Purpose We aimed to determine:(a)the chronic effects of interval training(IT)combined with blood flow restriction(BFR)on physiological adaptations(aerobic/anaerobic capacity and muscle responses)and performance enhanc...Purpose We aimed to determine:(a)the chronic effects of interval training(IT)combined with blood flow restriction(BFR)on physiological adaptations(aerobic/anaerobic capacity and muscle responses)and performance enhancement(endurance and sprints),and(b)the influence of participant characteristics and intervention protocols on these effects.Methods Searches were conducted in PubMed,Web of Science(Core Collection),Cochrane Library(Embase,ClinicalTrials.gov,and International Clinical Trials Registry Platform),and Chinese National Knowledge Infrastructure on April 2,with updates on October 17,2024.Pooled effects for each outcome were summarized using Hedge's g(g)through meta-analysis-based random effects models,and subgroup and regression analyses were used to explore moderators.Results A total of 24 studies with 621 participants were included.IT combined with BFR(IT+BFR)significantly improved maximal oxygen uptake(VO2_(max))(g=0.63,I^(2)=63%),mean power during the Wingate 30-s test(g=0.70,I^(2)=47%),muscle strength(g=0.88,I^(2)=64%),muscle endurance(g=0.43,I^(2)=0%),time to fatigue(g=1.26,I^(2)=86%),and maximal aerobic speed(g=0.74,I^(2)=0%)compared to IT alone.Subgroup analysis indicated that participant characteristics including training status,IT intensity,and IT modes significantly moderated VO2_(max)(subgroup differences:p<0.05).Specifically,IT+BFR showed significantly superior improvements in VO2_(max)compared to IT alone in trained individuals(g=0.76)at supra-maximal intensity(g=1.29)and moderate intensity(g=1.08)as well as in walking(g=1.64)and running(g=0.63)modes.Meta-regression analysis showed cuff width(β=0.14)was significantly associated with VO2_(max)change,identifying 8.23 cm as the minimum threshold required for significant improvement.Subgroup analyses regarding muscle strength did not reveal any significant moderators.Conclusion IT+BFR enhances physiological adaptations and optimizes aspects of endurance performance,with moderators including training status,IT protocol(intensity,mode,and type),and cuff width.This intervention addresses various IT-related challenges and provides tailored protocols and benefits for diverse populations.展开更多
Objectives:To investigate the impact of a supervised bloodflow restriction(BFR)training program performed at different times of the morning on body composition and muscle performance in older,inactive adults.Methods:A...Objectives:To investigate the impact of a supervised bloodflow restriction(BFR)training program performed at different times of the morning on body composition and muscle performance in older,inactive adults.Methods:A single-arm intervention of supervised BFR resistance training was performed three times per week for six weeks.Participants(n=24;aged 65+years)were categorized into early morning(n=13;05:00–08:59)or late morning(n=11;09:00–12:00)groups.Primary outcomes were changes in body composition,total work,average peak power,average peak torque,muscle strength,and physical function.Results:Mixed model analysis of variance revealed a significant within-subject effect of time for all strength measures(p ranging from 0.017 to<0.001)and some physical function measures including the 30 s chair stand test,30 s bicep curl test,and grip strength(p ranging from 0.015 to<0.001).No between-group or time by group interaction effect was observed for all outcomes.Conclusions:This study showed that only six weeks of BFR training,performed at different time of the morning,did not enhance muscle mass and performance,but provided similar changes in muscle strength and some physical function tests in older adults.展开更多
To simulate the actual flowfield at the exit of the supersonic/hypersonic inlet, a wind tunnel is designed to study the flow in the scramjet isolator under the asymmetric incoming flow. And compression fields in the i...To simulate the actual flowfield at the exit of the supersonic/hypersonic inlet, a wind tunnel is designed to study the flow in the scramjet isolator under the asymmetric incoming flow. And compression fields in the isolator are investigated using wall static and pitot pressure measurements. Three incoming Mach numbers are considered as 1.5, 1.8 and 2. Results show that the increase of the asymmetry of the flow at the isolator entrance leads to the increase of the shock train length in the isolator for a given pressure ratio. Based on the analysis of the flow asymmetry effect at the isolator entrance on the shock train length, a modified correlation is proposed to calculate the length of the shock train. Predicted results of the proposed correlation are in good agreement with the experimental data.展开更多
According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was ...According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was studied and eight types of flow regions were proposed. They are high pressure with air stagnant region, pressure decreasing with air accelerating region, low pressure with high air flow velocity region I, turbulent region, steady flow region, low pressure with high air flow velocity region II,pressure increasing with air decelerating region and wake region. The analysis of the vortex structure around the train shows that the vortex is mainly induced by structures with complex mutation and large curvature change. The head and rear of train, the underbody structure, the carriage connection section and the wake region are the main vortex generating sources while the train body with even cross-section has rare vortexes. The wake structure development law studied lays foundation for the train drag reduction.展开更多
The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automato...The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automaton models, in this paper, we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system. In the proposed model, we establish some sound rules to control the running processes of a train, where the rules include the departure rules in the intermediate stations, the overtaking rules, and the conditions of speed limitation for a train stopping at a station or passing through a station. With the consideration of the mixed ratio and the distance between two adjacent stations, the properties of the train traffic flow （including capacity and average speed） are simulated. The numerical results show that the interactions among different trains will affect the capacity, and a proper increase of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block.展开更多
This paper aims to present a simulation model for heterogeneous high-speed train traffic flow based on an improved discrete-time model（IDTM）.In the proposed simulation model,four train control strategies,including d...This paper aims to present a simulation model for heterogeneous high-speed train traffic flow based on an improved discrete-time model（IDTM）.In the proposed simulation model,four train control strategies,including departing strategy,traveling strategy,braking strategy,overtaking strategy,are well defined to optimize train movements.Based on the proposed simulation model,some characteristics of train traffic flow are investigated.Numerical results indicate that the departure time intervals,the station dwell time,the section length,and the ratio of fast trains have different influence on traffic capacity and train average velocity.The results can provide some theoretical support for the strategy making of railway departments.展开更多
In order to describe an investigation of the flow around high-speed train on a bridge under cross winds using detached-eddy simulation(DES), a 1/8th scale model of a three-car high-speed train and a typical bridge mod...In order to describe an investigation of the flow around high-speed train on a bridge under cross winds using detached-eddy simulation(DES), a 1/8th scale model of a three-car high-speed train and a typical bridge model are employed, Numerical wind tunnel technology based on computational fluid dynamics(CFD) is used, and the CFD models are set as stationary models. The Reynolds number of the flow, based on the inflow velocity and the height of the vehicle, is 1.9×10~6. The computations are conducted under three cases, train on the windward track on the bridge(WWC), train on the leeward track on the bridge(LWC) and train on the flat ground(FGC). Commercial software FLUENT is used and the mesh sensitivity research is carried out by three different grids: coarse, medium and fine. Results show that compared with FGC case, the side force coefficients of the head cars for the WWC and LWC cases increases by 14% and 29%, respectively; the coefficients of middle cars for the WWC and LWC increase by 32% and 10%, respectively; and that of the tail car increases by 45% for the WWC whereas decreases by 2% for the LWC case. The most notable thing is that the side force and the rolling moment of the head car are greater for the LWC, while the side force and the rolling moment of the middle car and the tail car are greater for the WWC. Comparing the velocity profiles at different locations, the flow is significantly influenced by the bridge-train system when the air is close to it. For the three cases(WWC, LWC and FGC), the pressure on the windward side of train is mostly positive while that of the leeward side is negative. The discrepancy of train's aerodynamic force is due to the different surface area of positive pressure and negative pressure zone. Many vortices are born on the leeward edge of the roofs. Theses vortices develop downstream, detach and dissipate into the wake region. The eddies develop irregularly, leading to a noticeably turbulent flow at leeward side of train.展开更多
Based on incompressible viscous fluid Navier-stokes equation and k-ε 2-equations turbulent model, an investigation on 3D turbulent flow field around four kinds of train models has been made by finite element method. ...Based on incompressible viscous fluid Navier-stokes equation and k-ε 2-equations turbulent model, an investigation on 3D turbulent flow field around four kinds of train models has been made by finite element method. From the calculation, the pressure distribution characters of now field around high-speed trains have been obtained. It is significant for strength design of the high-speed train body, for resisting wind design of the facilities beside the high-speed railways and for determining the aerodynamic force of induced air to the human body near the railways.展开更多
Microcirculation of the peripheral nerve is necessary for neural growth and regeneration. However, technical limitations have limited studies in this area. The few studies conducted have concerned active exercise effe...Microcirculation of the peripheral nerve is necessary for neural growth and regeneration. However, technical limitations have limited studies in this area. The few studies conducted have concerned active exercise effects on microcirculation of the peripheral nerve. Using an animal experiment, this study evaluated the effect of swimming training on microcirculation of injured peripheral nerve by laser Doppler flowmetry. The results showed that the blood vessel at the distal end of the peripheral nerve was the main blood supply for the nerve, and the internal blood supply for the nerve had strong compensatory ability. Swimming training promoted the functional recovery of rats with sciatic nerve injury and the regeneration of myelin sheath and blood vessels, but had no impact on neural blood flow.展开更多
为降低高速列车受电弓气动噪声,采用大涡模拟(Large Eddy Simulation,LES)和FW-H(Ffowcs Williams and Hawkings)声类比方法,在对空气流动及表面声辐射影响较大的原型受电弓圆形上下臂杆及绝缘子立柱进行尖椭圆化改型设计基础上,采用三...为降低高速列车受电弓气动噪声,采用大涡模拟(Large Eddy Simulation,LES)和FW-H(Ffowcs Williams and Hawkings)声类比方法,在对空气流动及表面声辐射影响较大的原型受电弓圆形上下臂杆及绝缘子立柱进行尖椭圆化改型设计基础上,采用三维流体分析软件STAR-CCM+对不同形状杆件受电弓进行流场特征和气动噪声数值模拟,并与原型受电弓进行对比。结果表明:受电弓远场辐射噪声主要集中在弓头、上下臂杆、底架及绝缘子等部位,尖椭圆化设计使受电弓上下臂杆和绝缘子迎流面压力减小,受电弓表面及周围流场的压力波动减弱,这是由于气流撞击受电弓形成的大尺度涡旋沿纵向方向发展破碎形成更小尺度的涡旋结构,进而降低了受电弓气动噪声;尖椭圆形状的改型受电弓较原型受电弓在横向、纵向方向均有气动降噪效果,时速350和400 km条件下改型受电弓纵向方向25 m处可分别降噪5.1和2.4 dB,降幅分别为6.7%和3.0%。研究结果可为设计制造新型低噪声高速列车受电弓提供基本数据支撑。展开更多
文摘Purpose We aimed to determine:(a)the chronic effects of interval training(IT)combined with blood flow restriction(BFR)on physiological adaptations(aerobic/anaerobic capacity and muscle responses)and performance enhancement(endurance and sprints),and(b)the influence of participant characteristics and intervention protocols on these effects.Methods Searches were conducted in PubMed,Web of Science(Core Collection),Cochrane Library(Embase,ClinicalTrials.gov,and International Clinical Trials Registry Platform),and Chinese National Knowledge Infrastructure on April 2,with updates on October 17,2024.Pooled effects for each outcome were summarized using Hedge's g(g)through meta-analysis-based random effects models,and subgroup and regression analyses were used to explore moderators.Results A total of 24 studies with 621 participants were included.IT combined with BFR(IT+BFR)significantly improved maximal oxygen uptake(VO2_(max))(g=0.63,I^(2)=63%),mean power during the Wingate 30-s test(g=0.70,I^(2)=47%),muscle strength(g=0.88,I^(2)=64%),muscle endurance(g=0.43,I^(2)=0%),time to fatigue(g=1.26,I^(2)=86%),and maximal aerobic speed(g=0.74,I^(2)=0%)compared to IT alone.Subgroup analysis indicated that participant characteristics including training status,IT intensity,and IT modes significantly moderated VO2_(max)(subgroup differences:p<0.05).Specifically,IT+BFR showed significantly superior improvements in VO2_(max)compared to IT alone in trained individuals(g=0.76)at supra-maximal intensity(g=1.29)and moderate intensity(g=1.08)as well as in walking(g=1.64)and running(g=0.63)modes.Meta-regression analysis showed cuff width(β=0.14)was significantly associated with VO2_(max)change,identifying 8.23 cm as the minimum threshold required for significant improvement.Subgroup analyses regarding muscle strength did not reveal any significant moderators.Conclusion IT+BFR enhances physiological adaptations and optimizes aspects of endurance performance,with moderators including training status,IT protocol(intensity,mode,and type),and cuff width.This intervention addresses various IT-related challenges and provides tailored protocols and benefits for diverse populations.
基金Public Health Agency of Canada:Healthy Seniors Pilot Project(project number:C0089).
文摘Objectives:To investigate the impact of a supervised bloodflow restriction(BFR)training program performed at different times of the morning on body composition and muscle performance in older,inactive adults.Methods:A single-arm intervention of supervised BFR resistance training was performed three times per week for six weeks.Participants(n=24;aged 65+years)were categorized into early morning(n=13;05:00–08:59)or late morning(n=11;09:00–12:00)groups.Primary outcomes were changes in body composition,total work,average peak power,average peak torque,muscle strength,and physical function.Results:Mixed model analysis of variance revealed a significant within-subject effect of time for all strength measures(p ranging from 0.017 to<0.001)and some physical function measures including the 30 s chair stand test,30 s bicep curl test,and grip strength(p ranging from 0.015 to<0.001).No between-group or time by group interaction effect was observed for all outcomes.Conclusions:This study showed that only six weeks of BFR training,performed at different time of the morning,did not enhance muscle mass and performance,but provided similar changes in muscle strength and some physical function tests in older adults.
文摘To simulate the actual flowfield at the exit of the supersonic/hypersonic inlet, a wind tunnel is designed to study the flow in the scramjet isolator under the asymmetric incoming flow. And compression fields in the isolator are investigated using wall static and pitot pressure measurements. Three incoming Mach numbers are considered as 1.5, 1.8 and 2. Results show that the increase of the asymmetry of the flow at the isolator entrance leads to the increase of the shock train length in the isolator for a given pressure ratio. Based on the analysis of the flow asymmetry effect at the isolator entrance on the shock train length, a modified correlation is proposed to calculate the length of the shock train. Predicted results of the proposed correlation are in good agreement with the experimental data.
基金Project(U1134203)supported by the National Natural Science Foundation of China
文摘According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was studied and eight types of flow regions were proposed. They are high pressure with air stagnant region, pressure decreasing with air accelerating region, low pressure with high air flow velocity region I, turbulent region, steady flow region, low pressure with high air flow velocity region II,pressure increasing with air decelerating region and wake region. The analysis of the vortex structure around the train shows that the vortex is mainly induced by structures with complex mutation and large curvature change. The head and rear of train, the underbody structure, the carriage connection section and the wake region are the main vortex generating sources while the train body with even cross-section has rare vortexes. The wake structure development law studied lays foundation for the train drag reduction.
基金Project supported by the State Social Science Fund Project, China (Grant No. 11CJY067)the Natural Science Foundation of Gansu Province, China (Grant No. 1107RJYA070)
文摘The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automaton models, in this paper, we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system. In the proposed model, we establish some sound rules to control the running processes of a train, where the rules include the departure rules in the intermediate stations, the overtaking rules, and the conditions of speed limitation for a train stopping at a station or passing through a station. With the consideration of the mixed ratio and the distance between two adjacent stations, the properties of the train traffic flow （including capacity and average speed） are simulated. The numerical results show that the interactions among different trains will affect the capacity, and a proper increase of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block.
基金Supported by the National Basic Research Program of China under Grant No.2012CB725400the National Natural Science Foundation of China under Grant No.71222101+1 种基金the Research Foundation of State Key Laboratory of Rail Traffic Control and Safety under Grant No.RCS2014ZT16the Fundamental Research Funds for the Central Universities No.2015YJS088,Beijing Jiaotong University
文摘This paper aims to present a simulation model for heterogeneous high-speed train traffic flow based on an improved discrete-time model（IDTM）.In the proposed simulation model,four train control strategies,including departing strategy,traveling strategy,braking strategy,overtaking strategy,are well defined to optimize train movements.Based on the proposed simulation model,some characteristics of train traffic flow are investigated.Numerical results indicate that the departure time intervals,the station dwell time,the section length,and the ratio of fast trains have different influence on traffic capacity and train average velocity.The results can provide some theoretical support for the strategy making of railway departments.
基金Project(U1534210)supported by the National Natural Science Foundation of ChinaProject(14JJ1003)supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2015CX003)supported by the Project of Innovation-driven Plan in Central South University,ChinaProject(14JC1003)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2015T002-A)supported by the Technological Research and Development program of China Railways Cooperation
文摘In order to describe an investigation of the flow around high-speed train on a bridge under cross winds using detached-eddy simulation(DES), a 1/8th scale model of a three-car high-speed train and a typical bridge model are employed, Numerical wind tunnel technology based on computational fluid dynamics(CFD) is used, and the CFD models are set as stationary models. The Reynolds number of the flow, based on the inflow velocity and the height of the vehicle, is 1.9×10~6. The computations are conducted under three cases, train on the windward track on the bridge(WWC), train on the leeward track on the bridge(LWC) and train on the flat ground(FGC). Commercial software FLUENT is used and the mesh sensitivity research is carried out by three different grids: coarse, medium and fine. Results show that compared with FGC case, the side force coefficients of the head cars for the WWC and LWC cases increases by 14% and 29%, respectively; the coefficients of middle cars for the WWC and LWC increase by 32% and 10%, respectively; and that of the tail car increases by 45% for the WWC whereas decreases by 2% for the LWC case. The most notable thing is that the side force and the rolling moment of the head car are greater for the LWC, while the side force and the rolling moment of the middle car and the tail car are greater for the WWC. Comparing the velocity profiles at different locations, the flow is significantly influenced by the bridge-train system when the air is close to it. For the three cases(WWC, LWC and FGC), the pressure on the windward side of train is mostly positive while that of the leeward side is negative. The discrepancy of train's aerodynamic force is due to the different surface area of positive pressure and negative pressure zone. Many vortices are born on the leeward edge of the roofs. Theses vortices develop downstream, detach and dissipate into the wake region. The eddies develop irregularly, leading to a noticeably turbulent flow at leeward side of train.
文摘Based on incompressible viscous fluid Navier-stokes equation and k-ε 2-equations turbulent model, an investigation on 3D turbulent flow field around four kinds of train models has been made by finite element method. From the calculation, the pressure distribution characters of now field around high-speed trains have been obtained. It is significant for strength design of the high-speed train body, for resisting wind design of the facilities beside the high-speed railways and for determining the aerodynamic force of induced air to the human body near the railways.
基金the Military Project during "Tenth Five-Year Plan" Period, No.200626Z000058
文摘Microcirculation of the peripheral nerve is necessary for neural growth and regeneration. However, technical limitations have limited studies in this area. The few studies conducted have concerned active exercise effects on microcirculation of the peripheral nerve. Using an animal experiment, this study evaluated the effect of swimming training on microcirculation of injured peripheral nerve by laser Doppler flowmetry. The results showed that the blood vessel at the distal end of the peripheral nerve was the main blood supply for the nerve, and the internal blood supply for the nerve had strong compensatory ability. Swimming training promoted the functional recovery of rats with sciatic nerve injury and the regeneration of myelin sheath and blood vessels, but had no impact on neural blood flow.
文摘[目的]探究实时姿势监测与反馈系统对血流限制(blood flow restriction,BFR)下跑者下肢运动学与肌电特征的变化.[方法]17名无BFR训练经验的新手健康跑者参与3次不同方案的跑步测试.第1次测试空白条件下单纯跑步(blank running,BR)状态;第2次测试BFR下跑步(BFR and running,BFRR)状态;第3次测试BFR并进行实时姿势监测与反馈(monitoring and feedback,MF)时的跑步状态.比较3次测试中跑者下肢髋、膝、踝关节峰值活动角度与下肢主要肌肉肌电参数变化.[结果]与BR方案相比,BFRR方案下跑者下肢关节峰值角度显著增加,肌肉激活程度与肌纤维募集频率范围也显著增加.使用实时姿势监测与反馈后,与BFRR方案相比,BFRR+MF方案下跑者下肢关节峰值活动角度与上述肌电参数显著下降.[结论]BFR训练将导致跑者初次应用时表现出过激运动表现,但实时监测与反馈系统将优化运动表现,降低运动损伤风险.
文摘为降低高速列车受电弓气动噪声,采用大涡模拟(Large Eddy Simulation,LES)和FW-H(Ffowcs Williams and Hawkings)声类比方法,在对空气流动及表面声辐射影响较大的原型受电弓圆形上下臂杆及绝缘子立柱进行尖椭圆化改型设计基础上,采用三维流体分析软件STAR-CCM+对不同形状杆件受电弓进行流场特征和气动噪声数值模拟,并与原型受电弓进行对比。结果表明:受电弓远场辐射噪声主要集中在弓头、上下臂杆、底架及绝缘子等部位,尖椭圆化设计使受电弓上下臂杆和绝缘子迎流面压力减小,受电弓表面及周围流场的压力波动减弱,这是由于气流撞击受电弓形成的大尺度涡旋沿纵向方向发展破碎形成更小尺度的涡旋结构,进而降低了受电弓气动噪声;尖椭圆形状的改型受电弓较原型受电弓在横向、纵向方向均有气动降噪效果,时速350和400 km条件下改型受电弓纵向方向25 m处可分别降噪5.1和2.4 dB,降幅分别为6.7%和3.0%。研究结果可为设计制造新型低噪声高速列车受电弓提供基本数据支撑。
