Aim
Despite males typically exhibiting greater muscle strength and fatigability than females, it remains unclear if there are sex‐based differences in neuromuscular recruitment strategies e.g. ...recruitment and modulation of motor unit firing rate (MU FR) at normalized forces and during progressive increases in force.
Methods
The study includes 29 healthy male and 31 healthy female participants (18‐35 years). Intramuscular electromyography (iEMG) was used to record individual motor unit potentials (MUPs) and near‐fibre MUPs from the vastus lateralis (VL) during 10% and 25% maximum isometric voluntary contractions (MVC), and spike‐triggered averaging was used to obtain motor unit number estimates (MUNE) of the VL.
Results
Males exhibited greater muscle strength (P < .001) and size (P < .001) than females, with no difference in force steadiness at 10% or 25% MVC. Females had 8.4% and 6.5% higher FR at 10% and 25% MVC, respectively (both P < .03), while the MUP area was 33% smaller in females at 10% MVC (P < .02) and 26% smaller at 25% MVC (P = .062). However, both sexes showed similar increases in MU size and FR when moving from low‐ to mid‐level contractions. There were no sex differences in any near‐fibre MUP parameters or in MUNE.
Conclusion
In the vastus lateralis, females produce muscle force via different neuromuscular recruitment strategies to males which is characterized by smaller MUs discharging at higher rates. However, similar strategies are employed to increase force production from low‐ to mid‐level contractions. These findings of similar proportional increases between sexes support the use of mixed sex cohorts in studies of this nature.
Aim
To investigate the relationships between motor unit action potential amplitudes (MUAPAMP), muscle cross‐sectional area (mCSA) and composition (mEI), per cent myosin heavy chain (%MHC) areas and ...sex in the vastus lateralis (VL).
Methods
Ten males and 10 females performed a submaximal isometric trapezoid muscle action that included a linearly increasing, steady torque at 40% maximal voluntary contraction, and linearly decreasing segments. Surface electromyographic decomposition techniques were utilized to determine MUAPAMPS in relation to recruitment thresholds (RT). Ultrasound images were taken to quantify muscle mCSA and mEI. Muscle biopsies were collected to calculate %MHC areas. Y‐intercepts and slopes were calculated for the MUAPAMP vs RT relationships for each subject. Independent‐samples t tests and ANOVA models examined sex‐related differences in mCSA, mEI, slopes and y‐intercepts for the MUAPAMP vs RT relationships and %MHC areas. Correlations were performed among type IIA and total type II %MHC area, mCSA and the slopes and y‐intercepts for the MUAPAMP vs RT relationships.
Results
Males exhibited greater slopes for the MUAPAMP vs RT relationships (P = .003), mCSA (P < .001) and type IIA %MHC (P = .011), whereas females had greater type I %MHC area (P = .010) and mEI (P = .024). The mCSA, type IIA and total II %MHC area variables were correlated (P < .001‐.015, r = .596‐.836) with the slopes from the MUAPAMP vs RT relationships.
Conclusion
Sex‐related differences in mCSA and MUAPAMPS of the higher‐threshold MUs were likely the result of larger muscle fibres expressing type II characteristics for males.
To describe the possible effects of chronic specific exercise training, the present study compared the anthropometric variables, muscle–tendon unit (MTU) architecture, passive stiffness, and force ...production capacity between a group of competitive cyclists and runners. Twenty-seven competitive male cyclists (n = 16) and runners (n = 11) participated. B-mode ultrasound evaluation of the vastus lateralis muscle and patellar tendon as well as passive stiffness of the knee extensors MTU were assessed. The athletes then performed a test of knee extensor maximal voluntary isometric contractions. Cyclists displayed greater thigh girths, vastus lateralis pennation angle and muscle thickness, patellar tendon cross-sectional area, and MTU passive stiffness than runners (
P
< .05). Knee extensor force production capacity also differed significantly, with cyclists showing greater values compared with runners (
P
< .05). Overall, the direct comparison of these 2 populations revealed specific differences in the MTU, conceivably related to the chronic requirements imposed through the training for the different disciplines.
Background
The skeletal muscle microbiopsy protocol was introduced to the Exercise and Sports Science (ESS) research field in 1999 and has been used as a protocol to directly examine muscular ...structural and biochemical changes. There is much variation in the reporting of the microbiopsy protocol and its related pre‐ and post‐procedure for participant care and sample collection. The purpose of this narrative and methodological review is to compare the microbiopsy to the traditional Bergström protocol used in the ESS field, identify and summarize all related microbiopsy protocols used in previous ESS studies and determine the most frequently used microbiopsy protocols aspects and associated pre‐ and post‐biopsy procedures.
Methods
A review of literature up to January 2022 was used following the PRISMA and Cochrane Methodological Review Guide to determine frequently used methods that may facilitate optimal and potential recommendations for muscle microbiopsy needle gauge (G), concentration or dose (% or ml) and administration of local anesthetic, co‐axial/cannula introducer gauge (G), muscle depth (cm), muscle sample size collected (mg), passes to collect samples, time points of muscle sampling, and promotion of participant compliance and minimization of adverse events.
Results
Eighty‐five articles were selected based on the inclusionary requirements related to the ESS field or methodological considerations. The most frequently reported aspects in previous research to suggest the location of the vastus lateralis is the midpoint between the patella and the greater trochanter of the femur or 1/3 or 2/3 the distance from the patella to anterior superior iliac spine, 14 G biopsy needle, subcutaneous injected lidocaine administration (2 ml, 1%), 13 G co‐axial/cannula, 1–2 cm muscle depth, 10–20 mg of muscle sample, ~3‐time points, and 2–3 passes.
Discussion
There is much variation in the reporting of the microbiopsy protocol and its related pre‐ and post‐biopsy procedures. Standardization in reporting may promote recommendations to optimize data integrity, participant safety, participant adherence to the study design, and increase reproducibility. Recommendations are made for the microbiopsy procedure based on frequently reported characteristics.
Highlights • The reliability of high-density surface electromyography (HDEMG) for the measurement and estimation of motor unit properties was assessed for the first time. • HDEMG-derived measures of ...motor unit behavior provide reliable results across and within sessions. • Motor unit decomposition is accurate enough to detect changes in motor unit behavior over a wide range of force levels (from 10% to 70% of maximum force).
Background and Objectives
Adequate coverage of the soft tissue defects from wide resection of sacropelvic malignancies remains challenging. The vastus lateralis flap has been described for coverage ...in the setting of trauma and infection. This flap has not been described for coverage of sacropelvic tumor defects.
Methods
This is a retrospective cohort study of adult patients who underwent wide resection of a primary sacropelvic malignancy with reconstruction employing a pedicled vastus lateralis flap at two tertiary care centers. Patient demographics, tumor staging, and rate of complications were assessed.
Results
Twenty‐eight patients were included, with a median age of 51 years. The most common primary tumor was chondrosarcoma followed by chondroblastic osteosarcoma. The median follow‐up was 1.1 years. There were 10 cases of wound infection requiring re‐operation and three cases of flap failure.
Conclusions
We describe a pedicled vastus lateralis flap for coverage of defects after wide resection of sacropelvic malignancies. A large proportion of our cohort had independent risk factors for wound complications. Even with a cohort with high baseline risk for wound complications, we show that the use of a pedicled vastus lateralis flap is a safe reconstructive option with a wound complication rate in line with the literature.
Patellofemoral osteoarthritis (PF OA) is exceptionally predominant and limiting. However, little is known about the risk factors that contribute to its onset and progression.
The aim of this study ...was to decide if women with PF OA descend stairs using different muscular activation strategies compared to similarly aged healthy controls.
Thirty-one women with isolated PF OA and 11 similarly aged healthy women took part in this study. The activation onset and duration of PF OA in vastus medialis oblique (VMO), vastus lateralis (VL), gluteus medius (GM), transversus abdominis (TrA), and multifidus muscles were evaluated during the stair descent task using surface electromyography (EMG).
There was a non-significant difference between women with PF OA and healthy controls regarding all tested variables, except for the GM activation onset that was significantly delayed in women with PF OA, with the
-value of 0.011.
The causes of PF OA differ and might not always be due to a lack of quadriceps strength or VMO activation deficiency, and prospective longitudinal studies are required to confirm this assumption.
Prostate cancer is the second most prevalent cancer in men. Robot-assisted radical prostatectomy (RARP) has altered the landscape of prostate cancer treatment. Despite the excellent oncological ...outcomes associated with RARP, the rate of erectile dysfunction (ED) remains high. Primary repair of disrupted cavernous nerves with interpositional nerve grafts has been described; however, the outcomes have been inconsistent. We hypothesize that this is attributed to Schwann cell atrophy and axonal regeneration limitations caused by long nerve grafts. We proposed the use of nerve transfer to support axonal regrowth via an inter-positional graft with additional donor axons. A cadaveric study was performed to evaluate the anatomical feasibility of a vastus lateralis nerve (VLN) transfer to the distal recipient cavernous nerve stump. The VLN is long with multiple branching patterns that allow tension-free coaptation of the cavernous nerve. We postulate that a dual innervation method using VLN nerve transfer together with interpositional nerve graft repair of the transacted cavernous nerves may improve the outcomes of ED post-RARP.
Studies have revealed an age-related decrease in the ability to produce force as well as an increase in the contractile stiffness and passive stress of single muscle fibres. However, further insight ...into age-related changes to the passive properties of human skeletal muscles is needed. The aim of this study was to characterize single muscle fibre passive properties from young and old males across a physiologic range of sarcomere lengths (SLs).
Ten young (YM: mean age: 25.4 years) and ten old (OM: mean age: 68.9 years) males participated. Vastus lateralis muscles were biopsied and 182 fibres were tested and analyzed (90 YM and 92 OM) using a cumulative stretch-relaxation protocol. Passive mechanical characteristics of each fibre were obtained by fitting the integral of the logistic function to experimental stress-SL data.
Muscle fibres from older individuals had significantly greater passive elastic moduli at short SL (1.9–2.65 μm) compared with young (p < 0.05). This resulted in a significantly larger passive stress for SLs between 2.1 μm and 3.55 μm for older individuals when compared with young (p < 0.05).
These results provide novel insight into the length dependency of changes in single muscle fibre passive mechanical properties with age.
•Single muscle fibres from older males were stiffer at short sarcomere lengths (SLs).•At longer SLs there was no significant difference in the passive stiffness between young and old.•This highlights a length dependency in the passive muscle properties between young and old males.
Shear wave elasticity imaging (SWEI) usually assumes an isotropic material; however, skeletal muscle is typically modeled as a transversely isotropic material with independent shear wave speeds in ...the directions along and across the muscle fibers. To capture these direction-dependent properties, we implemented a rotational 3-D SWEI system that measures the shear wave speed both along and across the fibers in a single 3-D acquisition, with automatic detection of the muscle fiber orientation. We tested and examined the repeatability of this system's measurements in the vastus lateralis of 10 healthy volunteers. The average coefficient of variation of the measurements from this 3-D SWEI system was 5.3% along the fibers and 8.1% across the fibers. When compared with estimated respective 2-D SWEI values of 16.0% and 83.4%, these results suggest using 3-D SWEI has the potential to improve the precision of SWEI measurements in muscle. Additionally, we observed no significant difference in shear wave speed between the dominant and non-dominant legs along (p = 0.26) or across (p = 0.65) the muscle fibers.
PDF
