This study aimed to examine the effects of single-session anodal high-definition transcranial direct current stimulation (HD-tDCS) on the strength of intrinsic foot muscles, passive ankle kinesthesia, and static balance. Methods: In this double-blinded self-controlled study, 14 healthy younger adults were asked to complete assessments of foot muscle strength, passive ankle kinesthesia, and static balance before and after a 20-minute session of either HD-tDCS or sham stimulation (i.e., control) at two visits separated by one week. Two-way repeated-measures analysis of variance was used to examine the effects of HD-tDCS on metatarsophalangeal joint flexor strength, toe flexor strength, the passive kinesthesia threshold of ankle joint, and the average sway velocity of the center of gravity. Results: All participants completed all study procedures and no side effects nor risk events were reported. Blinding was shown to be successful, with an overall accuracy of 35.7% in the guess of stimulation type (p = 0.347). No main effects of intervention, time, or their interaction were observed for foot muscle strength (p > 0.05). The average percent change in first-toe flexor strength following anodal HD-tDCS was 12.8 ± 24.2%, with 11 out of 14 participants showing an increase in strength, while the change following sham stimulation was 0.7 ± 17.3%, with 8 out of 14 participants showing an increase in strength. A main effect of time on the passive kinesthesia threshold of ankle inversion, dorsiflexion, and anteroposterior and medial-lateral average sway velocity of the center of gravity in one-leg standing with eyes closed was observed; these outcomes were reduced from pre to post stimulation (p < 0.05). No significant differences were observed for other variables between the two stimulation types. Conclusion: The results of this pilot study suggested that single-session HD-tDCS may improve the flexor strength of the first toe, although no statistically significant differences were observed between the anodal HD-tDCS and sham procedure groups. Additionally, passive ankle kinesthesia and static standing balance performance were improved from pre to post stimulation, but no significant differences were observed between the HD-tDCS and sham procedure groups. This may be potentially due to ceiling effects in this healthy cohort of a small sample size. Nevertheless, these preliminary findings may provide critical knowledge of optimal stimulation parameters, effect size, and power estimation of HD-tDCS for future trials aiming to confirm and expand the findings of this pilot study.

Purpose: Given the high incidence of patellofemoral pain syndrome (PFPS) in runners, this study aimed to investigate the immediate effect of shoes with different minimalist indices (MI) on the mechanical loads of the patellofemoral joint. Methods: Fifteen healthy male rearfoot strike runners were recruited to complete overground running trials at 3.33 m/s (±5%) in two running shoe conditions (MI = 26% versus MI = 86%). The amount of ten Vicon infrared cameras (100 Hz) and two Kistler force plates (1000 Hz) were used to collect kinematic and ground reaction force (GRF) data simultaneously. Quadriceps strength, patellofemoral contact force, patellofemoral contact area, and patellofemoral contact stress were calculated. Results: No significant differences were observed in the impact force and the second peak of the vertical GRF between the two shoe conditions. Compared to wearing low-MI shoes, wearing high-MI shoes showed that the maximum flexion angle of the knee, the contact area of patellofemoral joint and the peak knee extension moment reduced significantly (p < 0.01), and the peak patellofemoral contact force and stress decreased significantly (p < 0.05). Conclusion: These findings suggest that wearing high-MI shoes significantly decreases the patellofemoral contact force and patellofemoral joint stress by reducing the moment of knee extension, thus effectively reducing the load of the patellofemoral joint during the stance phase of running and potentially lowering the risk of PFPS.

Purpose: This systematic review aims to examine the efficacy of transcranial direct current stimulation (tDCS) combined with physical training on the excitability of the motor cortex, physical performance, and motor learning.Methods: A systematic search was performed on PubMed, Web of Science, and EBSCO databases for relevant research published from inception to August 2020. Eligible studies included those that used a randomized controlled design and reported the effects of tDCS combined with physical training to improve motor-evoked potential (MEP), dynamic posture stability index (DPSI), reaction time, and error rate on participants without nervous system diseases. The risk of bias was assessed by the Cochrane risk of bias assessment tool.Results: Twenty-four of an initial yield of 768 studies met the eligibility criteria. The risk of bias was considered low. Results showed that anodal tDCS combined with physical training can significantly increase MEP amplitude, decrease DPSI, increase muscle strength, and decrease reaction time and error rate in motor learning tasks. Moreover, the gain effect is significantly greater than sham tDCS combined with physical training.Conclusion: tDCS combined with physical training can effectively improve the excitability of the motor cortex, physical performance, and motor learning. The reported results encourage further research to understand further the synergistic effects of tDCS combined with physical training.

Understanding the origin and differentiation mechanism of coronary vascular smooth muscle cells (CoSMCs) is very important to cardiovascular biology. The early cardiovascular system is formed in a hypoxic microenvironment, and Tbx18-positive epicardial cells are a source of CoSMCs. However, the effects of hypoxia on the differentiation of Tbx18-positive epicardial cells to CoSMCs and the primary regulatory mechanism are insufficiently understood. Using Tbx18:Cre/R26REYFP/LacZ fate-tracing mice, we cultured highly purified Tbx18-positive epicardial cells. We further showed that hypoxia induced Tbx18-positive epicardial cells to differentiate into CoSMCs and promoted the epithelial-mesenchymal transition (EMT) process of the cells in vitro. The induction of differentiation was primarily achieved via the hypoxia inducible factor-1α (HIF-1α)-mediated effects exerted on Snail. Using a cell migration assay, we showed that hypoxia enhanced the motility of Tbx18-positive epicardial cells. By constructing a hypoxic model of the embryonic epicardium in vivo, we showed that hypoxia led to premature in situ differentiation of Tbx18-positive epicardial cells to CoSMCs. Furthermore, hypoxia was sufficient to induce Snail expression in Tbx18-positive epicardial cells in vivo. Our study suggests that hypoxia intervention was sufficient to induce the differentiation of Tbx18-positive epicardial cells to CoSMCs. Furthermore, this differentiation was achieved primarily via HIF-1α-mediated regulation of Snail.

Nowadays, compression garments (CGs) are widely used in winter racing sports, such as speed skating, short-track speed skating, alpine skiing, and crosscountry skiing. However, the effect of wearing CGs on athletic performance in these specific sports is still not fully examined. Thus, the aim of this narrative review is to summarize the research and application of CGs in winter racing sports and to discuss how the CGs help athletes improve their performance in an integrative manner (i.e., physiology, aerodynamics, and biomechanics). A total of 18 experimental studies dedicated to CGs in winter racing sports were identified from the peer-review scientific literature. The main findings are as follows. (1) Currently, CG studies have mainly focused on drag reduction, metabolism, muscle function, strength performance, and fatigue recovery. (2) The results of most studies conducted in wind tunnels showed that, for cylindrical structures similar to the human body, clothing with rough surfaces can reduce air drag. Notably, the effect of CGs on drag reduction in real competition has not been fully explored in the literature. (3) Compression can reduce muscle vibrations at high impact and help athletes control the center of pressure movement, a function that is important for alpine skiing. Future studies are needed to improve current understanding of the effects of compression clothing microstructure on drag reduction and their stretching in different parts of the body. Furthermore, the design of experimental protocol must be consistent with those during the competition, thus providing a full discussion on energy metabolism, fatigue, and recovery affected by CGs.

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Purpose: Although the Achilles tendon (AT) is the largest and strongest tendon, it remains one of the most vulnerable tendons among elite and recreational runners. The present study aims to explore the effects of 12-week gait retraining (GR) on the plantar flexion torque of the ankle and the morphological and mechanical properties of the AT. Methods: Thirty-four healthy male recreational runners (habitual rearfoot strikers) who never tried to run in minimal shoes were recruited, and the intervention was completed (20 in the GR group vs. 14 in the control (CON) group). The participants in the GR group were asked to run in minimal shoes (INOV-8 BARE-XF 210) provided by the investigators with forefoot strike patterns during the progressive 12-week GR. Meanwhile, the participants in the CON group were instructed to run in their own running shoes, which they were familiar with, with original foot strike patterns and intensities. The morphological properties of the AT, namely, length and cross-sectional area (CSA), were obtained by using an ultrasound device. A dynamometer was utilized simultaneously to measure and calculate the plantar flexion torque of the ankle, the rate of torque development, the peak force of the AT, and the stress and strain of the AT. Results: After 12-week GR, the following results were obtained: (1) A significant time effect in the peak ankle plantarflexion torque was observed (p = 0.005), showing a 27.5% increase in the GR group; (2) A significant group effect in the CSA was observed (p = 0.027), specifically, the increase in CSA was significantly larger in the GR group than the CON group; (3) A significant time effect in the peak AT force was observed (p = 0.005), showing a 27.5% increase in the GR group. Conclusion: The effect of 12 weeks of GR is an increase in AT CSA, plantar flexor muscle strength of the ankle, and peak AT force during a maximal voluntary isometric contraction test. These changes in AT morphology and function could be positive for tendon health and could prevent future AT injury.

Objective: This study aims to review existing literature regarding the effects of transcranial direct current stimulation (tDCS) on the physical performances of the foot and ankle of healthy adults and discuss the underlying neurophysiological mechanism through which cortical activities influence the neuromechanical management of the physical performances of the foot and ankle. Methods: This systematic review has followed the recommendations of the Preferred Reporting Items for Systematic reviews and Meta-Analyses. A systematic search was performed on PubMed, EBSCO, and Web of Science. Studies were included according to the Participants, Intervention, Comparison, Outcomes, and Setting inclusion strategy. The risk of bias was assessed through the Cochrane Collaboration tool, and the quality of each study was evaluated through the Physiotherapy Evidence Database (PEDro) scale. Results: The electronic search resulted in 145 studies. Only eight studies were included after screening. The studies performed well in terms of allocation, blinding effectiveness, and selective reporting. Besides, the PEDro scores of all the studies were over six, which indicated that the included studies have high quality. Seven studies reported that tDCS induced remarkable improvements in the physical performances of the foot and ankle, including foot sole vibratory and tactile threshold, toe pinch force, ankle choice reaction time, accuracy index of ankle tracking, and ankle range of motion, compared with sham. Conclusion: The results in these studies demonstrate that tDCS is promising to help improve the physical performances of the foot and ankle. The possible underlying mechanisms are that tDCS can ultimately influence the neural circuitry responsible for the neuromechanical regulation of the foot and ankle and then improve their physical performances. However, the number of studies included was limited and their sample sizes were small; therefore, more researches are highly needed to confirm the findings of the current studies and explore the underlying neuromechanical effects of tDCS.