Components of attack response inhibition in fencing: Components of attack response inhibition in fencing

Applying the Go/No-Go paradigm to fencing, we investigated the relationship between the moment at which the No-Go signal appeared after a movement had been initiated and the time required by fencers to suppress the motor execution of a step-lunge. Secondarily, we determined a time threshold from which movement inhibition results in an error. The No-Go stimulus was represented by a real attack movement. 18 elite fencers and a fencing master were included in the study. Four force plates measured the horizontal components of the fencer's and master's reaction forces, which were used to calculate the time components of the attack and the response inhibition process. Also, the velocity and displacement of the master's and fencer's respective centres of mass were estimated using inverse dynamics. In all cases, cognitive inhibition processes were completed after the onset of movement. Movement time was calculated using four time components (muscle activation, muscle deactivation, transition and braking time). The results obtained revealed that cognitive processes were not significantly affected by the timing of the appearance of the No-Go signal. In contrast, movement time and its time components tended to decrease when the time delay between the No-Go stimulus and the onset of the fencer's movement increased. In conclusion, any attempt to withhold an attack movement when it has already started leads to an error that increases the risk of being hit by the opponent, especially when attack is inhibited within 150?ms after the movement has started.     

Effect of defence response time during lunge in foil fencing

The aim of this study was to analyse the effect of stimulus change timing on reaction response time parameters, horizontal velocity of the centre of mass (CM) and precision during offensive actions in fencing. Twelve fencers from the Spanish National Foil Team were included in the study. Two 500 Hz force plates were used to register the horizontal component of the reaction force while a 3D video camera set at 250 Hz recorded the spatial position of 11 body markers and a projector connected to a programmed stopwatch projected a moving target (stimulus) on a screen. When the circle (target) appeared in the centre of the plastron, fencers had to execute a step-forward-lunge as fast as possible, trying to touch the circle with the tip of the foil. During the lunge, the position of the target could randomly shift or not to three different positions. The stimulus change was performed randomly at four different times with a progressive delay. The results show that target changes did not have any effect when they occurred at the beginning of the movement sequence. However, when the target change was delayed, reaction and movement times increased and the technical execution of the lunge changed, leading to more errors.     

Effect of target change during the simple attack in fencing

Abstract

The aim of this study was to test the effect that changing targets during a simple long lunge attack in fencing exerts on the temporal parameters of the reaction response, the execution speed, and the precision and the coordination of the movement pattern. Thirty fencers with more than 10 years of experience participated in this study. Two force platforms were used to record the horizontal components of the reaction forces and thereby to determine the beginning of the movement. A three-dimensional (3D) system recorded the spatial positions of the 9 markers situated on the fencer plus the epee, while a moving target was projected on a screen, enabling the control of the target change. The results indicated that when a target change is provoked the reaction time (RT), movement time (MT), and the time used in the acceleration phase of the centre of mass (CM) increases significantly with respect to the attack executed with a straight thrust. The speed and horizontal distance reached by the CM at the end of the acceleration phase (V_X(CM) and S_X(CM), respectively) significantly decreased, while the errors increased. However, the temporal sequence of the movement pattern did not appreciably change.     

The fatigue effect of a simulated futsal match protocol on sprint performance and kinematics of the lower limbs

This study aimed to investigate the fatigue effects induced by a futsal-specific protocol (FIRP) on sprint performance and the kinematics of the lower limbs. Twenty-one futsal players participated in this study and performed a protocol to simulate the futsal demands. At pre-protocol, half-time and post-protocol, the athletes performed 10-m sprints that were recorded for kinematic analysis. Continuous relative phase (CRP) was calculated to assess the inter-segmental coordination. In addition, vertical (K_VERT) and leg (K_LEG) stiffness were calculated. Analysis of variance (ANOVA) for repeated measures was used (P < 0.05). The main results showed that sprint time increased (P < 0.01) post-protocol when compared to pre- and half-time conditions. Lower values of the step rate (P = 0.01) and higher values of the leg angular velocity (P = 0.02) were verified at the end of the FIRP. The CRP of thigh–leg and leg–foot and the stiffness did not change over the protocol. In addition, the high correlation of CRP between the conditions revealed no changes in coordination pattern. We concluded that futsal related-fatigue induced a decrement on sprint time, changing the kinematics of the lower limbs (decreasing step rate and increasing leg angular velocity). However, neither stiffness nor intersegment coordination during sprints was affected by fatigue.     

Divided attention during cutting influences lower extremity mechanics in female athletes

Anterior cruciate ligament (ACL) injuries in basketball appear to be more common when players are in possession of the ball. The greater risk of ACL injury when in possession of the ball may result from the athlete’s inability to fully attend to their movement. However, it is also possible that having to carry/manipulate the ball restricts the athlete’s ability to utilise their upper extremities for stability during a manoeuvre. The purpose of this study was to explore how possession of a basketball and divided attention influence lower extremity mechanics during cutting and landing. Twenty uninjured females with basketball experience performed a baseline lateral cutting task, as well as lateral cuts while carrying a basketball, with and without a subsequent chest pass. Requiring participants to carry the basketball in isolation (i.e., without the additional pass) had minimal influence on lower extremity mechanics compared to baseline. However, participants demonstrated less knee flexion (40.9° vs. 47.3°) and greater knee abduction (12.2° vs. 10.1°) for trials that included the additional pass (divided attention condition) compared to trials conducted while carrying the basketball in isolation. Athletes may be at greater risk for ACL injury when they are unable to solely attend to their movement.     

A new index of flat breaststroke propulsion: A comparison of elite men and women

This study examined arm and leg coordination and propulsion during the flat breaststroke in nine elite male and eight elite female swimmers over three race paces (200?m, 100?m and 50?m). Coordination was expressed using four temporal gaps (T1, T2, T3, T4), which described the continuity between the propulsive phases of the limbs, as recorded on a video device (50 Hz). Glide duration was denoted T1, the time between the beginning of arm and leg recovery was denoted T2, the time between the end of arm and the leg recovery was denoted T3, and the time between 90° of flexion during arm recovery and 90° during leg recovery was denoted T4. Using these temporal gaps, four stroke phases (propulsion, glide, recovery and leg insweep) could be followed over a complete arm and leg stroke. The total duration of arm and leg propulsion was assessed by a new index of flat breaststroke propulsion (IFBP). Velocity, stroke rate and stroke length were also calculated for each pace. The elite swimmers showed short T2, T3 and T4; moreover, T1 decreased when the pace increased. Expertise in the flat breaststroke was thus characterized by synchronized arm and leg recoveries and increased continuity in the arm and leg propulsions with increasing velocity. Differences between the sexes in the spatio-temporal parameters were possibly due to anthropometric differences (the men were heavier, older and taller than the women) and different motor organization linked to arm and leg coordination (shorter T3, body glide and body recovery, and greater body propulsion and higher IFBP in the men). The men's propulsive actions showed greater continuity, particularly in the sprint. The best men adopted a superposition coordination and thus had the ability to overcome very great active drag. Temporal gap measurement and the IFBP are practical indicators of arm and leg coordination and propulsion that can be exploited by coaches and swimmers to increase the continuity between propulsive actions during the flat breaststroke.     

The effect of a secondary cognitive task on landing mechanics and jump performance

Anterior cruciate ligament (ACL) injuries commonly occur during jump-landing tasks when individuals’ attention is simultaneously allocated to other objects and tasks. The purpose of the current study was to investigate the effect of allocation of attention imposed by a secondary cognitive task on landing mechanics and jump performance. Thirty-eight recreational athletes performed a jump-landing task in three conditions: no counting, counting backward by 1 s from a randomly given number, and counting backward by 7 s from a randomly given number. Three-dimensional kinematics and ground reaction forces were collected and analysed. Participants demonstrated decreased knee flexion angles at initial contact (p = 0.001) for the counting by 1 s condition compared with the no counting condition. Participants also showed increased peak posterior and vertical ground reaction forces during the first 100 ms of landing (p ≤ 0.023) and decreased jump height (p < 0.001) for the counting by 1 s and counting by 7 s conditions compared with the no counting condition. Imposition of a simultaneous cognitive challenge resulted in landing mechanics associated with increased ACL loading and decreased jump performance. ACL injury risk screening protocols and injury prevention programmes may incorporate cognitive tasks into jump-landing tasks to better simulate sports environments.     

Response timing in the lunge and target change in elite versus medium-level fencers

Abstract

The aim of the present work is to examine the differences between two groups of fencers with different levels of competition, elite and medium level. The timing parameters of the response reaction have been compared together with the kinetic variables which determine the sequence of segmented participation used during the lunge with a change in target during movement. A total of 30 male sword fencers participated, 13 elite and 17 medium level. Two force platforms recorded the horizontal component of the force and the start of the movement. One system filmed the movement in 3D, recording the spatial positions of 11 markers, while another system projected a mobile target over a screen. For synchronisation, an electronic signal enabled all the systems to be started simultaneously. Among the timing parameters of the reaction response, the choice reaction time (CRT) to the target change during the lunge was measured. The results revealed differences between the groups regarding the flight time, horizontal velocity at the end of the acceleration phase, and the length of the lunge, these being higher for the elite group, as well as other variables related to the temporal sequence of movement. No significant differences have been found in the simple reaction time or in CRT. According to the literature, the CRT appears to improve with sports practice, although this factor did not differentiate the elite from medium-level fencers. The coordination of fencing movements, that is, the right technique, constitutes a factor that differentiates elite fencers from medium-level ones.     

The effects of control-display gain on performance of race car drivers in an isometric braking task

Abstract

To minimise lap times during car racing, it is important to build up brake forces rapidly and maintain precise control. We examined the effect of the amplification factor (gain) between brake pedal force and a visually represented output value on a driver's ability to track a target value. The test setup was a formula racing car cockpit fitted with an isometric brake pedal. Thirteen racing drivers performed tracking tasks with four control-display gains and two target functions: a step function (35 trials per gain) and a multisine function (15 trials per gain). The control-display gain had only minor effects on root mean-squared error between output value and target value, but it had large effects on build-up speed, overshoot, within-participants variability, and self-reported physical load. The results confirm the hypothesis that choosing an optimum gain involves balancing stability against physical effort.     

The kinematic differences between accurate and inaccurate squash forehand drives for athletes of different skill levels

ABSTRACT

To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball’s velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a “zeroing-in” effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the “functionality” of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot.     

Effect of hand paddles and parachute on butterfly coordination

This study investigated the effects of hand paddles, parachute and hand paddles plus parachute on the inter-limb coordination of butterfly swimming. Thirteen male swimmers were evaluated in four random maximal intensity conditions: without equipment, with hand paddles, with parachute and with hand paddles + parachute. Arm and leg stroke phases were identified by 2D video analysis to calculate the total time gap (T1: time between hands’ entry in the water and high break-even point of the first undulation; T2: time between the beginning of the hand’s backward movement and low break-even point of the first undulation; T3: time between the hand’s arrival in a vertical plane to the shoulders and high break-even point of the second undulation; T4: time between the hand’s release from the water and low break-even point of the second undulation). The swimming velocity was reduced and T1, T2 and T3 increased in parachute and hand paddles + parachute. No changes were observed in T4. Total time gap decreased in parachute and hand paddles + parachute. It is concluded that hand paddles do not influence the arm-to-leg coordination in butterfly, while parachute and hand paddles + parachute do change it, providing a greater propulsive continuity.     

Especial skill vs. quiet eye duration in basketball free throw: Evidence for the inhibition of competing task solutions

Abstract

The quiet eye (QE) is a gaze phenomenon that has been studied over more than two decades. However, the underlying mechanisms of the well-known expertise effect, namely, longer QE durations in experts when compared to less-skilled athletes remain unclear. Therefore, from a functional perspective, an inhibition hypothesis was proposed that explains long QE durations in experts with increased inhibition requirements over movement parametrisation. This hypothesis was tested by making use of the especial-skill effect in basketball free throw which refers to the observation of higher actual performance than would be predicted on the basis of performance at the nearby locations. In line with the expectations, from the distance of the free-throw line, higher actual than predicted shooting accuracy and longer actual than predicted QE duration were revealed. This suggests that when performing free throws prolonged QE durations are required to shield the optimal against alternative task solutions within the very dense sub-space of this especial skill. These findings suggest an inhibition function of long QE durations in expert athletes.     

The effect of carbohydrate mouth rinsing on fencing performance and cognitive function following fatigue-inducing fencing

This study investigated the impact that mouth rinsing carbohydrate solution has on skill-specific performance and reaction time following a fatigue-inducing bout of fencing in epee fencers. Nine healthy, national-level epee fencers visited a laboratory on two occasions, separated by a minimum of five days, to complete a 1-minute lunge test and Stroop test pre- and post-fatigue. Heart rate and ratings of perceived exertion (RPE) were recorded during completion of the fatiguing protocol. Between fights the participant’s mouth rinsed for 10?seconds, either 25?ml of 6.7% maltodextrin solution (MALT) or water (PLAC). Blood lactate and glucose were recorded at baseline, pre- and post-testing. Results showed an increase in heart rate and overall RPE over time in both conditions. There were no differences in blood glucose (F(1,8)?=?.63, P?=?.4, η^p?=?.07) or blood lactate levels (F(1,8)?=?.12, P?=?.70, η^p?=?.01) between conditions as a function of time. There was a significant improvement in lunge test accuracy during the MALT trial (F(1,8)?=?5.21, P?=?.05, η^p?=?.40) with an increase from pre (81.2?±?8.3%) to post (87.6?±?9.4%), whereas there was no significant change during the placebo (pre 82.1?±?8.8%, post 78.8?±?6.4%). There were no recorded differences between conditions in response time to congruent (F(1,8)?=?.33, P?=?.58, η^p?=?.04) or incongruent stimuli (F(1,8)?=?.19, P?=?.68, η^p?=?.02). The study indicates that when fatigued mouth rinsing MALT significantly improves accuracy of skill-specific fencing performance but no corresponding influence on reaction time was observed.     

400m跑的能力对提高400m栏成绩的影响

阐述了 4 0 0m跨栏跑的技术特点 ,就 4 0 0m栏和 4 0 0m跑的相关因素进行了分析。认为要提高 4 0 0m跨栏跑的成绩必须将 4 0 0m跑的训练与 4 0 0m跨栏跑的技术特点相结合。     

学步车对婴幼儿动作发展的影响

学步车于17世纪中后期出现并获得广泛使用,现如今国外许多学者对学步车的使用与婴幼儿动作发展的关系进行了研究,但研究结果并不一致。基于对国外相关文献的梳理,拟厘清学步车使用对婴幼儿动作发展的影响,从而提高家长和社会对学步车的正确认识,并为后续研究提供理论依据。研究发现:使用学步车会导致婴幼儿爬、站立、走等动作发展迟缓,且其影响程度可能与使用时间长短有关;使用学步车与婴幼儿脚尖走路的异常步态以及头部、躯干姿势控制能力低下有关。学步车使用对婴幼儿动作发展有不良影响,建议对其进行改造,并适度或慎重使用。     

中华剑术文化与当今剑术套路演练之研究

中华剑术文化的兴起与发展，有如下特征：即剑术的兴起与剑器的发生、发展关系密切，围绕剑器可形成的技击方法是剑术发展和演变过程的主要内涵。从此点出发，论述了当今剑术套路演练中剑术技法训练的主要内容及其功力训练等相关问题。     

反馈频率对追踪任务技能学习影响的实验研究

采用单维电脑追踪任务,探讨反馈频率对追踪任务技能学习的影响作用.48名右利手的在校大学生随机分为4组(每组男、女各6人),分别按反馈次数占总练习次数比例的25%、50%、75%、100%的频率方式向各组受试者提供当前反馈.结果显示:①获得阶段,频繁反馈有利于提高操作绩效;②保持阶段,减少反馈频率有利于简单追踪任务技能学习.结论:①当前反馈对于练习者学习动作技能具有很强的指导作用,并且容易使学习者对反馈产生依赖性;②通过减少反馈频率的方式可以减少学习者对反馈的依赖作用;③追踪任务技能学习过程中存在反馈频率适宜值.     

Effect of swim speed on leg-to-arm coordination in unilateral arm amputee front crawl swimmers

The aim of this study was to examine the effect of swimming speed on leg-to-arm coordination in competitive unilateral arm amputee front crawl swimmers. Thirteen well-trained swimmers were videotaped underwater during three 25-m front crawl trials (400 m, 100 m and 50 m pace). The number, duration and timing of leg kicks in relation to arm stroke phases were identified by video analysis. Within the group, a six-beat kick was predominantly used (n = 10) although some swimmers used a four-beat (n = 2) or eight-beat kick (n = 1). Swimming speed had no significant effect on the relative duration of arm stroke and leg kick phases. At all speeds, arm stroke phases were significantly different (P < 0.05) between the affected and unaffected sides. In contrast, the kicking phases of both legs were not different. Consequently, leg-to-arm coordination was asymmetrical. The instant when the leg kicks ended on the affected side corresponded with particular positions of the unaffected arm, but not with the same positions of the affected arm. In conclusion, the ability to dissociate the movements of the arms from the legs demonstrates that, because of their physical impairment, unilateral arm amputee swimmers functionally adapt their motor organisation to swim front crawl.     

Effect of movement speed on trunk and hip exercise performance

Abstract

The influence of speed on trunk exercise technique is poorly understood. The aim of this study was to analyse the effect of movement speed on the kinematics and kinetics of curl-up, sit-up and leg raising/lowering exercises. Seventeen healthy, recreationally trained individuals (13 females and 4 males) volunteered to participate in this study. Four different exercise cadences were analysed: 1 repetition/4 s, 1 repetition/2 s, 1 repetition/1.5 s and 1 repetition/1 s. The exercises were executed on a force plate and recorded by three cameras to conduct a 3D photogrammetric analysis. The cephalo-caudal displacement of the centre of pressure and range of motion (ROM) of six joints describing the trunk and hip movements were measured. As sit-up and curl-up speed increased, hip and knee ROM increased. Dorsal-lumbar and upper trunk ROM increased with speed in the curl-up. Faster cadence in the sit-up exercise had minimal effect on trunk ROM: only the upper trunk ROM decreased significantly. In the leg raising/lowering exercise there was a decrease in the pelvic tilt and hip ROM, and increased knee flexion ROM. During higher speed exercises, participants modified their technique to maintain the cadence. Thus, professionals would do well to monitor and control participants' technique during high-speed exercises to maintain performance specificity. Results also suggest division of speed into two cadence categories, to be used as a reference for prescribing exercise speed based on preferred outcome goals.     

The relationship between performance of a single-leg squat and leap landing task: moving towards a netball-specific anterior cruciate ligament (ACL) injury risk screening method

ABSTRACT

Field-based screening methods have a limited capacity to identify high-risk postures during netball-specific landings associated with anterior cruciate ligament (ACL) injuries. This study determined the biomechanical relationship between a single-leg squat and netball-specific leap landing, to examine the utility of including a single-leg squat within netball-specific ACL injury risk screening. Thirty-two female netballers performed single-leg squat and netball-specific leap landing tasks, during which three-dimensional (3D) kinematic/kinetic data were collected. One-dimensional statistical parametric mapping examined relationships between kinematics from the single-leg squat, and the 3D joint rotation and moment data from leap landings. Participants displaying reduced hip external rotation, reduced knee flexion, and greater knee abduction and knee internal rotation angles during the single-leg squat exhibited these same biomechanical characteristics during the leap landing (p < 0.001). Greater ankle dorsiflexion during the single-leg squat was associated with greater knee flexion during landing (p < 0.001). Ankle eversion during the single-leg squat was associated with frontal and transverse plane knee biomechanics during landing (p < 0.001). Biomechanics from the single-leg squat were associated with landing strategies linked to ACL loading or injury risk, and thus may be a useful movement screen for identifying netball players who exhibit biomechanical deficits during landing.