depth (p < 0.001 for both parameters) as well as window depth and gain (p < 0.001 for both) influencing the extracted values.

CONCLUSIONS

Frequently adjusted imaging settings influence some SFA statistics. PSFR and Mmax% appear to be most robust to small changes in image settings, making them best suited for comparison across individuals and between studies, which is appealing for the clinical utility of the SFA method.

Muscle Architecture and Maximal Strength between Male Practitioners of Functional Fitness Training and Strength Training

Functional Fitness Training (FFT) is a very popular training method in recent years. However, the combination of aerobic and strength components of this training method raised the hypothesis of impaired strength and muscle structure when compared to Strength Training (ST). Thus, the study aimed to compare muscle architecture and strength between FFT and ST, and the relationship between muscle architecture and maximum strength performance. Males (28.46 ± 6.03 years), nonathletes, and practitioners for two years in FFT (n = 8) and ST (n = 8), in addition to males classified as physically active (n = 8) were recruited. Muscle architecture of the rectus femoris (RF) and vastus lateralis (VL) of the thigh were evaluated with the aid of B-mode ultrasound and maximum strength in the back squat through the one-repetition maximum test. For muscle architecture, the fascicle length (FL), pennation angle (PAn), and muscle thickness (MT) were evaluated, in addition to the cross-sectional area (CSA). The FL, PAn, MT, and CSA of the RF and VL did not differ between the FFT and ST groups. Similarly, maximum strength did not differ between the FFT (152 ± 23.68 kg) and ST (151.88 ± 14.77 kg) groups. A significant relationship was observed between the PAn of the RF and the maximum strength (r =0.862; p =0.006) of FFT practitioners. The muscle architecture, CSA, and muscle strength do not differ between FFT and ST male practitioners, and PAn of the RF correlates with the maximum force for FFT practitioners.

Effects of Drop Sets on Skeletal Muscle Hypertrophy: A Systematic Review and Meta-analysis

BACKGROUND

One of the most popular time-efficient training methods when training for muscle hypertrophy is drop sets, which is performed by taking sets to concentric muscle failure at a given load, then making a drop by reducing the load and immediately taking the next set to concentric or voluntary muscle failure. The purpose of this systematic review and meta-analysis was to compare the effects of drop sets over traditional sets on skeletal muscle hypertrophy.

METHODS

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The SPORTDiscus and MEDLINE/PubMed databases were searched on April 9, 2022, for all studies investigating the effects of the drop set training method on muscle hypertrophy that meets the predefined inclusion criteria. Comprehensive Meta-Analysis Version 3 (Biostat Inc., Englewood Cliffs, NJ, USA) was used to run the statistical analysis. Publication bias was assessed through visual inspection of the funnel plots for asymmetry and statistically by Egger's regression test with an alpha level of 0.10.

RESULTS

Six studies met the predefined inclusion criteria. The number of participants in the studies was 142 (28 women and 114 men) with an age range of 19.2-27 years. The average sample size was 23.6 ± 10.9 (range 9-41). Five studies were included in the quantitative synthesis. Meta-analysis showed that both the drop set and traditional training groups increased significantly from pre- to post-test regarding muscle hypertrophy (drop set standardized mean difference: 0.555, 95% CI 0.357-0.921, p < 0.0001; traditional set standardized mean difference: 0.437, 95% CI 0.266-0.608, p < 0.0001). No significant between-group difference was found (standardized mean difference: 0.155, 95% CI - 0.199 to - 0.509, p = 0.392).

CONCLUSIONS

The results of this systematic review and meta-analysis indicate that drop sets present an efficient strategy for maximizing hypertrophy in those with limited time for training. There was no significant difference in hypertrophy measurements between the drop set and traditional training groups, but some of the drop set modalities took half to one-third of the time compared with traditional training.

ADAPTations to low load blood flow restriction exercise versus conventional heavier load resistance exercise in UK military personnel with persistent knee pain: protocol for the ADAPT study, a multi-centre randomized controlled trial

BACKGROUND

Muscle atrophy, muscle weakness and localised pain are commonly reported following musculoskeletal injury (MSKI). To mitigate this risk and prepare individuals to return to sport or physically demanding occupations, resistance training (RT) is considered a vital component of rehabilitation. However, to elicit adaptations in muscle strength, exercise guidelines recommend lifting loads ≥ 70% of an individual's one repetition maximum (1-RM). Unfortunately, individuals with persistent knee pain are often unable to tolerate such high loads and this may negatively impact the duration and extent of their recovery. Low load blood flow restriction (LL-BFR) is an alternative RT technique that has demonstrated improvements in muscle strength, hypertrophy, and pain in the absence of high mechanical loading. However, the effectiveness of high-frequency LL-BFR in a residential rehabilitation environment remains unclear. This study will compare the efficacy of high frequency LL-BFR to 'conventional' heavier load resistance training (HL-RT) on measures of physical function and pain in adults with persistent knee pain.

METHODS

This is a multicentre randomised controlled trial (RCT) of 150 UK service personnel (aged 18-55) admitted for a 3-week residential rehabilitation course with persistent knee pain. Participants will be randomised to receive: a) LL-BFR delivered twice daily at 20% 1-RM or b) HL-RT three-times per week at 70% 1-RM. Outcomes will be recorded at baseline (T1), course discharge (T2) and at three-months following course (T3). The primary outcome will be the lower extremity functional scale (LEFS) at T2. Secondary outcomes will include patient reported perceptions of pain, physical and occupational function and objective measures of muscle strength and neuromuscular performance. Additional biomechanical and physiological mechanisms underpinning both RT interventions will also be investigated as part of a nested mechanistic study.

DISCUSSION

LL-BFR is a rehabilitation modality that has the potential to induce positive clinical adaptations in the absence of high mechanical loads and therefore could be considered a treatment option for patients suffering significant functional deficits who are unable to tolerate heavy load RT. Consequently, results from this study will have a direct clinical application to healthcare service providers and patients involved in the rehabilitation of physically active adults suffering MSKI.

TRIAL REGISTRATION

ClinicalTrials.org reference number, NCT05719922.

Effect of sit-to-stand-based training on muscle quality in sedentary adults: a randomized controlled trial

The aim of this study was to compare the effects of sit-to-stand (STS) training programs with 5 vs. 10 repetitions on muscle architecture and muscle function in sedentary adults. Sixty participants were randomly assigned into three groups: five-repetition STS (5STS), 10-repetition STS (10STS), or a control group (CG). Participants performed three sets of five or 10 repetitions of the STS exercise three times per week for 8 weeks. Before and after 8 weeks, all groups performed ultrasound measures to evaluate muscle thickness (MT), pennation angle (PA), and fascicle length (FL), and the five-repetition STS test to estimate the relative STS power and muscle quality index (MQI). After 8 weeks, both experimental groups improved MQI (40-45%), relative STS power (29-38%), and MT (8-9%) (all p < 0.001; no differences between the 5STS vs. 10STS groups). These improvements in both groups resulted in differences regarding the CG, which did not present any change. In addition, only the 5STS group improved PA (15%; p = 0.008) without differences to the 10STS and CG.This suggests that STS training is time-effective and low-cost for improving muscle function and generating adaptations in muscle architecture.

Neuromuscular activation of the quadriceps femoris, including the vastus intermedius, during isokinetic knee extensions

The purpose of this study was to compare the neuromuscular activation patterns of the individual muscles of the quadriceps femoris (QF), including the vastus intermedius (VI), during isokinetic concentric (CON) and eccentric (ECC) contractions. Thirteen healthy men performed maximum isokinetic CON and ECC knee extensions at angular velocities of 30, 90, and 120°/sec at knee joint angles from 80 to 180° (180° = full extension). The surface electromyographic (EMG) activities of the four individual muscles of the QF were recorded. The root mean squares of the EMG signals were normalized by the root mean square (nRMS) during CON contraction at 30°/sec. To investigate the nRMS changes, we classified the range of motion into four subcategories for each CON and ECC contraction. The nRMS of the VI was significantly higher in the flexed position during CON and ECC contractions at all velocities, and gradually decreased toward the extended positions regardless of the type of muscle contraction or angular velocity. These results suggest that the QF undergoes neuromuscular activation in a joint angle-dependent manner. In particular, the VI may contribute greatly during flexed contractions, independent of the type of contraction and angular velocity.

Correlations Between Hamstring Muscle Architecture, Maturation, and Anthropometric Measures in Academy Soccer Players

PURPOSE

Muscle architecture is associated with motor performance and muscle injury. While muscle architecture and knee-flexor eccentric strength change with growth, the influence of anthropometric measures on these properties is rarely considered. This study aimed to investigate the relationship between hamstring muscle architecture and knee-flexor eccentric strength with anthropometric measurements.

METHODS

Sixty male footballers (16.6 [1.05] y) from the U16, U17, and U19 teams of an elite soccer club were included in this study. Fascicle length, pennation angle, and muscle thickness of the biceps femoris long head (BFlh) and semimembranosus muscles were measured in both legs using ultrasound. Knee-flexor eccentric strength, height, body mass, leg length, femur length, and peak height velocity (PHV) were measured within 1 week of the ultrasound images. A stepwise regression and 1-way analysis of variance tests were used to evaluate the effects of age, maturity, and anthropometric measurements on muscle properties.

RESULTS

Variance within BFlh and semimembranosus muscle thickness (r < .61), semimembranosus pennation angle (r < .58), and knee-flexor eccentric strength (r = .50) were highly related to body mass. We observed no significant correlations between muscle architecture and age (P > .29). However, moderately greater BFlh muscle thickness was shown for the post-PHV compared with the PHV group (effect size ± 90% CI: 0.72 ± 0.49).

CONCLUSIONS

In conclusion, weak correlations between muscle architecture and anthropometric measurements suggest that other factors (ie, genetics, training regimen) influence muscle architecture. The moderate effect of maturity on BFlh muscle thickness strongly suggests post-PHV hypertrophy of the BFlh muscle. Our results confirmed previous findings that eccentric knee-flexor strength is influenced by body mass.

Differing hypertrophy patterns from open and closed kinetic chain training affect quadriceps femoris center of mass and moment of inertia

Purpose: To determine whether kinetic chain pattern during knee extensor strength training influences quadriceps femoris center of mass and moment of inertia about the hip in a predictable manner as such changes can affect running economy.

Methods: Twelve participants completed 8 weeks of both unilateral open (OKC) and closed (CKC) kinetic chain resistance training on opposing legs. Changes in quadriceps femoris muscle volume (VOLQF), center of mass location (CoMQF), and moment of inertia (IQF) about the hip were determined from magnetic resonance images scans. Regional hemodynamics of the vastus lateralis taken at 30% and 70% of muscle length during OKC and CKC bouts early in the training program were measured using near-infrared spectroscopy (NIRS) and used post hoc to predict changes in CoMQF.

Results: While increases in VOLQF were similar between OKC (Δ79.5 ± 87.9 cm3) and CKC (Δ60.2 ± 110.5 cm3, p = 0.29), the patterns of hypertrophy differed; a distal shift in CoMQF (Δ2.4 ± 0.4 cm, p &lt; 0.001) and increase in IQF (Δ0.017 ± 0.014 kg m2, p &lt; 0.001) occurred in OKC but not in CKC (CoMQF: Δ-2.2 ± 2.0 cm, IQF: Δ-0.022 ± 0.020 kg m2, p &gt; 0.05). Regional hemodynamics assessed by NIRS during a single training session displayed similar exercise and regional differences and predicted 39.6% of observed changes in CoMQF.

Conclusions: Exercise selection influences muscle shape sufficiently to affect CoMQF and IQF, and these changes may be predicted in part from NIRS measurements during a single workout. Given IQF is inversely related to running economy and since CKC exercise provides a more proximal pattern of hypertrophy than OKC, it may be more preferential for running. The results from the present study also highlight the potential of NIRS as a tool for predicting patterns of hypertrophy between different exercises and exercise conditions.

New Perspectives in Resistance Training Periodization: Mixed Session vs. Block Periodized Programs in Trained Men

ABSTRACT

Bartolomei, S, Zaniboni, F, Verzieri, N, and Hoffman, JR. New perspectives in resistance training periodization: mixed session vs. block periodized programs in trained men. J Strength Cond Res 37(3): 537-545, 2023-The purpose of this investigation was to compare the effects of 2 different periodized resistance training programs on maximal strength, power, and muscle architecture, in trained individuals. Twenty-two resistance-trained men were randomly assigned to either a mixed session training group (MSP; n = 11; age = 23.7 ± 2.6 years; body mass = 80.5 ± 9.8 kg; height = 175.5 ± 6.1 cm) or a block periodization group (BP; n = 11; age = 25.7 ± 4.6 years; body mass = 81.1 ± 10.7 kg; height = 176.8 ± 8.4 cm). Both training programs were 10 weeks in duration and were equated in volume. Each training session of the MSP focused on power, maximal strength, and hypertrophy, whereas each mesocycle within the BP focused on one of these components. Subjects were assessed for body composition, muscle architecture, maximal strength, and power. In addition, perceived training load, and training volume were calculated. Subjects in MSP experienced greater improvements in fat free mass ( p = 0.021), muscle thickness of the pectoralis and vastus lateralis ( p < 0.05), and a greater improvement in 1RM bench press ( p < 0.001; +8.6% in MSP and +2% in BP) than in BP. By contrast, BP resulted in greater improvements in vertical jump ( p = 0.022; +7.2%) compared with MSP (+1.2%). No significant differences were noted between the groups for perceived training load ( p = 0.362) nor training volume ( p = 0.169). Results of this study indicated that in a 10-week training study, MSP may enhance muscle hypertrophy and maximal strength to a greater extent than BP, with the same training volume and perceived training load. However, BP may be more effective for vertical jump improvement.

The Influence of Hip and Knee Joint Angles on Quadriceps Muscle-Tendon Unit Properties during Maximal Voluntary Isometric Contraction

Determining how the quadriceps femoris musculotendinous unit functions, according to hip and knee joint angles, may help with clinical decisions when prescribing knee extension exercises. We aimed to determine the effect of hip and knee joint angles on structure and neuromuscular functioning of all constituents of the quadriceps femoris and patellar tendon properties. Twenty young males were evaluated in four positions: seated and supine in both 20° and 60° of knee flexion (SIT20, SIT60, SUP20, and SUP60). Peak knee extension torque was determined during maximal voluntary isometric contraction (MVIC). Ultrasound imaging was used at rest and during MVIC to characterize quadriceps femoris muscle and tendon aponeurosis complex stiffness. We found that peak torque and neuromuscular efficiency were higher for SUP60 and SIT60 compared to SUP20 and SIT20 position. We found higher fascicle length and lower pennation angle in positions with the knee flexed at 60°. The tendon aponeurosis complex stiffness, tendon force, stiffness, stress, and Young's modulus seemed greater in more elongated positions (60°) than in shortened positions (20°). In conclusion, clinicians should consider positioning at 60° of knee flexion rather than 20°, regardless if seated or supine, during rehabilitation to load the musculotendinous unit enough to stimulate a cellular response.

Muscle Architecture and Subcutaneous Fat Measurements of Rectus Femoris and Vastus Lateralis at Optimal Length Aided by a Novel Ultrasound Transducer Attachment

Purpose: This cross-sectional study determines the sensitivity of muscle architecture and fat measurements of the rectus femoris (RF) and vastus lateralis (VL) muscles from ultrasound images acquired with varying transducer tilt, using a novel transducer attachment, in healthy adults. Secondary objectives were to estimate intrarater and interrater reliability of image measurement and acquisition, respectively. Methods: Thirty healthy adults participated (15 women and 15 men; 25 [SD 2.5] y). Ultrasound image acquisition was conducted by two raters at different transducer tilts relative to the skin: estimated perpendicular, and five measured angles (80°, 85°, 90°, 95°, 100°) using the transducer attachment. Muscle thickness (MT), subcutaneous fat thickness (FT), pennation angle (PA), and fascicle length (FL) were measured. Sensitivity and reliability were assessed using intra-class correlation coefficients (ICCs) and standard error of measurements (SEMs). Results: MT and FT for RF and VL were not sensitive to transducer tilt. However, PA and FL were sensitive to transducer tilt. MT and FT for both muscles showed high ICCs and low SEMs for intrarater and interrater reliability. For PA of both muscles, standardizing transducer tilt improved interrater ICCs and lowered SEMs. Conclusion: MT and FT measurements of RF and VL acquired at 60° knee flexion are robust to varying transducer tilt angles. PA measurements benefit from standardizing transducer tilt.

Effects of superficial tissue and intermuscular connections on rectus femoris muscle shear modulus heterogeneity

INTRODUCTION

Intramuscular heterogeneity exists in the shear modulus of the rectus femoris (RF) muscle. However, the underlying heterogeneity mechanisms are not entirely understood. Previous research has reported that detachment of superficial tissues reduces the shear modulus by 50%. The aim of this study was to examine the effects of the skin, deep fascia, and intermuscular connections on the shear modulus of the RF at multiple sites.

MATERIALS AND METHODS

Eleven donors were fixed using the Thiel method. Measurements were performed at 0°, 60°, and 120° knee flexion in a neutral hip position. Tissue processing was performed under four conditions: superficial tissue (CONT), skin off (SKIN), deep fascia detachment (FASC), and intermuscular connections detachment (ALL). The shear modulus at the proximal, central, and distal regions were measured using ultrasound shear wave elastography. The study was approved by the Sapporo Medical University Ethical Committee.

RESULTS

Three-way ANOVA revealed no significant interaction between treatment, site, and angle (P = 0.156), treatment and angle (P = 0.067), or site and angle (P = 0.441). There was a significant effect of treatment (P < 0.001), site (P = 0.010), and angle (P < 0.001) and interaction between treatment and site (P < 0.001). The proximal shear modulus was greater than the central for CONT. There were no significant differences between the measurement sites for SKIN. The distal shear modulus was greater than the proximal for FASC. The distal shear modulus was also greater than the proximal and central for ALL.

CONCLUSIONS

Intramuscular regional differences that influence superficial tissue and intermuscular connections of RF elasticity heterogeneity were observed.

Does static stretching change uniformly the quadriceps elasticity in physically actives subjects?

PURPOSE

Verify the acute responses of static stretching (SS) on the rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) elasticity and knee/hip range of motion (ROM). Additionally, to investigate if there are consistency among quadriceps muscle elasticity after SS.

METHODS

Acute effect of SS on pre-post-intervention design. Thirtheen healthy participants (both genders) proposed for a pre-post experimental design. RF, VM, and VL elasticity (strain ratio, SR) was evaluated bilaterally by ultrasound with quasi-static elastography. Higher SR values refer to more rigid tissues. A SS protocol of 3 series of 30 s was applied at right lower limb. The left lower limb was considered as control group. Also, photogrammetry evaluated the knee/hip ROM.

RESULTS

For SR muscle comparisons, VM was lower (less stiff) than VL and RF at pre- and post-SS. For time comparisons, no differences were observed for SR and ROM at pre- and post-SS. However, the effect size of the quadriceps SR at SS lower limb was higher than control.

CONCLUSION

Acute effects of SS did not change the quadriceps SR or knee/hip ROM in healthy and active subjects. Non-uniform quadriceps SR are observed (VM < VL and RF) independently of SS. Future studies should consider different protocols, muscles, and populations.

Reliability and Comparison of Sonographic Methods for In Vivo Measurement of Human Biceps Femoris Long-Head Architecture

INTRODUCTION

Biceps femoris long-head fascicle length ( Lf ), fascicle angle (FA), and muscle thickness (MT) estimates obtained across 2 d from extended field-of-view (EFOV) sonographic images were compared with those measured from a collage of single ultrasound images (to visualize entire fascicles) as well as a range of geometric equations and extrapolation methods used on single images. Both test validity and intraday reliability were determined.

METHODS

Twenty healthy adults (10 men and 10 women) were tested on two occasions (day 1 and day 2), 7 d apart at the same time of day for test-retest measurements. Ultrasound imaging was performed using EFOV and static image acquisition sequences; in the latter, four single images were acquired in-series along the muscle. From these images, Lf was assessed using seven methods: EFOV, collage, manual linear extrapolation, and four different trigonometric equations (termed equations A, B, C, and D), and FA and MT were measured in EFOV, collage, and single images.

RESULTS

Lf , FA, and MT measured on days 1 and 2 were not different ( P > 0.05) for any method, reliabilities were very high (intraclass correlation coefficient, 0.91-0.98), and correlations were strong (≥0.84). Significant correlations ( P < 0.05; r = 0.67-0.98) were found between EFOV and the other measurement techniques for Lf , FA, and MT. The collage method had the highest reliability for Lf , and highest rank order and correlation with EFOV.

CONCLUSIONS

Although the six different techniques used to estimate Lf provided values similar to EFOV, higher between-subject measurement variability was observed with trigonometric equations, and the collage method described herein provided the most accurate and reliable results and is therefore recommended for biceps femoris long-head architectural analysis when EFOV is not available.

Intra- and Inter-Rater Reliability and Agreement of Ultrasound Imaging of Muscle Architecture and Patellar Tendon in Post-COVID-19 Patients Who Had Experienced Moderate or Severe COVID-19 Infection

COVID-19 is associated with musculoskeletal disorders. Ultrasound is a tool to assess muscle architecture and tendon measurements, offering an idea of the proportion of the consequences of the disease, since significant changes directly reflect the reduction in the ability to produce force and, consequently, in the functionality of the patient; however, its application in post-COVID-19 infection needs to be determined. We aimed to assess the intra- and inter-rater reliability of ultrasound measures of the architecture of the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), gastrocnemius lateralis (GL), gastrocnemius medialis (GM), soleus (SO), and tibialis anterior (TA) muscles, as well as the patellar tendon (PT) cross-sectional area (CSA) in post-COVID-19 patients. An observational, prospective study with repeated measures was designed to evaluate 20 post-COVID-19 patients, who were measured for the pennation angle (θp), fascicular length (Lf), thickness, echogenicity of muscles, CSA and echogenicity of the PT. The intra-class correlation coefficient (ICC) and 95% limits of agreement were used. The intra-rater reliability presented high or very high correlations (ICC = 0.71-1.0) for most measures, except the θp of the TA, which was classified as moderate (ICC = 0.69). Observing the inter-rater reliability, all the evaluations of the PT, thickness and echogenicity of the muscles presented high or very high correlations. For the Lf, only the RF showed as low (ICC = 0.43), for the θp, RF (ICC = 0.68), GL (ICC = 0.70) and TA (ICC = 0.71) moderate and the SO (ICC = 0.40) low. The ultrasound reliability was acceptable for the muscle architecture, muscle and tendon echogenicity, and PT CSA, despite the low reliability for the Lf and θp of the RF and SO, respectively.

Including the Eccentric Phase in Resistance Training to Counteract the Effects of Detraining in Women: A Randomized Controlled Trial

ABSTRACT

Coratella, G, Beato, M, Bertinato, L, Milanese, C, Venturelli, M, and Schena, F. Including the eccentric phase in resistance training to counteract the effects of detraining in women: a randomized controlled trial. J Strength Cond Res 36(11): 3023-3031, 2022-The current study compared the effects of concentric-based (CONC), eccentric-based (ECC), and traditional concentric-eccentric (TRAD) resistance training on muscle strength, mass, and architecture and the postdetraining retention of the training-induced effects in women. Sixty women were randomly assigned to unilateral volume-equated CONC, ECC, or TRAD knee extension training or control ( N = 15 per group). Before training, after an 8-week intervention period, and after an 8-week detraining period, isokinetic concentric, eccentric, and isometric torque were measured. In addition, thigh lean mass was assessed by dual X-ray absorptiometry and vastus lateralis thickness, pennation angle, and fascicle length by ultrasound. After training, concentric and isometric torque increased ( p < 0.05) similarly in all groups, whereas eccentric torque increased more in ECC than that in CONC (+13.1%, effect size (ES): 0.71 [0.04-1.38]) and TRAD (+12.6%, ES: 0.60 [0.12-1.08]). Thigh lean mass increased in ECC (+6.1%, ES: 0.47 [0.27-0.67]) and TRAD (+3.1%, ES: 0.33 [0.01-0.65]). Vastus lateralis thickness and pennation angle increased ( p < 0.05) similarly in all groups, whereas fascicle elongation was visible in ECC (+9.7%, ES: 0.92 [0.14-1.65]) and TRAD (+7.1%, ES: 0.64 [0.03-1.25]). After detraining, all groups retained ( p < 0.05) similar concentric torque. ECC and TRAD preserved eccentric torque ( p < 0.05), but ECC more than TRAD (+17.9%, ES: 0.61 [0.21-1.21]). All groups preserved isometric torque ( p < 0.05), but ECC more than CONC (+14.2%, ES: 0.71 [0.04-1.38]) and TRAD (+13.8%, ES: 0.65 [0.10-1.20]). Thigh lean mass and vastus lateralis fascicle length were retained only in ECC ( p < 0.05), pennation angle was preserved in all groups ( p < 0.05), and thickness was retained in CONC and ECC ( p < 0.05). Including the eccentric phase in resistance training is essential to preserve adaptations after detraining.

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.

Architectural Ultrasound Pennation Angle Measurement of Lumbar Multifidus Muscles: A Reliability Study

The pennation angle has been shown to be a relevant parameter of muscle architecture. This parameter has not previously been measured in the lumbar multifidus musculature, and it is for this reason that it has been considered of great interest to establish an assessment protocol to generate new lines of research in the future. Objective: The objective of this study was to establish a protocol for measuring the pennation angle of the multifidus muscles, with a study of intra-rater and interrater reliability values. Design: This was a reliability study following the recommendations of the Guidelines for Reporting Reliability and Agreement Studies (GRRAS). Setting: The study was carried out at University of Alcalá, Department of Physiotherapy. Subjects: Twenty-seven subjects aged between 18 and 55 years were recruited for this study. Methods: Different ultrasound images of the lumbar multifidus musculature were captured. Subsequently, with the help of ImageJ software, the pennation angle of this musculature was measured. Finally, a complex statistical analysis determined the intra- and interrater reliability. Results: The intra-rater reliability of the pennation angle measurement protocol was excellent for observer 1 in the measurement of the left-sided superficial multifidus 0.851 (0.74, 0.923), and for observer 2 in the measurement of the right-sided superficial 0.711 (0.535, 0.843) and deep multifidus 0.886 (0.798, 0.942). Interrater reliability was moderate to poor, and correlation analysis results were high for thickness vs. pennation angle. Conclusions: The designed protocol for ultrasound measurement of the pennation angle of the lumbar multifidus musculature has excellent intra-rater reliability values, supporting the main conclusions and interpretations. Normative ranges of pennation angles are reported. High correlation between variables is described.

Influence of subcutaneous adipose thickness and dominance on reliability of quadriceps muscle quality in healthy young individuals

BACKGROUND

Echo intensity (EI) can be useful to check muscle quality and has been widely used to identify tissue damage. In the clinical and sports context, it has been used to identify metabolic disorders and training muscle performance.

OBJECTIVE

To determine whether subcutaneous adipose thickness (SAT) influences the inter-session EI reliability of the quadriceps femoris and whether EI is influenced by dominance in young healthy subjects.

DESIGN

All procedures were approved by the local Institutional Research Ethics Committee (project number 2.620.204). This is a cross-sectional study where 19 healthy young individuals volunteered.

METHOD

The individuals were assessed at two time points by an experienced examiner. Imaging of the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles were performed bilaterally by ultrasonography. EI and SAT analysis was performed using ImageJ®software.

RESULTS/FINDINGS

Inter-session intraclass correlation coefficient (ICC) for EImeasured showed moderate reliability for RF (R = 0.578; P = 0.038) and VL (R = 0.735; P = 0.004) and low for VM (R = 0.402; P = 0.142). When corrected by SAT, inter-session (EIcorrected), ICC values showed good reliability for RF (R = 0.826; P < 0.001) and VM (R = 0.765; P = 0.002) and excellent for VL (R = 0.909; P < 0.001). Considering inter-side reliability, Student's paired t-test demonstrated no difference for EImeasured (P > 0.283), EIcorrected (P > 0.127), and SAT (P > 0.356).

CONCLUSIONS

SAT influenced the inter-session reliability values of EI in all muscles evaluated. Although they showed similarity, EI values were not influenced by dominance in young healthy subjects.

Associations of muscle volume of individual human plantar intrinsic foot muscles with morphological profiles of the foot

Human plantar intrinsic foot muscles consist of 10 muscles that originate and insert within the sole of the foot. It is known that the anatomical cross‐sectional area (ACSA) and muscle thickness of two plantar intrinsic foot muscles, the flexor hallucis brevis (FHB) and abductor hallucis (ABH), associate with morphological parameters of the foot, such as total and truncated foot length and navicular height. However, it is unclear how the size for each of the plantar intrinsic foot muscles associates with various morphological profiles of the foot. This study aimed to elucidate this subject. By using magnetic resonance imaging (MRI), serial images of the right foot were obtained in 13 young adult men without foot deformities. From the obtained MR images, ACSA for each of the individual plantar intrinsic foot muscles was analyzed along the foot length, and then its muscle volume (MV) was calculated. The analyzed muscles were the abductor digiti minimi (ABDM), ABH, adductor hallucis oblique head (ADDH‐OH), adductor hallucis transverse head (ADDH‐TH), flexor digitorum brevis (FDB), FHB, and quadratus plantae (QP). Furthermore, MV of the whole plantar intrinsic foot muscle (WHOLE) was defined as the total MVs of all the analyzed muscles. As morphological parameters, total foot length, truncated foot length, forefoot width, ball circumference, instep circumference, navicular height, great toe eversion angle, and little toe inversion angle were measured using a laser three‐dimensional foot scanner in standing and sitting conditions. In addition, navicular drop (ND) and normalized truncated navicular height (NTNH) were also calculated as medial longitudinal arch (MLA) height indices. The MV of WHOLE was significantly associated with the forefoot width, ball circumference, and instep circumference (r = 0.647–0.711, p = 0.006–0.013). Positive correlations were found between the forefoot width and MV of FHB, FDB, and QP (r = 0.564–0.653, p = 0.015–0.045), between the ball circumference and MV of QP (r = 0.559, p = 0.047), between the instep circumference and MV of FHB (r = 0.609, p = 0.027), and between the little toe inversion angle and MV of QP (r = 0.570, p = 0.042). The MVs of ABH, ABDM, and ADDH‐OH were not significantly correlated with any morphological parameters of the foot. Similarly, no significant correlations were found between MV of each muscle and either of the MLA height indices (ND and NTNH). Thus, the current results indicate that forefoot width and circumferential parameters (instep and ball circumference), not MLA height, associate with the size of the whole plantar intrinsic foot muscles, especially those specialized in toe flexion (FHB, FDB, and QP).

A Novel Plant-Based Protein Has Similar Effects Compared to Whey Protein on Body Composition, Strength, Power, and Aerobic Performance in Professional and Semi-Professional Futsal Players

Introduction

The effects of dietary protein on body composition and physical performance seemingly depend on the essential amino acid profile of the given protein source, although controversy exists about whether animal protein sources may possess additional anabolic properties to plant-based protein sources.

Purpose

To compare the effects of a novel plant-based protein matrix and whey protein supplementation on body composition, strength, power, and endurance performance of trained futsal players.

Methods

Fifty male futsal players were followed during 8 weeks of supplementation, with 40 completing the study either with plant-based protein (N = 20) or whey protein (N = 20). The following measures were assessed: bone mineral content, lean body mass, and fat mass; muscle thickness of the rectus femoris; total body water; blood glucose, hematocrit, C-reactive protein, aspartate aminotransferase, alanine aminotransferase, creatine kinase, creatinine, and estimated glomerular filtration rate; salivary cortisol; maximal strength and 1-RM testing of the back squat and bench press exercises; muscle power and countermovement jump; VO2max and maximal aerobic speed. Subjects were asked to maintain regular dietary habits and record dietary intake every 4 weeks through 3-day food records.

Results

No differences in any variable were observed between groups at baseline or pre- to post-intervention. Moreover, no time*group interaction was observed in any of the studied variables, and a time effect was only observed regarding fat mass reduction.

Conclusions

Supplementing with either a novel plant-based protein matrix or whey protein did not affect any of the variables assessed in high-level futsal players over 8 wks. These results suggest that whey protein does not possess any unique anabolic properties over and above those of plant-based proteins when equated to an essential amino acid profile in the population studied. Furthermore, when consuming a daily protein intake &gt;1.6 g/kg BW.day−1, additional protein supplementation does not affect body composition or performance in trained futsal players, regardless of protein type/source.

Age-related differences of vastus lateralis muscle morphology, contractile properties, upper body grip strength and lower extremity functional capability in healthy adults aged 18 to 70 years

Background

There is a lack of of cross-sectional research that has investigated muscle morphology, function, and functional capability in all age-bands of healthy adults. The primary aim of this study was to evaluate age-related differences in indices of vastus lateralis (VL) muscle morphology, function and functional capability in a sample of healthy males and females aged 18-70yrs. Secondary aims were to evaluate relationships between age and VL muscle morphology and function and functional capability.

Methods

B mode Ultrasonography and Tensiomyography were used to measure VL muscle thickness, pennation angle, fascicle length, and contractile properties in 274 healthy adults aged 18-70yrs. Measurements of grip strength and functional capability (1-min chair rise test) were also taken. Data analysis included descriptive statistics, correlations, one-way ANOVAs, and multiple regressions.

Results

Negative correlations were found between age and muscle thickness (r_s = -.56), pennation angle (r_s = -.50), fascicle length (r_s = -.30), maximal displacement (r_s = -.24), grip strength (r_s = -.27) and the 1-min chair rise test (r_s = -.32). Positive correlations were observed between age and the echo intensity of the muscle (r_s = .40) and total contraction time (r_s = .20). Differences in the indices of muscle health were noticeable between the 18–29 age band and the 50–59 and 60–70 age bands (p < 0.05). The interaction of age and level of physical activity predicted changes in the variables (r² = .04—.32).

Conclusion

Age-related differences in muscle health are noticeable at 50 years of age, and age-related differences are larger in females compared to males. It was suggested that the thickness of the VL changed the most with age across the adult lifespan and that physical activity likely acts to abate detrimental change.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03183-4.

SPATIAL DISTRIBUTION PATTERN OF THE ELECTROMYOGRAPHIC POTENTIAL IN THE VASTUS MEDIALIS AND LATERALIS MUSCLES FOR THREE KNEE FLEXION ANGLES DURING ISOMETRIC KNEE EXTENSION

Understanding the function of the vastus lateralis (VL) and vastus medialis (VM) muscles is important since these muscles are essential for daily and sport activities. The association between the knee flexion angle and spatial muscle activation is controversial. This study compares the distribution patterns of multi-channel electromyographic activities of the VL and VM muscles at three knee flexion angles for three intensities of isometric contraction. Sixteen men performed isometric knee extensions at 30%, 50% and 70% maximal voluntary contraction (MVC), at [Formula: see text], [Formula: see text] and [Formula: see text] knee flexion. Alterations in the spatial electromyographic potential distribution were determined by the root mean square (RMS), modified entropy, and coefficient of variation in the spatial electromyographic potential. Modified entropy and the coefficient of variation showed differences in the VM muscle between [Formula: see text] and [Formula: see text] knee flexion. The RMS at the three angles was similar between the VL and VM muscles, with no differences in contraction intensities at 30%, 50%, or 70% MVC. The VL and VM muscle function differed among knee flexion angles, as did activity in the distal and proximal VM muscles. These findings suggest the need for functional evaluation of the VL and VM muscles at each knee flexion angle.

Effects of growth on muscle architecture of knee extensors

This study aimed to investigate the effects of growth on the muscle architecture of knee extensors. The present study included 123 male children and adolescents. The muscle thicknesses of the rectus femoris (RF) and vastus intermedius (VI), and pennation angles and fascicle lengths of RF were measured in three regions using ultrasonography technique at rest. The relative muscle thickness was calculated by dividing the absolute muscle thickness by body mass^1/3 . The years from age at peak height velocity were estimated for each participant, and used as a maturity index. The maturity index was significantly correlated with the relative muscle thicknesses of RF and VI in all regions. The slope of the relationship between the maturity index and the relative muscle thickness did not differ significantly between muscles within the same region or between regions within the individual muscles. The fascicle length and pennation angle of RF were significantly correlated with the absolute muscle thickness in all regions. In the proximal RF region, the coefficient of correlation between the muscle thickness and fascicle length was significantly greater than that between the muscle thickness and pennation angle. The present results showed that growth changes in muscle thickness were uniform between and within RF and VI. Our findings suggest that growth changes in the muscle thickness of RF depend on the increases in both pennation angle and fascicle length, but their contributions to the growth of muscle thickness differ among muscle regions.

Test-Retest Reliability of Ultrasonographic Measurements from the Rectus Femoris Muscle 1-5 Years after Anterior Cruciate Ligament Reconstruction in the Ipsilateral and Contralateral Legs: An Observational, Case-Control Study

About 40% of traumatic injuries in sports are related to the knee. Of these, 33% require arthroscopic surgery. The rehabilitative ultrasound imaging technique is a simple method to obtain objective real-time results on the state and measurement of the musculoskeletal tissue and its use can represent an important change in the process of functional diagnosis and recovery of these injuries. The aim was to quantify the differences in the thickness, muscle contraction time, and muscle relaxation time of the rectus femoris muscle between individuals with knee arthroscopy and healthy individuals and to verify the reliability of the inter-examiner measurements in these ultrasound variables. An observational case-control study with individuals (18−60 years aged) who underwent surgery for anterior cruciate ligament through knee arthroscopy a year or more before. A total of 38 subjects were divided into 2 groups, case and control. Ultrasound measurements were taken of the following outcomes: thickness at rest and contraction, muscle contraction time, and muscle relaxation time of the rectus femoris muscle. Excellent inter-examiner reliability was obtained for all ultrasound measurements (ICC3.3 > 0.90). No significant changes were found in the rate of contraction or rest of the rectus femoris muscle. On the other hand, if significant changes in the thickness of the rectus femoris muscle were found between control and case group. Arthroscopic surgery for anterior cruciate ligament reconstruction does not appear to modify function but does modify the thickness of the rectus femoris muscle on ultrasound examination. Ultrasound appears to be a reliable tool for the study of these measurements in the rectus femoris muscle.

Evaluating Electromyography and Sonomyography Sensor Fusion to Estimate Lower-Limb Kinematics Using Gaussian Process Regression

Research on robotic lower-limb assistive devices over the past decade has generated autonomous, multiple degree-of-freedom devices to augment human performance during a variety of scenarios. However, the increase in capabilities of these devices is met with an increase in the complexity of the overall control problem and requirement for an accurate and robust sensing modality for intent recognition. Due to its ability to precede changes in motion, surface electromyography (EMG) is widely studied as a peripheral sensing modality for capturing features of muscle activity as an input for control of powered assistive devices. In order to capture features that contribute to muscle contraction and joint motion beyond muscle activity of superficial muscles, researchers have introduced sonomyography, or real-time dynamic ultrasound imaging of skeletal muscle. However, the ability of these sonomyography features to continuously predict multiple lower-limb joint kinematics during widely varying ambulation tasks, and their potential as an input for powered multiple degree-of-freedom lower-limb assistive devices is unknown. The objective of this research is to evaluate surface EMG and sonomyography, as well as the fusion of features from both sensing modalities, as inputs to Gaussian process regression models for the continuous estimation of hip, knee and ankle angle and velocity during level walking, stair ascent/descent and ramp ascent/descent ambulation. Gaussian process regression is a Bayesian nonlinear regression model that has been introduced as an alternative to musculoskeletal model-based techniques. In this study, time-intensity features of sonomyography on both the anterior and posterior thigh along with time-domain features of surface EMG from eight muscles on the lower-limb were used to train and test subject-dependent and task-invariant Gaussian process regression models for the continuous estimation of hip, knee and ankle motion. Overall, anterior sonomyography sensor fusion with surface EMG significantly improved estimation of hip, knee and ankle motion for all ambulation tasks (level ground, stair and ramp ambulation) in comparison to surface EMG alone. Additionally, anterior sonomyography alone significantly improved errors at the hip and knee for most tasks compared to surface EMG. These findings help inform the implementation and integration of volitional control strategies for robotic assistive technologies.

The Dose-Response of the Nordic Hamstring Exercise on Biceps Femoris Architecture and Eccentric Knee Flexor Strength: A Randomized Interventional Trial

PURPOSE

To examine the dose-response of the Nordic hamstring exercise (NHE) on biceps femoris long head (BFlh) architecture and eccentric knee flexor strength.

DESIGN

Randomized interventional trial.

METHODS

Forty recreationally active males completed a 6-week NHE training program consisting of either intermittent low volumes (group 1; n = 10), low volumes (group 2; n = 10), initial high volumes followed by low volumes (group 3; n = 10), or progressively increasing volumes (group 4; n = 10). A 4-week detraining period followed each program. Muscle architecture was assessed weekly during training and after 2 and 4 weeks of detraining. Eccentric knee flexor strength was assessed preintervention and postintervention and after 2 and 4 weeks of detraining.

RESULTS

Following 6 weeks of training, BFlh fascicle length (FL) increased in group 3 (mean difference = 0.83 cm, d = 0.45, P = .027, +7%) and group 4 (mean difference = 1.48 cm, d = 0.94, P = .004, +14%). FL returned to baseline following detraining in groups 3 and 4. Strength increased in group 2 (mean difference = 53.6 N, d = 0.55, P = .002, +14%), group 3 (mean difference = 63.4 N, d = 0.72, P = .027, +17%), and group 4 (mean difference = 74.7, d = 0.83, P = .006, +19%) following training. Strength returned to baseline following detraining in groups 2 and 3 but not in group 4.

CONCLUSIONS

Initial high volumes of the NHE followed by lower volumes, as well as progressively increasing volumes, can elicit increases in BFlh FL and eccentric knee flexor strength. Low volumes of the NHE were insufficient to increase FL, although as few as 48 repetitions in 6 weeks did increase strength.

Muscle-Skeletal Abnormalities and Muscle Oxygenation during Isokinetic Strength Exercise in Heart Failure with Preserved Ejection Fraction Phenotype: A Cross-Sectional Study

Exercise intolerance, a hallmark of patients with heart failure (HF), is associated with muscle weakness. However, its causative microcirculatory and muscle characteristics among those with preserved or reduced ejection fraction (HFpEF or HFrEF) phenotype is unclear. The musculoskeletal abnormalities that could result in impaired peripheral microcirculation are sarcopenia and muscle strength reduction in HF, implying lowered oxidative capacity and perfusion affect transport and oxygen utilization during exercise, an essential task from the microvascular muscle function. Besides that, skeletal muscle microcirculatory abnormalities have also been associated with exercise intolerance in HF patients who also present skeletal muscle myopathy. This cross-sectional study aimed to compare the muscle microcirculation dynamics via near-infrared spectroscopy (NIRS) response during an isokinetic muscle strength test and ultrasound-derived parameters (echo intensity was rectus femoris muscle, while the muscle thickness parameter was measured on rectus femoris and quadriceps femoris) in heart failure patients with HFpEF and HFrEF phenotypes and different functional severities (Weber Class A, B, and C). Twenty-eight aged-matched patients with HFpEF (n = 16) and HFrEF (n = 12) were assessed. We found phenotype differences among those with Weber C severity, with HFrEF patients reaching lower oxyhemoglobin (O₂Hb, μM) (−10.9 ± 3.8 vs. −23.7 ± 5.7, p = 0.029) during exercise, while HFpEF reached lower O₂Hb during the recovery period (−3.0 ± 3.4 vs. 5.9 ± 2.8, p = 0.007). HFpEF with Weber Class C also presented a higher echo intensity than HFrEF patients (29.7 ± 8.4 vs. 15.1 ± 6.8, p = 0.017) among the ultrasound-derived variables. Our preliminary study revealed more pronounced impairments in local microcirculatory dynamics in HFpEF vs. HFrEF patients during a muscle strength exercise, combined with muscle-skeletal abnormalities detected via ultrasound imaging, which may help explain the commonly observed exercise intolerance in HFpEF patients.

Effect of the Knee and Hip Angles on Knee Extensor Torque: Neural, Architectural, and Mechanical Considerations

This study examined the influence of knee extensors' hip and knee angle on force production capacity and their neuromuscular and architectural consequences. Sixteen healthy men performed sub-maximal and maximal voluntary isometric contractions (MVIC) of knee extensors with four different combinations of the knee and hip angles. Muscle architecture, excitation-contraction coupling process, muscular activity, and corticospinal excitability were evaluated on the vastus lateralis (VL) and rectus femoris (RF) muscles. MVIC and evoked peak twitch (Pt) torques of knee extensors increased significantly (p < 0.05) by 42 ± 12% and 47 ± 16% on average, respectively, under knee flexed positions (110° flexion, 0° = full extension) compared to knee extended positions (20° flexion) but were not different between hip positions (i.e., 0° or 60° flexion). Knee flexion also affected VL and RF muscle and fascicle lengths toward greater length than under knee extended position, while pennation angle decreased for both muscles with knee flexion. Pennation angles of the VL muscle were also lower under extended hip positions. Alternatively, no change in maximal muscle activation or corticospinal activity occurred for the VL and RF muscles across the different positions. Altogether these findings evidenced that MVIC torque of knee extensors depended particularly upon peripheral contractile elements, such as VL and RF muscle and fascicle lengths, but was unaffected by central factors (i.e., muscle activation). Furthermore, the hip position can affect the pennation angle of the VL, while VL muscle length can affect the pennation angle of the RF muscle. These elements suggest that the VL and RF muscles exert a mutual influence on their architecture, probably related to the rectus-vastus aponeurosis.