Zhiqiang Liang

Background and aim: Traditional marker-based optical motion capture systems are costly, time-consuming to operate, and constrained by laboratory environments, limiting their broader adoption in clinical practice and naturalistic settings. Markerless motion capture based on a sums-of-Gaussians (SoG) body model is a potential alternative; however, its metrological properties for kinematic assessment during walking and slow running remain insufficiently validated. Using a conventional marker-based Vicon system as the reference, this study evaluated the reliability and concurrent validity of an SoG-based markerless system (MocapGS) for bilateral lower-limb joint range of motion (ROM) during gait. Methods: Thirty-six healthy adults completed self-selected-pace speed walking and slow running tasks while both systems synchronously acquired bilateral lower-limb kinematics. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), SEM percentage (SEM%), minimal detectable change (MDC), MDC percentage (MDC%), and root mean square error (RMSE) were used to assess reliability. Concurrent validity was evaluated using the Pearson correlation coefficient, paired-sample t-tests, and the concordance correlation coefficient (CCC) to compare the ROM. Results: Vicon showed moderate-to-high reliability for ROM in most joints across both tasks. By contrast, the MocapGS achieved acceptable ICC values mainly for the sagittal-plane ROM at the hip and knee. The CCC analysis showed no significant agreement between the two systems. Bland–Altman plots showed systematic biases with spatially heterogeneous random errors. During walking, MocapGS systematically overestimated ROM relative to Vicon at several joint axes; the widest limits of agreement (LOA) occurred at the left knee X-axis and right hip Z-axis. During running, overestimation was consistent across all bilateral joints at the X-axis and the right hip at the Y-axis, while the widest LOA were found at the bilateral hip X-axes. These specific discrepancies highlighted the joint–axis combinations with the greatest measurement variance. In walking, the test–retest reliability of the knee flexion–extension ROM measured by the MocapGS approached that of Vicon; however, the SEM% and MDC% were generally larger for MocapGS than for Vicon. The RMSE exceeded 5 degrees for ROM in most joint planes, especially in the frontal and transverse planes and at distal joints; errors increased further during slow running. Conclusions: MocapGS may be used for coarse monitoring of large-magnitude changes in sagittal-plane kinematics during gait; however, it is currently unlikely to replace Vicon for clinical decision-making or detecting subtle gait changes, and its outputs should be interpreted with caution, particularly for ankle kinematics and non-sagittal-plane motion.

The cerebral cortex, as the pinnacle of human complexity, poses formidable challenges to contemporary neuroscience. Recent advancements in non-invasive brain stimulation have been pivotal in enhancing human locomotor functions, a burgeoning area of interest in exercise science. Techniques such as transcranial direct current stimulation, transcranial alternating current stimulation, transcranial random noise stimulation, and transcranial magnetic stimulation are widely recognized for their neuromodulator capabilities. Despite their broad applications, these methods are not without limitations, notably in spatial and temporal resolution and their inability to target deep brain structures effectively. The advent of innovative non-invasive brain stimulation modalities, including transcranial focused ultrasound stimulation and temporal interference stimulation technology, heralds a new era in neuromodulation. These approaches offer superior spatial and temporal precision, promising to elevate athletic performance, accelerate sport science research, and enhance recovery from sports-related injuries and neurological conditions. This comprehensive review delves into the principles, applications, and future prospects of non-invasive brain stimulation in the realm of exercise science. By elucidating the mechanisms of action and potential benefits, this study aims to arm researchers with the tools necessary to modulate targeted brain regions, thereby deepening our understanding of the intricate interplay between brain function and human behavior.

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that applies a stable, low-intensity (1–2 mA) direct current to modulate neuronal activity in the cerebral cortex. This technique is effective, simple to operate, affordable, and widely employed across various fields. tDCS has been extensively used in clinical and translational research, with growing applications in military and competitive sports domains. In recent years, the use of tDCS in sports science has garnered significant attention from researchers. Numerous studies have demonstrated that tDCS can enhance muscle strength, explosive power, and aerobic metabolism, reduce fatigue, and improve cognition, thereby serving as a valuable tool for enhancing athletic performance. Additionally, recent research has shed light on the physiological mechanisms underlying tDCS, including its modulation of neuronal resting membrane potential to alter cortical excitability, enhancement of synaptic plasticity to regulate long-term potentiation, modulation of neurovascular coupling to improve regional cerebral blood flow, and improvement of cerebral network functional connectivity, which activates and reinforces specific brain regions. tDCS also enhances the release of excitatory neurotransmitters, further regulating brain function. This article, after outlining the role of tDCS in improving physical performance, delves into its mechanisms of action to provide a deeper understanding of how tDCS enhances athletic performance and offers novel approaches and perspectives for physical performance enhancement.

This investigation aimed to explore the relationship between Chinese elite wrestlers and the polymorphic loci of explosive strength genes, and to further explore the feasibility of its application to athlete selection. The snapshot technique was used to resolve the polymorphic loci of explosive power genes in the wrestler group (59 elite wrestlers) and the control group (180 ordinary college students), and to analyze the genotype frequencies and allele frequencies of each group. A chi-square test was performed on the genotype and allele distribution data of each group to analyze the loci of explosive power genes that were associated with elite wrestlers. The loci that had an association with elite wrestlers were combined with the genotyping data, and the dominance ratios of the genotypes were calculated using the chi-square test to determine the dominant genotypes associated with elite wrestlers. The VDR gene rs2228570 locus exhibited statistically significant differences in genotype and allele distributions between elite wrestlers and the general population (p < 0.01). At the rs2228570 locus of the VDR gene, the difference between the CC genotype and other genotypes was statistically significant (p < 0.05). The rs2228570 locus of the VDR gene was identified as the locus associated with Chinese elite wrestlers. The polymorphism of the VDR gene can be used as a biomarker for Chinese wrestlers, and the CC genotype can be used as a molecular marker for the selection of Chinese elite athletes in this sport. However, expanding the sample size of elite athletes is necessary to further validate the scientific validity and feasibility of these findings.

We aimed to investigate the impact of a single bout of endurance exercise on the brain-derived neurotrophic factor (BDNF) in humans and analyze how a single bout of endurance exercise impacts the peripheral BDNF types by age group. We performed a systematic literature review by searching PubMed, Elsevier, and Web of Science for studies that included a single bout of endurance exercise in the experimental group and other exercise types in the control group. Eight interventions were included in the study. Overall, a single bout of endurance exercise significantly increased BDNF expression (SMD = 0.30; 95% CI = [0.08, 0.52]; p = 0.001), which was confirmed in the serum BDNF (SMD = 0.30; 95% CI = [0.04, 0.55]; p < 0.001). A non-significant trend was observed in the plasma BDNF (SMD = 0.31; 95% CI = [−0.13, 0.76]; p = 0.017). The serum and plasma BDNF levels significantly increased regardless of age (SMD = 0.35; 95% CI = [0.11, 0.58]; p = 0.004; I² = 0%). In conclusion, a single bout of endurance exercise significantly elevates BDNF levels in humans without neurological disorders, regardless of age. The serum BDNF is a more sensitive index than the plasma BDNF in evaluating the impact of a single bout of endurance exercise on the BDNF.

Objective: This systematic review aims to analyze existing literature of the effects of transcranial direct current stimulation (tDCS) on motor skills learning of healthy adults and discuss the underlying neurophysiological mechanism that influences motor skills learning.Methods: This systematic review has followed the recommendations of the Preferred Reporting Items for Systematic reviews and Meta-Analyses. The PubMed, EBSCO, and Web of Science databases were systematically searched for relevant studies that were published from database inception to May 2022. Studies were included based on the Participants, Intervention, Comparison, Outcomes, and Setting inclusion strategy. The risk of bias was evaluated by using the Review manager 5.4 tool. The quality of each study was assessed with the Physiotherapy Evidence Database (PEDro) scale.Results: The electronic search produced 142 studies. Only 11 studies were included after filtering. These studies performed well in terms of distribution, blinding availability and selective reporting. They reported that tDCS significantly improved motor skills learning. The main outcomes measure were the improvement of the motor sequence tasks and specific motor skills. Nine studies showed that tDCS interventions reduced reaction time to complete motor sequence tasks in healthy adults and two studies showed that tDCS interventions improved golf putting task performance.Conclusion: The included studies showed that tDCS can help healthy adults to improve the motor skills learning by activating different brain regions, such as the primary motor cortex, left dorsolateral prefrontal cortex and right cerebellum. However, the number of included studies was limited, and the sample sizes were small. Therefore, more studies are urgently needed to validate the results of current studies and further explore the underlying neurophysiological mechanisms of tDCS in the future.

Aim: This study aimed to analyze the kinematic characteristics of snatch techniques in a world-class weightlifter who holds the world record in the 73 kg category. Methods: Two high-speed cameras (Sony, Tokyo, Japan, 25 Hz) were used to collect kinematic data at the 2019 Weightlifting World Championships. The SIMI° motion capture system (Simi Reality Motion Systems GmbH, Munich, Germany, 50 Hz) was used to analyze the snatch performance. Results: The lower limb movement during the first pulling stage showed a similar trajectory to elite weightlifters. The athlete showed 5.62° of knee flexion along with continuously increasing barbell velocity (maximal velocity up to 1.90 m/s) in the second pulling. Considering the perimeters of technical stability, the maximal value of the distance between the center of gravity of the human body and that of the barbell was 17.20 cm after the second pull. In addition, the barbell center simultaneously shifted 7.00 cm to the right. Conclusions: These results suggest that the world-record weightlifter possesses special technical characteristics. This personalized technical model provides basic information for the training of other elite weightlifters.

Endurance, which is dependent at least partly upon the activation of the brain cortex, is important for performance in rowing. Transcranial direct current stimulation (tDCS) has shown benefits for endurance, but its effects on the endurance performance of elite rowing athletes are unknown, and are examined in this study. Eight elite female rowers completed 5 km of rowing on an ergometer following stimulation of the tDCS and sham over motor cortices. Each session lasted 20 min and the current was set at 2.2 mA. Time, 500 m/split, power, time corresponding to 500 m (TC500) and power corresponding to 500 m (PC500) were recorded continuously throughout the tests. No significant differences in time, 500 m/split and power were observed between baseline, tDCS and sham. Compared to the sham, tDCS induced a percentage reduction in TC500 from baseline to 2500 m and 4000 m, and a percentage increase in PC500 from baseline to 500 m, 1000 m, 1500 m, 2000 m, 2500 m, 4000 m, 4500 m and 5000 m. One-session tDCS did not have significant benefits for rowing endurance performance in elite professional rowers, and had only marginally greater efficacy compared to sham. These findings offer knowledge helpful to the design of future studies exploring the effects of tDCS on the endurance performance of elite rowers.

Purpose: The aim of this study was to analyze plantar pressure during the open stance forehand (OSF) in female tennis players. Methods: Seven female players executed the tennis forehand technique with open stance in the biomechanical laboratory. A portable pressure insole system was adopted to collect mean pressure (MP), peak pressure (PP), force (F), pressure-time integral (PTI) and contact area (CA) in 7 regions of the feet. Independent sample T-test was used to analyze the difference among these parameters. Results: F, PP in the first phalangeal region (BT) and the remaining four toe regions (OT) of the right foot (RF) were both larger than the left foot (LF); F in the fourth and fifth metatarsophalangeal joint (M4-5), the middle foot region (MF), hind foot region(HF)and PP in M4-5 of LF were significantly greater than the same region in RF; MP in BT and OT of RF showed significantly higher pressure than LF. While MP among areas of M4-5 and HF of LF was significantly greater than RF; PTI, CA in OT, M4-5 and MF of RF were significantly higher than LF while M1, M2-3, M4-5 and MF of LF showed significant smaller. Conclusion: RF role was to generate the power and LF role was to stabilize the balance of the body during the OFS. However, long-term and repeated open stance was likely to lead to the overuse injuries in the regions of M1 and HF of both feet.