头和非持拍手臂在网球击球中的作用

通过对世界优秀网球选手击球时的观察和分析，并结合多年的教学实践，认为头和非持拍手臂在网球击球时起到了维持身体平衡、保持良好的体轴、增大击球力量的作用，从而提高了击球的稳健性和威胁性。     

Effects of 10-week eccentric overload training on kinetic parameters during change of direction in football players

ABSTRACT

The aim of the current study was to analyse the effect of 10-week eccentric overload training on kinetic parameters during change of direction (COD) in U-19 football players. The outcome measured included relative peak braking (rPB) and propulsive force (rPF), contact time (CT), time spent during braking (BT) and propulsive phase (PT), relative total (rTOT_IMP), braking (rB_IMP) and propulsive (rP_IMP) impulses. Between-group results showed a substantial better improvement (likely) in CT (ES: 0.72) and BT (ES: 0.74) during side-step cutting, and in rPB (ES: 0.84) and rB_IMP (ES: 0.72) during crossover cutting, in the experimental group (EXP) in comparison to control group (CON). Within-group analysis showed a substantially better performance (likely to almost certain) in CT (ES: 1.19), BT (ES: 1.24), PT (ES: 0.70), rPB (ES: 0.75), rPF (ES: 0.68), rTOT_IMP (ES: 0.48) and rB_IMP (ES: 0.50) in EXP during side-step cutting. Regarding crossover cutting, within-group analysis showed a substantial better performance (likely to almost certain) in CT (ES: 0.75), rPB (ES: 0.75), rPF (ES: 1.34), rTOT_IMP (ES: 0.61), rB_IMP (ES: 0.76) and rP_IMP (ES: 0.46) in EXP. In conclusion, the eccentric overload-based programme led to an improvement in kinetic parameters during COD football tasks.     

The effects of maximal and submaximal arm crank ergometry and cycle ergometry on postural sway

Abstract

This study aimed to determine whether arm crank ergometry (ACE) disturbed postural sway to the same extent as cycle ergometry (CE). Nine healthy, none specifically trained adults undertook posturographic tests before and after five separate exercise trials consisting of: two incremental exercise tests to exhaustion for ACE and CE to examine postural sway responses to maximal exercise and to determine peak power output (W_max); two subsequent tests of 30 min duration for ACE and CE at a relative workload corresponding to 50% of the ergometer-specific W_max (ACE_rel; 53 ± 8 W and CE_rel; 109 ± 16 W). A final CE trial was performed at the same absolute power output (CE_abs) as the submaximal ACE trial to match absolute exercise intensity (i.e., 53 ± 8 W). The centre of pressure (COP) displacement was recorded using a force platform before, immediately after exercise and during a 30-min recovery period. ACE had no effects on postural sway (P > 0.05). An increase in mediolateral COP displacement was observed following maximal CE only (P = 0.001), while anteroposterior COP displacement and COP path length increased following maximal and submaximal CE (P < 0.05). These differences in postural sway according to exercise mode likely stem from the activity of postural muscles when considering that CE recruits lower limb muscles involved in balance. This study provides evidence of an exercise mode which does not elicit post-exercise balance impairments, therefore possesses applications to those at an increased risk of falling.     

The effects of arm crank strategy on physiological responses and mechanical efficiency during submaximal exercise

The purpose of this study was to compare submaximal physiological responses and indices of mechanical efficiency between asynchronous and synchronous arm ergometry. Thirteen wheelchair-dependent trained athletes performed eight steady-state incremental bouts of exercise (0 to 140 W), each lasting 4 min, using synchronous and asynchronous arm-cranking strategies. Physiological measures included oxygen uptake (VO2), heart rate, and blood lactate concentration. The power outputs corresponding to fixed whole blood lactate concentrations of 2.0 to 4.0 mmol x l(-1) were calculated using linear interpolation. Mechanical efficiency indices - gross efficiency, net efficiency, and work efficiency - were also calculated. An analysis of variance with repeated measures was applied to determine the effect of crank mode on the physiological parameters. Oxygen uptake was on average 10% lower (P < 0.01), and both net efficiency (P < 0.01) and gross efficiency (P < 0.01) were higher, during the asynchronous strategy at both 60 and 80 W (gross efficiency: 16.9 +/- 2.0% vs. 14.7 +/- 2.4% and 17.5 +/- 1.8% vs. 15.9 +/- 2.6% at 60 and 80 W respectively). There were no differences in heart rate, blood lactate concentration or power output at either of the blood lactate reference points between the asynchronous and synchronous strategies (P > 0.05). In conclusion, test specificity is an important consideration. If a synchronous strategy is to be adopted, it is likely to result in lower efficiency than an asynchronous strategy. The exercise testing scenario may help dictate which method is ultimately chosen.     

The placebo and nocebo effects on peak minute power during incremental arm crank ergometry

Abstract

This investigation aimed to explore the effects of inert sugar-free drinks described as either ‘performance enhancing’ (placebo) or ‘fatigue inducing’ (nocebo) on peak minute power (PMP;W) during incremental arm crank ergometry (ACE). Twelve healthy, non-specifically trained individuals volunteered to take part. A single-blind randomised controlled trial with repeated measures was used to assess for differences in PMP;W, oxygen uptake, heart rate (HR), minute ventilation, respiratory exchange ratio (RER) and subjective reports of local ratings of perceived exertion (LRPE) and central ratings of perceived exertion (CRPE), between three separate, but identical ACE tests. Participants were required to drink either 500 ml of a ‘sports performance’ drink (placebo), a ‘fatigue-inducing’ drink (nocebo) or water prior to exercise. The placebo caused a significant increase in PMP;W, and a significant decrease in LRPE compared to the nocebo (p=0.01; p=0.001) and water trials (p=0.01). No significant differences in PMP;W between the nocebo and water were found. However, the nocebo drink did cause a significant increase in LRPE (p=0.01). These results suggest that the time has come to broaden our understanding of the placebo and nocebo effects and their potential to impact sports performance.     

The effects of arm crank strategy on physiological responses and mechanical efficiency during submaximal exercise

Abstract

The purpose of this study was to compare submaximal physiological responses and indices of mechanical efficiency between asynchronous and synchronous arm ergometry. Thirteen wheelchair-dependent trained athletes performed eight steady-state incremental bouts of exercise (0 to 140 W), each lasting 4 min, using synchronous and asynchronous arm-cranking strategies. Physiological measures included oxygen uptake ([Vdot]O₂), heart rate, and blood lactate concentration. The power outputs corresponding to fixed whole blood lactate concentrations of 2.0 to 4.0 mmol · l^?1 were calculated using linear interpolation. Mechanical efficiency indices – gross efficiency, net efficiency, and work efficiency – were also calculated. An analysis of variance with repeated measures was applied to determine the effect of crank mode on the physiological parameters. Oxygen uptake was on average 10% lower (P < 0.01), and both net efficiency (P < 0.01) and gross efficiency (P < 0.01) were higher, during the asynchronous strategy at both 60 and 80 W (gross efficiency: 16.9 ± 2.0% vs. 14.7 ± 2.4% and 17.5 ± 1.8% vs. 15.9 ± 2.6% at 60 and 80 W respectively). There were no differences in heart rate, blood lactate concentration or power output at either of the blood lactate reference points between the asynchronous and synchronous strategies (P > 0.05). In conclusion, test specificity is an important consideration. If a synchronous strategy is to be adopted, it is likely to result in lower efficiency than an asynchronous strategy. The exercise testing scenario may help dictate which method is ultimately chosen.     

The effects of dehydration and rehydration on electrocardiographic and echocardiographic parameters in Greco-Roman wrestlers

Abstract

The effects of exercise training on heart have been widely explored. However, less understood are the effects of dehydration and rehydration on electrocardiographic (ECG) and echocardiographic (Echo) parameters in wrestlers. The aim of this study was to determine the effect of dehydration and rehydration on some ECG and Echo parameters. Fourteen healthy high school wrestlers (age 18.1±2.6 years, weight 77.2±10.2 kg, BMI 25.2±2.9 kg · m^?2; mean±s) were randomly assigned to an experimental (loss of 3–4% of their weight through 10-min bouts in dry sauna) or a control (dry sauna exposure with mineral water proportionate to their body weight loss) group. Blood and urine sampling, 12-lead ECG, and echocardiogram were recorded in euhydration, dehydration, and 18 h after sauna. Moreover, a 6-min high-intensity arm ergometer cranking test (8×15 s intervals at maximum workload and 30 s active recovery) was completed in each of the three stages. Data were analysed with repeated-measures analysis of variance, independent t-tests, and Pearson correlations. Dehydration by 3–4% of body weight in sauna resulted in augmentation of the sum of amplitudes of P waves and QRS complexes (mm), but decreased left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (ml). As expected, rehydration was associated with recovery of the P wave and ECG parameters. In general, QRS amplitude correlated poorly with LVESV, LVEDV, and P wave, but was inversely related to stroke volume (r=–0.387, P=0.011). In conclusion, dehydration in Greco-Roman wrestlers results in physiological alterations (amplitude of the P wave and QRS complex, LVESV, LVEDV, and stroke volume) of the electrical properties of the passive volume conductor. Further research is necessary to assess the potential for adverse events and appropriateness of this short-term weight loss strategy for young wrestlers or other populations.     

The compatibility of zero-sum logic and mutualism in sport

This essay argues that within competitive sport zero-sum logic and the theory of mutualism are compatible and complementary. Drawing on Robert Simon’s theory of mutualism and Scott Kretchmar’s argument for zero-sum logic, this article shows how athletes can strive for a clear-cut victory and shared benefits such as athletic excellence fully and wholeheartedly at the same time. This paper will also consider how acknowledgment of this dynamic could advance understandings for ethical theories for sport. It will then conclude by describing a subjective approach that will make the affinity of zero-sum logic and mutualism more accessible for sports people.     

The effects of differential and variable training on the quality parameters of a handball throw

The aim of this study was to undertake a comprehensive temporal, effective, and practical training study (variable and differential learning) that would offer athletes the opportunity to increase their performance, and to analyse the effects by measuring kinematics and quality parameters. Two participants of differing standards--a player of the first Austrian League and an Olympic and World Champion--but of similar anthropometric characteristics were recruited. One of the participants (Austrian League) was tested on five different occasions (pre-test and four retests) to measure the effects of four different training phases using kinematic analysis. The results of the study indicate an increase in ball velocity within the differential training phases (first, second, and fourth phases), different proximal-to-distal sequences of the participants, and a change of movement pattern during training measured by the segment velocities and the angle-time courses.     

The effects of differential and variable training on the quality parameters of a handball throw

The aim of this study was to undertake a comprehensive temporal, effective, and practical training study (variable and differential learning) that would offer athletes the opportunity to increase their performance, and to analyse the effects by measuring kinematics and quality parameters. Two participants of differing standards – a player of the first Austrian League and an Olympic and World Champion – but of similar anthropometric characteristics were recruited. One of the participants (Austrian League) was tested on five different occasions (pre-test and four retests) to measure the effects of four different training phases using kinematic analysis. The results of the study indicate an increase in ball velocity within the differential training phases (first, second, and fourth phases), different proximal-to-distal sequences of the participants, and a change of movement pattern during training measured by the segment velocities and the angle–time courses.     

浅谈速度滑冰摆臂技术

针对我国运动员摆臂技术的现状,对摆臂技术加以分析,并着重剖析摆臂的加速和制动的关系,及对蹬冰和自由滑行的作用.介绍了摆臂技术的训练原则、手段和应注意的问题.     

刍议高校高水平冰上运动队的发展方向

通过对高校创建高水平运动队的历史回顾,以及对北方高校部分冬季项目创建高水平运动队的分析,就如何使北方高校冰上高水平运动队健康成长并成为名符其实的高水平运动队,提出一些发展方向方面的建议和办法.     

"后奥运时代"武术的发展方向

武术的“后奥运时代”即将来临。未来武术的发展不单是要进入奥运会,更应该关注竞技武术进奥以后具有多大的生存空间以及整个武术体系的完善性重建,最终目的是推广一种独具魅力的东方文化;把以人为本作为发展的基石,在健康体育领域展现自身魅力,为构建和谐社会和弘扬民族文化作出贡献。     

我国竞技健美操科学研究的现状与走向

运用献资料法，对1990－2001年间我国竞技健美操研究论的主要内容、所采用的方法以及论的总体分布进行了论述，了解目前我国竞技健美操科学研究的现状及存在的问题。指出今后应在学科理论知识的指导下进行实证性的科学研究，并加强对竞技健美操成套动作编排、运动员选材、形体与舞蹈训练，以及运动员的心理素质训练等方面的研究。     

运动领域中自我设限的研究进展和方向

自我设限(self handicapping)是人们经常采用的一种保护自我价值的行为,在日常生活和运动领域中都广泛存在。对国外自我设限的概念、自我设限量表以及自我设限与群体凝聚力的关系等方面的研究进行分析说明,指出体育运动领域自我设限的未来研究方向,以期对拓宽体育研究者的视野有所帮助。     

关于摆臂技术对跳远起跳效果影响的研究

随着世界各大体育赛事对田径项目越来越重视,而跳远作为田径重要技巧性项目,跳远质量和运动受素质不断提高,起跳动作是跳远技术的主要环节,人们还渐研究起跳技巧来提高自己的运动成绩,俗话说：细节决定成败,跳远不但要求运动员综合素质要高,更讲究运动过程中的细节给跳远带来的作用,目前,在高校教学和训练中,很多老师重视助跑和下肢的技术,以便更直接更快速的提高跳远成绩,而忽视对上肢摆臂技术的教学和训练。该文针对目前这种教学误区,分析了正确的上肢摆臂对起跳的速度、力量以震技术带来的影响,对助跑和起跳起到非常重要作用。     

体育学两种主义研究范式的对立与融合

对体育学的理解都可以归及到科学主义和人文主义这一文化思潮上,这两种思潮形成了两种不同的研究范式:从科学精神层次来看,体育学是科学,这是对体育学的低层次理解。从人文精神层次看,体育学是人文的,这是对体育学的高层次的理解。科学主义与人文主义研究范式从对立走向融合是我国体育科学研究的未来走向。     

论散打竞赛临场指挥的艺术

散打竞赛是中华武术的对抗性项目。是竞赛双方比技能、战术、体能、智力等运动。论述在竞赛中短暂的局间休息时教练指挥的特点和基本原则，认为教练临场指挥必须具备良好的心理素质、敏锐的洞察力、优秀的语言表达能力及应变能力等。     

Head, eye and arm coordination in table tennis

The aim of this study was to determine the role of head, eye and arm movements during the execution of a table tennis forehand stroke. Three-dimensional kinematic analysis of line-of-gaze, arm and ball was used to describe visual and motor behaviour. Skilled and less skilled participants returned the ball to cued right or left target areas under three levels of temporal constraint: pre-, early- and late-cue conditions. In the pre- and early-cue conditions, both high and low skill participants tracked the ball early in flight and kept gaze stable on a location in advance of the ball before ball-bat contact. Skilled participants demonstrated an earlier onset of ball tracking and recorded higher performance accuracy than less skilled counterparts. The manipulation of cue condition showed the limits of adaptation to maintain accuracy on the target. Participants were able to accommodate the constraints imposed by the early-cue condition by using a shorter quiet eye duration, earlier quiet eye offset and reduced arm velocity at contact. In the late-cue condition, modifications to gaze, head and arm movements were not sufficient to preserve accuracy. The findings highlight the functional coupling between perception and action during time-constrained, goal-directed actions.     

Psychophysics of arm movements and human aging.

The purpose of this study was to investigate possible age-related differences in the physical stimulus-psychological response relationship. Young and older adult subjects moved their arm to three standard locations or extents (25 cm, 50 cm, and 75 cm) on a linear positioning device. Seven standard comparison combinations were presented 20 times each. Subjects were asked to determine whether the comparison was different from the standard. Just noticeable difference, constant error, absolute constant error, and Weber ratios were calculated. In contrast to previous studies, the results clearly indicate that the physical stimulus-psychological response magnitude relationship for location and extent movements is best described by a metathetic continuum. We offer an explanation to account for the differences between location and extent movements for the just noticeable difference and Weber ratio. The failure to find differences between the age groups suggests that age-related declines cannot be generalized to all perceptual systems.