Cerebral hemodynamics underlying ankle force sense modulated by high-definition transcranial direct current stimulation.

This study aimed to investigate the effects of high-definition transcranial direct current stimulation on ankle force sense and underlying cerebral hemodynamics. Sixteen healthy adults (8 males and 8 females) were recruited in the study. Each participant received either real or sham high-definition transcranial direct current stimulation interventions in a randomly assigned order on 2 visits. An isokinetic dynamometer was used to assess the force sense of the dominant ankle; while the functional near-infrared spectroscopy was employed to monitor the hemodynamics of the sensorimotor cortex. Two-way analyses of variance with repeated measures and Pearson correlation analyses were performed. The results showed that the absolute error and root mean square error of ankle force sense dropped more after real stimulation than after sham stimulation (dropped by 23.4% vs. 14.9% for absolute error, and 20.0% vs. 10.2% for root mean square error). The supplementary motor area activation significantly increased after real high-definition transcranial direct current stimulation. The decrease in interhemispheric functional connectivity within the Brodmann's areas 6 was significantly correlated with ankle force sense improvement after real high-definition transcranial direct current stimulation. In conclusion, high-definition transcranial direct current stimulation can be used as a potential intervention for improving ankle force sense. Changes in cerebral hemodynamics could be one of the explanations for the energetic effect of high-definition transcranial direct current stimulation.

Activation of MnO6 Units via an Interfacial Electric Field: Electron Injection into Mn t2g for Rapid and Stable Sodium Ion Storage in CeO2 /MnOx.

Manganese-based oxides (MnOx ) suffer from sluggish charge diffusion kinetics and poor cycling stability in sodium ion storage. Herein, an interfacial electric field (IEF) in CeO2 /MnOx is constructed to obtain high electronic/ionic conductivity and structural stability of MnOx . The as-designed CeO2 /MnOx exhibits a remarkable capacity of 397 F g-1 and favorable cyclic stability with 92.13% capacity retention after 10,000 cycles. Soft X-ray absorption spectroscopy and partial density of states results reveal that the electrons are substantially injected into the Mn t2g orbitals driven by the formed IEF. Correspondingly, the MnO6 units in MnOx are effectively activated, endowing the CeO2 /MnOx with fast charge transfer kinetics and high sodium ion storage capacity. Moreover, In situRaman verifies a remarkably increased structural stability of CeO2 /MnOx , which is attributed to the enhanced Mn─O bond strength and efficiently stabilized MnO6 units. Mechanism studies show that the downshift of Mn 3d-band center dramatically increases the Mn 3d-O 2p orbitals overlap, thus inhibiting the Jahn-Teller (J-T) distortion of MnOx during sodium ion insertion/extraction. This work develops an advanced strategy to achieve both fast and sustainable sodium ion storage in metal oxides-based energy materials.

Anodal transcranial direct current stimulation enhances ankle force control and modulates the beta-band activity of the sensorimotor cortex.

This study aimed to investigate the cortical responses to the ankle force control and the mechanism underlying changes in ankle force control task induced by transcranial direct current stimulation (tDCS). Sixteen young adults were recruited, and they completed the electroencephalogram (EEG) assessment and high-definition tDCS (HD-tDCS) sessions. Root mean square (RMS) error was used to evaluate ankle force control task performance. Spectral power analysis was conducted to extract the average power spectral density (PSD) in the alpha (8-13 Hz) and beta (13-30 Hz) bands for resting state and tasking (i.e. task-PSD). The ankle force control task induced significant decreases in alpha and beta PSDs in the central, left, and right primary sensorimotor cortex (SM1) and beta PSD in the central frontal as compared with the resting state. HD-tDCS significantly decreased the RMS and beta task-PSD in the central frontal and SM1. A significant association between the percent change of RMS and the percent change of beta task-PSD in the central SM1 after HD-tDCS was observed. In conclusion, ankle force control task activated a distributed cortical network mainly including the SM1. HD-tDCS applied over SM1 could enhance ankle force control and modulate the beta-band activity of the sensorimotor cortex.

Effects of a 12-week gait retraining program on the Achilles tendon adaptation of habitually shod runners.

PURPOSE: This study investigated the effects of a 12-week gait retraining program on the morphological and mechanical properties of the Achilles tendon (AT) during running on the basis of real-time dynamic ultrasound imaging. METHODS: A total of 30 male recreational runners who were used to wearing cushioned shoes with a rearfoot strike (RFS) pattern were recruited. They were randomized into a retraining group (RG, n = 15) and a control group (CG, n = 15). The RG group was asked to run in five-fingered minimalist shoes with a forefoot strike (FFS) pattern, and the CG group was asked to keep their strike pattern. Three training sessions were performed per week. All the participants in RG uploaded running tracks obtained through a mobile application (.jpg) after each session for training supervision. The ground reaction force, kinematics, and kinetics of the ankle joint at 10 km/h were collected using an instrumented split-belt treadmill and a motion capture system. The morphological (length and cross-sectional area) and mechanical characteristics (force, stress, strain, etc.) of AT in vivo were recorded and calculated with a synchronous ultrasonic imaging instrument before and after the intervention. Repeated two-way ANOVA was used to compare the aforementioned parameters. RESULTS: A total of 28 participants completed the training. The strike angle of RG after training was significantly smaller than that before training and significantly smaller than that of CG after training (F (1, 13) = 23.068, p < 0.001, partial η2 = 0.640). The length (F (1, 13) = 10.086, p = 0.007, partial η2 = 0.437) and CSA (F (1, 13) = 7.475, p = 0.017, partial η2 = 0.365) of AT in RG increased after training. A significant main effect for time was observed for the time-to-peak AT force (F (1, 13) = 5.225, p = 0.040, partial η2 = 0.287), average (F (1, 13) = 7.228, p = 0.019, partial η2 = 0.357), and peak AT loading rate (F (1, 13) = 11.687, p = 0.005, partial η2 = 0.473). CONCLUSION: Preliminary evidence indicated that a 12-week gait retraining program could exert a beneficial effect on AT. 57% (8/14) runners in RG shifted from RFS to FFS pattern. Although not all runners were categorized as FFS pattern after the intervention, their foot strike angle was reduced. Retraining primarily positively promoted AT morphological properties (i.e., CSA and length) to strengthen AT capability for mechanical loading.

Effects of gait retraining using minimalist shoes on the medial gastrocnemius muscle-tendon unit behavior and dynamics during running.

The effects of a 12-week gait retraining program on the adaptation of the medial gastrocnemius (MG) and muscle-tendon unit (MTU) were investigated. 26 runners with a rearfoot strike pattern (RFS) were randomly assigned to one of two groups: gait retraining (GR) or control group (CON). MG ultrasound images, marker positions, and ground reaction forces (GRF) were collected twice during 9 km/h of treadmill running before and after the intervention. Ankle kinetics and the MG and MTU behavior and dynamics were quantified. Runners in the GR performed gradual 12-week gait retraining transitioning to a forefoot strike pattern. After 12-week, (1) ten participants in each group completed the training; eight participants in GR transitioned to non-RFS with reduced foot strike angles; (2) MG fascicle contraction length and velocity significantly decreased after the intervention for both groups, whereas MG forces increased after intervention for both groups; (3) significant increases in MTU stretching length for GR and peak MTU recoiling velocity for both groups were observed after the intervention, respectively; (4) no significant difference was found for all parameters of the series elastic element. Gait retraining might potentially influence the MG to operate at lower fascicle contraction lengths and velocities and produce greater peak forces. The gait retraining had no effect on SEE behavior and dynamics but did impact MTU, suggesting that the training was insufficient to induce mechanical loading changes on SEE behavior and dynamics.

Unlocking Spin Gates of Transition Metal Oxides via Strain Stimuli to Augment Potassium Ion Storage.

Transition metal oxides (TMOs) are key in electrochemical energy storage, offering cost-effectiveness and a broad potential window. However, their full potential is limited by poor understanding of their slow reaction kinetics and stability issues. This study diverges from conventional complex nano-structuring, concentrating instead on spin-related charge transfer and orbital interactions to enhance the reaction dynamics and stability of TMOs during energy storage processes. We successfully reconfigured the orbital degeneracy and spin-dependent electronic occupancy by disrupting the symmetry of magnetic cobalt (Co) sites through straightforward strain stimuli. The key to this approach lies in the unfilled Co 3d shell, which serves as a spin-dependent regulator for carrier transfer and orbital interactions within the reaction. We observed that the opening of these 'spin gates' occurs during a transition from a symmetric low-spin state to an asymmetric high-spin state, resulting in enhanced reaction kinetics and maintained structural stability. Specifically, the spin-rearranged Al-Co3O4 exhibited a specific capacitance of 1371 F g-1, which is 38 % higher than that of unaltered Co3O4. These results not only shed light on the spin effects in magnetic TMOs but also establish a new paradigm for designing electrochemical energy storage materials with improved efficiency.

Spin Symmetry Breaking-induced Hubbard Gap Near-Closure in N-coordinated MnO2 for Enhanced Aqueous Zinc-Ion Battery Performance.

Transition metal oxides (TMOs) are promising cathode materials for aqueous zinc ion batteries (ZIBs), however, their performance is hindered by a substantial Hubbard gap, which limits electron transfer and battery cyclability. Addressing this, we introduce a heteroatom coordination approach, using triethanolamine to induce axial N coordination on Mn centers in MnO2, yielding N-coordinated MnO2 (TEAMO). This approach leverages the change of electronegativity disparity between Mn and ligands (O and N) to disrupt spin symmetry and augment spin polarization. This enhancement leads to the closure of the Hubbard gap, primarily driven by the intensified occupancy of the Mn eg orbitals. The resultant TEAMO exhibit a significant increase in storage capacity, reaching 351 mAh g-1 at 0.1 A g-1. Our findings suggest a viable strategy for optimizing the electronic structure of TMO cathodes, enhancing the potential of ZIBs in energy storage technology.

High Flux and Stability of Cationic Intercalation in Transition-Metal Oxides: Unleashing the Potential of Mn t2g Orbital via Enhanced π-Donation.

Transition-metal oxides (TMOs) often struggle with challenges related to low electronic conductivity and unsatisfactory cyclic stability toward cationic intercalation. In this work, we tackle these issues by exploring an innovative strategy: leveraging heightened π-donation to activate the t2g orbital, thereby enhancing both electron/ion conductivity and structural stability of TMOs. We engineered Ni-doped layered manganese dioxide (Ni-MnO2), which is characterized by a distinctive Ni-O-Mn bridging configuration. Remarkably, Ni-MnO2 presents an impressive capacitance of 317 F g-1 and exhibits a robust cyclic stability, maintaining 81.58% of its original capacity even after 20,000 cycles. Mechanism investigations reveal that the incorporation of Ni-O-Mn configurations stimulates a heightened π-donation effect, which is beneficial to the π-type orbital hybridization involving the O 2p and the t2g orbital of Mn, thereby accelerating charge-transfer kinetics and activating the redox capacity of the t2g orbital. Additionally, the charge redistribution from Ni to the t2g orbital of Mn effectively elevates the low-energy orbital level of Mn, thus mitigating the undesirable Jahn-Teller distortion. This results in a subsequent decrease in the electron occupancy of the π*-antibonding orbital, which promotes an overall enhancement in structural stability. Our findings pave the way for an innovative paradigm in the development of fast and stable electrode materials for intercalation energy storage by activating the low orbitals of the TM center from a molecular orbital perspective.

Research on Accurate Motion Trajectory Control Method of Four-Wheel Steering AGV Based on Stanley-PID Control.

With the continuous progress and application of robotics technology, the importance of mobile robots capable of adapting to specialized work environments is gaining prominence. Among them, achieving precise and stable control of AGVs (Automated Guided Vehicles) stands as a paramount task propelling the advancement of mobile robotics. Consequently, this study devises a control system that enables AGVs to attain stable and accurate motion through equipment connection and debugging, kinematic modeling of the four-wheel steering AGV, and a selection and comparative analysis of motion control algorithms. The effectiveness of the Stanley-PID control algorithm in guiding the motion of a four-wheel steering AGV is validated through MATLAB 2021a simulation software. The simulation results illustrate the outstanding stability and precise control capabilities of the Stanley-PID algorithm.

Mechanics of The Medial Gastrocnemius-Tendon Unit in Behaving more Efficiently in Habitual Non-Rearfoot Strikers than in Rearfoot Strikers during Running.

This study aims to quantify how habitual foot strike patterns would affect ankle kinetics and the behavior and mechanics of the medial gastrocnemius-tendon unit (MTU) during running. A total of 14 runners with non-rearfoot strike patterns (NRFS) and 15 runners with rearfoot strike patterns (RFS) ran on an instrumented treadmill at a speed of 9 km/h. An ultrasound system and a motion capture system were synchronously triggered to collect the ultrasound images of the medial gastrocnemius (MG) and marker positions along with ground reaction forces (GRF) during running. Ankle kinetics (moment and power) and MG/MTU behavior and mechanical properties (MG shortening length, velocity, force, power, MTU shortening/lengthening length, velocity, and power) were calculated. Independent t-tests were performed to compare the two groups of runners. Pearson correlation was conducted to detect the relationship between foot strike angle and the MTU behavior and mechanics. Compared with RFS runners, NRFS runners had 1) lower foot strike angles and greater peak ankle moments; 2) lower shortening/change length and contraction velocity and greater MG peak force; 3) greater MTU lengthening, MTU shortening length and MTU lengthening velocity and power; 4) the foot strike angle was positively related to the change of fascicle length, fascicle contraction length, and MTU shortening length during the stance phase. The foot strike angle was negatively related to the MG force and MTU lengthening power. The MG in NRFS runners appears to contract with greater force in relatively isometric behavior and at a slower shortening velocity. Moreover, the lengthening length, the lengthening velocity of MTU, and the MG force were greater in habitual NRFS runners, leading to a stronger stretch reflex response potentially.

Bacillus Subtilis Promotes the Release of 5-HT to Regulate Intestinal Peristalsis in STC Mice via Bile Acid and Its Receptor TGR5 Pathway.

BACKGROUND: Slow transit constipation (STC) is caused by intestinal peristalsis dysfunction and is closely associated with disturbance of the intestinal microecological balance. Bacillus subtilis plays a positive role in the treatment of STC, but its mechanism needs to be further explored. AIMS: The purpose of the present study was to explore the effects and mechanism of B. subtilis on the pathophysiology of STC. METHODS: A STC mouse model was established with compound diphenoxylate, following which B. subtilis was used to treat STC. The effects and possible mechanism of B. subtilis on STC were investigated by assessing intestinal motility, histology of the colon, release of 5-HT in enterochromaffin cells (ECs) and the TGR5/TRPA1 pathway. Moreover, LC-MS targeted metabolomics was used to analyze the regulation of Bacillus subtilis on bile acid metabolisms in STC mice. RESULTS: Bacillus subtilis significantly increased 24 h defecations, fecal moisture and intestinal transport rate of STC mice, improved pathological damage of the colon and showed protective effects on the intestinal tract. The release of 5-HT from ECs and the bile acid receptor TGR5/TRPA1 pathway were significantly increased in STC mice treated with B. subtilis. In addition, the metabolomics results showed that the bile acid contents of STC mice were significantly decreased, and B. subtilis could increase the bile acid composition and content of STC mice. CONCLUSION: Bacillus subtilis regulates intestinal peristalsis of STC by promoting the release of 5-HT from ECs through bile acid metabolism and its receptor TGR5 pathway and plays a positive role in the treatment of STC.

Effects of intervention combining transcranial direct current stimulation and foot core exercise on sensorimotor function in foot and static balance.

OBJECTIVE: This study aimed to examine the effects of combining transcranial direct current stimulation (tDCS) and foot core exercise (FCE) on the sensorimotor function of the foot (i.e., toe flexor strength and passive ankle kinesthesia) and static balance. METHODS: In this double-blinded and randomized study, 30 participants were randomly assigned into two groups: tDCS combined with FCE and sham combined with FCE (i.e., control group). The participants received 2 mA stimulation for 20 min concurrently with FCE over 4 weeks (i.e., three sessions per week). After the first two groups completed the intervention, a reference group (FCE-only group) was included to further explore the placebo effects of sham by comparing it with the control group. Foot muscle strength, passive ankle kinesthesia, and static balance were assessed at baseline and after the intervention. RESULTS: Compared with the control group and baseline, tDCS combined with FCE could increase toe flexor strength (p < 0.001) and decrease the passive kinesthesia threshold of ankle eversion (p = 0.002). No significant differences in static balance were observed between tDCS + FCE and control groups. The linear regression models showed an association towards significance between the percent changes in metatarsophalangeal joint flexor strength and the anteroposterior average sway velocity of the center of gravity in one-leg standing with eyes closed following tDCS + FCE (r2 = 0.286; p = 0.057). The exploratory analysis also showed that compared with FCE alone, the sham stimulation did not induce any placebo effects during FCE. CONCLUSION: Participating in 4 weeks of intervention using tDCS in combination with FCE effectively enhances toe flexor strength and foot-ankle sensory function.

Investigation on whistle directivity in the Indo-Pacific humpback dolphin (Sousa chinensis) through numerical modeling.

Odontocetes have evolved special acoustic structures in the forehead to modulate echolocation and communication signals into directional beams to facilitate feeding and social behaviors. Whistle directivity was addressed for the Indo-Pacific humpback dolphin (Sousa chinensis) by developing numerical models in the current paper. Directivity was first examined at the fundamental frequency 5 kHz, and simulations were then extended to the harmonics of 10, 15, 20, 25, and 30 kHz. At 5 kHz, the -3 dB beam widths in the vertical and horizontal planes were 149.3° and 119.4°, corresponding to the directivity indexes (DIs) of 4.4 and 5.4 dB, respectively. More importantly, we incorporated directivity of the fundamental frequency and harmonics to produce an overall beam, resulting in -3 dB beam widths of 77.2° and 62.9° and DIs of 8.2 and 9.7 dB in the vertical and horizontal planes, respectively. Harmonics can enhance the directivity of fundamental frequency by 3.8 and 4.3 dB, respectively. These results suggested the transmission system can modulate whistles into directional projection, and harmonics can improve DI.

Comparative Effect of Liuzijue Qigong and Conventional Respiratory Training on Trunk Control Ability and Respiratory Muscle Function in Patients at an Early Recovery Stage From Stroke: A Randomized Controlled Trial.

OBJECTIVES: To compare the effects of Liuzijue Qigong and conventional respiratory training on trunk control ability and respiratory muscle functions in patients at an early recovery stage from stroke. DESIGN: A single-blind, randomized controlled trial. SETTING: A hospital. PARTICIPANTS: Patients (N=60) within 2 months poststroke. INTERVENTIONS: The experimental group (n=30) received conventional rehabilitation training combined with Liuzijue exercise, and the control group (n=30) received conventional rehabilitation training combined with conventional respiration training. The training in the 2 groups was conducted 5 times per week for 3 weeks. MAIN OUTCOME MEASURES: Trunk Impairment Scale (TIS), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF), maximum expiratory mid-flow (MMEF), diaphragmatic movement, the change of intra-abdominal pressure (IAP), Berg Balance Scale (BBS), and Modified Barthel Index (MBI). All outcome measures were assessed twice (at baseline and 3 weeks). RESULTS: Both groups significantly improved in TIS, MIP, FVC, PEF, and the change of IAP, BBS, and MBI when pre- and postassessments (P<.05) were compared. Compared with the control group, there was a significant difference in the experimental group in the static sitting balance subscale (P=.014), dynamic balance subscale (P=.001), coordination subscale (P<.001), TIS total scores (P<.001; effect size [ES]=0.9), MIP (P=.012; 95% confidence interval [CI], 2.23-17.69; ES=0.67), MEP (P=.015; 95% CI, 1.85-16.57; ES=0.65), change of IAP (P=.001), and MBI (P=.016; 95% CI, 1.51-14.16; ES=0.64). No significant differences were found between the 2 groups in FEV1 (P=.24), FVC (P=.43), PEF (P=.202), MMEF (P=.277), the diaphragmatic movement of quiet breathing (P=.146), deep breathing (P=.102), and BBS (P=.124). CONCLUSIONS: Liuzijue exercise showed more changes than conventional respiratory training in improving trunk control ability, respiratory muscle functions, and activities of daily living ability in patients at an early recovery stage from stroke.

Compression Garments Reduce Soft Tissue Vibrations and Muscle Activations during Drop Jumps: An Accelerometry Evaluation.

OBJECTIVES: To explore the effects of wearing compression garments on joint mechanics, soft tissue vibration and muscle activities during drop jumps. METHODS: Twelve healthy male athletes were recruited to execute drop jumps from heights of 30, 45 and 60 cm whilst wearing compression shorts (CS) and control shorts (CON). Sagittal plane kinematics, ground reaction forces, accelerations of the quadriceps femoris (QF), hamstrings (HM) and shoe heel-cup, and electromyography images of the rectus femoris (RF) and biceps femoris (BF) were collected. RESULTS: Compared with wearing CON, wearing CS significantly reduced the QF peak acceleration at 45 and 60 cm and the HM peak acceleration at 30 cm. Wearing CS significantly increased the damping coefficient for QF and HM at 60 cm compared with wearing CON. Moreover, the peak transmissibility when wearing CS was significantly lower than that when wearing CON for all soft tissue compartments and heights, except for QF at 30 cm. Wearing CS reduced the RF activity during the pre-, post-, and eccentric activations for all heights and concentric activations at 45 cm; it also reduced the BF activity during post- and eccentric activations at 30 and 60 cm, respectively. The hip and knee joint moments and power or jump height were unaffected by the garment type. CONCLUSION: Applying external compression can reduce soft tissue vibrations without compromising neuromuscular performance during strenuous physical activities that involve exposure to impact-induced vibrations.

[Progress on in vivo ankle biomechanics based on dual fluoroscopic imaging technology].

The technical deficiencies in traditional medical imagining methods limit the study of in vivo ankle biomechanics. A dual fluoroscopic imaging system (DFIS) provides accurate and non-invasive measurements of dynamic and static activities in joints of the body. This approach can be used to quantify the movement in the single bones of the ankle and analyse different morphological and complex bone positions and movement patterns within these organs and has been widely used in the field of image diagnosis and evaluation of clinical biomechanics. This paper reviews the applications of DFIS that were used to measure the in vivo kinematics of the ankle in the field of clinical and sports medicine. The advantages and shortcomings of DFIS in the practical application are summarised. We further put forward effective research programs for understanding the movement as well as injury mechanism of the ankle in vivo, and provide constructive research direction for future study.

Plantar load characteristics among runners with different strike patterns during preferred speed.

OBJECTIVES: This study aimed to compare the plantar loads between habitual rearfoot strike (RFS) and non-RFS (NRFS) during running under the participant's preferred speed. METHODS: A total of 66 (36 RFS, 30 NRFS) healthy amateur male runners were included in our study. In-shoe pressure sensors were utilised to the test plantar loads when participants were running using their preferred foot strike pattern and running speed (RFS: 3.2 ± 0.3 m/s; NRFS: 3.4 ± 0.4 m/s). RESULTS: Results indicated that running speed has a significant effect on the total contact area [F (1, 64) = 7.061, P = 0.01, η 2  = 0.101], which also affects midfoot and forefoot regions. No significant difference was found on the total maximum force, force-time-integral, peak pressure (PP) and pressure-time-integral (PTI), but the total contact area of RFS was higher than that of NRFS runners [F (1, 64) = 77.406, P < 0.001, η 2  = 0.551]. Plantar loads were mainly focused on the heel and midfoot for RFS runners in all variables, and NRFS runners experienced increased PP and PTI in medial forefoot regions. CONCLUSION: Habitual runners tend to adjust their contact area according to the running speed through midfoot and forefoot regions. RFS runners remain susceptible to high impact force on the heel and midfoot, and NRFS runners experience high impact force in the first metatarsal regions. Therefore, runners should note this situation to avoid running-related injuries.

Kinematic Comparisons of the Shakehand and Penhold Grips in Table Tennis Forehand and Backhand Strokes when Returning Topspin and Backspin Balls.

Identifying the factors associated with table tennis performance may provide training information for competitive athletes and guide the general population for active participation. The purpose was to compare the joint, racket, and ball kinematics between the shakehand and penhold grips in table tennis forehand and backhand strokes when returning topspin and backspin balls in advanced male players. Nine penhold-grip players and 18 matched shakehand-grip players performed forehand and backhand strokes when returning topspin and backspin balls using their habitual grip styles, while the kinematics of the trunk, upper extremities, racket, and ball were collected. Racket angles were calculated as the relative motion of the racket to the forearm. For the forehand strokes, no significant differences were observed for ball or racket velocities between the two grips. The shakehand grip tended to demonstrate greater shoulder external rotation angles compared to the penhold grip. The shakehand grip resulted in racket flexion angular velocity compared to racket extension velocity for the penhold grip. For the backhand strokes, greater ball and racket velocities were observed for the shakehand grip. The shakehand grip generally demonstrated decreased final trunk left rotation angles, increased trunk right rotation angular velocities, decreased final shoulder abduction angles, increased shoulder adduction angular velocities, and increased forearm supination angular velocities. The two grips demonstrated similar peak racket and ball velocities but different shoulder rotation range of motion and racket motion in forehand strokes. The penhold grips resulted in decreased peak racket and ball velocities in backhand strokes, likely due to its decreased shoulder, elbow, and forearm motion and less aligned longitudinal axes between the racket and forearm. These findings may help understand the dominance of the shakehand grip over the penhold grip in elite athletes and provide information for grip selection, technique improvements, and exercise training.

Systematic Review of the Role of Footwear Constructions in Running Biomechanics: Implications for Running-Related Injury and Performance.

Although the role of shoe constructions on running injury and performance has been widely investigated, systematic reviews on the shoe construction effects on running biomechanics were rarely reported. Therefore, this review focuses on the relevant research studies examining the biomechanical effect of running shoe constructions on reducing running-related injury and optimising performance. Searches of five databases and Footwear Science from January 1994 to September 2018 for related biomechanical studies which investigated running footwear constructions yielded a total of 1260 articles. After duplications were removed and exclusion criteria applied to the titles, abstracts and full text, 63 studies remained and categorised into following constructions: (a) shoe lace, (b) midsole, (c) heel flare, (d) heel-toe drop, (e) minimalist shoes, (f) Masai Barefoot Technologies, (g) heel cup, (h) upper, and (i) bending stiffness. Some running shoe constructions positively affect athletic performance-related and injury-related variables: 1) increasing the stiffness of running shoes at the optimal range can benefit performance-related variables; 2) softer midsoles can reduce impact forces and loading rates; 3) thicker midsoles can provide better cushioning effects and attenuate shock during impacts but may also decrease plantar sensations of a foot; 4) minimalist shoes can improve running economy and increase the cross-sectional area and stiffness of Achilles tendon but it would increase the metatarsophalangeal and ankle joint loading compared to the conventional shoes. While shoe constructions can effectively influence running biomechanics, research on some constructions including shoe lace, heel flare, heel-toe drop, Masai Barefoot Technologies, heel cup, and upper requires further investigation before a viable scientific guideline can be made. Future research is also needed to develop standard testing protocols to determine the optimal stiffness, thickness, and heel-toe drop of running shoes to optimise performance-related variables and prevent running-related injuries.

Relationship between Muscle Mass/Strength and Hepatic Fat Content in Post-Menopausal Women.

Background and Objectives: Recent studies have shown that low skeletal muscle mass can contribute to non-alcoholic fatty liver disease through insulin resistance. However, the association between muscle mass/strength and hepatic fat content remains unclear in postmenopausal women. Methods: In this study, we assessed the associations between muscle mass/strength and various severities of non-alcoholic fatty liver disease. Using single-voxel proton magnetic resonance spectroscopy, 96 postmenopausal women between the ages of 50 and 65 were divided into four groups (G0-G3) by hepatic fat content: G0 (hepatic fat content <5%, n = 20), G1 (5% ≤ hepatic fat content < 10%, n = 27), G2 (10% ≤ hepatic fat content < 25%, n = 31), and G3 (hepatic fat content ≥25%, n = 18). Muscle mass indexes were estimated as skeletal muscle index (SMI)% (total lean mass/weight × 100) and appendicular skeletal muscular mass index (ASM)% (appendicular lean mass/weight × 100) by dual energy X-ray absorptiometry. Maximal isometric voluntary contraction of the handgrip, elbow flexors, and knee extensors was measured using an adjustable dynamometer chair. Fasting plasma glucose, insulin, and follicle-stimulating hormones were assessed in venous blood samples. Results: The results showed negative correlations between hepatic fat content and SMI% (r = -0.42, p < 0.001), ASM% (r = -0.29, p = 0.005), maximal voluntary force of grip (r = -0.22, p = 0.037), and knee extensors (r = -0.22, p = 0.032). Conclusions: These significant correlations almost remained unchanged even after controlling for insulin resistance. In conclusion, negative correlations exist between muscle mass/strength and the progressed severity of non-alcoholic fatty liver disease among post-menopausal women, and the correlations are independent of insulin resistance.