多党合作和政治协商——中国共产党对马克思主义联合民主政党思想的继承与创新     

谭元敏 《黄石理工学院学报(人文社科版)》2013,(5):45-48

马克思主义创始人马克思在《共产党宣言》一文中,明确提出了共产党联合各民主政党的策略思想;列宁在领导俄国革命和建设的过程中,对马克思、恩格斯联合民主政党的思想进行了继承和发展,提出了不同历史时期对民主政党采取不同联合策略的思想。中国共产党在领导中国革命、建设及改革的不同时期,将马克思主义联合民主政党的策略思想与中国实际相结合,逐渐形成了中国特色的政党合作形式——多党合作和政治协商,并加以制度化,实现了制度创新。  相似文献   

A biomechanical analysis of common lunge tasks in badminton     

Gregor Kuntze  Neil Mansfield  William Sellers 《Journal of sports sciences》2013,31(2):183-191

Abstract

The lunge is regularly used in badminton and is recognized for the high physical demands it places on the lower limbs. Despite its common occurrence, little information is available on the biomechanics of lunging in the singles game. A video-based pilot study confirmed the relatively high frequency of lunging, ～15% of all movements, in competitive singles games. The biomechanics and performance characteristics of three badminton-specific lunge tasks (kick, step-in, and hop lunge) were investigated in the laboratory with nine experienced male badminton players. Ground reaction forces and kinematic data were collected and lower limb joint kinetics calculated using an inverse dynamics approach. The step-in lunge was characterized by significantly lower mean horizontal reaction force at drive-off and lower mean peak hip joint power than the kick lunge. The hop lunge resulted in significantly larger mean reaction forces during loading and drive-off phases, as well as significantly larger mean peak ankle joint moments and knee and ankle joint powers than the kick or step-in lunges. These findings indicate that, within the setting of this investigation, the step-in lunge may be beneficial for reducing the muscular demands of lunge recovery and that the hop lunge allows for higher positive power output, thereby presenting an efficient lunging method.  相似文献   

Correlation of axial impact forces with knee joint forces and kinematics during simulated ski-landing     

Chen-Hua Yeow  Chin-Yang Kong  Peter Vee-Sin Lee  James Cho-Hong Goh 《Journal of sports sciences》2013,31(11):1143-1151

Abstract

Anterior cruciate ligament (ACL) rupture, during ski-landing, is caused by excessive knee joint forces and kinematics, like anterior tibial translation, internal tibial rotation, and valgus rotation. It is not well understood how these forces/kinematics are directly related to ski-landing impact. In the present study, we applied simulated ski-landing impact to knee specimens, and examined joint force/kinematic responses and their correlations with impact force. Ten human cadaveric knees were subjected to axial impact loading at 70° of flexion to simulate ski-landing impact. Impact was repeated with incremental magnitude until ACL failure. Axial impact forces, anterior-posterior and medial-lateral tibial forces were measured using a tri-axial load cell. Anterior-posterior tibial translation, internal-external tibial rotation, and valgus-varus rotation were determined using a motion-capture system. We found positive correlations of axial impact force with anterior tibial force, medial tibial force, anterior tibial translation, internal tibial rotation, and valgus joint rotation. Axial impact forces were more strongly correlated with anterior tibial forces (R ² = 0.937 ± 0.050), anterior tibial translation (R ² = 0.916 ± 0.059), and internal tibial rotation (R ² = 0.831 ± 0.141) than medial tibial force (R ² = 0.677 ± 0.193) and valgus joint rotation (R ² = 0.630+0.271). During ski-landing, these joint forces/kinematics can synergistically act to increase ACL injury risk, whereby the failure mechanism would be dominated by anterior tibial forces, anterior tibial translation, and internal tibial rotation.  相似文献   

Acute effects of static and dynamic stretching on hamstrings’ response times     

Francisco Ayala  Mark De Ste Croix  Pilar Sainz de Baranda  Fernando Santonja 《Journal of sports sciences》2013,31(9):817-825

Abstract

The main purposes of this study were to (a) investigate acute effects of static and dynamic lower limb stretching routines on total response time, pre-motor time and motor time of the medial and lateral hamstrings during maximal eccentric isokinetic knee flexion; and (b) determine whether static and dynamic routines elicit similar responses. A total of 38 active adults completed the following intervention protocols in a randomised order on separate days: (a) non-stretching (control condition), (b) static stretching and (c) dynamic stretching. After the stretching or control intervention, total response time, pre-motor time and motor time of the medial and lateral hamstrings were assessed during eccentric knee flexion movements with participants prone. Measures were compared via a mixed-design factorial ANOVA. There were no main effects for total response time, pre-motor time and motor time. The results suggest that dynamic and static stretching has no influence on hamstrings response times (total response time, pre-motor time and motor time) and hence neither form of stretching reduces this primary risk factor for anterior cruciate ligament injury.  相似文献   

Does whole body vibration training affect knee kinematics and neuromuscular control in healthy people?     

Borja Sañudo  Adrian Feria  Luis Carrasco  Moisés de Hoyo  Rui Santos  Hugo Gamboa 《Journal of sports sciences》2013,31(14):1537-1544

Abstract

This study aimed to investigate the effect of whole body vibration (WBV) training on the knee kinematics and neuromuscular control after single-legged drop landings. Surface electromyographic (EMG) activity of the rectus femoris and hamstring muscles and knee and ankle accelerometry signals were acquired from 42 healthy volunteers. Participants performed three pre-test landings and after a recovery period of three minutes, they completed one set of six bouts of WBV each of one minute duration (30 Hz – 4 mm), followed by a single-leg drop landing. After the WBV intervention no significant changes were observed in the kinematic outcomes measured, although the time to stabilise the lower-limb was significantly lower after the vibration training (F(8,41) = 6.55; P < 0.01). EMG analysis showed no significant differences in the amplitude of rectus femoris or hamstring muscles after WBV training, however, significant differences in EMG frequency of the rectus femoris were found before (F(8,41) = 7.595; P < 0.01) and after toe-down (F(8,41) = 4.440; P < 0.001). Finally, no significant changes were observed in knee or ankle acceleration after WBV. Results suggest that WBV can help to acutely enhance knee neuromuscular control, which may have clinical significance and help in the design of rehabilitation programmes.  相似文献   

The potential of toe flexor muscles to enhance performance     

Jan-Peter Goldmann  Maximilian Sanno  Steffen Willwacher  Kai Heinrich  Gert-Peter Brüggemann 《Journal of sports sciences》2013,31(4):424-433

Abstract

The metatarsal phalangeal joint (MPJ) and its crossing toe flexor muscles (TFM) represent the link between the large energy generating leg extensor muscles and the ground. The purpose of this study was to examine the functional adaptability of TFM to increased mechanical stimuli and the effects on walking, running and jumping performance.

Fifteen men performed a heavy resistance TFM strength training with 90% of the maximal voluntary isometric contraction (MVIC) for 7 weeks (560 contractions) for the left and right foot. Maximal MPJ and ankle plantar flexion moments during MVICs were measured in dynamometers before and after the intervention. Motion analyses (inverse dynamics) were performed during barefoot walking, running, and vertical and horizontal jumping. Athletic performance was determined by measuring jump height and distance.

Left (0.21 to 0.38 Nm · kg^?1; P < 0.001) and right (0.24 to 0.40 Nm · kg^?1; P < 0.001) MPJ plantar flexion moments in the dynamometer, external MPJ dorsiflexion moments (0.69 to 0.75 Nm · kg^?1; P = 0.012) and jump distance (2.25 to 2.31 m; P = 0.006) in horizontal jumping increased significantly.

TFM responded highly to increased loading within a few weeks. The increased force potential made a contribution to an athlete's performance enhancement.  相似文献   

乒乓球运动员肩关节损伤原因及预防对策     

顾晓飞 《辽宁体育科技》2013,(6):47-48,62

肩关节损伤在乒乓球运动损伤中最为常见,损伤不仅影响运动员运动成绩的提高、运动寿命的减短,甚至给运动员的生理、心理造成严重的影响。本文分析了乒乓球运动员肩关节损伤的原因,并相应提出有效的预防措施,旨在为保证训练的正常进行及提高运动员的运动寿命提供参考。  相似文献   

Kinetics and kinematics analysis of incremental cycling to exhaustion     

Rodrigo R. Bini  Fernando Diefenthaeler 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):223-235

Technique changes in cyclists are not well described during exhaustive exercise. Therefore the aim of the present study was to analyze pedaling technique during an incremental cycling test to exhaustion. Eleven cyclists performed an incremental cycling test to exhaustion. Pedal force and joint kinematics were acquired during the last three stages of the test (75%, 90% and 100% of the maximal power output). Inverse dynamics was conducted to calculate the net joint moments at the hip, knee and ankle joints. Knee joint had an increased contribution to the total net joint moments with the increase of workload (5–8% increase, p < 0.01). Total average absolute joint moment and knee joint moment increased during the test (25% and 39%, for p < 0.01, respectively). Increases in plantar flexor moment (32%, p < 0.01), knee (54%, p < 0.01) and hip flexor moments (42%, p = 0.02) were found. Higher dorsiflexion (2%, for p = 0.03) and increased range of motion (19%, for p = 0.02) were observed for the ankle joint. The hip joint had an increased flexion angle (2%, for p < 0.01) and a reduced range of motion (3%, for p = 0.04) with the increase of workload. Differences in joint kinetics and kinematics indicate that pedaling technique was affected by the combined fatigue and workload effects.  相似文献   

Effects of workload and pedalling cadence on knee forces in competitive cyclists     

Rodrigo R. Bini  Patria A. Hume 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):93-107

Limited evidence showed that higher workload increases knee forces without effects from changes in pedalling cadence. This study assessed the effects of workload and cadence on patellofemoral and tibiofemoral joint forces using a new model. Right pedal force and lower limb joint kinematics were acquired for 12 competitive cyclists at two levels of workload (maximal and second ventilatory threshold) at 90 and 70 rpm of pedalling cadence. The maximal workload showed 18% larger peak patellofemoral compressive force PFC (large effect size, ES) than the second ventilatory threshold workload (90 rpm). In the meantime, the 90-rpm second ventilatory threshold was followed by a 29% smaller PFC force (large ES) than the 70-rpm condition. Normal and anterior tibiofemoral compressive forces were not largely affected by changes in workload or pedalling cadence. Compared to those of previous studies, knee forces normalized by workload were larger for patellofemoral (mean = 19 N/J; difference to other studies = 20–45%), tibiofemoral compressive (7.4 N/J; 20–572%), and tibiofemoral anterior (0.5 N/J; 60–200%) forces. Differences in model design and testing conditions (such as workload and pedalling cadence) may affect prediction of knee joint forces.  相似文献   

A three-dimensional analysis of the contributions of upper limb joint movements to horizontal racket head velocity at ball impact during tennis serving     

Satoru Tanabe  Akira Ito 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):418-433

In this study, we examined the relationship between upper limb joint movements and horizontal racket head velocity to clarify joint movements for developing racket head speed during tennis serving. Sixty-six male tennis players were videotaped at 200 Hz using two high-speed video cameras while hitting high-speed serves. The contributions of each joint rotation to horizontal racket velocity were calculated using vector cross-products between the angular velocity vectors of each joint movement and relative position vectors from each joint to the racket head. Major contributors to horizontal racket head velocity at ball impact were shoulder internal rotation (41.1%) and wrist palmar flexion (31.7%). The contribution of internal rotation showed a significant positive correlation with horizontal racket head velocity at impact (r = 0.490, P < 0.001), while the contribution of palmar flexion showed a significant negative correlation (r = ? 0.431, P < 0.001). The joint movement producing the difference in horizontal racket head velocity between fast and slow servers was shoulder internal rotation, and angular velocity of shoulder internal rotation must be developed to produce a high racket speed.  相似文献