Vol. 20 No. 2 (2023)

Published: 2023-12-23

Latest Articles

  • Open Access

    Articles

    Can PAPE-Induced Increases in Jump Height Be Explained by Jumping Kinematics?

    Xiaojie Jiang, Xin Li, Yining Xu, Dong Sun, Julien S. Baker, Yaodong Gu


    The aim of this study was to investigate whether kinematic data during a countermovement jump (CMJ) could explain the post-activation performance enhancement (PAPE) effects following acute resistance exercise. Twenty-four male participants with resistance training and jumping experience were recruited and randomly assigned to either the experimental group (PAPE-stimulus) (n = 12) or the control group (n = 12). In the experimental group, participants performed 5 reps of squats at 80% 1RM to induce PAPE, while the control group received no intervention. Both groups performed three CMJ tests before (PRE) and at immediate (POST0), 4 (POST4), 8 (POST8), and 12 (POST12) min after the intervention, with kinematic data recorded during the CMJ. Kinematic parameters analyzed in this study included jump height, hip-knee-ankle flexion angles at the lowest position of the countermovement, eccentric and concentric time durations, and the temporal changes of hip-knee-ankle flexion angles during the entire jumping phase. The presence of PAPE was determined by the change in jump height. The results showed that in the experimental group, jump height significantly increased at POST4 ( p  < 0.001) and POST8 ( p  < 0.001) and significantly decreased at POST0 ( p  = 0.008), with no significant change at POST12. The control group showed no significant changes at any measured time point. Kinematic parameters showed that there was no significant difference in joint flexion angle of the lower body during the CMJ between pre- and post-intervention, regardless of PAPE or fatigue. However, eccentric time significantly decreased at 4 and 8 min ( p  = 0.013 and  p  = 0.001, respectively) after the intervention. These findings suggest that PAPE-induced increases in jump height after acute resistance exercise can be attributed to the decrease in eccentric phase duration, but not joint flexion angle. Additionally, the fatigue-induced decrease in jump height cannot be reflected by jumping kinematics. Based on these findings, coaches may use complex training to utilize the PAPE effects to increase jump height while reducing the eccentric time during vertical jumps. This method can enhance an athlete’s eccentric ability to generate force in a short amount of time which is crucial for performance enhancement.

  • Open Access

    Articles

    CFD Study on Hemodynamic Characteristics of Inferior Vena Cava Filter Affected by Blood Vessel Diameter

    Shiyue Zhang, Xue Song, Jingying Wang, Wen Huang, Yue Zhou, Mingrui Li


    Pulmonary embolism (PE), caused by deep venous thrombosis (DVT), is a disease with high morbidity and mortality. Implantation of inferior vena cava filters is an important method for the clinical prevention of PE. The hemodynamic characteristics of filters implanted in the inferior vena cava (IVC) have a significant impact on their performance. However, IVC diameters vary among patients. This may have a direct impact on the hemodynamic properties of the filter. At present, there is no research on this kind of problem to be investigated. In this paper, the hemodynamic properties of the VenaTech convertible filter were simulated in three different IVC models of 15, 20 and 25 mm diameters, using computational fluid dynamics (CFD) as a control variable (only the IVC diameter is varied). The results showed that the diameter has a significant impact on the hemodynamic characteristics after filter implantation. The IVC diameter has a great influence on the stagnation zone of the blood flow, the maximum wall shear stress (WSS) on the upstream side along the filter wire, and the flow resistance. The case of 15 mm diameter was the most prone to thrombus formation downstream of the filter head in the IVC, but the larger WSS on the upstream along the filter wire may facilitate thrombus lysis. Therefore, the change in vessel diameter should be considered when performing filter implantation for patients.

  • Open Access

    Articles

    Biomechanical Analysis of Tai Chi (Eight Methods and Five Steps) for Athletes’ Body Balance Control

    Yuanyuan Feng


    Background:  The increasing number of Tai Chi practitioners has led to extensive attention from researchers regarding the role of Tai Chi exercise. Numerous studies have been conducted through various experiments to examine the effects of Tai Chi on physical and mental improvement.  Objective:  This paper aims to investigate the effect of practicing Tai Chi (eight methods and five steps) on athletes’ body balance control ability from a biomechanical perspective.  Methods:  Twenty male athletes were randomly divided into two groups. They had no significant differences in age, height, weight, and training time. The Tai Chi group performed Tai Chi (eight methods and five steps) exercises for nine weeks. Practice sessions were scheduled for every Monday, Wednesday, and Friday, each lasting 50 min. The blank group did not perform any exercises. After nine weeks, the athletes in both groups underwent testing for the one-legged stance with eyes closed, Y-balance test (YBT) score, and plantar pressure.  Results:  After the experiment, the one-legged stance with eyes closed of the Tai Chi group was 151.36 ± 48.77 s. The scores of the left and right sides of the YBT were 101.84 ± 5.97 and 100.59 ± 5.66, which were significantly higher than 80.33 ± 31.52 s, 96.12 ± 7.33, and 97.64 ± 8.12 in the pre-experimental period. In the results of the plantar pressure test, when the athletes stood with both feet and eyes closed, the EA was 23.46 ± 6.86 mm 2 , Delta X was 7.64 ± 1.03 mm, and Delta Y was 5.88 ± 0.75 mm, which were significantly different from those in the blank group (55.64 ± 7.98 mm 2 , 12.21 ± 1.27 mm, and 8.97 ± 50.86 mm) ( p  < 0.05); when they stood with both feet and eyes open, the EA was 27.64 ± 6.73 mm 2 , and Delta X was 7.31 ± 0.56 mm, which were significantly different from those in the blank group (40.66 ± 5.84 mm 2  and 9.87 ± 0.84 mm.  Conclusion:  Practicing Tai Chi (eight methods and five steps) can extend the duration of standing with eyes closed, improve YBT scores, and reduce EA, Delta X, and Delta Y values, thus enhancing athletes’ body balance control.

  • Open Access

    Review

    Reconstruction of the Hindlimb Locomotion of Confuciusornis (Aves) and Its Implication for the Origin of Avian Flight

    Xinsen Wei, Ying Guo, Yan Zhao


    As one of the most basal avian clades, the Confuciusornithids are ideal in revealing the early evolution of avian flight. Birds’ hindlimbs are functionally diverse and contain a wealth of information about their behavior. The hindlimb of  Confuciusornis , however, has only been studied in detail in terms of functional morphology, and quantitative studies that directly assess locomotor ability are relatively lacking. This has led to certain controversies on the behavior of  Confuciusornis . This paper reviews the debates over the life habits and take-off ability of  Confuciusornis , which are closely related to their hindlimb function. Several methodologies adopted engineering techniques, including the geometrical analysis of long bones, physiological reconstruction of muscles, kinematic and kinetic characteristics estimating, and appendage locomotor mechanism analysis, are recommended for estimating the hindlimb functions of  Confuciusornis . Considering that the fossil bones are fragile, irregular in shape, and usually deformed, it is appropriate to apply computer numerical simulation techniques to such studies. A sufficient functional quantitative study will help clarify early bird locomotor behavior, which will provide clues and evidence for further exploration of the origin of bird flight and early bird movement.

  • Open Access

    Editorial

    Hot Topics of Molecular and Cellular Biomechanics in 2022

    Guixue Wang


    The analysis of biomechanical characteristics plays an important role in mastering the technical characteristics of athletes, providing guidance for the formulation and prevention of sports injury training plans and providing theoretical support for research on injury prevention and stability control in the sports field. With the importance of data analysis, the application scope of artificial intelligence methods is more extensive. For example, intelligent training systems can be used for athletes’ personalized and professional training, real-time monitoring and feedback of training data, and further reduce the risk of sports injury. However, deep learning methods process a large number of medical images to identify and predict diseases such as cancer.

  • Open Access

    Editorial