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Purpose: We investigated the effects of manipulating running velocity and hypoxic exposure on vastus lateralis muscle oxygenation levels during treadmill running. Methods: Eleven trained male distance runners performed 7 randomized runs at different velocities (8, 10, 12, 14, 16, 18, and 20 km·h−1), each lasting 45 seconds on an instrumented treadmill in normoxia (fraction of inspired oxygen [FiO2] = 20.9%), moderate hypoxia (FiO2 = 16.1%), high hypoxia (FiO2 = 14.1%), and severe hypoxia (FiO2 = 13.0%). Continuous assessment of Tissue Saturation Index (TSI) in the vastus lateralis muscle was conducted using near-infrared spectroscopy. Subsequently, changes in TSI (ΔTSI) data over the final 20 seconds of each run were compared between velocities and conditions. Results: There was a significant velocity × condition interaction for ΔTSI% (P <.001, η p 2 =.19), with a smaller ΔTSI% decline in normoxia compared with high hypoxia and severe hypoxia at 8 km·h−1 (g = 1.30 and 1.91, respectively), 10 km·h−1 (g = 0.75 and 1.43, respectively), and 12 km·h−1 (g = 1.47 and 1.95, respectively) (pooled values for all conditions: P <.037). The ΔTSI% decline increased with each subsequent velocity increment from 8 km·h−1 (−9.2% [3.7%]) to 20 km·h−1 (−22.5% [4.1%]) irrespective of hypoxia severity (pooled values for all conditions: P <.048). Conclusions: Running at slower velocities in conjunction with high and severe hypoxia reduces vastus lateralis muscle oxygenation levels. Muscle ΔTSI% proves to be a sensitive indicator, underscoring the potential use of near-infrared spectroscopy as a reference index of internal load during treadmill runs. [ABSTRACT FROM AUTHOR]

Purpose: Performing back squats with elastic bands has been widely used in resistance training. Although research demonstrated greater training effects obtained from adding elastic bands to the back squat, little is known regarding the optimal elastic resistance and how it affects neuromuscular performance. This study aimed to compare the force, velocity, power, and muscle activity during back squats with different contributions of elastic resistance. Methods: Thirteen basketball players performed 3 repetitions of the back squat at 85% of 1-repetition maximum across 4 conditions: (1) total load from free weight and (2) 20%, (3) 30%, and (4) 40% of the total load from elastic band and the remaining load from free weight. The eccentric and concentric phases of the back squat were divided into upper, middle, and bottom phases. Results: In the eccentric phase, mean velocity progressively increased with increasing elastic resistance, and muscle activity of the vastus medialis and rectus femoris significantly increased with the largest elastic resistance in the upper phase (P ≤.036). In the concentric phase, mean power (P ≤.021) and rate of force development (P ≤.002) significantly increased with increasing elastic resistance. Furthermore, muscle activity of the vastus lateralis and vastus medialis significantly improved with the largest elastic resistance in the upper phases (P ≤.021). Conclusion: Velocity, power, rate of force development, and selective muscle activity increased as the elastic resistance increased in different phases during the back-squat exercise. [ABSTRACT FROM AUTHOR]

Following anterior cruciate ligament reconstruction (ACLR), patients exhibit abnormal walking mechanics and quadriceps dysfunction. Quadriceps dysfunction has been largely attributed to muscle atrophy and weakness. While important, these factors do not capture intrinsic properties of muscle that govern its ability to generate force and withstand load. While fascicle abnormalities after ACLR have been documented in early stages of recovery (<12 mo), long-term effects of ACLR on fascicle mechanics remain unexplored. We evaluated quadriceps fascicle mechanics during walking 3 years post-ACLR and examined the relationship with knee mechanics. Participants included 24 individuals with ACLR and 24 Controls. Linear mixed models compared the ACLR, Contralateral, and Controls limbs for (1) quadriceps strength, (2) fascicle architecture and mechanics, and (3) knee mechanics. No difference in strength or overall fascicle length excursions was found between limbs. The ACLR limb exhibited longer fascicles at heel strike and peak knee extension moment (P <.001–.004), and smaller fascicle angles at heel strike, peak knee extension moment, and overall suppressed fascicle angle excursions (P <.001–.049) relative to the Contralateral and/or Control limb. This indicates an abnormality in fascicle architecture and mechanics following ACLR and suggests abnormalities in contractile function that cannot be explained by muscle weakness and may contribute to long-term gait irregularities. [ABSTRACT FROM AUTHOR]

Context: Injury-related fear and quadriceps strength are independently associated with secondary anterior cruciate ligament (ACL) injury risk. It is not known whether injury-related fear and quadriceps strength are associated, despite their individual predictive capabilities of secondary ACL injury. The purpose of this study was to examine the association between injury-related fear and quadriceps strength in individuals at least 1 year after ACL reconstruction (ACLR). Design: Cross-sectional study. Methods: Forty participants between the ages of 18 and 35 years at least 1 year post unilateral primary ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) and a standard isokinetic quadriceps strength assessment using the Biodex Isokinetic Dynamometer. Pearson Product-Moment correlations were used to examine the linear association between the TSK-11 scores and peak torque (in nanometers per kilogram) for each limb and between the TSK-11 scores and limb symmetry indices for each limb. Pearson Product-Moment correlation coefficients (r) were interpreted as very high (.90--1.00), high (.70--.90), moderate (.50--.70), low (.30--.50), and no correlation (.00--.30). Results: The average TSK-11 score was 18.2 (5.3), average ACLR peak quadriceps torque was 1.9 (0.50) N·m/kg, average contralateral peak quadriceps torque was 2.3 (0.48) N·m/kg, and average limb symmetry index was 85.3% (12.6%). There was no statistically significant correlation between the TSK-11 and peak quadriceps torque on the ACLR limb (r = .12, P = .46), the TSK-11 and contralateral limb (r = .29, P = .07), or the TSK-11 and limb symmetry index (r = -.18, P = .27). Conclusions: There was no association between kinesiophobia and peak isokinetic quadriceps strength in individuals at least 1 year post-ACLR. Both factors, independently, have been shown to influence risk of secondary injury in patients after ACLR. [ABSTRACT FROM AUTHOR]

Purpose: An inspiratory muscle warm-up (IMW) improves inspiratory muscle function, but the effects of high-intensity exercise are inconsistent. We aimed to determine the effects of high-intensity IMW on high-intensity exercise performance and muscle oxygenation. Methods: Ten healthy men (maximal oxygen uptake [ V ˙ O 2 max ] 52.2 [5.0] mL·kg–1·min–1) performed constant-load exercise to exhaustion on a cycle ergometer at V ˙ O 2 max under 2 IMW conditions: a placebo condition (PLA) and a high-intensity IMW condition (HIGH). The inspiratory loads were set at 15% and 80% of maximal inspiratory pressure, respectively. Maximal inspiratory pressure was measured before and after IMW. Oxyhemoglobin was measured in the vastus lateralis by near-infrared spectroscopy during exercise. Rating of perceived exertion (RPE) for a leg was measured after 1 and 2 minutes of exercise. Results: Exercise tolerance was significantly higher under HIGH than PLA (228 [49] s vs 218 [49] s, P =.003). Maximal inspiratory pressure was significantly increased by IMW under HIGH (from 125 [20] to 136 [25] cm H2O, P =.031). Oxyhemoglobin was significantly higher under HIGH than PLA at 80% of the total duration of exercise (P =.048). RPE for the leg was significantly lower under HIGH than PLA after 2 minutes of exercise (P =.019). Conclusions: Given that oxyhemoglobin is an index of local oxygen supply, the results of this study suggest that high-intensity IMW increases the oxygen supply to active limbs. It may also reflect a reduction in RPE in the leg. In addition, high-intensity IMW may improve exercise performance. [ABSTRACT FROM AUTHOR]

Context: Flossing is still a relatively new technique that has yielded varied results in the research literature; therefore, it requires further investigation. Previous research has shown that thigh tissue flossing might improve performance in countermovement jump, sprint time, maximum voluntary contraction, and rate of force development. Design. The present study aims to investigate the effect of the floss band on performance during the Wingate test (30-WAT), muscle oxygen saturation (SpO2), and total hemoglobin in vastus lateralis. Methods: Twenty-two students of physical education and sport (11 men and 11 women) were randomly selected to complete either the Wingate test with the application of a floss band in warm-up or the Wingate test without the use of a floss band, followed by the alternative 24 hours apart. Results: Throughout the testing, the floss band did not affect performance values during the Wingate test (relative peak power, relative average power, and fatigue index). However, there was a medium to large effect difference during 1 minute prior to 30-WAT (PRE), during the 30-WAT, and 10-minute recovery (REC) in values of SpO2 and total hemoglobin. Use of floss band displayed a higher SpO2 during PRE, 30-WAT, and REC by ~13.55%, d<2; ~19.06%, d = 0.89; and ~8.55%, d = 0.59, respectively. Conclusion: Collectively, these findings indicate that the application of thigh flossing during warm-up has no effect on 30-WAT performance; however, SpO2 was significantly increased in all stages of testing. This could lead to potential improvement in repeated anaerobic exercise due to increased blood flow. Increased muscle oxygen saturation can also lead to improved tissue healing as oxygen supply is essential for tissue repair, wound healing, and pain management. [ABSTRACT FROM AUTHOR]

The present study aimed to clarify the development of motor unit (MU) firing properties and the association between those neural properties and force steadiness (FS)/neurological tests in 6- to 12-year-old children. Fifty-eight school-aged children performed maximal voluntary knee extension contraction, a submaximal FS test at 10% of maximal voluntary knee extension contraction, knee extension reaction time to light stimulus test, and single-leg standing test, and data from 38 children who passed the criteria were subject to analysis. During the FS test, high-density surface electromyography was recorded from the vastus lateralis muscle to identify individual MU firing activity. FS was improved with an increase in age (r = −.540, P <.001). The MU firing rate (MUFR) was significantly decreased with an increase in age (r = −.343, P =.035). MUFR variability was not associated with age. Although there was no significant correlation between FS and MUFR, FS was significantly correlated with MUFR variability even after adjustment for the effect of age (r =.551, P =.002). Neither the reaction time nor the single-leg standing test was correlated with any MU firing properties. These findings suggest that MUFR variability makes an important contribution to precise force control in children but does not naturally develop with age. [ABSTRACT FROM AUTHOR]

Context: Contusion and soft tissue injuries are common in sports. Photobiomodultion, light and laser therapy, is an effective aid to increase healing rates and improve function after various injury mechanisms. However, it is unclear how well photobiomodulation improves function after a contusion soft tissue injury. This study aimed to determine the effects of a pulsed red and blue photobiomodulation light patch on muscle function following a human thigh contusion injury. Design: Single-blinded randomized control trial design. Methods: We enrolled 46 healthy participants. Participants completed 5 visits on consecutive days. On the first visit, participants completed a baseline isokinetic quadriceps strength testing protocol at 60°/s and 180°/s. On the second visit, participants were struck in the rectus femoris of the anterior thigh with a tennis ball from a serving machine. Immediately following, participants were treated for 30 minutes with an active or placebo photobiomodulation patch (CareWear light patch system, CareWear Corp). Following the treatment, participants completed the same isokinetic quadriceps strength testing protocol. Participants completed the treatment and isokinetic quadriceps strength test during the following daily visits. We normalized the data by calculating the percent change from baseline. We used a mixed model analysis of covariance, with sex as a covariate, to determine the difference between treatment groups throughout the acute recovery process. Results: We found the active photobiomodulation treatment significantly increased over the placebo group, quadriceps peak torque during the 180°/s test (P =.030), and average power during both the 60°/s (P =.041) and 180°/s (P ≤.001) assessments. The mean peak torque and average power of 180°/s, at day 4, exceeded the baseline levels by 8.9% and 16.8%, respectively. Conclusions: The red and blue photobiomodulation light patch improved muscle strength and power during the acute healing phase of a human thigh contusion injury model. [ABSTRACT FROM AUTHOR]

Resistance exercise training (RET) can be applied effectively to increase muscle mass and function in older adults (65–75 years). However, it has been speculated that older adults above 85 years are less responsive to the benefits of RET. This study compares the impact of RET on muscle mass and function in healthy older adults 65–75 years versus older adults above 85 years. We subjected 17 healthy older adults 65–75 years (OLDER 65–75, n = 13/4 [female/male]; 68 ± 2 years; 26.9 ± 2.3 kg/m2) and 12 healthy older adults above 85 years (OLDER 85+, n = 7/5 [female/male]; 87 ± 3 years; 26.0 ± 3.6 kg/m2) to 12 weeks of whole-body RET (three times per week). Prior to, and after 6 and 12 weeks of training, quadriceps and lumbar spine vertebra 3 muscle cross-sectional area (computed tomography scan), whole-body lean mass (dual-energy X-ray absorptiometry scan), strength (one-repetition maximum test), and physical performance (timed up and go and short physical performance battery) were assessed. Twelve weeks of RET resulted in a 10% ± 4% and 11% ± 5% increase in quadriceps cross-sectional area (from 46.5 ± 10.7 to 51.1 ± 12.1 cm2, and from 38.9 ± 6.1 to 43.1 ± 8.0 cm2, respectively; p <.001; η2 =.67); a 2% ± 3% and 2% ± 3% increase in whole-body lean mass (p =.001; η2 =.22); and a 38% ± 20% and 46% ± 14% increase in one-repetition maximum leg extension strength (p <.001; η2 =.77) in the OLDER 65–75 and OLDER 85+ groups, respectively. No differences in the responses to RET were observed between groups (Time × Group, all p >.60; all η2 ≤.012). Physical performance on the short physical performance battery and timed up and go improved (both p <.01; η2 ≥.22), with no differences between groups (Time × Group, p >.015; η2 ≤.07). Prolonged RET increases muscle mass, strength, and physical performance in the aging population, with no differences between 65–75 years and 85+ years older adults. [ABSTRACT FROM AUTHOR]

Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction. [ABSTRACT FROM AUTHOR]

Spasticity is a common impairment within pediatric neuromusculoskeletal disorders. How spasticity contributes to gait deviations is important for treatment selection. Our aim was to evaluate the pathophysiological mechanisms underlying gait deviations seen in children with spasticity, using predictive simulations. A cluster analysis was performed to extract distinct gait patterns from experimental gait data of 17 children with spasticity to be used as comparative validation data. A forward dynamic simulation framework was employed to predict gait with either velocity- or force-based hyperreflexia. This framework entailed a generic musculoskeletal model controlled by reflexes and supraspinal drive, governed by a multiobjective cost function. Hyperreflexia values were optimized to enable the simulated gait to best match experimental gait patterns. Three experimental gait patterns were extracted: (1) increased knee flexion, (2) increased ankle plantar flexion, and (3) increased knee flexion and ankle plantar flexion when compared with typical gait. Overall, velocity-based hyperreflexia outperformed force-based hyperreflexia. The first gait pattern could mostly be explained by rectus femoris and hamstrings velocity-based hyperreflexia, the second by gastrocnemius velocity-based hyperreflexia, and the third by gastrocnemius, soleus, and hamstrings velocity-based hyperreflexia. This study shows how velocity-based hyperreflexia from specific muscles contributes to different spastic gait patterns, which may help in providing targeted treatment. [ABSTRACT FROM AUTHOR]

Background: Changes in cortical activation patterns after rupture of the anterior cruciate ligament (ACL) have been described. However, evidence of these consequences in the early stages following the incident and through longitudinal monitoring is scarce. Further insights could prove valuable in informing evidence-based rehabilitation practices. Purpose: To analyze the angular accuracy, neuromuscular, and cortical activity during a knee joint position sense (JPS) test over the initial six months following ACL reconstruction. Study design: Cohort Study Methods: Twenty participants with ACL reconstruction performed a JPS test with both limbs. The measurement time points were approximately 1.5, 3-4 and 6 months after surgery, while 20 healthy controls were examined on a single occasion. The active JPS test was performed seated with a target angle of 50° for two blocks of continuous angular reproduction (three minutes per block). The reproduced angles were recorded simultaneously by an electrogoniometer. Neuromuscular activity of the quadriceps muscles during extension to the target angle was measured with surface electromyography. Spectral power for theta, alpha-2, beta-1 and beta-2 frequency bands were determined from electroencephalographic recordings. Linear mixed models were performed with group (ACL or controls), the measurement time point, and respective limb as fixed effect and each grouping per subject combination as random effect with random intercept. Results: Significantly higher beta-2 power over the frontal region of interest was observed at the first measurement time point in the non-involved limb of the ACL group in comparison to the control group (p = 0.03). Despite individual variation, no other statistically significant differences were identified for JPS error, neuromuscular, or other cortical activity. Conclusion: Variation in cortical activity between the ACL and control group were present, which is consistent with published results in later stages of rehabilitation. Both indicate the importance of a neuromuscular and neurocognitive focus in the rehabilitation. Level of Evidence: 3 [ABSTRACT FROM AUTHOR]

Introduction: Heart failure (HF) is caused by functional and structural irregularity leading to impaired ejection or filling capacity of the heart. HF leads to chronic inflammatory conditions in the heart leads to weight loss, anorexia, and muscle atrophy known as cachexia. The present study was carried out to investigate the role of Ezetimibe, an NRF2 activator, in cardiac cachexia and to develop a treatment strategy for cardiac cachexia. Method: Balb/c mice of either sex at 6–8 weeks of age were given 2 mg/kg of doxorubicin in 0.9% sodium chloride solution intraperitoneally (i.p.) for the alternate days for the first week and then once a week for the next 4 weeks. After induction of cardiac atrophy, treatment with Ezetimibe (1.5 mg/kg, p.o) was given for the next 4 weeks. Result: In the cardiac cachectic animals, a significant decrease in body weight, food, and water intake was observed. Cardiac cachectic animals showed a significant increase in serum glucose, total cholesterol, LDL, triglyceride, VLDL, CK‐MB, LDH, and CRP levels. Cardiac atrophic index, heart weight to body weight ratios (HW/BW), right ventricular weight to heart weight ratios (RV/HW), and left ventricular weight to heart weight ratios (LV/HW), were significantly decreased in cardiac cachectic animals. The weights of the skeletal muscles such as EDL, gastrocnemius, soleus, tibialis anterior, and quadriceps muscles, and the weight of adipose tissue such as subcutaneous, visceral, perirenal, and brown adipose tissue were significantly decreased in the cardiac cachectic group relative to the normal group. Treatment with ezetimibe improves body weight, food intake, and water intake. Ezetimibe decreases serum glucose, total cholesterol, LDL, triglyceride, VLDL, CK‐MB, LDH and CRP levels. Cardiac atrophic markers such as HW/BW, RV/HW, and LV/HW were improved. The weight of skeletal muscles and adipose tissue was increased after treatment with ezetimibe. Conclusion: Our data showed that the NRF2 activator, Ezetimibe produces a beneficial effect on cardiac cachexia in the doxorubicin‐induced cardiac cachexia model. Ezetimibe was successful to reduce the levels of inflammatory cytokines, ameliorate the effects on cardiac muscle wasting, lipid levels, fat tissues, and skeletal muscles. [ABSTRACT FROM AUTHOR]

Background: Research findings on skeletal muscle degeneration in post-stroke sarcopenic obesity are limited. Thus, this study aimed to investigate the association between post-stroke sarcopenic obesity and quantitative and qualitative changes in skeletal muscles. Methods: This was a cross-sectional study conducted on patients with stroke admitted to the convalescent rehabilitation ward. For skeletal muscle assessment, an ultrasound system was used to measure quadriceps muscle thickness and echo intensity (QMT and QEI) on the paretic and non-paretic sides. Sarcopenic obesity was defined as the presence of both sarcopenia and obesity. Multiple regression analysis was performed to determine the relationships between sarcopenic obesity and QMT and QEI. Results: A total of 130 patients with stroke were included in this study (mean age: 69.4 ± 12.7 years). The prevalence of sarcopenic obesity was 23.1%. The multiple regression analysis showed that sarcopenic obesity was significantly negatively associated with QMT on both the paretic and non-paretic sides (paretic side: β = −0.28, p < 0.001; non-paretic side: β = −0.37, p < 0.001) and significantly positively associated with QEI (paretic side β = 0.21, p = 0.034; non-paretic side: β = 0.20, p = 0.029). Conclusions: Post-stroke sarcopenic obesity was independently associated with quantitative and qualitative changes in skeletal muscles on both the paretic and non-paretic sides. [ABSTRACT FROM AUTHOR]

The detection of a secondary inorganic phosphate (Pi) resonance, a possible marker of mitochondrial content in vivo, using phosphorus magnetic resonance spectroscopy (31P‐MRS), poses technical challenges at 3 Tesla (T). Overcoming these challenges is imperative for the integration of this biomarker into clinical research. To evaluate the repeatability and reliability of measuring resting skeletal muscle alkaline Pi (Pialk) using with 31P‐MRS at 3 T. After an initial set of experiments on five subjects to optimize the sequence, resting 31P‐MRS of the quadriceps muscles were acquired on two visits (~4 days apart) using an intra‐subjects design, from 13 sedentary to moderately active young male and female adults (22 ± 3 years old) within a whole‐body 3 T MR system. Measurement variability attributed to changes in coil position, shimming procedure, and spectral analysis were quantified. 31P‐MRS data were acquired with a 31P/‐proton (1H) dual‐tuned surface coil positioned on the quadriceps using a pulse‐acquire sequence. Test–retest absolute and relative repeatability was analyzed using the coefficient of variation (CV) and intra‐class correlation coefficients (ICC), respectively. After sequence parameter optimization, Pialk demonstrated high intra‐subject repeatability (CV: 10.6 ± 5.4%, ICC: 0.80). Proximo‐distal change in coil position along the length of the quadriceps introduced Pialk quantitation variability (CV: 28 ± 5%), due to magnetic field inhomogeneity with more distal coil locations. In contrast, Pialk measurement variability due to repeated shims from the same muscle volume (0.40 ± 0.09mM; CV: 6.6%), and automated spectral processing (0.37 ± 0.01mM; CV: 2.3%), was minor. The quantification of Pialk in skeletal muscle via surface coil 31P‐MRS at 3 T demonstrated excellent reproducibility. However, caution is advised against placing the coil at the distal part of the quadriceps to mitigate shimming inhomogeneity. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine if anodal transcutaneous spinal direct current stimulation (tsDCS) affects corticospinal excitability (CSE) and voluntary activation (VA) of the quadriceps femoris muscle (QM). This was a double‐blind, randomized study in which spine‐shoulder anodal tsDCS (active electrode centered over T11–12, 2.5 mA, 20 min) was applied in a seated position. Transcranial magnetic stimulation (TMS) was used to measure motor evoked potentials (MEP) and construct stimulus–response curves in healthy participants (eight females and five males, Experiment 1). VA was measured via the interpolated twitch technique, whereby muscle twitches were evoked using electrical femoral nerve stimulation and TMS (seven females and six males, Experiment 2). Measurements were carried out before, directly, and 30 min after sham and anodal tsDCS (with ≥4 days between sessions). There was no interaction between stimulation × time on stimulus–response curve expressed by slope, stimulus intensity corresponding to 50% of the maximal MEP, and peak‐to‐peak amplitude of the maximal MEP. Maximal voluntary isometric contraction (MVIC) torque did not change and VA was not affected regardless of the QM torque level (25, 50, or 100% of MVIC). A single, twenty‐minute session of spine‐shoulder anodal tsDCS did not increase CSE and VA of QM during submaximal and maximal contraction. This suggests that neither excitability to a known input nor responsiveness of motoneurons to submaximal and maximal cortical drive were affected by anodal tsDCS. [ABSTRACT FROM AUTHOR]

Background Limitations exist with current ACLR functional testing assessments that may be mitigated by including single-leg multi-directional testing. Hypothesis/Purpose To compare Anterior Cruciate Ligament-Return to Sport after Injury Scale (ACL-RSI) scores, limb symmetry index (LSI) of the single-leg vertical jump (SLVJ), single-leg medial rotation hop (SLMRH), single-leg lateral hop (SLLH), and isokinetic quadriceps strength between participants with an ACLR and healthy controls and assess predictors of quadriceps strength asymmetry. It was hypothesized that ACL-RSI scores and LSIs for all tests would differ between ACLR and healthy control groups and within the ACLR group a strong correlation would exist between all outcome measures and quadriceps strength. Study Design Cross-Sectional Study Methods Twenty-six participants with an ACLR (median 13 months after surgery) and twenty-six matched healthy controls were recruited to participate in this study. Performance was assessed via SLVJ, SLMRH, SLLH, and isokinetic quadriceps strength. Between-group comparisons were made with independent t-tests and Mann-Whitney U test. Within the ACLR group, bivariate correlation and multivariate regression analysis were performed to assess the relationship between the outcome measures and quadriceps strength asymmetry. Results Significant between-limb differences were only identified in the ACLR group (p< 0.05): SLVJ LSI: 88.5%, SLMRH LSI: 93.6%, SLLH LSI: 92.7%, quadriceps strength LSI 80.9% - 83.9%, which were significantly lower (p <0.05) than the healthy control group. Within the ACLR group, a moderate-strong significant (p < 0.05) correlations existed with quadriceps strength and SLVJ (r=0.44-0.65), SLMRH (r =0.43-0.83), and SLLH (r=0.54-0.63); while ACL-RSI had a weak non-significant (p > 0.05) correlation with quadriceps strength (r= 0.12-0.30). Conclusion Single-leg multidirectional test LSIs were less in ACLR participants than matched healthy controls and all were directly related to quadriceps strength. Psychological readiness to return to sport was not related to quadriceps strength. [ABSTRACT FROM AUTHOR]

Arthrogenic Muscle Inhibition (AMI) is a phenomenon observed in individuals with joint injury or pathology, characterized by a reflexive inhibition of surrounding musculature, altered neuromuscular control, and compromised functional performance. After anterior cruciate ligament reconstruction (ACLR) one of the most obvious consequences of AMI is the lack of quadriceps activation and strength. Understanding the underlying mechanisms of AMI is crucial for developing effective therapeutic interventions. The surgical procedure needed to reconstruct the ACL has biochemical et physiological consequences such as inflammation, pain, and altered proprioception. These alterations contribute to the development of AMI. Therapeutic interventions aimed at addressing AMI encompass a multidimensional approach targeting pain reduction, inflammation management, proprioceptive training, and quadriceps activation. Early management focusing on pain modulation through modalities like ice, compression, and pharmacological agents help mitigate the inflammatory response and alleviate pain, thereby reducing the reflexive inhibition of quadriceps. Quadriceps activation techniques such as neuromuscular electrical stimulation (NMES) and biofeedback training aid in overcoming muscle inhibition and restoring muscle strength. NMES elicits muscle contractions through electrical stimulation, bypassing the inhibitory mechanisms associated with AMI, thus facilitating muscle activation and strength gains. Comprehensive rehabilitation programs tailored to individual needs and stage of recovery are essential for optimizing outcomes in AMI. The objective of this clinical viewpoint is to delineate the significance of adopting a multimodal approach for the effective management of AMI, emphasizing the integration of pain modulation, proprioceptive training, muscle activation techniques, and manual therapy interventions. Highlighting the critical role of early intervention and targeted rehabilitation programs, this article aims to underscore their importance in restoring optimal function and mitigating long-term complications associated with AMI. [ABSTRACT FROM AUTHOR]

Introduction/Aims Methods Results Discussion The number of clinical trials in facioscapulohumeral muscular dystrophy (FSHD) is expected to increase in the near future. There is a need for clinical outcome assessments (COAs) that can capture disease progression over the relatively short time span of a clinical trial. In this study, we report the natural progression of FSHD and determine the feasibility of COAs for clinical trials.Genetically confirmed FSHD patients underwent various COAs at baseline and after 5 years. COAs consisted of the Motor Function Measure (MFM), manual muscle testing using the Medical Research Council score, six‐minute walk test, quantitative muscle strength assessment of the quadriceps muscle, clinical severity score, and FSHD evaluation score (FES). Statistical significance and the minimal clinically important difference (MCID) were calculated and power calculations were performed.One hundred fifty‐four symptomatic FSHD patients were included, with a mean (SD) age of 51.4 (14.6) years old. All COAs showed a minimal, yet statistically significant progression after 5 years. MCID was reached for the MFM Domain 1, MFM total score, and FES. These three COAs showed the lowest sample size requirements for clinical trials (185, 156, and 201 participants per group, respectively, for a trial duration of 2 years).The captured FSHD disease progression rate in 5 years was generally minimal. The COAs in this study are not feasible for clinical trials with a duration of 2 years. Extended trial durations or novel outcome assessments might be necessary to improve trial feasibility in FSHD. [ABSTRACT FROM AUTHOR]

AbstractObjectiveMethodsResultsConclusionsThe prevalence of asthma is increasing gradually worldwide. The pathophysiological process of asthma causes some alterations in the respiratory system and decreases oxygen-carbon dioxide exchange and respiration volume. These alterations may affect maximal exercise capacity, peripheral muscle strength, sleep quality, and disease-specific quality of life but have yet to be comprehensively investigated. To compare maximal exercise capacity, pulmonary function, peripheral muscle strength, dyspnea, sleep quality, and quality of life in adult patients with asthma, healthy controls were aimed.Forty-one adult stable asthmatic patients (GINA I–III) and 41 healthy subjects were compared. Exercise capacity (cardiopulmonary exercise test [CPET]), pulmonary function (spirometry), peripheral muscle strength (dynamometer), dyspnea (modified Medical Research Council [mMRC] dyspnea scale), quality of life (Asthma Quality of Life Questionnaire [AQLQ]) and sleep quality (Pittsburgh Sleep Quality Index [PSQI]) were evaluated.Peak VO2, VO2kg, MET, VE, HR, %VE, %HR, VCO2 parameters of CPET, FVC, FEV1, FEF25–75%, and FEV1/FVC and quadriceps femoris, shoulder abductors, and hand grip muscle strength were significantly decreased in patients with asthma (p < 0.05). MMRC dyspnea scale score was increased, and AQLQ and PSQI scores decreased in asthma patients (p < 0.05).Cardiac and pulmonary system responses to peak exercise worsened, and maximal exercise capacity and peripheral muscle strength decreased in adult patients with stable asthma. In addition, dyspnea during daily activities increases, and quality of life and sleep quality are impaired. A variety of exercise training that would benefit asthmatic patients’ outcomes should be investigated. [ABSTRACT FROM AUTHOR]

To investigate the effect of moderate or heavy slow resistance training on structural and mechanical properties of patellar and Achilles tendons in older men, in vivo. Healthy older men (n = 27) undertook a 12‐week resistance training program (3 times/week) of triceps surae and quadriceps muscle‐tendon complexes. Participants were randomly assigned to either a moderate load of 55% 1RM (O55, n = 13, age: 70.0 ± 4.6 years) or a progressively heavier load from 55% up to 80% 1RM (O80, n = 14, age: 69.8 ± 4.4 years). Tendon morphology was investigated using a 1.5 T MRI scanner. Mechanical properties of the free Achilles tendon (AT) and medial gastrocnemius (MG) aponeurosis, patellar tendon (PT), and deep aponeurosis of the vastus lateralis (VL) muscle were assessed using ultrasound imaging. Both training programs led to an increase in mean CSA of the PT (O55; +2.7%, O80; +1.7%, p = 0.002) and AT (O55; +2.8%, O80; +2.5%, p < 0.001). Force and stress were increased for all the four regions investigated, while stiffness and Young's modulus assessed at a common force level were only increased for the AT and VL aponeurosis. No interaction between group and time was demonstrated for any of the outcomes. No interaction between time and the four tendon sites was observed for any of the outcomes at common force. A supervised short‐term heavy or moderate slow resistance training of equal volume yielded an increase in tendon size and altered mechanical properties of tendinous tissue. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is the gold standard for measuring muscle size. However, postural conditions for thigh musculature have not been standardized across studies, with some employing supine or prone positions and the thigh either placed on the examination table or suspended to avoid contact. In either case, the thigh is compressed or sagged by gravity, potentially affecting muscle size. This study aimed to examine the effects of postural conditions on thigh muscle size. Twenty Olympic‐style weightlifters and 20 untrained controls (10 men and 10 women in each group) underwent 3‐Tesla MRI in the supine and prone positions, with the thigh in compressed and suspended conditions to determine the maximal anatomical cross‐sectional area (ACSAmax) and muscle volume of 15 thigh muscle groups/individual muscles. Postural conditions changed the ACSAmax of the quadriceps (range of postural‐related changes: 1.0%–7.9%), hamstrings (0.8%–19.1%), and adductors (2.4%–19.2%). Regardless of measurement position, the total volume of thigh muscles decreased under compressed conditions (0.6%–3.8%). Quadriceps and adductors decreased in muscle volume under compressed conditions (0.9%–4.0% and 0.8%–6.6%), while hamstrings increased (1.4%–9.3%). Male weightlifters, who possessed the largest thigh muscle volume, showed greater postural‐related changes in the muscle volume of quadriceps, hamstrings, and adductors than the other subgroups. Therefore, postural conditions during MRI substantially change thigh muscle size, and the magnitude of the change depends on muscle size. Our results provide in vivo evidence of the compressive behavior of thigh muscles and a new technical perspective for assessing thigh muscle size. [ABSTRACT FROM AUTHOR]

Panoramic ultrasound (US) is an extended field‐of‐view (EFOV) imaging technique that enables visualization of large‐scale skeletal muscles. This technique has previously been found to produce valid and reliable quantifications of muscle morphology in primarily young male subjects. The purpose was to investigate the intra‐rater between‐session test–retest reliability of panoramic US imaging for determining vastus lateralis (VL) and rectus femoris (RF) cross‐sectional area (mCSA) in healthy middle‐aged to elderly adults. In this cross‐sectional study, axial panoramic US images of the RF and VL muscles were captured in 23 healthy females and males aged 47 to 78. Assessed across two sessions 3–7 days apart, intra‐rater reliability was evaluated by intraclass correlation coefficients (ICC3,2), within‐subject coefficient of variation CVw−s$$ \left({\mathrm{CV}}_{\mathrm{w}-\mathrm{s}}\right) $$, standard error of measurement (SEM), and minimal detectable change (MDC). Mean mCSA for RF was mean ± SD, 7.5 ± 2.7 cm2 on both test days, with a numeric difference of 0.8%. Mean VL mCSA was 20.6 ± 6.6 cm2 and 20.5 ± 6.5 cm2 on test days 1 and 2, respectively. Test–retest ICC were: 0.997 (95% CI: 0.994–0.999) for RF and 0.995 (95% CI: 0.989–0.998) for VL. CVw−s$$ {\mathrm{CV}}_{\mathrm{w}-\mathrm{s}} $$ was 2.6% for RF and 2.4% for VL. SEM was 0.2 cm2 for RF and 0.5 cm2 for VL. MDC was 0.4 cm2 for RF and 1.3 cm2 for VL. In conclusion, panoramic EFOV US is a highly reliable imaging technique for assessing RF and VL mCSA in middle‐aged and elderly adults. These findings endorse the clinical and research utility of EFOV US and its sensitivity for detecting even minor changes in skeletal muscle size. [ABSTRACT FROM AUTHOR]

Although the landing phases of the single-leg hop for distance (SLHD) are commonly assessed, limited work reflects how the take-off phase influences hop performance in patients with anterior cruciate ligament reconstruction (ACLR). To compare trunk and lower extremity biomechanics between individuals with ACLR and matched uninjured controls during take-off of the SLHD. Cross-sectional study design. Laboratory setting. Sixteen individuals with ACLR and 18 uninjured controls. Normalized quadriceps isokinetic torque, hop distance, and respective limb symmetry indices were collected for each participant. Sagittal and frontal kinematics and kinetics of the trunk, hip, knee, and ankle as well as vertical and horizontal ground reaction forces were recorded for loading and propulsion of the take-off phase of the SLHD. Those with ACLR had weaker quadriceps peak torque in the involved limb (P =.001) and greater strength asymmetry (P <.001) than control individuals. Normalized hop distance was not statistically different between limbs or between groups (P >.05), and hop distance symmetry was not different between groups (P >.05). During loading, the involved limb demonstrated lesser knee flexion angles (P =.030) and knee power (P =.007) than the uninvolved limb and lesser knee extension moments than the uninvolved limb (P =.001) and controls (P =.005). During propulsion, the involved limb demonstrated lesser knee extension moment (P =.027), knee power (P =.010), knee (P =.032) and ankle work (P =.032), and anterior-posterior ground reaction forces (P =.047) and greater knee (P =.016) abduction excursions than the uninvolved limb. Between-limb differences in SLHD take-off suggest a knee underloading strategy in the involved limb. These results provide further evidence that distance covered during SLHD assessment can overestimate function and fail to identify compensatory biomechanical strategies. [ABSTRACT FROM AUTHOR]

The study aimed to compare the effects of foam roller (FR) and vibration foam roller (VFR) on blood flow parameters, measured by Doppler ultrasonography in professional soccer players. A randomized crossover design was used, and 10 professional soccer players participated in 3 experimental sessions: FR, VFR, and a control condition (CC). The maximum velocity (MVel) and maximum volume (MVol) blood flow parameters were measured in the common femoral artery of the dominant leg at 5 different time points as follows: before (pre), immediately after (post 09), 10 (post 109), 20 (post 209), and 30 minutes (post 309) after the intervention. Both FR and VFR involved two 45-second sets with 15-second rest between sets in the quadriceps and hamstring, while CC required sitting for 240 seconds. The FR condition showed a significant increase in MVel (p, 0.01) at all time points after the intervention, and an increase in MVol (p< 0.05) only at post 09 compared with pre. The VFR condition showed a significant (p, 0.05) increase in MVel at post 09 and post 109 and an increase (p< 0.05) in MVol at post 09 compared with pre. In comparison with CC, the FR and VFR conditions presented significantly (p<0.05) higher MVel values at post 09, post 109, post 209, and post 309 than CC. For both FR and VFR conditions, the MVol not only revealed a significant (p< 0.05) increase at post 09 but also at post 109 for VFR compared with CC. In summary, the FR and VFR interventions demonstrated a similar increase in blood flow parameters, suggesting that both strategies may accelerate physiological recovery in elite soccer players. [ABSTRACT FROM AUTHOR]

High-altitude landing maneuvers can pose a significant injury risk, particularly when performed with different landing techniques. This study aims to compare the biomechanical parameters and injury risks associated with two landing positions—staggered foot landing and simultaneous bilateral landing—using Xsens inertial units and electromyography (EMG) sensors. A total of 26 university students (13 males, 13 females) participated in this study. Kinematic data were collected using inertial measurement units (IMUs), muscle activity was recorded with EMG, and ground reaction forces were captured using 3D force plates. The data were processed and analyzed using the AnyBody modeling system to simulate joint forces, moments, and muscle activation. This study found that simultaneous bilateral landing exhibited greater hip flexion-extension, knee flexion-extension, and ankle inversion. Vertical joint forces were also significantly higher in the hip, knee, and ankle during simultaneous bilateral landing. Staggered foot landing showed higher muscle forces in the gluteus maximus, iliopsoas, and quadriceps femoris (p < 0.001). The EMG analysis revealed significant differences in the biceps femoris (p = 0.008) and quadriceps femoris (p < 0.001). These findings suggest that simultaneous bilateral landing increases joint load, while staggered foot landing increases muscle activation, which may lead to different injury risks between the two techniques. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effects of mild fatigue on the biomechanics of the lower limbs of young male volleyball players while performing single leg landing tasks. Methods: A total of ten young male volleyball players were recruited as participants in this study. After the single leg landing was performed, we compared the performance between those with and without fatigue (post- and non-fatigue, respectively). Kinematics and kinetics were collected using instruments, and related captured data were imported into OpenSim to analyze the hip, knee, and ankle joints. Results: We found that the ankle dorsiflexion angle at initial contact was significantly decreased in the post-fatigue group compared to the non-fatigue one. Meanwhile, the peak gluteus maximus force, peak gluteus medius force, peak tibialis posterior force, and peak gastrocnemius force significantly increased. There were no significant differences in the hip and knee joint flexion angles as well as the quadriceps and biceps femoris long head forces between the two groups. Conclusions: Mild fatigue can affect the performance of single leg landing, and players need to control the lower limbs by generating a higher muscle force to cope with the instability induced by fatigue. In a fatigued state, following initial contact with the ground, a decreased ankle dorsiflexion angle necessitates an increase in gastrocnemius and tibialis posterior muscle force to maintain stance during landing. [ABSTRACT FROM AUTHOR]

Background: Platelet-rich plasma (PRP) is increasingly used for the injection treatment of knee osteoarthritis (OA). However, the role of leukocytes contained in PRP is controversial, with some preclinical studies suggesting detrimental effects and others emphasizing their contribution in secreting bioactive molecules. Purpose: To compare the safety and effectiveness of leukocyte-rich PRP (LR-PRP) and leukocyte-poor PRP (LP-PRP) for the treatment of knee OA. Hypothesis: That leukocytes could influence results both in terms of adverse events and clinical outcomes. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: This double-blind randomized controlled trial included 132 patients with Kellgren-Lawrence grade 1-3 knee OA who were randomized to a 3-injection cycle of either LR-PRP or LP-PRP. Patients were prospectively assessed at baseline and at 2, 6, and 12 months with subjective evaluations comprising the International Knee Documentation Committee (IKDC) subjective score, the KOOS (Knee injury and Osteoarthritis Outcome Score), the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index), the visual analog scale for pain, the EuroQol–visual analog scale, the EuroQol–5 dimensions, and the Tegner activity scale. Objective evaluations consisted of the IKDC objective score, active/passive range of motion, and circumference of the index and contralateral knees. Patient judgment of the treatment was recorded as well as adverse reactions and failures. Results: An overall improvement in subjective and objective outcomes was documented, with no differences between the 2 groups, except for the improvement in the IKDC subjective score at 2 months, which was greater for the LR-PRP group compared with the LP-PRP group (14.8 ± 14.8 vs 8.6 ± 13.3, respectively; P =.046), as well as for active (P =.021) and passive (P =.040) ROM of the index knee at 6 months, showing statistically significant higher values in the LP-PRP group; and for quadriceps circumference of the index (P =.042) and contralateral (P =.045) knees at 12 months, which were significantly greater in the LR-PRP group. The IKDC subjective score improved from 42.5 ± 17.6 at baseline to 55.6 ± 21.4 at 12 months for the LR-PRP group (P <.0005) and from 45.7 ± 16.4 to 55.3 ± 20.4 for the LP-PRP group (P =.001). No differences in terms of patient treatment judgment were observed at all follow-up time points. No severe adverse events related to the treatment were reported, but some mild adverse events related to the treatment were observed: 16 in the LR-PRP group and 17 in the LP-PRP group. Treatment failed in 5 patients in the LR-PRP group and 2 in the LP-PRP group. Conclusion: This double-blind randomized controlled trial demonstrated that leukocytes did not affect the safety and efficacy of intra-articular PRP injections for the treatment of patients with knee OA. Both LR-PRP and LP-PRP demonstrated comparable clinical outcomes at all follow-up time points, without showing differences in subjective and objective outcomes or in adverse events and treatment failures. Registration: NCT04187183 (ClinicalTrials.gov). [ABSTRACT FROM AUTHOR]

Acute sleep restriction (SR) reduces strength through an unknown mechanism. Purpose: To determine how SR affects quadriceps contractile function and recruitment. Methods: Eighteen healthy subjects (9 M, 9F, age 23.8 ± 2.8y) underwent isometric (maximal and submaximal), isokinetic (300–60°·s−1), and interpolated twitch (ITT) assessment of knee extensors following 3d of adequate sleep (SA; 7–9 h·night−1), 3d of SR (5 h·night−1), and 7d of washout (WO; 7-9 h·night−1). Results: Compared to SA (227.9 ± 76.6Nm) and WO (228.19 ± 62.9Nm), MVIC was lesser following SR (209.9 ± 73.9Nm; p = 0.006) and this effect was greater for males (− 9.8 v. − 4.8%). There was no significant effect of sleep or sleep x speed interaction on peak isokinetic torque. Peak twitch torque was greater in the potentiated state, but no significant effect of sleep was noted. Males displayed greater potentiation of peak twitch torque (12 v. 7.5%) and rate of torque development (16.7 v. 8.2%) than females but this was not affected by sleep condition. ITT-assessed voluntary activation did not vary among sleep conditions (SA: 81.8 ± 13.1% v. SR: 84.4 ± 12.6% v. WO 84.9 ± 12.6%; p = 0.093). SR induced a leftward shift in Torque-EMG relationship at high torque output in both sexes. Compared to SA, females displayed greater y-intercept and lesser slope with SR and WO and males displayed lesser y-intercept and greater slope with SR and WO. Conclusions: Three nights of SR decreases voluntary isometric knee extensor strength, but not twitch contractile properties. Sex-specific differences in neuromuscular efficiency may explain the greater MVIC reduction in males following SR. [ABSTRACT FROM AUTHOR]

Isokinetic knee tests mostly evaluate reciprocal concentric-concentric flexor-extensor movements in a seated position. Discrete tests generate higher moments, but time requirements impede their widespread implementation. This study examined if hip angle (flexed vs. extended) and test modality (discrete vs. reciprocal) affect camera-based data (100 fps). Sixteen healthy males performed concentric (con) and eccentric (ecc) isokinetic knee flexor (H) and extensor (Q) movements (60°/s). Peak moments and contractional work of discrete and reciprocal tests (QconQecc, HconHecc) strongly correlated for extended (Q:91%≥R2≥71%; H:95%≥R2≥87%) and flexed hip (Q:88%≥R2≥70%; H:81%≥R2≥75%) without significant differences (p>0.05) between test modalities. Discrete and "traditional" seated QconHcon-tests revealed substantially lower correlations for extended (Q:44%≥R2≥43%; H:55%≥R2≥54%) and flexed hip (Q:81%≥R2≥77%; H:48%≥R2≥47%). Although most mean values did not significantly differ, moderate correlations were predominant and the respective limits of agreement demonstrated considerable effects of hip angle and test modality. These insights assist practitioners in interpreting isokinetic data of different test procedures. If time constraints prevent discrete knee tests (gold standard), concentric-eccentric movements provide highly correlated outcomes, independent of the hip angle. [ABSTRACT FROM AUTHOR]

Background: The unfolded protein response (UPR) is a proteostatic process that is activated in response to endoplasmic reticulum stress. It is currently unclear how aging influences the chronic and adaptive UPR in human skeletal muscle. Here we determined the effect of aging on UPR activation at rest, in response to exercise, and the associations with muscle function. Methods: Thirty young (20-35 yr) and 50 older (65-85 yr) individuals were enrolled. Vastus lateralis biopsies were performed at rest and 3 and 48 h after a single bout of resistance exercise. The abundance of UPR-related transcripts and proteins was measured by RNA sequencing and Western blotting, respectively. Fractional synthetic rates of muscle protein were determined by mass spectrometry after intravenous infusion of 13C6 phenylalanine. Results: Older adults demonstrated elevated transcriptional and proteomic markers of UPR activation in resting muscle. Resting UPR gene expression was negatively associated with muscle strength and power in older adults. The UPR is similarly activated by acute resistance exercise in young and older adults and positively associated with muscle function but not the anabolic response to exercise. Conclusions: Skeletal muscle from older adults exhibits chronically activated UPR, which accompanies functional decline. The adaptive UPR is a proteostatic mechanism that is upregulated in response to exercise in young and older adults and positively associated with muscle function. [ABSTRACT FROM AUTHOR]

Introduction: Skeletal muscle satellite cells (SC) contribute to the adaptive process of resistance exercise training (RET) and may be influenced by nutritional supplementation. However, little research exists on the impact of multi-ingredient supplementation on the SC response to RET. Purpose: We tested the effect of a multi-ingredient supplement (MIS) including whey protein, creatine, leucine, calcium citrate, and vitamin D on SC content and activity as well as myonuclear accretion, SC and myonuclear domain compared with a collagen control (COL) throughout a 10-wk RET program. Methods: Twenty-six participants underwent a 10-wk linear RET program while consuming either the MIS or COL supplement twice daily. Muscle biopsies were taken from the vastus lateralis at baseline and 48 h after a bout of damaging exercise, before and after RET. Muscle tissue was analyzed for SC and myonuclear content, domain, acute SC activation, and fiber cross-sectional area (fCSA). Results: MIS resulted in a greater increase in type II fCSA following 10 wk of RET (effect size (ES) = 0.89) but not myonuclear accretion or SC content. Change in myonuclei per fiber was positively correlated with type I and II and total fiber hypertrophy in the COL group only, indicating a robust independent effect of MIS on fCSA. Myonuclear domain increased similarly in both groups, whereas SC domain remained unchanged following RET. SC activation was similar between groups for all fiber types in the untrained state but showed a trend toward greater increases with MIS after RET (ES = 0.70). Conclusions: SC responses to acute damaging exercise and long-term RET are predominantly similar in MIS and COL groups. However, MIS can induce greater increases in type II fCSA with RET and potentially SC activation following damage in the trained state. [ABSTRACT FROM AUTHOR]

Objective: The aim of the study is to evaluate the muscle thickness and walking test in people with hemophilia A and their correlation to joint health and functional impairments. Design: This is a cross-sectional study. Results: Twenty-nine severe/moderate people with hemophilia Awere enrolled. Muscle thickness of quadriceps and medial gastrocnemius was measured using ultrasound. Joint health and functional capacity were assessed using Hemophilia Joint Health Score, Hemophilia Early Arthropathy Detection with Ultrasound, 6-Minute Walking test, Hemophilia Quality of Life Questionnaire for Adults, and Hemophilia Activities List. Quadriceps muscle thickness significantly correlated with Hemophilia Joint Health Score knee, Hemophilia Early Arthropathy Detection with Ultrasound knee, and Hemophilia Activities List. Calf muscle thickness significantly correlated with the Hemophilia Joint Health Score ankle. After adjusted age and body mass index, calf muscle thickness was inversely associated with the Hemophilia Joint Health Score ankle. Six-Minute Walking test was found to significantly correlate with Hemophilia Joint Health Score total, Hemophilia Early Arthropathy Detection with Ultrasound total, Hemophilia Quality of Life Questionnaire for Adults, and Hemophilia Activities List. Conclusions: Muscle thickness and the distance of 6-Minute Walking Test were linked to assessment of joint health, quality of life, and activity participation in people with hemophilia A. Ultrasound measurement of muscle thickness and walking test seem to be useful tools for the assessment of joint health and functional status in people with hemophilia A. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease, pathologically characterized by TDP‐43 aggregates. Recent evidence has been indicated that phosphorylated TDP‐43 (pTDP‐43) is present not only in motor neurons but also in muscle tissues. However, it is unclear whether testing pTDP‐43 aggregation in muscle tissue would assist in the diagnosis of ALS. We propose three key questions: (i) Is aggregation of pTDP‐43 detectable in routine biopsied muscles? (ii) Can detection of pTDP‐43 aggregation discriminate between ALS and non‐ALS patients? (iii) Can pTDP‐43 aggregation be observed in the early stages of ALS? We conducted a diagnostic study comprising 2 groups: an ALS group in which 18 cases underwent muscle biopsy screened from a registered ALS cohort consisting of 802 patients and a non‐ALS control group, in which we randomly selected 54 muscle samples from a biospecimen bank of 684 patients. Among the 18 ALS patients, 3 patients carried pathological GGGGCC repeats in the C9ORF72 gene, 2 patients carried SOD1 mutations, and 7 patients were at an early stage with only one body region clinically affected. The pTDP‐43 accumulation could be detected in routine biopsied muscles, including biceps brachii, deltoid, tibialis anterior, and quadriceps. Abnormal aggregation of pTDP‐43 was present in 94.4% of ALS patients (17/18) compared to 29.6% of non‐ALS controls (16/54; p < 0.001). The pTDP‐43 aggregates were mainly close to the sarcolemma. Using a semi‐quantified pTDP‐43 aggregates score, we applied a cut‐off value of 3 as a diagnostic biomarker, resulting in a sensitivity of 94.4% and a specificity of 83.3%. Moreover, we observed that accumulation of pTDP‐43 occurred in muscle tissues prior to clinical symptoms and electromyographic lesions. Our study provides proof‐of‐concept for the detection of pTDP‐43 accumulation via routine muscle biopsy which may serve as a novel biomarker for diagnosis of ALS. [ABSTRACT FROM AUTHOR]

To evaluate the muscle thickness and prevalence of muscle atrophy of the biceps brachii/brachialis (BB) and quadriceps femoris (QF) in critically ill children using ultrasound (US). The prospective longitudinal study was conducted in the pediatric intensive care unit (PICU) of a tertiary hospital in southern Brazil with children and adolescents of both sexes, aged 1 month to 12 years, on invasive mechanical ventilation for 24 h. US measurements were taken up to 24 h after admission, 72 h after, and weekly until discharge from the PICU. One hundred one patients were selected, of whom 97 underwent two evaluations, 68 three evaluations, and 26 four ultrasound evaluations. The median age was 6 months, with 63 (62.4%) < 1 year old. The most prevalent clinical diagnosis was respiratory diseases (70.3%). There was a reduction in BB thickness from 1 to 2 weeks (− 0.10 cm, p = 0.009) and in QF from 24 h to 2 weeks (− 0.20 cm, p = 0.013) and 72 h to 2 weeks (− 0.18 cm, p = 0.045). The prevalence of muscle atrophy (decrease > 10% in thickness) was 41.2% in at least one muscle group between 24 and 72 h, 39.7% between 24 h and 1 week, and 59.3% between 24 h and 2 weeks. The US allows the evaluation of BB and QF muscle thickness in critically ill children, and monitoring muscles during PICU hospitalization is important. The prevalence of muscle atrophy was 30.8% in the biceps brachii and 46.2% in the quadriceps femoris at the end of 2 weeks of PICU hospitalization, regardless of age and diagnosis. What is Known: • Ultrasound has emerged as a promising method, being a clinically valuable tool for bedside muscle monitoring in critical patients. • Using the ultrasound to measure the muscle thickness in adults has demonstrated good sensitivity for detecting muscle atrophy. However, this method has only been previously validated in few studies with small sample of pediatric patients. What is New: • Using the ultrasound, we observed that critically ill children experienced a loss of muscle thickness and muscle atrophy, especially during the second week of intubation. • The significant prevalence of muscle atrophy at the end of PICU hospitalization highlights the importance of ultrasound in identifying muscle loss. [ABSTRACT FROM AUTHOR]

Introduction: A bidirectional relationship has been observed between type 2 diabetes mellitus and sarcopenia, especially among older adults. While previous studies have reported that imeglimin improves mitochondrial function, they have not assessed its effects on muscle strength in patients with type 2 diabetes. Therefore, we aimed to investigate the effects of imeglimin on muscle strength in patients with type 2 diabetes. Methods: In this prospective cohort study, we recruited consenting patients with type 2 diabetes (20–75 years). Changes in lean body mass (LBM), fat mass, quadriceps muscle strength, and grip strength from baseline (week 0) to week 24 were evaluated and compared between patients treated with imeglimin therapy (group I) and those who did not take imeglimin (controls, group C). Results: We recruited 27 patients treated with imeglimin (group I) and 29 controls (group C), and 50 of them completed the study (group I: n = 23; group C: n = 27). The change in LBM, total body fat mass, or skeletal muscle index from baseline to week 24 did not differ significantly between the two groups. However, group I exhibited a significantly higher percent change in quadriceps knee extension strength from baseline to week 24 than group C (13 ± 19% and 2.1 ± 14%, p = 0.022). Conversely, the difference in percent change in grip strength was not significant. Multivariable analysis showed that imeglimin use was significantly associated with a percent change in quadriceps knee extension strength, independent of age, sex, body mass index, and skeletal mass index (β = 0.325, p = 0.0014). Conclusions: Imeglimin positively affected muscle strength in patients with type 2 diabetes without altering LBM. Therefore, imeglimin exerts a unique effect on skeletal muscles in humans. Further randomized controlled trials are needed to validate these findings. Trial Registration: This research was registered in the University Hospital Medical Information Network (UMIN, UMIN000054715). [ABSTRACT FROM AUTHOR]

This article discusses a case study of a young female patient with a painful mass in the quadriceps compartment. The diagnosis was fibro-adipose vascular anomaly (FAVA), a rare condition characterized by intramuscular replacement with fibro-fatty tissue, complex vascular malformation, venous thrombosis, and lymphatic involvement. The article presents various imaging findings, including radiographs, ultrasounds, MRIs, and CT scans, to support the diagnosis. The treatment options for FAVA include surgical removal, minimally invasive ablative procedures, and the use of sirolimus. The article emphasizes the importance of collaboration among specialists in diagnosing and managing FAVA. [Extracted from the article]

Aim: To examine factors associated with lower urinary tract symptoms (LUTS) and lower urinary tract dysfunction (LUTD) in children with Duchenne muscular dystrophy (DMD). Methods: This cross‐sectional study included 45 individuals diagnosed with DMD between the ages of 5 and 18 years. LUTS were evaluated with the Dysfunctional Voiding and Incontinence Scoring System, functional levels with the Brooke Upper Extremity Functional Classification and the Vignos Scale, lumbar lordosis angle with a bubble inclinometer, pelvic inclination angles with a digital inclinometer, and muscle strength with a hand‐held dynamometer. Results: The mean age of the children was calculated as 9.00 ± 3.32 years, body weight as 31.10 ± 12.59 kg, and height as 125.87 ± 18.46 cm. LUTD was detected in 20 children (44.44%). There was an association between high LUTD severity and low strength of the following muscles: bilateral hip flexor (Dominant: r = −0.338, p = 0.023; nondominant: r = −0.411, p = 0.005), quadriceps femoris (Dominant: r = −0.445, p = 0.002; nondominant: r = −0.504, p < 0.001), elbow flexor (Dominant: r = −0.461, p = 0.001; nondominant: r = −0.455, p = 0.002), and elbow extensor (Dominant: r = −0.442, p = 0.002; nondominant: r = −0.450, p = 0.002). Upper extremity functionality level was significantly higher in the LUTD‐negative group (p = 0.004). There was no relationship between lumbar lordosis and pelvic inclination angles and LUTS symptoms (p > 0.05). Conclusion: To provide the adequate care for bladder health in children with DMD, it is essential to focus on parameters that will increase functionality and independence in this population. [ABSTRACT FROM AUTHOR]

Background: Athletes with patellar tendinopathy (PT) have postural stability deficits; however, the underlying mechanisms and factors responsible remain unknown. The effect on postural stability in PT of decreased quadriceps strength, altered proprioception, lower-limb muscle tightness, and knee pain, which explain postural stability deficiency in other populations, is uninvestigated. Hypothesis: Proprioceptive acuity, muscle tightness, quadriceps strength, and pain predict postural stability in athletes with PT. Study Design: Cross-sectional comparative study. Level of Evidence: Level 2. Methods: A total of 43 athletes with PT and 43 healthy athletes were enrolled. Static and dynamic postural stability, proprioceptive acuity, muscle tightness, quadriceps strength, and pain were evaluated using a force platform, Y-balance test (YBT), a weight discrimination protocol, a goniometer, an isometric dynamometer, and a valid questionnaire, respectively. Results: Athletes with PT had significantly worse static and dynamic postural stability in the affected limb (AL) compared with the nonaffected limb (NAL) (P < 0.01) and the control group (P < 0.01). Athletes suffering from PT revealed lower quadriceps strength (P < 0.01), proprioceptive acuity (P = 0.02), and higher muscle tightness in the AL compared with the NAL and controls. Quadriceps weakness of the AL and pain in athletes with PT explained the variance of dynamic postural stability impairment. Conclusion: Athletes with PT have postural stability deficiency compared with healthy peers. Our results demonstrate that quadriceps muscle weakness and pain are the factors that explain postural stability impairment. Clinical Relevance: These results can assist clinicians in the design of therapeutic balance rehabilitation programs by acting not only on pain relief but also on quadriceps strengthening through resistance training to avoid subsequent injuries in athletes with PT. [ABSTRACT FROM AUTHOR]

Background: Reduced muscle mass upon admission and development of muscle wasting are frequent in critically ill patients, and linked to unfavorable outcomes. Muscle ultrasound is a promising instrument for evaluating muscle mass. We summarized the findings of lower limb muscle ultrasound values and investigated how the muscle ultrasound parameters of the examination or the patient characteristics influence the results. Methods: Systematic review and meta-analysis of studies of lower limb ultrasound critically ill adults. PubMed, CINAHL, Embase, PEDro and Web of Science were searched. PRISMA guidelines were followed, and studies evaluated with the appropriate NIH quality assessment tool. A meta-analysis was conducted to compare the values at admission, short and long follow-up during ICU stay, and the association between baseline values and patient characteristics or ultrasound parameters was investigated with a meta-regression. Results: Sixty-six studies (3839 patients) were included. The main muscles investigated were rectus femoris cross-sectional area (RF-CSA, n = 33/66), quadriceps muscle layer thickness (n = 32/66), and rectus femoris thickness (n = 19/66). Significant differences were found in the anatomical landmark and ultrasound settings. At ICU admission, RF-CSA ranged from 1.1 [0.73–1.47] to 6.36 [5.45–7.27] cm2 (pooled average 2.83 [2.29–3.37] cm2) with high heterogeneity among studies (I2 = 98.43%). Higher age, higher BMI, more distal landmark and the use of probe compression were associated with lower baseline muscle mass. Conclusions: Measurements of muscle mass using ultrasound varied with reference to patient characteristics, patient position, anatomical landmarks used for measurement, and the level of compression applied by the probe; this constrains the external validity of the results and highlights the need for standardization. Study registration: PROSPERO CRD42023420376. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) knee is one of the most common chronic degenerative conditions that imposes clinical and economic burdens on individuals and societies worldwide. Previous studies showed vitamin D levels correlated positively with lean muscle mass and grip strength, implying that vitamin D supplementation may improve muscle health in knee OA subjects. This randomized controlled trial (RCT) aims to compare the effects of vitamin D supplementation on knee muscle strength, physical function, pain, and sarcopenia status in patients with end-stage knee OA. Patients and outcome assessors will be blinded to group allocation. Fifty-six end-stage knee OA patients with vitamin D insufficiency fulfilling our inclusion criteria will be invited to participate in this study. Patients will be randomly assigned to take vitamin D supplementation (4,000 IU capsule daily) or placebo for six months. Measurements will be taken at baseline, three and six-month after the commencement of the vitamin D supplement, and 6-month after the interventional period. The primary outcome includes the isometric quadriceps and hamstring muscle strength measured by a hand-held dynamometer. Secondary outcomes include pain, performance-based and self-reported physical function and sarcopenia status. The success of this study will provide scientific evidence of whether the relatively cheap and well-tolerated vitamin D supplement can improve quadriceps muscle strength, physical function, pain symptoms, and sarcopenia status of this increasingly large population for end-stage knee OA patients. The study has great clinical significance given Hong Kong's lengthy and growing waiting list for complete knee replacement procedures. Trial registration: The trial was registered on clinicaltrials.gov (NCT05981534) on 31st July 2023. [ABSTRACT FROM AUTHOR]

Background: Symptomatic heart failure (HF) negatively affects the quantity and quality of skeletal muscles. However, the association between asymptomatic HF and skeletal muscle function remains unclear. We aimed to use ultrasonography to elucidate the association between asymptomatic HF and skeletal muscle function in community-dwelling older adults. Methods: This cross-sectional study comprised community-dwelling older adults aged ≥ 60 years who could perform activities of daily living independently and had never had symptomatic HF (n = 52, 76.3 ± 6.1 years). The participants were classified into three groups namely, non-HF (n = 26), stage A (n = 19), and stage B (n = 7) according to the HF stage criteria of the American Heart Association /American College of Cardiology /Heart Failure Society of America guideline. Skeletal muscle quantity and quality were assessed using ultrasonography (thickness and echo intensity) of the rectus femoris (RF) and vastus intermedius (VI) muscles. The group effects on muscle thickness and echo intensity in each group were assessed using a multivariate analysis. Results: Both muscles consistently demonstrated significant group effects on the thickness and echo intensity. Thicknesses of the RF (p = 0.020) and VI (p = 0.035) were lower in the stage B group than that in the non-HF group. The echo intensities in the RF (p = 0.006) and VI (p = 0.009) were higher in the stage B group than that in the non-HF group. Conclusion: Asymptomatic HF negatively associated with the characteristics of skeletal muscle function, as assessed by ultrasonography in community-dwelling older adults. The stage B HF contributes to reduced skeletal muscle function as well as symptomatic HF. [ABSTRACT FROM AUTHOR]

Background: Post-streptococcal myalgia and myositis are very rare complications of streptococcal infections with group A β-haemolytic streptococci. Data on this condition are scarce and even less is known about findings in clinical imaging. Until today, there are no descriptions of ultrasonographic changes in this condition. Case presentation: We present a case of a 31-year-old female patient with immobilizing myalgia of the left outer thigh following a streptococcal upper respiratory tract infection, accompanied with erythemata nodosa on both shins. Laboratory results indicated post-streptococcal myositis since Creatine kinase, Lactate dehydrogenase and Antistreptolysin antibodies were significantly elevated. An ultrasound of the affected vastus medialis of the left quadriceps femoris muscle was performed, which showed a focal increase in muscle echogenicity with loss of architecture and hypervascularisation in Power Doppler Mode. The diagnosis of focal myositis was confirmed with magnetic resonance imaging. The patient's symptoms as well as the ultrasonographic changes fully resolved under therapy with Ibuprofen and intravenous Ampicillin/Sulbactam. Conclusions: This is the first description of ultrasound findings in this rare condition. We conclude that muscular ultrasound is helpful to identify myositis in post-streptococcal myalgia and myositis. [ABSTRACT FROM AUTHOR]

Background: Vitamin D deficiency has been linked to poor muscle function, cartilage degeneration, and the development of knee osteoarthritis. However, the impact of serum 25-hydroxyvitamin D [25(OH)D] level on quadriceps muscle strength remains inconclusive, largely due to variations in study designs, differences in study populations, and the influence of confounding factors such as co-supplementation with other vitamins. The existing literature presents mixed findings, highlighting the need for a comprehensive evaluation of the available evidence. Purpose: This systematic review and meta-analysis aim to summarise. Study design: Systematic review; Level of evidence, 4. Methods: Searches were conducted using Medline (Ovid), Embase (Ovid), CINAHL (EBSCOhost), and SPORTDiscus (EBSCOhost), which aimed to summarise recent (published after 2000 and before March 1st, 2024) studies reporting the effects of serum 25(OH)D levels on quadriceps strength. Appraisal tool for Cross-Sectional Studies (AXIS) for cross-sectional studies and Quality in Prognosis Studies (QUIPS) for longitudinal studies. Results from the AXIS and QUIPS tools were used for GRADE quality assessment. The review was carried out using PRIMSA guidelines and registered in PROSPERO (ID: CRD42022313240). Results: Four hundred studies were screened and 28 studies with 5752 participants were included. 28 published studies (24 cross-sectional and 4 longitudinal) were identified. Key results supported the significant positive correlation between serum 25(OH)D levels and isokinetic quadriceps strength at 180°/s in elderly and athletic populations with a correlation coefficient of 0.245 (95%CI: 0.078–0.398, p = 0.004). However, no significant correlation was found with isometric quadriceps strength or isokinetic strength at 60°/s (r = 0.190, p = 0.085). There was only a weak negative correlation with MVC. Conclusion: This review found a statistically significant positive correlation between serum 25(OH)D levels and isokinetic quadriceps strength. This has important clinical implications, especially in the elderly cohort, with higher 25(OH)D levels being associated with a reduced incidence of falls and fragility fractures. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate the effect of two protocols of high-intensity interval exercise (HIIE) on performance fatigability and its neural and muscular determinants. On different days, 14 healthy males performed two HIIE protocols with different work and recovery durations (matched for total duration, work and recovery intensities, and density): 1) 4 × 4 min at 90% HRpeak,180-s recovery at 70% HRpeak; and 2) 16 × 1 min at 90% HRpeak, 45-s recovery at 70% HRpeak. Pre- to post-HIIE reduction in maximal voluntary isometric contraction (MVIC) was used as marker of performance fatigability, while voluntary activation (VA) and potentiated quadriceps twitch force (Qtw) as markers of the neural (i.e. central fatigue) and muscular (i.e. peripheral fatigue) determinants, respectively. In addition, pre- to post-HIIE reduction in twitch force stimulated at 100 Hz (Qtw100) and 10:100 Hz ratio (Qtw10:Qtw100) were used as markers of high- and low-frequency performance fatigability, respectively. The MVIC, VA, Tw, Qtw100, and Qtw10:Qtw100 ratio decreased similarly from pre- to post-HIIE in both HIIE protocols (p < .05). The rating of perceived effort, blood pH, and plasma lactate responses were similar between HIIE protocols (p > .05), but the heart rate was higher in the longer HIIE protocol (p < .05). In conclusion, performance fatigability and its neural and muscular determinants seemed to be independent of the work and recovery durations of the HIIE, at least when HIIE protocols were matched for total work duration, work and recovery intensities, and density. Further, HIIE with long work and recovery might be preferable when the intention is to stress the chronotropic response. [ABSTRACT FROM AUTHOR]

Background: Isokinetic normative data in females' soccer players is scarce in comparison to males. Furthermore, evaluation protocols employed to obtain those data in female's studies, strongly differ from each other, using different ranges of speeds and movement patterns, thus producing different output data. Thus, it is difficult for the researcher and the clinician to choose a correct protocol for knee isokinetic test in female soccer players. Aim of this paper is to review the literature to provide updated information on how to interpret a knee isokinetic testing in healthy females. Methods: Google Scholar, PubMed, Sport Discus, and Psych info databases were queried, and 17 papers were selected. Following PRISMA methodology and PEDro scale, we classified the retrieved papers and assessed the quality. Results: In this review some common features of isokinetic testing in female soccer players of various levels of qualification are highlighted. The isokinetic performance indexes widely accepted are the hamstring/quadriceps (H/Q) ratio and dominant/non-dominant (D/ND) ratio. It also emerges that, 3 reps at the speed of 60°/sec in knee flexion/extension are preferable due to the higher reliability and that the optimal H/Q ratio in healthy female soccer players of different level of qualification and age is 50%, while the interlimb differences (D/ND) should be below 10%. Conclusions: Normative data and methodologies reviewed can be useful for the isokinetic test of female soccer players. It emerges that simplifying test procedures limiting at few testing speed and considering selected H/Q and D/ND gives all the necessary relevant informations. [ABSTRACT FROM AUTHOR]

Purpose: To investigate sex‐based recovery differences in patients undergoing anterior cruciate ligament reconstruction (ACLR) with a hamstring (HT) or quadriceps (QT) tendon autograft. Methods: This study included 97 patients, including 50 females (HT = 25, QT = 25) and 47 males (HT = 24, QT = 23), assessed presurgery and at 12‐ and 24‐month postoperatively via surveys, laxity, isokinetic knee extensor and flexor torque and a 6‐hop performance battery. Limb symmetry indices (LSIs) were calculated. Outcomes were compared between males and females, as well as within each graft type. Results: Males reported significantly higher Tegner scores at 12 (p = 0.029) and 24 (p = 0.031) months, Anterior Cruciate Ligament Return to Sport after Injury scores at 12 (p = 0.009) and 24 (p = 0.010) months, and a significantly higher lateral hop LSI at 12 (p = 0.045) months, knee extensor torque LSI at 12 (p = 0.020) months, and knee flexor torque LSI at 12 (p = 0.001) and 24 (p = 0.039) months. Females undergoing ACLR with a QT (vs. HT) graft demonstrated a lower knee extensor torque LSI at 12 (p = 0.006) months, a lower lateral hop LSI at 12 (p = 0.038) months, and a lower medial hop LSI at 12 (p = 0.042) months. Conclusions: Females reported less activity and psychological readiness, as well as strength symmetry. Furthermore, the recovery of quadriceps strength and hop symmetry was delayed in females (vs. males) undergoing ACLR with a QT graft. A better understanding of these differences will assist in counselling on expectations, determining the most appropriate graft construct and permitting more targeted rehabilitation. Level of Evidence: Level IV. [ABSTRACT FROM AUTHOR]

Background: Measures that assess muscle strength and its development, either voluntarily or involuntarily, are important in the clinical and research context. The main aim of this study was to verify the interday reliability and the minimum detectable change (MDC) of the knee extensors muscles torque using evoked contractions and explosive voluntary contractions (EVC), across six different joint angles. Methods: 20 participants, 16 men and 4 women (26.5 ± 6.6 years; 174.5 ± 11.1 cm; 73.7 ± 11.3 kg), participated in this study. Evoked twitch contractions and voluntary explosive contractions of the knee extensors were performed in 2 days (test-retest) at 20, 40, 70, 90, 105 and 115 degrees. Results: The most reliable twitch parameters were peak torque (PT), contraction time (CT), half relaxation-time (½ time), total impulse and peak rate of torque development (RTDPeak), with coefficient of variation (CV) ranging from ~ 8% at 20° to 5% at 115° angle. It was verified that CT and ½ time become more reliable as the knee angle changed from 20 to 115 degrees, from shorter to longer muscle lengths (7.3 to 2.7% and 8.8% to 4.0%, respectively). The more reliable parameters for voluntary contraction were PT, RTD250 ms, RTDPeak and impulse250 ms (CV from around ~ 8% at 20°/115° and 5% at 70°/90°). For voluntary contractions, all measures performed at 70° angle were more reliable compared to the other angles. Conclusion: It was concluded that for the knee extensor muscles, evoked twitch contractions presented greater reliability across knee angles, with lower CV values when compared to the voluntary measures for the same time windows. Specifically, for the evoked twitch contractions, angles from 70 to 115 degree proved to be highly reliable. On the other hand, for the voluntary contractions, the central angles (70 and 90 degree) were the most reliable. [ABSTRACT FROM AUTHOR]

Context: The fate of kids born in dairy goat production systems is a growing concern. Aims: This study aimed to evaluate the carcass characteristics and meat quality of Saanen and Saanen × Boer goat kids slaughtered at 30 and 60 days of age. Methods: We used 32 entire male goats, suckler and with access to solid food from 30 to 60 days, distributed in a completely randomised design, in a 2 (breed) × 2 (age at slaughter) factorial arrangement. We evaluated animal performance, carcass characteristics, instrumental analyses of the Quadriceps femoral muscle, and consumer perception. Key results: There was no interaction between breed and age of the goats (P > 0.05) on the initial and final liveweight, weight gain, cold carcass weight, hot carcass weight, and hot and cold carcass yields. However, age at slaughter influenced these variables (P < 0.05). The breed did not influence pH, meat colour, water-retention capacity, weight loss by cooking, or shear force (P > 0.05). However, shear force increased when goats were slaughtered at 60 days of age (P < 0.05). The muscle pH determined at 24 h after slaughter, and lipid oxidation, were lower in the meat of goats slaughtered at 60 days of age (P < 0.05), but did not differ between breeds. Higher consumer scores for flavour and appearance (P < 0.05) were attributed to the meat of crossbred animals in sensory analysis. Conclusions: Slaughtering goat kids at 60 days of age (versus 30 days of age) is an alternative for improving some aspects of meat quality. We recommend crossing Saanen × Boer to increase consumer acceptance of meat. Implications: This study is important for Saanen goat kids producers to understand that crossbreeding with the Boer breed improves carcass characteristics and meat acceptance by consumers. We compared Saanen and Saanen × Boer kid meats and found that the Saanen × Boer crossbreed contributes to increased carcass yield and greater acceptance of the meat by consumers. When comparing different slaughter ages (30 and 60 days), we observed that the carcass fat content increased and lipid oxidation in the meat decreased when the kids were slaughtered at 60 days of age. [ABSTRACT FROM AUTHOR]