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Disruptions in gait function are common after concussion in adolescents; however, the neuromotor control deficits driving these gait disruptions are not well known. Fifteen concussed (age mean [SD]): 17.4 [0.6], 13 females, days since injury: 26.3 [9.9]) and 17 uninjured (age: 18.0 [0.7], 10 females) adolescents completed 3 trials each of single-task gait and dual-task gait (DT). During DT, participants simultaneously walked while completing a serial subtraction task. Gait metrics and variability in instantaneous mean frequency in lower extremity muscles were captured by inertial sensors and surface electromyography, respectively. A 2-way analysis of covariance was used to compare gait metrics across groups and conditions. Functional principal components analysis was used to identify regions of variability in instantaneous mean frequency curves. Functional principal component scores were compared across groups using a Welch statistic. Both groups displayed worse performance on gait metrics during DT condition compared to single-task, with no differences between groups (P <.001). Concussed adolescents displayed significantly greater instantaneous mean frequency, indicated by functional principal component 1, in the tibialis anterior, biceps femoris, and semitendinosus (P <.05) during single-task and DT compared with uninjured adolescents. Our observations suggest that concussed adolescents display inefficient motor unit recruitment lasting longer than 2 weeks following injury, regardless of the addition of a secondary task. [ABSTRACT FROM AUTHOR]

Context: Decreased muscle strength and balance in patients with functional ankle instability (FAI) can be effectively improved by ankle strength training. Low-load blood flow restriction (LL-BFR) training increases muscle size and strength, but there is limited evidence from studies on muscle strength and balance in FAI patients. Objective: To study the effects of LL-BFR training versus high-load training (HLT) on muscle strength and balance in FAI patients. Design: Randomized controlled trial. Participants: Forty-six young adults with a history of FAI. Interventions: Participants in the LL-BFR and HLT groups performed 4 sets (30 x 15 x 15 x 15) of ankle training at 20% to 40% of the one-repetition maximum and 70% to 85% one-repetition maximum, respectively, twice a week for 6 weeks. Main Outcome Measure(s): Plantar flexion, dorsiflexion, inversion, and eversion muscle strength, and the Y-balance test scores were assessed at baseline and after 3 and 6 weeks; the thickness of the tibialis anterior, triceps surae, and peroneus longus muscles were assessed at baseline and after 6 weeks. Results: Inversion, eversion, dorsiflexion, and plantar flexion muscle strength; tibialis anterior, triceps surae, and peroneus longus thickness; and Y-balance test scores were significantly increased in the LL-BFR group after 3 and 6 weeks compared with baseline (P < .05), with no significant difference between the LL-BFR and HLT groups after 6 weeks (P > .05). However, at the end of 3 weeks, eversion muscle strength and Y-balance test scores were significantly higher in the LL-BFR group than in the HLT group (P < .05). Conclusions: Over 6 weeks, LL-BFR training was as effective as HLT in improving ankle muscle strength, muscle thickness, and balance in FAI patients, but LL-BFR training improved the ankle eversion muscle strength and dynamic balance more than HLT did in the early stages of the intervention. This finding will provide a new intervention strategy for the clinical rehabilitation of FAI patients. [ABSTRACT FROM AUTHOR]

Humans experience unanticipated external postural perturbations and recover their posture faster via involuntary responses than voluntary responses. Previous cross-sectional comparisons between athletes and untrained populations have suggested that daily motor experiences can lead to adaptations in the reftex system, but the temporal aspect of this adaptation has been unclear. Here we show that judokas have an earlier muscle activation response to even non-judo-specific external perturbations compared with an untrained population. The response latency to a backward push-and-release type postural perturbation was compared between male judokas (n = 7. career >13 years. ranging from world champions to prefectural competitors) and untrained nonjudokas (n = 7). Latency was defined as the instant of tibialis anterior muscle activity onset. Judokas exhibited shorter latency (20.6 ± 7.1 ms) than nonjudokas (28.3 ± 8.9 ms). The rank order of latency in judokas did not correlate with their competition performance. We suggest that daily training in responding to perturbations might improve some parts of the sensorimotor pathway relating to postural response latency, and that this excellence in involuntary response is independent of athletic performance. The findings provide a novel perspective for understanding postural control ability in humans. [ABSTRACT FROM AUTHOR]

Wearing loose footwear, such as slippers, poses a risk factor for tripping. Previous studies liave examined obstacle crossing to find strategies to avoid tripping. However, the effect of wearing slippers on the likelihood of tripping remains unclear. Therefore, this study aimed to determine whether wearing slippers while level walking and obstacle crossing affects kinematic characteristics and muscle activity. Sixteen healthy, young adults performed two tasks (a) while wearing slippers and (b) while barefoot: (1) level walking and (2) crossing a 10-cm obstacle. Toe clearance, joint angles, muscle activity. and cocontraction were measured for both the leading and trailing lower limbs. In the slipper-wearing condition, knee flexion and hip flexion angles were significantly increased in the swing phase for the leading limb (p< .001 andp <.001, respectively) and trailing liinb (p <.001 and p =.004, respectively) compared with the barefoot condition. Tibialis anterior activity (p = .01) and muscle cocontraction of the tibialis anterior and the medial head of the gastrocnemius (p = .047) were significantly increased in the swing phase of the trailing limb for the slipper-wearing condition compared with the barefoot condition in the obstacle crossing task. Wearing slippers increased knee and hip flexion angles, and muscle cocontraction of the tibialis anterior and medial head of gastrocnemius increased during obstacle crossing. The results revealed that obstacle crossing while wearing slippers would require foot fixation adjustment in addition to increased knee and hip flexion to avoid toe collision. [ABSTRACT FROM AUTHOR]

Purpose: We tested the hypothesis that heat stress influences the closed-loop cardio-postural control by an increased blood pressure (BP) drop and postural sway. Methods: Fourteen healthy individuals (eight women) performed two orthostatic tests under thermal reference (TC; ~ 24 ºC) and HOT (~ 38 ºC) conditions. The center-of-pressure (COP) displacements and the electromyography (EMG) activity of the calf muscles (medial gastrocnemius and tibialis anterior) were recorded during the initial orthostasis (ORT onset) after the supine-to-stand challenge. At the same period, BP (beat-to-beat) was continuously monitored, and supine-to-stand variations (∆%) were calculated. Sublingual temperature (Tsl) was measured as a surrogate of internal temperature. Results: Tsl increased in HOT compared to TC (TC 36.5 ± 0.3 vs. HOT 36.7 ± 0.3 ºC; p < 0.01). COP distance was greater in HOT compared to TC condition (TC 596.6 ± 242.4 vs. HOT 680.2 ± 249.1 mm; p < 0.01). EMG activity of the gastrocnemius decreased in HOT compared to TC condition (TC 95.5 ± 19.8 vs. HOT 78.4 ± 22.8%mV; p = 0.02). EMG of tibialis did not change between TC and HOT (TC 83.5 ± 42.9 vs. HOT 66.1 ± 31.9% mV; p = 0.29). BP showed a greater fall in HOT compared to TC condition (∆%TC − 24.5 ± 13.2 vs. ∆%HOT − 33.2 ± 20.2%; p = 0.01). Conclusion: Heat stress causes a greater fall in blood pressure and a reduction in musculoskeletal pump activity during orthostatic onset. These effects could be potential mechanisms that underlie augmented postural instability under a heated environment. [ABSTRACT FROM AUTHOR]

Unloader braces are a treatment modality for medial compartment knee osteoarthritis. The functional mechanisms involved are not yet fully understood. Therefore, this two-part systematic review examines the following research questions: How is muscle activation altered by medial compartment knee osteoarthritis, and do medial tibiofemoral compartment unloader braces alter muscle activation? If so, could this alteration be part of the unloading mechanism by affecting the altered muscle activity in medial compartment knee osteoarthritis? A systematic literature search was conducted using PubMed, LIVIVO, Web of Science, Google Scholar, and CENTRAL for articles published until August 2023. The first systematic review, examining neuromuscular alterations, identified 703 articles, with a final inclusion of 20. The second systematic review, which evaluated the neuromuscular effects of unloader braces, identified 123 articles with the final inclusion of 3. Individuals with medial compartment knee osteoarthritis demonstrated increased activity and co-contraction of the periarticular knee muscles, whereas medial tibio-femoral compartment unloader braces seemed to reduce activity and co-contraction. In contrast to the belief that unloader braces result in muscle weakness as they decrease muscle activity and co-contraction, our limited insights indicate that they rather might reduce the pathological increase. This may result in joint load reduction due to lower compressive forces. However, further investigation is required. [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]

Reciprocal inhibition and coactivation are strategies of the central nervous system used to perform various daily tasks. In automatic postural responses (APR), coactivation is widely investigated in the ankle joint muscles, however reciprocal inhibition, although clear in manipulative motor actions, has not been investigated in the context of APRs. The aim was to identify whether reciprocal inhibition can be observed as a strategy in the recruitment of gastrocnemius Medialis (GM), Soleus (So) and Tibialis Anterior (TA) muscles in low- and high-velocity forward and backward perturbations. We applied two balance perturbations with a low and a high velocity of displacement of the movable platform in forward and backward conditions and we evaluated the magnitude and latency time of TA, GM and So activation latency, measured by electromyography (EMG). In forward perturbations, coactivation of the three muscles was observed, with greater activation amplitude of the GM and lesser amplitude of the So and TA muscles. For backward, the pattern of response observed was activation of the TA muscle, a decrease in the EMG signal, which characterizes reciprocal inhibition of the GM muscle and maintenance of the basal state of the So muscle. This result indicates that backward perturbations are more challenging. [ABSTRACT FROM AUTHOR]

BACKGROUND: Trolley bags have gained popularity among students, but there is limited research comparing them to backpack-style school bags. OBJECTIVE: This study aimed to compare how carrying a backpack versus a trolley bag affects the activity of trunk and lower limb muscles in secondary school students. METHODS: Electromyographic activity was measured in 25 students (13.4±1.1 years) as they walked on level ground and up/down stairs while carrying both types of bags. The activity of the gastrocnemius, tibialis anterior, semitendinosus, rectus femoris, lumbar erector spinae, and rectus abdominis muscles was assessed on both the dominant and non-dominant sides. RESULTS: The study found significantly reduced muscle activation in most of the targeted muscles when walking on level ground with the trolley bag and when going up/down stairs with the backpack. CONCLUSIONS: Lifting a trolley bag depends on the slope of the walking surface and is more efficient on level ground, while carrying a backpack is more efficient when going up and down stairs. Since it is not practical to switch bags when encountering stairs in schools, a bag with a mixed model design incorporating features of both trolley and backpack may be more beneficial and practical for students to use. Students, parents, and teachers should be aware of the injury risks associated with carrying different types of bags. [ABSTRACT FROM AUTHOR]

Purpose: The few previous researches on the impact of calf compression garments (CG) on running performance while assessing physiological and perceptual factors. Therefore, this study investigated how the clothing pressure of two types of Calf CG, CG1 and CG2, affects muscle fatigue and activation during running. Design/methodology/approach: Five healthy amateur runners(three female and two male)were recruited for a 30-min running trial. They wear a Calf CG on their right leg (CG group), but not on their left leg(CON group). After obtaining the clothing pressure of Calf CG on the gastrocnemius lateral head (GL), gastrocnemius medial head (GM) and tibialis anterior(TA) of the right leg, surface electromyography (sEMG)of four muscles of GL, GM, TA and rectus femoris (RF) of the left and right legs were measured during running, and heart rate, cardiopulmonary rate, and human RPE were also measured. Blood bleed oxygen before and after the running trial were measured. The root mean square (RMS) of the characteristic values was selected as an index for the analysis of sEMG signals, and the data were analyzed using statistical and computational methods. Findings: The results showed that the indexes of heart rate, blood oxygen, and RPE were significantly increased, indicating that the subjects had reached the fatigue level. The comparison of mean clothing pressure at GL, GM and TA locations reveals that the TA location consistently exhibits the highest pressure for both types of CG. When wearing CG1, the mean clothing pressure at the GL and GM test points is greater than that of CG2(CG1-GL = 0.2059 kPa > CG2-GL = 0.148 kPa; CG1-GM = 0.1633 kPa > CG2-GM = 0.127 kPa). This is attributed to the double-layered fabric on the sides of CG1, which precisely covers the GL and GM areas, thereby resulting in higher mean clothing pressure at these locations compared to CG2. Conversely, the mean clothing pressure at the TA location for CG1 is lower than that for CG2(CG1-TA = 0.3852 kPa < CG2-TA = 0.426 kPa). The pressure exerted by the CG1 on the lower limb test areas has both positive and negative effects, though neither are statistically significant. The pressure exerted by CG2 alleviates fatigue at the directly affected locations GL and GM, but exerts excessive pressure on TA, resulting in a negative effect. Additionally, CG2 pressure alleviates fatigue at the indirectly affected location RF on the same side. Based on the specific clothing pressure data, it is concluded that when the pressure at the GM location is 0.127 kPa, 30 min of running has a fatigue-relieving effect. However, the pressure should not be excessively high, at 0.1633 kPa it exhibits an insignificant adverse effect. At the TA location, a garment pressure mean between 0.3852 and 0.426 kPa does not alleviate fatigue after 30 min of running, and the negative effect becomes more pronounced as the pressure increases. The pressure exerted by the CG at GL, GM, TA and RF locations shows significant changes from the previous time period during the 15–18 min interval after running. Therefore, in the design of CG, attention should be paid to the changes in clothing pressure effects on muscles during this specific time period. Originality/value: The few previous researches on the impact of calf compression garments (CG) on running performance while assessing physiological and perceptual factors. Therefore, this study investigated how the clothing pressure of two types of Calf CG, CG1 and CG2, affects muscle fatigue and activation during running. [ABSTRACT FROM AUTHOR]

The foot structure is associated with different running mechanics. The central nervous system is responsible for using the muscles through synergies during locomotion. The purpose of the present study was to examine the effect of foot structure on the electromyography factors and the synergy of the selected muscles of the lower extremity. Tibialis anterior, extensor digitorum longus, peroneus longus, soleus, biceps femoris, vastus lateralis, gastrocnemius lateralis and medialis muscles activity of 60 barefoot recreational runners with different foot structures was recorded while running at a speed of 3.3 m/s. Muscle activity was measured in the running cycle. Besides, muscle synergies were extracted using non-negative matrix factorization algorithm. The results showed that there were differences between groups with different foot type in muscle activity under different phases of running in some muscles. Furthermore, the findings indicated that the number of synergies was similar in different groups and the relative weight of muscles was not different across groups. In conclusion, despite the difference in muscle activity under different phases of the running cycle, muscle synergies are similar among the groups. This can indicate similar control by the central nervous system in runners with different arch structures while running and the observed changes in muscle activity can be attributed to the type of forces exerted on the body, the length-tension relationship, and changes in the direction of the lower limbs in people with different arch structures. [ABSTRACT FROM AUTHOR]

Exoskeleton robots have the potential to augment human motor capabilities. however, current control strategies often require task-specific control laws tailored for different scenarios, which limits the applicability of exoskeletons. In this study, we propose a control strategy for exoskeleton robots that is adaptable across various scenarios. We employ adaptive oscillators (AO) with feedback control to rapidly estimate the wearer'smotion phase and subsequently provide torque assistance to the wearer's hip joint based on a TCN-LSTM model. During experiments, we collected surface electromyographic (sEMG) signals from the tibialis anterior, gastrocnemius, and rectus muscles of seven groups of subjects performing treadmill walking and inclined treadmill exercises. We utilized the short-time Fourier transform to extract frequency characteristics of the signals and statistically analyzed the rate of frequency change in each muscle group under different strategies. The results indicate that when wearing the exoskeleton, the overall muscle frequency changes more slowly, suggesting that subjects can maintain activity for a longer duration before fatigue sets in. This control strategy effectively reduces the energetic cost of lower limb work for the wearer and enhances the exoskeleton's versatility in various applications. [ABSTRACT FROM AUTHOR]

Myofibers are large multinucleated cells that have long thought to have a rather simple organization. Single-nucleus transcriptomics, spatial transcriptomics and spatial metabolomics analysis have revealed distinct transcription profiles in myonuclei related to myofiber type. However, the use of local tissue collection or dissociation methods have obscured the spatial organization. To elucidate the full tissue architecture, we combine two spatial omics, RNA tomography and mass spectrometry imaging. This enables us to map the spatial transcriptomic, metabolomic and lipidomic organization of the whole murine tibialis anterior muscle. Our findings on heterogeneity in fiber type proportions are validated with multiplexed immunofluorescence staining in tibialis anterior, extensor digitorum longus and soleus. Our results demonstrate unexpectedly strong regionalization of gene expression, metabolic differences and variable myofiber type proportion along the proximal-distal axis. These new insights in whole-tissue level organization reconcile sometimes conflicting results coming from previous studies relying on local sampling methods. Multi-dimensional analysis of gene expression, myofiber types and metabolic activity in whole skeletal muscle reveals specific regionalization of gene expression and metabolites related to the glycolytic and oxidative potential of myofibers [ABSTRACT FROM AUTHOR]

Falls and fall-induced injuries are common and consequential in older adults. Ballet emphasizes full-body coordination, leg strength, and postural control. However, it remains unknown whether ballet can indeed reduce falls in older adults. This study examined biomechanical and neuromuscular responses of older recreational ballet dancers to an unexpected standing-slip. Twenty older ballet dancers (17 females, 3 males) and 23 age- and sex-matched nondancers (19 females, 4 males) were exposed to an unexpected slip during treadmill standing. The slip-faller rate was the primary outcome. The secondary outcomes were kinematic measurements, including dynamic gait stability, slip distance, and recovery stepping performance (step latency, duration, length, and speed). The tertiary outcome was the electromyography latency of leg muscles (bilateral tibialis anterior, medial gastrocnemius, rectus femoris, and biceps femoris). Fewer dancers fell than nondancers after the standing-slip (45% vs. 83%, P = 0.005, d = 0.970). Dancers displayed better stability at recovery foot liftoff (P = 0.006) and touchdown (P = 0.012), a shorter step latency (P = 0.020), shorter step duration (P = 0.011), faster step speed (P = 0.032), and shorter slip distance (P = 0.015) than nondancers. They also exhibited shorter latencies than nondancers for the standing leg rectus femoris (P = 0.028) and tibialis anterior (P = 0.002), and the stepping leg biceps femoris (P = 0.031), tibialis anterior (P = 0.017), and medial gastrocnemius (P = 0.030). The results suggest that older ballet dancers experience a lower fall risk and are more stable than nondancers following an unexpected standing-slip. The greater stability among dancers could be attributed to more biomechanically effective recovery stepping, possibly associated with the ballet-induced neuromuscular benefit—an earlier leg muscle activation. NEW & NOTEWORTHY: This is the first study to examine how older ballet dancers respond to an unexpected external slip perturbation while standing. The results suggest that older ballet dancers experience a reduced fall risk after the slip than their nondancer counterparts. The lower fall risk can be accounted for by dancers' quicker neuromuscular reactions to the slip that result in a more effective recovery step and thus higher stability against backward falls due to the slip. [ABSTRACT FROM AUTHOR]

Objective: To clarify the effect of growth and advancing age on lymphatic capillarization in rat skeletal muscles, we examined the histological and biochemical changes of lymphatic capillaries in different fiber types of skeletal muscles across juvenile, young, and middle‐aged generations. Methods: We collected the tibialis anterior (TA), extensor digitorum longus (EDL), and soleus (SOL) muscles. Immunohistochemical staining using LYVE‐1 and CD31 markers was used for lymphatic and blood capillaries, respectively. Real‐time PCR was used to analyze mRNA expression of lymphangiogenic factors. Results: The density of LYVE‐1‐positive lymphatic capillaries in the muscles peaked during the juvenile period and subsequently decreased with increasing age. In contrast to blood capillaries, fast‐twitch dominant muscles (i.e., TA and EDL) exhibited an age‐related decrease in lymphatic capillaries. Similar to blood capillaries, lymphatic capillaries were abundant in SOL, a slow‐twitch dominant muscle, which showed less susceptibility to age‐related lymphatic decline. The mRNA expression of lymphangiogenic factors was significantly upregulated in SOL and decreased in all muscles of middle‐aged rats. Conclusions: The age‐related decrease of lymphatic capillaries in fast‐twitch muscles might be associated with age‐related muscle atrophy. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effects of magnifying the damage caused by obesity induced by monosodium glutamate, using a model of maternal periodontitis, on the structure of the anterior tibialis muscle of the offspring. Materials and Methods: Twenty‐four female Wistar rats were divided into four experimental groups: control (n = 6), obese (n = 6), control with periodontitis (n = 6) and obese with periodontitis (n = 6). At 78 days of life, the rats were mated with males without any experimental intervention. The offspring of these rats (n = 1/L), at 120 days of life, were weighed and measured, then euthanized. Plasma was collected for analysis of cytokines IL‐6, IL‐10, IL‐17 and TNF‐α. Adipose tissues were collected and weighed, and the anterior tibial muscle was designated for histomorphological analyses (n = 6/group). Results: Monosodium glutamate offspring showed significant muscle changes, such as a reduction in the size of fibres and neuromuscular junctions, and an increase in the nucleus and capillaries. However, all these changes were more expressed in monosodium glutamate‐obese with periodontitis offspring. Conclusion: This leads us to suggest a magnifying effect promoted by periodontitis to the damage already well described by monosodium glutamate‐obesity, determined by low‐intensity inflammation, causing greater muscle damage. [ABSTRACT FROM AUTHOR]

Decoding the activity of individual neural cells during natural behaviours allows neuroscientists to study how the nervous system generates and controls movements. Contrary to other neural cells, the activity of spinal motor neurons can be determined non-invasively (or minimally invasively) from the decomposition of electromyographic (EMG) signals into motor unit firing activities. For some interfacing and neuro-feedback investigations, EMG decomposition needs to be performed in real time. Here, we introduce an open-source software that performs real-time decoding of motor neurons using a blind-source separation approach for multichannel EMG signal processing. Separation vectors (motor unit filters) are optimised for each motor unit from baseline contractions and then re-applied in real time during test contractions. In this way, the firing activity of multiple motor neurons can be provided through different forms of visual feedback. We provide a complete framework with guidelines and examples of recordings to guide researchers who aim to study movement control at the motor neuron level. We first vali- dated the software with synthetic EMG signals generated during a range of isometric contraction patterns. We then tested the software on data collected using either surface or intramuscular electrode arrays from five lower limb muscles (gastrocnemius lateralis and medialis, vastus later- alis and medialis, and tibialis anterior). We assessed how the muscle or variation of contraction intensity between the baseline contraction and the test contraction impacted the accuracy of the real-time decomposition. This open-source software provides a set of tools for neuroscientists to design experimental paradigms where participants can receive real-time feedback on the output of the spinal cord circuits. [ABSTRACT FROM AUTHOR]

Background: To study the effects of different interventions on automatic gait processing in contrast with voluntary gait processing in healthy subjects. Methods: A double-blind randomised controlled trial was designed (120 able-body persons between 18 and 65 years old entered and completed the study), with pre-intervention and post-intervention assessments using the 6-Minute Walk Test (6MWT). The participants were randomly distributed into four groups. Prior to intervention, all participants performed voluntary gait on the ground (VoG) in a calibrated circuit following the 6MWT. The presence of automatic gait (AG) was explored post-intervention without a voluntary demand in the same circuit following the 6MWT. Each group received a different intervention for 30 min: Vojta stimulation, MOTOMED® at no less than 60 revolutions/minute, treadmill walking at 3 km/h, and resting in a chair (control). The main assessment, conducted by a blinded rater, was the difference in distance covered (in meters) during the 6MWT between pre- and post-intervention. Surface electromyography (sEMG) average root mean square (RMS) signals in the right tibialis anterior, right soleus, right rectus femoris, and right biceps femoris were also considered outcome measures. Results: The Vojta group was the only one that initiated AG after the intervention (476.4 m ± 57.1 in VoG versus 9.0 m ± 8.9 in AG, p < 0.001) with comparable kinematics and EMG parameters during voluntary gait, except for ankle dorsal flexion. Within the Vojta group, high variability in kinematics, sEMG activity, and distance covered was observed. Conclusions: AG isolation is approachable through Vojta at only one session measurable with the 6MWT without any voluntary gait demand. No automatic gait effects were observed post-intervention in the other groups. Trial registration: NCT04689841 (ClinicalTrials.gov). [ABSTRACT FROM AUTHOR]

• qEMG showed superior sensitivity to MScanFit MUNE in detecting abnormalities in amyotrophic lateral sclerosis (ALS) at diagnosis. • MScanFit MUNE parameters exhibited good correlations with both muscle strength and qEMG measures in muscles of ALS patients. • MScanFit MUNE and qEMG offered complementary insights for ALS diagnosis. Motor Unit Number Estimation (MUNE) techniques are crucial in assessing lower motor neuron loss. MScanFit MUNE (MScanFit) is a novel tool which estimates MUNE values from compound muscle action potential (CMAP) scans by considering the probabilistic nature of motor unit firing. We conducted a prospective study to evaluate the diagnostic utility of MScanFit compared to quantitative electromyography (qEMG) in ALS patients. We enrolled 35 patients diagnosed with amyotrophic lateral sclerosis (ALS) and 14 healthy controls, assessing qEMG and MScanFit MUNE in abductor pollicis brevis, abductor digiti minimi and tibialis anterior muscles. We found higher sensitivity of qEMG in detecting abnormalities compared to MScanFit, with a high concordance rate between the two techniques. Notably, a few muscles exhibited abnormal MUNE but normal qEMG findings, suggesting a potential complementary role for MScanFit in ALS diagnosis. Neurophysiological parameters from MScanFit showed good correlations with qEMG measures. Subclinical neurophysiological involvement was observed in muscles with normal strength, emphasizing the importance of sensitive diagnostic tools. MScanFit demonstrated validity in distinguishing ALS patients from healthy subjects and correlated well with qEMG parameters. Our study confirmed the diagnostic utility of MScanFit MUNE in ALS, highlighting its role as a supplementary diagnostic tool. [ABSTRACT FROM AUTHOR]

The near-infrared spectroscopy (NIRS) vascular occlusion test (VOT) assesses microvascular reperfusion. Two strategies have been used to quantify reperfusion following reactive hyperemia, but it is unclear whether both yield similar results when comparing biological sex. This study aimed to determine whether sex differences in NIRS-based microvascular reperfusion are similarly apparent using the 10-s reactive hyperemia slope of the tissue saturation index (StO2) signal (slope 2) and the halftime to maximal reperfusion (T ½). Healthy, recreationally active males (n = 31) and females (n = 31) between 18 and 82 years took part in this study. A NIRS VOT was performed on the tibialis anterior muscle, and reperfusion was quantified using slope 2 (% s−1) and T ½ (s). Adipose tissue thickness (ATT) was higher in females (P = 0.009), which was associated with a lower StO2 (P = 0.001) and oxygenated hemoglobin (O2Hb) (P = 0.05) signal range. The StO2 slope 2 was significantly steeper in males versus females (P = 0.001) but not after correcting for ATT (P = 0.295). There were no sex differences in StO2 T ½ (P = 0.067) or O2Hb T ½ (P = 0.197). In a subset of males (n = 26) and females (n = 21) with similar ATT, there were no sex differences in StO2 slope 2 (P = 0.068), StO2 T ½ (P = 0.491), or O2Hb T ½ (P = 0.899). An ATT-corrected StO2 slope 2 or the T ½ approach is recommended for analysis of NIRS-based microvascular reperfusion when differences in ATT are present between sexes. NEW & NOTEWORTHY: Sex differences in near-infrared spectroscopy (NIRS)-based microvascular reperfusion have been previously reported. We found that greater adipose tissue thickness in females reduces kinetic measures of NIRS-based microvascular reperfusion. Sex differences are eliminated when performing an adipose tissue thickness correction, when the NIRS signal range is accounted for, or when adipose tissue thickness is similar between sexes. This highlights the importance of considering factors that affect NIRS signals, such as adipose tissue thickness, when drawing comparisons between groups. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of maturation on vertical jumping performance, in adolescent boys and girls, concerning plantar flexor activity and Achilles tendon (AT) stiffness. Thirty-nine adolescents were tested in a counter-movement jump (CMJ) at three different time points: 18 and 9 months before peak height velocity (PHV) and at PHV. The EMG activity of the medialis gastrocnemius (MG) and tibialis anterior (TA) muscles was evaluated, in relation to jump height. Boys showed higher jumping ability and AT stiffness than girls. Additionally, boys revealed increased eccentric (ecc) and concentric (con) MG activity, along with decreased ecc and con TA activity, near PHV. On the other hand, girls showed increased ecc and con TA/MG co-contraction compared to boys, mainly near PHV. In conclusion, a different mechanism of vertical jumping performance is adopted between early adolescent boys and girls. Nevertheless, no notable alterations in jumping capability were detected over time, indicating that the maturation process does not influence stretch-shortening cycle (SSC) performance. [ABSTRACT FROM AUTHOR]

Background and Objectives: Remodeling and healing of the graft are crucial processes for long-term graft survival after anterior cruciate ligament reconstruction (ACLR). However, few studies have objectively evaluated the differences in graft healing between autografts and allografts. This study aimed to compare the status of the anterior cruciate ligament (ACL) grafts between hamstring tendon (HT) autografts and tibialis anterior tendon (TAT) allografts using second-look arthroscopy. Materials and Methods: The outcomes of 193 consecutive patients (153 males and 40 females, with an average age of 30.38 and BMI of 25.43 kg/m2) who underwent second-look arthroscopy following primary ACLR were retrospectively reviewed. Prior to participating in this study, all patients provided written informed consent. The patients were divided into two groups: those with HT autografts and those with TAT allografts. Confounding factors were matched between the two groups using propensity score matching (PSM). ACL graft status was assessed during second-look arthroscopy using a numeric scale system based on the degree of four parameters: graft tension, continuity, synovium coverage, and vascular marking. Clinical outcomes were assessed using the Lysholm and International Knee Documentation Committee (IKDC) scores. Graft status and clinical outcomes were compared between the two groups. Additionally, a subgroup analysis based on the timing of the second-look arthroscopy (12–24 months vs. >24 months after the initial ACLR) was conducted. Results: After PSM, 62 patients were included in each group. The second-look arthroscopy was conducted at 23.6 ± 6.6 months for the HT group and at 24.0 ± 7.9 months for the TAT group (p = 0.749). The continuity and tension of the ACL graft were not significantly different between the two groups (p = 0.146 and 0.075, respectively). However, the TAT group exhibited significantly inferior synovial coverage and vascular marking of the ACL graft compared with the HT group (p = 0.021 and 0.007, respectively). These findings were consistent regardless of the timing of the second-look arthroscopy. Clinical outcomes, according to the Lysholm and IKDC scores, significantly improved in both groups with no significant differences (p = 0.386 and 0.733, respectively). Conclusions: Although there were no differences in graft tension and continuity between HT autografts and TAT allografts, the biological healing of ACL grafts, in terms of synovialization and vascularization, was superior in HT autografts compared to TAT allografts. [ABSTRACT FROM AUTHOR]

Introduction/Aims Methods Results Discussion Fat‐referenced magnetic resonance imaging (MRI) has emerged as a promising volumetric technique for measuring muscular volume and fat in neuromuscular disorders, but the experience in inflammatory myopathies remains limited. Therefore, this work aimed at describing how sporadic inclusion body myositis (sIBM) manifests on standardized volumetric fat‐referenced MRI muscle measurements, including within‐scanner repeatability, natural progression rate, and relationship to clinical parameters.Ten sIBM patients underwent whole‐leg Dixon MRI at baseline (test–retest) and after 12 months. The lean muscle volume (LMV), muscle fat fraction (MFF), and muscle fat infiltration (MFI) of the quadriceps, hamstrings, adductors, medial gastrocnemius, and tibialis anterior were computed. Clinical assessments of IBM Functional Rating Scale (IBMFRS) and knee extension strength were also performed. The baseline test–retest MRI measurements were used to estimate the within‐subject standard deviation (sw). 12‐month changes were derived for all parameters.The MRI measurements showed high repeatability in all muscles; sw ranged from 2.7 to 18.0 mL for LMV, 0.7–1.3 percentage points (pp) for MFF, and 0.2–0.7 pp for MFI. Over 12 months, average LMV decreased by 7.4% while MFF and MFI increased by 3.8 pp and 1.8 pp, respectively. Mean IBMFRS decreased by 2.4 and mean knee extension strength decreased by 32.8 N.The MRI measurements showed high repeatability and 12‐month changes consistent with muscle atrophy and fat replacement as well as a decrease in both muscle strength and IBMFRS. Our findings suggest that fat‐referenced MRI measurements are suitable for assessing disease progression and treatment response in inflammatory myopathies. [ABSTRACT FROM AUTHOR]

Purpose: We previously reported that a Hammerobics exercise using weights can enhance trunk and lower extremity muscles, some studies suggested that training effects could also be expected without heavy weights. If the muscle activity induced by Hammerobics swinging with a 'light plastic ball' equals or surpasses that of the isometric static squat and synchronized squat with a heavy ball, this training approach could alleviate joint strain, fostering an exercise regimen universally accessible across generations, benefit for workouts sports and rehabilitation. Methods: Fifteen healthy men participated in this study. By using surface electromyography, muscle activities for the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, rectus femoris, biceps femoris long head, semitendinosus, gluteus maximus, multifidus, and internal oblique muscles were measured during a light Hammerobics synchronized squat (HSS-light), Hammerobics synchronized squat, and conventional isometric squat, and statistically compared. Results: The front-to-back tibialis anterior activity of HSS-light was significantly higher than that of conventional isometric squat. The activities of all other muscles, except for the multifidus, were not significantly different between these exercises in the front-to-back and back-to-front phases. Compared to the Hammerobics synchronized squat, the light Hammerobics synchronized squat showed no differences in front-to-back tibialis anterior, rectus femoris, biceps femoris long head, and internal oblique activities and back-to-front abductor hallucis, tibialis anterior, rectus femoris, and internal oblique activities. Conclusion: The HSS-light could stimulate muscles to the same level as the conventional isometric squat without weight bearing. While the HSS-light was less effective than the Hammerobics synchronized squat, there was no significant difference in internal oblique, rectus femoris, and tibialis anterior activities between these exercises. Hence, the HSS-light is an exercise method that can be viable approach to promoting accessible workouts sports and rehabilitation. [ABSTRACT FROM AUTHOR]

Task-specific focal dystonia (TSFD), characterized by the loss of fine motor control and coordination, affects drummers' lower-limb movements. This study explores lower-limb dystonia's impact on drumming performance and underlying muscle activity in a professional rock drummer. The drummer executed an eight-beat pattern on a drum kit. The participant reported the occurrence of symptoms when he felt the abnormality such as the loss of control related to involuntary aspects of movement. We measured the peak amplitude of the bass drumhead vibration, synchronization errors as the time elapsed between the metronome onset and the bass drum onset, and amplitude of electromyographic (EMG) recordings centered on metronome beat. Dystonia symptoms primarily manifested in the initial beat, with fewer symptoms on syncopation of the third beat. Analysis revealed decreased bass-drum peak amplitude and earlier synchronization error during the initial beat. EMG measurements of 10 muscles in the affected right lower limb showed significant changes in the Biceps Femoris (BF), Tibialis Anterior (TA), Extensor Digitorum Longus (EDL), and Extensor Digitorum Brevis (EDB) muscles during symptom onset. We observed (1) earlier overactivation of the TA and EDL muscles during the leg lift-up motion or preparatory phase of pedaling, (2) reduced activation of the EDB muscle, and (3) increased activation of the BF muscle during the final pedaling movement when symptoms occurred. These findings suggest that lower-limb dystonia symptoms are characterized by a reduction in amplitude of the bass drumhead vibration and an increase in synchronization error, potentially due to premature overactivation of the ankle dorsiflexor muscles. [ABSTRACT FROM AUTHOR]

Skeletal muscle injury affects the quality of life in many pathologies, including volumetric muscle loss, contusion injury, and aging. We hypothesized that the nicotinamide phosphoribosyltransferase (Nampt) activator P7C3 improves muscle repair following injury. In the present study, we tested the effect of P7C3 (1‐anilino‐3‐(3,6‐dibromocarbazol‐9‐yl) propan‐2‐ol) on chemically induced muscle injury. Muscle injury was induced by injecting 50 µL 1.2% barium chloride (BaCl2) into the tibialis anterior (TA) muscle in C57Bl/6J wild‐type male mice. Mice were then treated with either 10 mg/kg body weight of P7C3 or Vehicle intraperitoneally for 7 days and assessed for histological, biochemical, and molecular changes. In the present study, we show that the acute BaCl2‐induced TA muscle injury was robust and the P7C3‐treated mice displayed a significant increase in the total number of myonuclei and blood vessels, and decreased serum CK activity compared with vehicle‐treated mice. The specificity of P7C3 was evaluated using Nampt+/− mice, which did not display any significant difference in muscle repair capacity among treated groups. RNA‐sequencing analysis of the injured TA muscles displayed 368 and 212 genes to be exclusively expressed in P7C3 and Veh‐treated mice, respectively. There was an increase in the expression of genes involved in cellular processes, inflammatory response, angiogenesis, and muscle development in P7C3 versus Veh‐treated mice. Conversely, there is a decrease in muscle structure and function, myeloid cell differentiation, glutathione, and oxidation–reduction, drug metabolism, and circadian rhythm signaling pathways. Chromatin immunoprecipitation‐quantitative polymerase chain reaction (qPCR) and reverse transcription‐qPCR analyses identified increased Pax7, Myf5, MyoD, and Myogenin expression in P7C3‐treated mice. Increased histone lysine (H3K) methylation and acetylation were observed in P7C3‐treated mice, with significant upregulation in inflammatory markers. Moreover, P7C3 treatment significantly increased the myotube fusion index in the BaCl2‐injured human skeletal muscle in vitro. P7C3 also inhibited the lipopolysaccharide‐induced inflammatory response and mitochondrial membrane potential of RAW 264.7 macrophage cells. Overall, we demonstrate that P7C3 activates muscle stem cells and enhances muscle injury repair with increased angiogenesis. [ABSTRACT FROM AUTHOR]

Dynamic muscle fatigue during repetitive movements can lead to changes in communication between the central nervous system and peripheral muscles. This study investigated these changes by examining electromyogram (EMG) characteristics from agonist and antagonist muscles during a fatiguing task. Twenty-two healthy male university students (age: 22.92 ± 2.19 years) performed heel raises until fatigue. EMG signals from lateral gastrocnemius (GL) and tibialis anterior (TA) muscles were processed using synchrosqueezed wavelet transform (SST). Root mean square (RMS), mean frequency (MF), power across frequency ranges, wavelet coherence, and co-activation ratio were computed. During the initial 80% of the task, RMS and EMG power increased for both muscles, while MF declined. In the final 20%, GL parameters stabilized, but TA showed significant decreases. Beta and gamma intermuscular coherence increased upon reaching 60% of the task. Alpha coherence and co-activation ratio remained constant. Results suggest that the central nervous system adopts a differentiated control strategy for agonist and antagonist muscles during fatigue progression. Initially, a coordinated "common drive" mechanism enhances both muscle groups' activity. Later, despite continued increases in muscle activity, neural-muscular coupling remains stable. This asynchronous, differentiated control mechanism enhances our understanding of neuromuscular adaptations during fatigue, potentially contributing to the development of more targeted fatigue assessment and management strategies. [ABSTRACT FROM AUTHOR]

This study aimed to identify changes in the architecture and performance of the peri‐ankle muscles in patients with chronic ankle instability (CAI) and investigate the relationship between them. In total, 17 subjects were evaluated retrospectively. Each subject underwent anthropometric and isokinetic test, and peroneus longus (PL) and brevis (PB), medial gastrocnemius (MGCM), and tibialis anterior (TA) ultrasound imaging were performed at rest and maximum voluntary contraction (MVC) conditions. Regarding muscle architectural variables, the pennation angle (PA) of the MGCM at rest and the PA of the TA, MGCM, and PL in MVC were significantly reduced on the injured side compared to the intact side. There were no significant differences in muscle thickness of PL, PB, MGCM, and TA observed between intact and injured side during both rest and MVC. Regarding muscle performance parameters, significant decreased were observed in the muscle strength for both limbs in all four directions under the two different conditions. A secondary finding was that the relative PA ratio of the TA showed moderate correlation with the relative dorsiflexion ratio at 30°/s. These findings can provide opportunities to better understand how injuries in patients with CAI may be related to changes in ankle and foot function. [ABSTRACT FROM AUTHOR]

We studied simultaneous EMG and midline EEG responses, including over the cerebellum, in 10 standing subjects (35 ± 15 yr; 5 females, 5 males). Recordings were made following repeated taps to the sternum, stimuli known to evoke short-latency EMG responses in leg muscles, consistent with postural reflexes. EEG power had relatively more high-frequency components (>30 Hz) when recorded from electrodes over the cerebellum (Iz and SIz) compared with other midline electrodes. We confirmed a previous report using a similar stimulus that evoked short-latency potentials over the cerebellum. We showed clear midline-evoked EEG potentials occurring at short latency over the cerebellum (P23, N31, N42, and P54) and frontally (N28 and N57) before the previously described perturbation-evoked potential (P1/N1/P2). The P23 response correlated with the subsequent EMG response in the tibialis anterior muscles (r = 0.72, P = 0.018), confirming and extending previous observations. We did not find a correlation with the N1 amplitude. We conclude that early activity occurs from electrodes over the inion in response to a brief tap to the sternum. This is likely to represent cerebellar activity and it appears to modulate short-latency postural EMG responses. NEW & NOTEWORTHY: We studied the effects of a brief tap to the sternum in human subjects, known to evoke short-latency postural responses. Using an extended EEG recording system, we showed early evoked responses over the midline cerebellum, including the P23 potential, which correlated with the EMG responses in tibialis anterior, consistent with a cerebellar role in postural reflexes. The stimulus also evoked later EEG responses, including the perturbation potential. [ABSTRACT FROM AUTHOR]

This study investigated the coactivation of plantar flexor and dorsiflexor muscles and oxygen uptake during running with forefoot and rearfoot strikes at 15 and 19 km/h. We included 16 male runners in this study. The participants ran each foot strike pattern for 5 min at 15 and 19 km/h on a treadmill. During the running, respiratory gas exchange data and surface electromyographic (EMG) activity of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus, and tibialis anterior muscles of the right lower limb were continuously recorded. The indices of oxygen uptake, energy expenditure (EE), and muscle activation were calculated during the last 2 min in each condition. During the stance phase of running at 15 and 19 km/h, activation of the tibialis anterior and MG muscles was lower and higher, respectively, with forefoot strike than with rearfoot strike. The foot strike pattern did not influence the oxygen uptake. These results suggest that the foot strike pattern has no clear effect on the oxygen uptake when running at 15 and 19 km/h. However, forefoot strike leads to plantar flexion dominance during co‐contraction of the tibialis anterior and MG muscles, which are an antagonist and agonist for plantar flexion, respectively, during the stance phase. [ABSTRACT FROM AUTHOR]

Background: Thoracolumbar transcutaneous spinal cord stimulation (tSCS) non-invasively evokes posterior root-muscle reflexes (PRMR) with the aim of neuromodulating sensorimotor function following spinal cord injury. Research is still in its infancy regarding the effect of body position on the nature of these spinally evoked responses. Therefore, the aim of this study was to investigate the influence of body position on the nature of PRMR responses during tSCS. Methods: A total of 11 (6M, 5F) participants completed a full PRMR recruitment curve from 10 ma up to 120 ma (10 ma increments) at the T11/12 intervertebral space using a singular 3.2 cm diameter cathode. At each intensity, three paired pulses (50 ms inter-pulse interval), followed by three singular pulses with a six-second delay were applied in each body position (supine, supine 90-90, sitting and standing) in a randomised order. The PRMR responses in lower limb muscles were recorded using wireless electromyographic sensors placed on the Soleus, Tibialis Anterior, Rectus Femoris and Bicep Femoris long head. A two-way (body position × muscle) repeated measures analysis of variance was used to investigate the effect of body position on PRMR-evoked responses. Results: There was a significant main effect of body position on PRMR resting motor threshold (RMT) (p < 0.001), first response peak-to-peak amplitude (p = 0.003) and percentage post-activation depression (%PAD) (p = 0.012). Sitting had significantly higher RMT and significantly lower first response peak-to-peak amplitudes compared to all other positions, but significant differences in %PAD were only detectible between supine and standing. Conclusions: Body position influences the nature of PRMR-evoked responses during tSCS. [ABSTRACT FROM AUTHOR]

The functional role of intrinsic foot muscles in the control of standing balance is often overlooked in rehabilitation, partly because the interactions with ankle muscles are poorly understood. How does coactivation of Flexor Digitorum Brevis (FDB) and soleus (SOL) vary across standing tasks of increasing difficulty. Postural sway (Centre of Pressure, CoP) and the electromyographic (EMG) activity of FDB, SOL, Medial Gastrocnemius (MG) and Tibialis Anterior (TA) were measured during bipedal standing, tandem stance, one-legged balance, and standing on toes. Coherence of the rectified EMG signals for SOL and FDB in two bandwidths (0–5 and 10–20 Hz) was calculated as a coactivation index. The CoP sway and the EMG activity of all muscles was greater (P<0.05) for the three difficult tasks. Significant coherence between the SOL and FDB EMG activity was found in both frequency regions: 0–5 and 10–20 Hz. The coherence integral increased with the difficulty of the postural task, especially in the 10–20 Hz band. The findings underscore the important role of FDB in the control of standing balance across tasks and its coactivation with SOL. Clinical recommendations to improve balance control need to consider the interaction between the plantar flexor and intrinsic-foot muscles. • Greater intermuscular coherence in electromyogram recordings observed in challenging tasks. • Increased concurrent activation of Flexor Digitorum Brevis and Soleus in two frequency bands. • Flexor Digitorum Brevis muscle has a critical role in maintaining standing balance. • Concurrent modulation of activity in the plantar flexor and intrinsic foot muscles is crucial for balance control. [ABSTRACT FROM AUTHOR]

Motoneuronal persistent inward currents (PICs) are facilitated by neuromodulatory inputs but are highly sensitive to local inhibitory circuits. Estimates of PICs are reduced by group Ia reciprocal inhibition, and increased with the diffuse actions of neuromodulators released during remote muscle contraction. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit discharge patterns and estimated PICs during voluntary co‐contraction of ankle muscles, which simultaneously demands the contraction of agonist–antagonist pairs. Twenty participants performed triangular ramps of both co‐contraction (simultaneous dorsiflexion and plantar flexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high‐density surface EMG activity recorded from tibialis anterior using blind source separation algorithms. Voluntary co‐contraction altered motor unit discharge rate characteristics. Discharge rate at recruitment and peak discharge rate were modestly reduced (∼6% change; P < 0.001; d = 0.22) and increased (∼2% change; P = 0.001, d = −0.19), respectively, in the entire dataset but no changes were observed when motor units were tracked across conditions. The largest effects during co‐contraction were that estimates of PICs (ΔF) were reduced by ∼20% (4.47 vs. 5.57 pulses per second during isometric dorsiflexion; P < 0.001, d = 0.641). These findings suggest that, during voluntary co‐contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co‐contraction of the antagonist muscle, which constrains PIC behaviour. Key points: Voluntary co‐contraction is a unique motor behaviour that concurrently provides excitatory and inhibitory synaptic input to motoneurons.Co‐contraction of agonist–antagonist pairs alters agonist motor unit discharge characteristics, consistent with reductions in persistent inward current magnitude. [ABSTRACT FROM AUTHOR]

• Tc-MEP are important to prevent intraoperative neurological deficit. • Post-tetanic Tc-MEPs (p-MEP) can augment the amplitudes of CMAPs. • Patients with preoperative motor deficit with MMT 3 and below highly needed p-MEP. • Using p-MEP in such cases increases the success rate of baseline MEP monitoring. Transcranial electrical stimulation motor-evoked potentials (Tc-MEPs) are the current trend and are important in preventing intraoperative neurological deficits. Posttetanic Tc-MEPs (p-MEP) can augment the amplitudes of compound muscle active potentials (CMAPs), especially in the case of insufficient conventional Tc-MEPs (c-MEP). To retrospectively investigate pre- and intraoperative factors necessitating p-MEP monitoring and to examine changes in the success rates of baseline Tc-MEP monitoring before and after tetanic stimulation in patients with such factors. Retrospective observational study. Patients (n=184) who underwent spinal surgery with Tc-MEP monitoring in our department between August 2020 and July 2022. Manual muscle testing (MMT) scores were calculated to identify patients with preoperative motor deficits. c-MEP and p-MEP amplitudes were recorded from the defined muscles. We compared preoperative and intraoperative factors between the c-MEP and p-MEP groups (study 1). In cases where the factors were identified, we investigated the success rate of the baseline MEP measurement of each muscle before and after tetanic stimulation (study 2). One hundred fifty-seven patients were included. Of those, 87 showed sufficient CMAPs with c-MEP. Meanwhile, 70 needed p-MEP because of insufficient CMAPs. In univariate analysis, cervical/thoracic surgery (p<.001), preoperative MMT 3 or below (p=.009), shorter duration of illness (p=.037), previous cerebrovascular disease (p=.014), and dialysis (p=.031) were significantly associated with p-MEP group. Preoperative MMT 3 or below was the only factor requiring p-MEP (odds ratio, 3.34; 95% confidence interval, 1.28-8.73, p=.014) in multivariate analysis. In the p-MEP group, 24 patients had preoperative motor deficits; 16 patients with complete data were included in the analysis (study 2). The success rates of MEP monitoring before and after tetanic stimulation of the entire lower-extremity muscles were 42.7 and 57.3%, respectively (p<.001). The success rates for each muscle before and after tetanic stimulation were abductor pollicis brevis: 81.3% and 96.9%, tibialis anterior: 34.4% and 50.0%, gastrocnemius: 25% and 40.6%, and abductor hallucis: 68.8% and 81.3%, respectively. No significant differences were observed in success rates for any of the muscles. Patients with preoperative MMT 3 or below highly needed p-MEP. The success rate of baseline MEP monitoring increased with tetanic stimulation, even in patients with preoperative motor deficits. We believe that p-MEP monitoring can result in reliable CMAP recording, especially in cases of preoperative motor deficits with MMT scores of 3 or below. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is one of the key signaling factors regulating skeletal muscle adaptation to muscle contractions. Eccentric (ECC) and concentric (CONC) contractions drive different muscle adaptations with ECC resulting in greater changes. The present investigation tested the hypothesis that ECC produces higher cytosolic and mitochondrial H2O2 concentrations [H2O2] and alters gene expression more than CONC. Cytosolic and mitochondrial H2O2-sensitive fluorescent proteins, HyPer7 and MLS-HyPer7, were expressed in the anterior tibialis muscle of C57BL6J male mice. Before and for 60 min after either CONC or ECC (100 Hz, 50 contractions), [H2O2]cyto and [H2O2]mito were measured by in vivo fluorescence microscopy. RNA sequencing was performed in control (noncontracted), CONC, and ECC muscles to identify genes impacted by the contractions. [H2O2]cyto immediately after ECC was greater than after CONC (CONC: +6%, ECC: +11% vs. rest, P < 0.05) and remained higher for at least 60 min into recovery. In contrast, the elevation of [H2O2]mito was independent of the contraction modes (time; P < 0.0042, contraction mode; P = 0.4965). The impact of ECC on [H2O2]cyto was abolished by NADPH oxidase 2 (Nox2) inhibition (GSK2795039). Differentially expressed genes were not present after CONC or ECC + GSK but were found after ECC and were enriched for vascular development and apoptosis-related genes, among others. In conclusion, in mouse anterior tibialis, ECC, but not CONC, evokes a pronounced cytosolic H2O2 response, caused by Nox2, that is mechanistically linked to gene expression modifications. NEW & NOTEWORTHY: This in vivo model successfully characterized the effects of eccentric (ECC) and concentric (CONC) contractions on cytosolic and mitochondrial [H2O2] in mouse skeletal muscle. Compared with CONC, ECC induced higher and more sustained [H2O2]cyto—an effect that was abolished by Nox2 inhibition. ECC-induced [H2O2]cyto elevations were requisite for altered gene expression. [ABSTRACT FROM AUTHOR]

Repetitive passive movement (RPM) enhances reciprocal inhibition. RPM is more effective when performed rapidly and at wide joint angles. However, patients with limited joint range of motion may not receive the most effective RPM. Therefore, having an alternative method for performing RPM in patients who cannot perform actual exercise due to limited joint motion is necessary. This study investigated the effects of RPM on spinal excitability using a visual kinesthetic illusion. Participants included 17 healthy adults (7 women). Measurements were taken before, during, and immediately after the intervention. We established two intervention conditions: the control condition, in which participants focused their attention forward, and the illusion condition, in which participants watched a video about RPM. F-waves from the tibialis anterior and soleus muscles were measured, and F-wave persistence and F/M amplitude ratios were analyzed. Under the illusion condition, compared with the preintervention condition, the F/M amplitude ratio of the tibialis anterior increased by approximately 44% during the intervention (p < 0.05), whereas the F-wave persistence of the soleus decreased by approximately 23% from the immediate start of the intervention (p < 0.05). This study suggests that a visual kinesthetic illusion can increase the spinal excitability of the tibialis anterior, whereas reciprocal inhibition can decrease the spinal excitability of the soleus. [ABSTRACT FROM AUTHOR]

Background: Previous studies have found that inhibitory priming with continuous theta burst stimulation (cTBS) can enhance the effect of subsequent excitatory conditioning stimuli with intermittent theta burst stimulation (iTBS) in the upper limbs. However, whether this combined stimulation approach elicits a comparable compensatory response in the lower extremities remains unclear. This study aimed to investigate how cTBS preconditioning modulated the effect of iTBS on motor cortex excitability related to the lower limb in healthy individuals. Methods: Using a randomised cross-over design, a total of 25 healthy participants (19 females, mean age = 24.80 yr) were recruited to undergo three different TBS protocols (cTBS + iTBS, sham cTBS + iTBS, sham cTBS + sham iTBS) in a random order. Each TBS intervention was administered with one-week intervals. cTBS and iTBS were administered at an intensity of 80% active motor threshold (AMT) delivering a total of 600 pulses. Before intervention (T0), immediately following intervention (T1), and 20 min after intervention (T2), the corticomotor excitability was measured for the tibialis anterior muscle of participants' non-dominant leg using a Magneuro100 stimulator and matched double-cone coil. The average amplitude of the motor-evoked potential (MEP) induced by applying 20 consecutive monopulse stimuli at an intensity of 130% resting motor threshold (RMT) was collected and analysed. Results: Compare with T0 time, the MEP amplitude (raw and normalised) at T1 and T2 showed a statistically significant increase following the cTBS + iTBS protocol (p < 0.01), but no significant differences were observed in amplitude changes following other protocols (sham cTBS + iTBS and sham cTBS + sham iTBS) (p > 0.05). Furthermore, no statistically significant difference was found among the three protocols at any given time point (p > 0.05). Conclusions: Preconditioning the lower extremity motor cortex with cTBS prior to iTBS intervention can promptly enhance its excitability in healthy participants. This effect persists for a minimum duration of 20 min. [ABSTRACT FROM AUTHOR]

This paper presents Part 2 of a study that investigated the effects of an 8-week (3x/week) underwater treadmill (UT) walking intervention on knee osteoarthritis (KOA) outcomes in 6 adults with KOA (62.7 ± 14.2 years). The Knee Outcome Survey (KOS) for activities of daily living and muscle activity during a 10-m walk and a 20 cm step down were measured before and after the intervention. The following KOS measures improved after the UT walking program (p < 0.05; g > 0.8): stiffness, swelling, weakness, walking, going up stairs, going downstairs, kneeling on the front of the knee, squatting, and sitting with the knee bent. Knee flexion excursion during stance of walking increased after the UT walking intervention (p = .01). Co-activation between the tibialis anterior and medial gastrocnemius decreased during the 20 cm step down (p = .04). The findings of this study support using the WWE as a model for UT walking interventions in KOA. [ABSTRACT FROM AUTHOR]

The objective was to investigate the effects of running shoes with midsole hollow structure span and height on the biomechanics of the lower limbs during running. We collected 21 adults with running habits who wore two pairs of running shoes with different midsole hollow structures and ran at a speed of 3.3m/s on a force-measuring treadmill. The lower limb kinematics, ground reaction force (GRF) and lower limb muscle activation characteristics were simultaneously captured by a motion capture system, a 3D force treadmill, and a surface electromyography (sEMG) system. Paired t-tests were performed on data for the two shoe conditions that fit the normal distribution assumptions; otherwise, Wilcoxon signed-rank tests were used. The statistical parameter mapping (SPM) technology was used for the analysis of 1D parameters of kinematic, dynamic, and sEMG activation characteristics. The result showed that the time to the peak impact force at touchdown of Hollow shoe2 was significantly increased (P<0.01), the maximum loading rate (P<0.01) and average loading rate (P<0.05) were significantly reduced, braking time (P<0.05), push time (P<0.05), contact time (P<0.01) of Hollow shoe2 were significantly increased compared with Hollow shoe1. Hollow shoe2 push phase of the tibialis anterior muscle activation characteristics was significantly lower (SPM, P<0.05) than Hollow shoe1. Our conclusion is that running shoes offer the solution as they have the advantage of the complex structure of the hollow midsole. [ABSTRACT FROM AUTHOR]

Summary A reduction of physiological muscle atonia during rapid eye movement sleep is characteristic in patients with rapid eye movement sleep behaviour disorder, however, it can also be found in narcolepsy patients. We evaluated rapid eye movement sleep associated electromyographic activity to set cut‐off values of rapid eye movement sleep without atonia, differentiating rapid eye movement sleep behaviour disorder and narcolepsy patients from controls to enable more precise future diagnostic criteria for these disorders. We retrospectively analysed polysomnography recordings of 16 rapid eye movement sleep behaviour disorder patients, 15 narcolepsy patients, and 19 controls. The combination of phasic and tonic electromyographic activity was recorded in the mentalis and tibialis anterior muscles and analysed in 3 second miniepochs. The cut‐off value for a diagnosis of rapid eye movement sleep behaviour disorder was 17.07% (100% sensitivity, 94.7% specificity, area under the curve 0.997). For the diagnosis of narcolepsy, we yielded a cut‐off value of 8.4% (86.4% sensitivity, 68.4% specificity, area under the curve 0.850). Rapid eye movement sleep without atonia significantly (p = 0.046) increased in the second night half in rapid eye movement sleep behaviour disorder patients, while it remained moderately increased in the narcolepsy group. Polysomnographic evaluation proves significantly higher rates of rapid eye movement sleep without atonia in rapid eye movement sleep behaviour disorder than in narcolepsy patients, allowing differentiation from controls with high sensitivity and specificity. An increase throughout the night is characteristic for rapid eye movement sleep behaviour disorder, whereas a consistent elevation is typical in narcolepsy patients. [ABSTRACT FROM AUTHOR]

Background: Dynamic knee valgus (DKV) is a risk factor for non-contact anterior cruciate ligament (ACL) injuries. Understanding the changes in the electromyographic activity of the lower extremity muscles in individuals with DKV helps trainers design ACL injury prevention exercises. Therefore, the present meta-analysis aimed to investigate the muscle activation of the lower limb muscles in individuals with DKV during single-leg and overhead squats. Methods: Articles with titles, abstracts, and full texts were searched and screened independently by two reviewers in the Web of Science, Scopus, PubMed, and Google Scholar databases, without restrictions on publication date and in English using specified keywords from their inception to January 5, 2024. The quality of articles was evaluated using a modified version of the Downs and Black quality checklist. This meta-analysis used mean difference (MD) to compare the muscle activity patterns between individual with DKV and healthy individuals. Heterogeneity was detected using I-square (I2) test. Results: In total, four papers with 130 participants were included in the study. Evidence showed a significant difference between the DKV group and the healthy group regarding the activities of the adductor magnus (MD: 6.25, P < 0.001), vastus medialis (MD: 13.23, P = 0.002), vastus lateralis (MD: 11.71, P = 0.004), biceps femoris (MD: 3.06, P = 0.003), and tibialis anterior muscles (MD: 8.21, P = 0.02). Additionally, muscle activity in the DKV group was higher than that in the healthy group. Conclusions: This meta-analysis reveals distinct muscle activation patterns in individuals with dynamic knee valgus (DKV), with increased activity in key muscles suggesting compensatory responses. These findings underscore the need for targeted rehabilitation to address muscle imbalances and improve knee stability. [ABSTRACT FROM AUTHOR]

Featured Application: The main practical application of this research is the presentation of a new type of outdoor fitness equipment (OFE) available to both trainers and users, with scientific support regarding its ability to recruit the desired muscles in a similar way to conventional gym machinery. In addition, it was possible to improve the effectiveness of the OFE by including an intensity regulation system, thus allowing the principle of intensity progression to be considered, as well as increasing the control of training intensity in this type of machinery. This study compares the electromyographic activity (EMG) of different muscle groups (rectus femoris, vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius) of the lower limbs when performing a traditional seated leg press (SLP) with a classic piece of outdoor fitness equipment (OFE-SLP), and with a new OFE leg press that allows the user to adjust the intensity of the exercise by means of a selectorized system (BIOFIT-LP). It was found that the EMG of the OFE-SLP was significantly lower than that of the SLP, but similar activations to those of the SLP were achieved with the BIOFIT-LP. In conclusion, the inclusion of a system to be able to change intensity of the exercise in OFE achieves an EMG activity similar to traditional machinery in trained young men. [ABSTRACT FROM AUTHOR]

Purpose: Review the literature and describe the complications associated with each of the anterior tibial tendon transfer (ATTT) techniques described. Methods: A systematic review of the literature was performed with the keywords ''clubfoot", ''Ponseti" and ''anterior tibial". Studies in patients with clubfoot recurrence, who underwent ATTT, whose method of tendon fixation was different from the classical method, were included. Results: Six studies were included in this systematic review, which described multiple techniques for tibialis anterior fixation: bone anchors, interference screws, endobotton, K-wires, transosseous suture, and suture to the plantar fascia. In the papers that described postoperative complications, no major complications were reported, however the samples are generally small. Conclusion: Several options have now emerged for tendon fixation in tendon transfers around the foot and ankle, including ATTT for treatment of relapsed clubfoot. To our knowledge this is the first paper that questioned the potential complications associated with the use of these new techniques. Due to the scarcity of published works in favor of other fixation methods, we believe that the traditional method is the optimal one for the transfer of the tendon of the tibialis anterior muscle. [ABSTRACT FROM AUTHOR]

AbstractThe pharmacokinetics and tissue distribution of renadirsen sodium, a dystrophin exon-skipping phosphorothioate-modified antisense oligonucleotide with 2’-O,4’-C-ethylene-bridged nucleic acid (ENA), after subcutaneous or intravenous administration to cynomolgus monkeys were investigated. The plasma concentration of renadirsen after subcutaneous administration at 1, 3, and 10 mg/kg increased with the dose. The absolute bioavailability at 3 mg/kg after subcutaneous administration was calculated as 88.6%, and the time to reach maximum plasma concentration of renadirsen was within 4 h, indicating the efficient and rapid absorption following subcutaneous administration. The exposure of muscle tissues to renadirsen was found to increase with repeated dosing at 6 mg/kg, and higher exposure was observed in the diaphragm and heart than in the quadriceps femoris and anterior tibialis muscles. Renadirsen achieved more exon 45-skipped dystrophin mRNA in the diaphragm and heart than in the quadriceps femoris and anterior tibialis muscles. Renadirsen also showed a cumulative skipping effect in a repeated-dose study. The findings on exon 45-skipped dystrophin mRNA in these muscle tissues were consistent with the concentration of renadirsen in these tissues. Because it is not feasible to directly evaluate drug concentration and exon skipping in the heart and diaphragm in humans, the pharmacokinetics and pharmacodynamics of renadirsen in these tissues in monkeys are crucial for the design and interpretation of clinical settings. [ABSTRACT FROM AUTHOR]

Background: We aimed to elucidate the quantitative relationship between the neuromuscular blockade depth and intraoperative motor-evoked potential amplitudes. Methods: This prospective, single-arm, open-label, observational study was conducted at a single university hospital in Seoul, Korea, and included 100 adult patients aged ≥19 years undergoing brain tumor removal surgery under general anesthesia. We measured the neuromuscular blockade degree and motor-evoked potential amplitude in the deltoid, abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles until dural opening. Results: The pharmacokinetic-pharmacodynamic model revealed the exposure-response relationship between the rocuronium effect-site concentration and motor-evoked potential amplitudes. The mean motor-evoked potential amplitudes decreased proportionally with increasing neuromuscular blockade depth. As the mean amplitude increased, the coefficient of variation decreased bi-exponentially. The critical ratio of the first evoked response to the train-of-four stimulation (T1)/control response (Tc) thresholds beyond which the coefficient of variation exhibited minimal change were found to be 0.63, 0.65, 0.68, and 0.63 for the deltoid, abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles, respectively. Conclusions: Our results reveal that the motor-evoked potential amplitude exhibits deterioration proportional to the degree of neuromuscular blockade. In light of the observed bi-exponential decline of the coefficient of variation with the motor-evoked potential amplitude, we recommend maintaining a T1/Tc ratio higher than 0.6 for partial neuromuscular blockade. [ABSTRACT FROM AUTHOR]

Previous research has primarily focused on evaluating the activity of individual muscles in dancers, often neglecting their synergistic interactions. Investigating the differences in lower limb muscle synergy during landing between dancers and healthy controls will contribute to a comprehensive understanding of their neuromuscular control patterns. This study enrolled 22 Latin dancers and 22 healthy participants, who performed a task involving landing from a 30 cm high platform. The data were collected using Vicon systems, force plates, and electromyography (EMG). The processed EMG data were subjected to non-negative matrix factorization (NNMF) for decomposition, followed by classification using K-means clustering algorithm and Pearson correlation coefficients. Three synergies were extracted for both Latin dancers and healthy participants. Synergy 1 showed increased contributions from the tibialis anterior (p < 0.001) and medial gastrocnemius (p = 0.024) in Latin dancers compared to healthy participants. Synergy 3 highlighted significantly greater contributions from the vastus lateralis in healthy participants compared to Latin dancers (p = 0.039). This study demonstrates that Latin dancers exhibit muscle synergies similar to those observed in healthy controls, revealing specific adjustments in the tibialis anterior and medial gastrocnemius muscles among dancers. This research illustrates how dancers optimize control strategies during landing tasks, offering a novel perspective for comprehensively understanding dancers' neuromuscular control patterns. [ABSTRACT FROM AUTHOR]

Background: Neuromuscular electrical stimulation (NMES) can generate muscle contractions and elicit excitability of neural circuits. However, the optimal stimulation frequency for effective neuromodulation remains unclear. Methods: Eleven able‐bodied individuals participated in our study to examine the effects of: (1) low‐frequency NMES at 25 Hz, (2) high‐frequency NMES at 100 Hz; and (3) mixed‐frequency NMES at 25 and 100 Hz switched every second. NMES was delivered to the right tibialis anterior (TA) muscle for 1 min in each condition. The order of interventions was pseudorandomized between participants with a washout of at least 15 min between conditions. Spinal reflexes were elicited using single‐pulse transcutaneous spinal cord stimulation applied over the lumbar enlargement to evoke responses in multiple lower‐limb muscles bilaterally and maximum motor responses (Mmax) were elicited in the TA muscle by stimulating the common peroneal nerve to assess fatigue at the baseline and immediately, 5, 10, and 15 min after each intervention. Results: Our results showed that spinal reflexes were significantly inhibited immediately after the mixed‐frequency NMES, and for at least 15 min in follow‐up. Low‐frequency NMES inhibited spinal reflexes 5 min after the intervention, and also persisted for at least 10 min. These effects were present only in the stimulated TA muscle, while other contralateral and ipsilateral muscles were unaffected. Mmax responses were not affected by any intervention. Conclusions: Our results indicate that even a short‐duration (1 min) NMES intervention using low‐ and mixed‐frequency NMES could inhibit spinal reflex excitability of the TA muscle without inducing fatigue. [ABSTRACT FROM AUTHOR]

Purpose: Tibialis anterior tendon shortening combined with tendon Achilles lengthening showed satisfactory short- and long-term outcomes for pes equinus treatment. This retrospective study aimed to evaluate the effectiveness of a single tibialis anterior tendon shortening-tendon Achilles lengthening procedure for treating pes equinus, in a homogeneous unilateral cerebral palsy patient group. Methods: Gait analysis was conducted on 22 unilateral cerebral palsy patients (mean age at surgery = 13.3 years, standard deviation = 3 years) before and within 2.5 years (standard deviation = 0.61 years) after the tibialis anterior tendon shortening-tendon Achilles lengthening procedure. Primary outcome measures included foot drop occurrence in swing, foot dorsiflexion and the first ankle rocker presence compared to healthy reference data. Movement analysis profile and gait profile score were also calculated for the entire gait cycle. The clinical exam and the A2 peak ankle power were analyzed. Statistical analysis used the paired Wilcoxon's sign rank test (p < 0.05). Results: Post-operatively, significant improvements were observed in ankle dorsiflexion during swing (p = 0.0006) and reduced foot drop in swing (p = 0.0107). The occurrence of a first ankle rocker did not significantly change (p = 0.1489). Significant improvements in gait profile score and movement analysis profile for all joints and planes indicate overall gait quality improvement. The foot progression changed significantly (p = 0.0285), with a greater external orientation. Nineteen out of 22 patients were able to quit wearing their ankle foot orthoses. Conclusion: Tibialis anterior tendon shortening and tendon Achilles lengthening combination yielded positive outcomes, showing increased foot dorsiflexion, first ankle rocker presence, and overall improved gait quality. These findings support the effectiveness of this surgical approach for treating pes equinus in children with unilateral spastic cerebral palsy. [ABSTRACT FROM AUTHOR]

Reacting and responding to an external stimulus is an important component of human performance, and they inform us about a participant's neurophysiological capabilities. Our purpose in this study was to determine whether reaction times (REACT), response times (RT), and countermovement jump (CMJ) performance differ when responding to an auditory (AUD) versus visual (VIS) stimulus. Participants were 17 college-aged volunteers (6 females and 11 males; M age = 23.0, SD = 3.4 years; M height = 174.57, SD = 10.37 cm; M body mass = 73.37, SD = 13.48 kg). Participants performed CMJs on force plates immediately upon receiving an AUD or a VIS stimulus. The AUD stimulus was a beep noise, while the VIS stimulus was a light on a screen in front of the participants. We determined REACT for the tibialis anterior (TA), medial gastrocnemius (GM), vastus lateralis (VL), and biceps femoris (BF) muscles to be the amount of time between stimulus onset and the initiation of the muscle's electromyographic (EMG) signal. We determined RT to be the amount of time between stimulus onset and the beginning of the participant's force production. We assessed CMJ performance via ground reaction forces during the unweighting, braking, and propulsive phases of the jump. We quantified EMG amplitude and frequency during each CMJ phase. We found RT to be faster to the AUD versus the VIS stimulus (p =.007). VL and BF muscles had faster REACT than TA and GM muscles (p ≤.007). The AUD stimulus was associated with faster CMJ unweighting phase metrics (p ≤.005). Thus, individuals may react and respond faster to an AUD versus VIS stimulus, with limited improvements in their subsequent physical performance. [ABSTRACT FROM AUTHOR]

Architectural parameters of skeletal muscle such as pennation angle provide valuable information on muscle function, since they can be related to the muscle force generating capacity, fiber packing, and contraction velocity. In this paper, we introduce a 3D ultrasound-based workflow for determining 3D fascicle orientations of skeletal muscles. We used a custom-designed automated motor driven 3D ultrasound scanning system for obtaining 3D ultrasound images. From these, we applied a custom-developed multiscale-vessel enhancement filter-based fascicle detection algorithm and determined muscle volume and pennation angle. We conducted trials on a phantom and on the human tibialis anterior (TA) muscle of 10 healthy subjects in plantarflexion (157 ± 7 ∘ ), neutral position (109 ± 7 ∘ , corresponding to neutral standing), and one resting position in between (145 ± 6 ∘ ). The results of the phantom trials showed a high accuracy with a mean absolute error of 0.92 ± 0.59 ∘ . TA pennation angles were significantly different between all positions for the deep muscle compartment; for the superficial compartment, angles are significantly increased for neutral position compared to plantarflexion and resting position. Pennation angles were also significantly different between superficial and deep compartment. The results of constant muscle volumes across the 3 ankle joint angles indicate the suitability of the method for capturing 3D muscle geometry. Absolute pennation angles in our study were slightly lower than recent literature. Decreased pennation angles during plantarflexion are consistent with previous studies. The presented method demonstrates the possibility of determining 3D fascicle orientations of the TA muscle in vivo. [ABSTRACT FROM AUTHOR]