运动性疲劳与pH值

运动性疲劳是一个复杂的现象。众多研究表明，pH的下降与运动性疲劳具有很高的相关性。PH值的下降可通过影响骨骼肌、脑、心脏、呼吸、肝脏等器官系统而促发运动性疲劳的产生。     

我国高水平短跑运动员途中跑摆动技术的肌肉用力特征

运用表面肌电遥测和高速摄像同步测试方法,揭示我国部分高水平短跑运动员途中跑摆动技术的肌肉用力特征。结果表明:短跑途中跑摆动技术的肌电特征表现为明显的时序性,肌肉间的收缩具有高度协调性。折叠前摆阶段,摆动腿屈髋肌的主要电位活动是在摆动初期:运动员足蹬离地面至(另一腿)垂直支撑时刻前;垂直支撑时刻后,摆动腿股二头肌长头、半腱肌的活动明显,活动时间较长;下压着地阶段,其工作性质由被动拉长转为向心收缩使髋关节伸,同时还作用于膝关节使膝关节屈,神经肌肉活动的机制十分复杂。在专项力量训练实践中,教练员应结合摆动腿髋关节屈伸肌群的发力特点,优选专项力量训练的手段,提高训练效果。     

人工智能背景下应用型本科院校会计专业人才培养及课程改革研究

随着科学技术的发展,互联网应用于各个领域已是大势所趋,"互联网+"的人工智能应用在会计领域对应用型本科院校会计专业人才培养而言,既是挑战,又是机遇.人工智能背景下,对高校会计人才培养提出了新的要求.应用型本科院校应当采取:以社会需求为导向,重塑人才培养方案设计理念;探索多学科融合的培养模式;引入企业导师,充实实践教材、...     

Physical activity and nutrition guidelines to help with the fight against COVID-19

ABSTRACT

As the world is witnessing the epidemic of coronavirus disease 2019, emerging genetics and clinical pieces of evidence suggest a similar immunopathology to those of severe acute respiratory syndrome and Middle East respiratory syndrome. Staying at home to prevent the spread of the virus and consequently being largely inactive is associated with unintended consequences. These can actually enhance the infection risk and exacerbate poor health conditions including impaired immune function. Physical activity is a feasible way of improving health, particularly physical and mental health in a time of social isolation. However, people with certain health conditions in these circumstances may need a special physical activity programme in addition to any exercise they may already be performing via online programmes. This review aims to provide practical guidelines during the COVID-19 quarantine period. We suggest performing aerobic, resistance training, respiratory muscle training and yoga in the healthy, and in those with upper respiratory tract illness, patients with lower respiratory tract illness should be restricted to respiratory muscle training and yoga. In addition, vitamins D and C, omega-3 fatty acids, and regular consumption of fruit and vegetables might be considered as nutritional aids to support the immune system in those affected by COVID-19.     

Fatigue increases ankle sprain risk in badminton players: A biomechanical study

ABSTRACT

Ankle sprains are the most common injury in regular badminton players and usually occur at the end of a match or training. The purpose of the present study was to examine the influence of fatigue produced by badminton practice on the lower limb biomechanics of badminton players. It was hypothesized that fatigue induces ankle kinematic and lower leg muscle activity changes which may increase the risk of ankle sprain. Ankle kinematics, ankle kinetics and muscles activities of 17 regular badminton players were recorded during lateral jumps before and after an intense badminton practice session. Post-fatigue, ankle inversion at foot strike and peak ankle inversion increased (+2.6°, p = 0.003 and +2.5°, p = 0.005, respectively). EMG pre-activation within 100 ms before foot landing significantly decreased after fatigue for soleus (?23.4%, p = 0.031), gastrocnemius lateralis (?12.2%, p = 0.035), gastrocnemius medialis (?23.3%, p = 0.047) and peroneus brevis (?17.4%, p = 0.036). These results demonstrate impaired biomechanics of badminton players when fatigue increases, which may cause a greater risk of experiencing an ankle sprain injury.     

The cumulative and residual fatigue response associated with soccer-specific activity performed on different playing surfaces

ABSTRACT

This study aimed to assess the effect of playing surface (Natural [NT] and Artificial [AT] Turf) on the fatigue response to a soccer-specific exercise protocol (SSEP). Eighteen male soccer players completed the SSEP on NT and AT with pre-, post-, and 48 h post-assessments of eccentric knee flexor (eccKF) and concentric knee extensor peak torque (PT), peak countermovement (CMJ) and squat jump (SJ) height, and Nordic hamstring break angle. No significant main effects for surface or any surface and time interactions were observed for any of the outcome measures, except for eccKF PT recorded at 3.14 rad·s^-1, which was significantly lower 48 h post-trial in the AT condition (AT = 146.3 ± 20.4 Nm; NT = 158.8 ± 24.7 Nm). Main effects for time were observed between pre- and post-trial measures for eccKF PT at all angular velocities, Nordic break angle, CMJ and SJ height. Nordic break angle, and both CMJ and SJ height were significantly impaired 48 h post-trial when compared to pre-trial. The findings of the current study suggest surface dependent changes in eccKF PT which may have implications for recovery and subsequent performance after competition on AT.     

Reliability of arterial spin labelling measurements of perfusion within the quadriceps during steady-state exercise

Arterial spin labelling (ASL) provides a potential method to non-invasively determine muscle blood flow and examine the impact of interventions such as supplementation and training. However, it's a method with intrinsically low signal, leading to limitations in accuracy and temporal resolution. To examine these limitations, the current study measured perfusion via ASL on three occasions in the rectus femoris of 10 healthy adults, during light and moderate exercise, over three different exercise durations. For data sampled over 9 min, light intensity exercise gave an average perfusion of 35.0 ± 5.1 ml/min.100g^?1 with a coefficient of variation (COV) of 16% and single intraclass correlation coefficient (ICC) of 0.67. For the moderate bout, perfusion was 51.3 ± 5.6 ml/min.100g^?1 (COV 10%, ICC 0.82). When the same data were analyzed over 5 min 24 s, perfusion was 37.8 ± 11.13 (COV 30%, ICC 0.13) during light and 49.5 ± 8.8 ml/min.100g^?1 (COV 18%, ICC 0.52) during moderate exercise. When sampling was reduced to 1 min 48 s, perfusion was 41.2 ± 13.7 (COV 33%, ICC 0.26) during light and 49.5 ± 13.6 ml/min.100g^?1 (COV 28%, ICC 0.04) during moderate exercise. For 9 min a significant perfusion difference was found between the exercise intensities; however, this was not the case for sampling over 5 min 24 s or 1 min 48 s. Such findings illustrate the potential of ASL to non-invasively monitor muscle perfusion under steady-state conditions, but highlight that extended exercise protocols are necessary in order to generate date of sufficient reliability to be able to discriminate intervention dependent perfusion differences.     

Low-intensity electrical muscle stimulation induces significant increases in muscle strength and cardiorespiratory fitness

The aim of this study was to investigate the effect of low-intensity exercise training using belt electrode skeletal muscle electrical stimulation on muscle strength and cardiorespiratory fitness in healthy subjects. Nineteen healthy subjects were allocated into control or intervention groups; in both groups the participants kept regular physical activity while the intervention group underwent 30 min B-SES training at 3–4 METs for four weeks. Knee extensor muscle strength and cardiorespiratory endurance during incremental exercise test were measured at baseline and after four weeks for all participants. The relative change of knee extensor muscle strength in the intervention group was significantly higher than control group (p?p?相似文献   

Effects of load mass carried in a backpack upon respiratory muscle fatigue

Purpose: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20?kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60?min walking at 6.5?km?h^?1 wearing a backpack of either 0 (LC₀), 10 (LC₁₀), 15 (LC₁₅) or 20?kg (LC₂₀). Inspiratory (P_Imax) and expiratory (P_Emax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60?s of each trial. Results: Group mean P_Imax and P_Emax were unchanged following 60-min load carriage in all conditions (p?>?.05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p?p?>?.05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20?kg in a backpack for up to 60?min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.     

沥青洒布车的智能控制

沥青洒布车智能控制，即沥青洒布车能根据洒布车的工作环境的变化，如速度波动、负载的变化等，进行逻辑判断、智能决策，保证其喷洒恒定，满足工程施工的要求。利用人工智能的自适应性、模糊推理、经验推理等优点，结合神经网络的自学习、分布式信息处理等，采用人工智能和专家系统对沥青洒布车进行控制。