Rate of Torque Development and Feedforward Control of the Hip and Knee Extensors: Gender Differences

The purpose of this study was to determine whether women demonstrate decreased rate of torque development (RTD) of the hip and knee extensors and altered onset timing of the vastus lateralis and gluteus maximus during a drop-jump task when compared with men. On average, women demonstrated significantly lower normalized RTD of the hip extensors (women: 11.6 ± 1.3 MVT.s^?1, men: 13.1 ± 0.9 MVT.s^?1; p ≤ .01); however, there was no significant difference in knee extensor RTD. Women also demonstrated significantly earlier activation of their vastus lateralis (women: 206.0 ± 130.6 ms, men: 80.9 ± 69.6 ms; p ≤ .01) and gluteus maximus (women: 85.7 ± 58.6 ms, men: 54.5 ± 35.4 ms; p = .02). In both men and women, there was a significant negative correlation between the hip extensor RTD and the vastus lateralis electromyographic onset time (men: r = –.386, p = .046; women: r = –.531, p = .008). The study findings suggest that women may utilize a feedforward control strategy in which they activate their knee extensors earlier than men to compensate for deficits in hip extensor RTD. The impaired capacity to rapidly stabilize the hip and knee joints during dynamic maneuvers may contribute to the increased risk of anterior cruciate ligament injury observed in women.     

词边界信息在中文阅读眼跳目标选择中的作用：来自中文二语学习者的证据

采用EyeLink 1000眼动仪, 选取韩、美、日、泰四国留学生各20名, 在正常无空格和词间空格两种呈现方式下阅读中文语句, 以此来探讨二语学习者在阅读中文时词边界信息在眼跳目标选择中的作用。结果发现, 二语学习者在中文阅读中存在着一致的眼动模式, 即在单次注视事件中, 倾向于注视词的中间部分, 在多次注视事件中, 倾向于注视其开端部分, 然后再计划一次词内再注视。词边界信息能够有效地引导中文二语学习者的眼动行为和眼跳计划, 更多地将首次注视位置落在词的中间部分。最后, 词边界信息在眼跳目标选择中的促进作用没有受到母语文本呈现方式熟悉性的调节。我们认为, 中文二语学习者在阅读中的眼跳目标选择可能采用的是战略-战术策略。     

Enhanced retention of drop vertical jump landing technique: A randomized controlled trial

External focus instructions have been shown to result in superior motor performance compared to internal focus instructions. Using an EF may help to optimize current anterior cruciate ligament (ACL) injury prevention programs. The purpose of the current study was to investigate the effects of instructions on landing technique and performance by comparing an external focus (EF), internal focus (IF), video (VI) and control (CTRL) group. Subjects (age 22.50 ± 1.62 years, height 179.70 ± 10.43 cm, mass 73.98 ± 12.68 kg) were randomly assigned to IF (n = 10), EF (n = 10), VI (n = 10) or CTRL group (n = 10). Landing was assessed from a drop vertical jump (DVJ) in five sessions: pretest, two training blocks (TR1 and TR2) and directly after the training sessions (post test) and retention test 1 week later. Group specific instructions were offered in TR1 and TR2. Landing technique was assessed with the Landing Error Scoring System (LESS) and jump height was taken as performance measure. The results show that males in the VI group and females both in the VI and EF groups significantly improved jump-landing technique. Retention was achieved and jump height was maintained for males in the VI group and females both in the VI and EF groups. It is therefore concluded that EF and VI instructions have great potential in ACL injury prevention.     

Single leg landing movement differences between male and female badminton players after overhead stroke in the backhand-side court

Females showed higher anterior cruciate ligament (ACL) injuries rate on the opposite side of dominant hand compared with males during single leg landing in the backhand-side court after overhead stroke. The purpose of this study was to conduct biomechanics testing including kinematics and kinetics to provide some insights on the ACL injuries risks during single leg landing in the backhand-side court after overhead stroke between females and males. Twenty collegiate badminton players (10 females, 10 males) voluntarily participated in this study. Sagittal plane kinematic and kinetic data of the lower limb, and their ground reaction forces during the single leg landing in the backhand-side court after overhead stroke were collected. Results shown that, at the peak posterior ground reaction force (GRF) moment, the ankle dorsiflexion, knee and hip flexion angles of the female were lower than that of male. Meantime, the knee extension moment of the female was lower than that of males but the hip extension moment of the female was larger compared to males at the peak posterior GRF moment. The peak vertical and posterior GRF of female badminton players were larger than that of males. Decreased hip, knee, and ankle flexion angles at the peak posterior GRF moment and greater peak vertical and posterior GRF may expose female badminton players to the higher risk ACL injuries compared to males during single leg landing after overhead stroke in the backcourt-side. Preventative training programs designed to prevent the ACL injuries rate of female badminton players should take these factors into consideration.     

Neuromuscular control in individuals with chronic ankle instability: A comparison of unexpected and expected ankle inversion perturbations during a single leg drop-landing

While neuromuscular control deficits during inversion perturbations in chronic ankle instability (CAI) cohorts are well documented in the literature, anticipatory motor control strategies to inversion perturbations in CAI are largely unknown. The purpose of this study was to examine neuromuscular control and ankle kinematics in individuals with CAI (n = 15) and matched controls (n = 15) during unexpected and expected single leg drop-landings onto a tilted surface rotated 20° in the frontal plane. Muscle activity from 200 ms pre- to post-landing was recorded from the tibialis anterior (TA), medial gastrocnemius (MG), peroneus longus (PL) and peroneus brevis (PB). Mean muscle activity, co-contraction index (CCI), and peroneal latency was analyzed. Ankle inversion angle at initial contact, time to maximum inversion angle, maximum inversion angle and velocity were also assessed. Significantly longer PL latency, less time to maximum inversion and greater maximum inversion angle was found in CAI compared to controls. Regarding landing condition, significantly greater maximum inversion angle, less inversion at initial contact, longer PB latency, less TA activity and frontal plane CCI during the post-landing phase was found during the unexpected perturbation. Prolonged PL latency and altered ankle kinematics suggests reduced frontal plane ankle stabilization in CAI. However, similar motor control strategies were utilized in both groups during the ankle inversion perturbations.     

汉语阅读眼动控制:20年研究的总结

本文系统总结了20年来汉语阅读眼动控制的研究成果。在阅读过程中眼动控制主要回答两个问题:(1)哪些因素决定眼睛的注视时间(when);(2)哪些因素决定眼睛的注视位置(where)。对于第一个问题,已有研究从词边界信息、词频、熟悉性、预测性、语义透明度、具体性、非注视词的特性、词汇获得年龄进行了探讨;对于第二个问题,已有研究从汉字字号、笔画数、字结构、词长、词结构、词间空格、词频、预测性、合理性、年龄和阅读能力进行了探讨。通过比较发现,汉语阅读的眼动控制特点与拼音文字的眼动控制特点既有共同之处,又有差异之处。因此,汉语阅读的研究者需要在现有眼动控制模型的基础上,构建适合于汉语特性的眼动控制模型。     

词频、可预测性及合理性对目标词首次注视位置的影响

采用三项实验分别考察了目标词的词频、可预测性和合理性对读者眼动模式的影响。结果显示:(1)词频、可预测性和合理性对目标词语的凝视时间和总注视时间都有显著影响,但在首次注视时间上主效应不显著;(2)词频和可预测性不影响目标词的跳读率和再注视概率,而合理性对目标词的再注视概率产生显著的影响;(3)远注视点眼跳倾向于将首次注视位置着落于目标词的开端部位,而近注视点眼跳倾向于将首次注视着落于目标词的中央部位;词频、可预测性和合理性均不影响首次注视位置。     

阅读成语时最佳注视位置的实验研究

本研究以大学生为被试,探讨阅读成语时最佳注视位置的问题。按成语的结构,将其分为四种类型,实验一用DMDX系统完成,通过操纵被试首次注视成语的位置．要求他们完成语义判断任务。实验二用EyelinkⅡ眼动仪完成,要求被试阅读句子,分析他们再注视成语的次数和时间。两个实验的结果表明,在阅读成语时存在最佳注视位置,这个位置因成语结构的不同而变化。     

Anticipating ankle inversion perturbations during a single-leg drop landing alters ankle joint and impact kinetics

Anticipatory responses to inversion perturbations can prevent an accurate assessment of lateral ankle sprain mechanics when using injury simulations. Despite recent evidence of the anticipatory motor control strategies utilized during inversion perturbations, kinetic compensations during anticipated inversion perturbations are currently unknown. The purpose of this investigation was to examine the influence of anticipation to an inversion perturbation during a single-leg drop landing on ankle joint and impact kinetics. Fifteen young adults with no lateral ankle sprain history completed unanticipated and anticipated single-leg drop landings onto a 25° laterally inclined platform from a height of 30 cm. One-dimensional statistical parametric mapping (SPM) was used to analyze net ankle moments and ground reaction forces (GRF) during the first 150 ms post-landing, while peak GRFs, time to peak GRF, peak and average loading rates were compared using a dependent samples t-test (p ≤ 0.05). Results from the SPM analysis revealed significantly greater plantar flexion moment from 58 to 83 ms post-landing (p = 0.004; d = 0.64–0.77), inversion moment from 89 to 91 ms post-landing (p = 0.050; d = 0.58–0.60), and medial GRF from 62 to 97 ms post-landing (p < 0.001; d = 1.00–2.39) during the unanticipated landing condition. Moreover, significantly greater peak plantarflexion (p < 0.001; d = 1.10) and peak inversion moment (p = 0.007; d = 0.94), as well as greater peak (p = 0.002; d = 1.03) and average (p = 0.042; d = 0.66) medial loading rates, were found during the unanticipated landing condition. Our findings suggest alterations to ankle joint and impact kinetics occur during a single-leg drop landing when inversion perturbations are anticipated. Researchers and practitioners using drop-landings onto a tilted surface to assess lateral ankle sprain injury risk should consider implementing protocols that mitigate anticipatory responses.     

并列和偏正结构双字合成词的注视位置效应

采用EyeLink II眼动仪, 选取并列结构和偏正结构两种类型的目标词, 要求大学生被试阅读包含有目标词的句子, 以探讨两种双字合成词的注视位置效应。结果发现：在阅读并列和偏正结构的目标词时, 单次注视条件下读者往往将首次注视定位于词的中心位置, 多次注视时首次注视往往落在词的开端部分; 当首次注视落在词的开端时再注视该词的概率增加, 而且再注视往往落在词的结尾部分。结果提示：在单次注视条件下存在偏向注视位置; 双字合成词结构不影响偏向和最佳注视位置; 研究结果支持“战略-战术”模型。