Changes in Limb Stiffness Under Conditions of Mental Stress

In 2 experiments, the effects of mental stress on limb stiffness were investigated. The relative contribution to arm stiffness of individual muscle activity, co-contraction, muscle reflexes, and postural adjustments were examined. In each experiment, participants (N = 24, Experiment 1; N = 16, Experiment 2) held their supinated hand under a tray that they were required to return to horizontal after it had been suddenly released. Electromyographic activity in the biceps and triceps muscles was recorded, as were elbow and wrist angles and tray displacement. In Experiment 1, mental arithmetic stress was shown to lead to decreased tray displacement (i.e., increased resistance) compared with displacements under the control, unstressed condition, as well as to increased elbow flexion before tray release. In Experiment 2, the increased resistance to perturbation caused by mental stress was found to be independent of initial elbow angle, but to vary as a function of the amount of upward force exerted before tray release. The authors conclude that stress-induced increases in limb stiffness result from changes in the initial position of the elbow, specified by its angle, together with the initial force exerted by participants to counteract the mechanical perturbations.     

Distraction Affects the Performance of Obstacle Avoidance During Walking

In this study, dual-task interference in obstacle-avoidance tasks during human walking was examined. Ten healthy young adults participated in the experiment. While they were walking on a treadmill, an obstacle suddenly fell on the treadmill in front of their left leg during either midswing, early stance, or late stance of the ipsilateral leg. Participants were instructed to avoid the obstacle, both as a single task and while they were concurrently performing a cognitive secondary task (dual task). Rates of failure, avoidance strategy, and a number of kinematic parameters were studied under both task conditions. When only a short response time was available, rates of failure on the avoidance task were larger during the dual task than during the single task. Smaller crossing swing velocities were found during the dual task as compared with those observed in the single task. The difference in crossing swing velocities was attributable to increased stiffness of the crossing swing limb. The results of the present study indicated that divided attention affects young and healthy individuals' obstacle-avoidance performance during walking.     

Memory Drum Theory

Two experiments investigated the memory drum theory’s prediction (Henry & Rogers, 1960) that simple reaction time (SRT) increased with the complexity of the response to be initiated. Experiment 1 (N = 9) matched the Experiment 1, Group 1, SRT condition described by Henry and Rogers. Results of Experiment 1 replicated those of Henry and Rogers and indicated that the memory drum theory’s prediction of increased SRT as a function of increased complexity of response was tenable. Experiment 2 (N = 11) tested the effects of anatomical unit, extent, and target size on SRT, premotor time, and motor time. The results supported the contention that alternative explanations for SRT were possible. With complexity constant, increases in anatomical unit lead to increases in SRT, but only in the motor time component which indicated electromechanical rather than neuromotor program delays. It is proposed that the increased motor time could be explained by peripheral events such as the duration maximum torque must be applied by the agonist muscle(s) to generate the angular acceleration required to initiate rapid movement. SRT, premotor time, and motor time increased when target size was reduced from 6.35 cm to .79 cm. The increased premotor time could be a function of the determining of new equilibrium points for the elbow joint during response initiation. No effects on SRT were observed for extent.     

高血压患者对称动态动脉硬化指数与尿NAG的相关性研究

对称动态动脉硬化指数(S-AASI)是一种评价动脉顺应性的检测技术,具有无创、易操作、有效的特点,在预测高血压靶器官损害、心血管事件和死亡方面具有广阔的应用前景。本文通过探讨S-AASI与尿N-乙酰-β-D-氨基葡萄糖苷酶(NAG)之间的相关性,为临床使用S-AASI作为一种预测和评价高血压靶器官损害的指标提供科学的依据。     

冠状动脉搭桥术后再狭窄研究的思考

冠状动脉搭桥术(CABG)是目前外科治疗冠心病的成熟、定型的手术方法,但术后再狭窄影响了病人的远期疗效,其研究也越来越受到人们重视。随着生物医学模式向生物心理社会医学模式的转变,研究者对CABG术后再狭窄也有了更深入的认识,更加注重整体性、动态化和系统最优化。试用系统论方法探讨CABG术后再狭窄的防治。     

冠状动脉慢性闭塞病变的治疗决策

虽然越来越多的冠状动脉慢性闭塞病变正在采用经皮冠状动脉介入治疗,但其临床疗效是否能够与冠状动脉旁路移植术相媲美,目前尚不能妄下结论。经皮冠状动脉介入治疗和冠状动脉旁路移植术在冠状动脉慢性闭塞病变的治疗中各有其最佳适应证,相互之间是不可替代、但可以互补的。而且联合治疗、杂交技术和微创治疗是其未来发展方向。     

β受体阻滞剂是冠心病中的重要一线治疗药物

冠心病的治疗包括三个层面:血管重建治疗解决局部狭窄;改善生活方式是基础;全面合理的药物治疗是核心.而β受体阻滞剂又是重要的一线治疗药物,不仅能降低动脉粥样硬化及急性冠脉综合征的发生发展,还能有效预防、缓解心绞痛发生,改善梗死后左室重构和心功能;降低心肌再梗死率,降低心性猝死和病死率.临床上应用β受体阻滞剂的时机和剂量非常重要.     

Leg stiffness: Comparison between unilateral and bilateral hopping tasks

Leg stiffness is a predictor of athletic performance and injury and typically evaluated during bilateral hopping. The contribution of each limb to bilateral leg stiffness, however, is not well understood. This study investigated leg stiffness during unilateral and bilateral hopping to address the following research questions: (1) does the magnitude and variability of leg stiffness differ between dominant and non-dominant legs? (2) Does unilateral leg stiffness differ from bilateral leg stiffness? and (3) Is bilateral leg stiffness determined by unilateral leg stiffness? Thirty-two physically active males performed repeated hopping tests on a force platform for each of the three conditions: bilateral hopping, unilateral hopping on the dominant leg, and unilateral hopping on the non-dominant leg. Leg stiffness was estimated as the ratio of the peak vertical force and the maximum displacement using a simple 1-D mass-spring model. Neither the magnitude nor variability of leg stiffness differed between dominant and non-dominant limbs. Unilateral leg stiffness was 24% lower than bilateral stiffness and showed less variability between consecutive hops and subjects. Unilateral leg stiffness explained 76% of the variance in bilateral leg stiffness. We conclude that leg stiffness estimates during unilateral hopping are preferable for intervention studies because of their low variability.     

Psychometric properties of the Type D scale (DS14) in Norwegian cardiac patients

Bergvik, S., Sørlie, T., Wynn, R. & Sexton, H. (2010). Psychometric properties of the Type D scale (DS14) in Norwegian cardiac patients. Scandinavian Journal of Psychology. The combination of negative affectivity (NA) and social inhibition (SI) – the Type D Personality – is associated with poor outcomes in coronary artery disease (CAD) patients. A Norwegian translation of the standard instrument measuring Type D (DS14) was tested on 432 CAD patients receiving coronary revascularization treatment. Factor analysis produced two factors with high inter‐item reliability, indicating that the Norwegian DS14 has acceptable psychometric properties. Eighteen percent were classified as Type D, lower than has been reported elsewhere. Type D was associated with anxiety, depression, and passive coping. NA correlated positively with depression, anxiety, and passive coping. SI correlated positively with depression and anxiety, and negatively with active coping. The prevalence of Type D was higher among women, and negatively correlated with time since treatment. The variation in Type D prevalence among studies needs further elucidation as does the predictive power of continuous scoring of the Type D trait.     

心脏冠状动脉多层CT检查——临床上我们是否应用得当?

心脏冠状动脉多层CT扫描目前在对心脏进行整体扫描进而发现冠状动脉狭窄或冠状动脉钙化方面应用较多,但从经济费用-临床效益比值考虑,是否所有患者均需进行此项检查值得商榷。为降低患者就诊成本,我们认为,对于年轻非糖尿病患者可先根据Framingham冠心病危险量表进行测算患者未来10年出现冠心病的危险度,如果根据此量表计算的患者未来10年出现冠心病的危险度10%的中度以上危险度的患者,才应该给予心脏冠状动脉多层CT扫描检查以了解其是否需要进一步深入治疗。