Maturation in rate of high-velocity, low-amplitude force development

Objectives

The purpose of this study was to examine the maturation of force development during a thoracic high-velocity, low-amplitude displacement procedure at stages throughout chiropractic education. The hypothesis posed a natural development in rate of force directly related to the duration of experience. The analysis sought to define interrelationships between key characteristics within the procedure.

Methods

Fifty volunteers (17 women and 33 men) from a Canadian chiropractic college participated in this study. Participants were block randomized into 5 cohorts of 10 subjects, representing years 1 to 4 and graduates with more than 5 years of practice experience. Participants performed a hypothenar transverse push procedure on the upper thoracic spine, with the subjects lying on a force-sensing table. The average of 3 force-time profiles of the procedures was compared across cohorts using analysis of variance for differences between groups, and pairwise comparisons by Scheffé test, using Holms method for P value adjustment.

Results

Peak force, force rate, and rise time revealed strong differences based on cohort (P < .001). A natural maturation in high-velocity, low-amplitude force development occurs during training. Little change in peak force occurs in the first 2 years. The majority of development occurs in year 3, with tapering through year 4. A reciprocal coupling exists between peak force and force rate.

Conclusions

Group means revealed statistically significant and monotonic increase in force rate, a decreased rise time, and decreased peak force during delivery of the therapeutic peak force. These differences paralleled growth in experience but with an asymptotic leveling of change between the fourth year of training and 5 years of clinical practice experience. This study showed a systematic maturation in performance associated with educational experience. The reciprocal coupling between rate of force development and peak force created a relatively stable impulse.     

Specific cerebellar regions are related to force amplitude and rate of force development

The human cerebellum has been implicated in the control of a wide variety of motor control parameters, such as force amplitude, movement extent, and movement velocity. These parameters often covary in both movement and isometric force production tasks, so it is difficult to resolve whether specific regions of the cerebellum relate to specific parameters. In order to address this issue, the current study used two experiments and SUIT normalization to determine whether BOLD activation in the cerebellum scales with the amplitude or rate of change of isometric force production or both. In the first experiment, subjects produced isometric pinch-grip force over a range of force amplitudes without any constraints on the rate of force development. In the second experiment, subjects varied the rate of force production, but the target force amplitude remained constant. The data demonstrate that BOLD activation in separate sub-areas of cerebellar regions lobule VI and Crus I/II scales with both force amplitude and force rate. In addition, BOLD activation in cerebellar lobule V and vermis VI was specific to force amplitude, whereas BOLD activation in lobule VIIb was specific to force rate. Overall, cerebellar activity related to force amplitude was located superior and medial, whereas activity related to force rate was inferior and lateral. These findings suggest that specific circuitry in the cerebellum may be dedicated to specific motor control parameters such as force amplitude and force rate.     

Effects of utterance rate and length on the spatiotemporal index in Parkinson’s disease

Abstract

Purpose: To characterise labial articulatory pattern variability using the spatiotemporal index (STI) in speakers with idiopathic Parkinson’s disease (PD) across different speaking rates and syllable-sentence conditions compared to age- and sex-matched healthy controls.

Method: Ten speakers with mild–severe idiopathic PD and 10 controls produced “pa” and the Rainbow Passage at slow, typical and fast speech rates. Upper lip and lower lip kinematics were digitised during a motion capture system. Data were analysed using linear mixed modelling.

Result: Regardless of the participant group, a high STI value was observed in the fast speech rate for the “pa” syllable condition, particularly for movements of the lower lip. As utterance rate increased, the control group showed the highest variability, followed by PD OFF and PD ON conditions. Syllable “pa” showed a greater STI value compared to both the first and second utterance of Rainbow Passage.

Conclusion: PD manifests sufficient residual capacity to achieve near-normal motor compensation to preserve the consistency of lower lip movements during speech production. The lack of a significant difference in lip STI values between ON-OFF medication states suggests that dopaminergic treatment does not influence stability of speech for individuals with mild-moderate stage PD.     

Neuroprotective therapy in Parkinson disease

During the past decade, there has been a remarkable progress in our understanding of the biology of Parkinson disease (PD), which has been translated into searching for novel therapy for PD. Much focus is shifted from the development of drugs that only relieve PD symptoms to new generation of remedies that can potentially protect dopaminergic neurons and modify the disease course. Several novel therapeutic approaches have been tested in preclinical experiments and in clinical trials, including molecules targeting on genes involved in the pathogenesis of the disease, neurotrophic factors critical for dopaminergic neuron survival and function, new generation of dopamine receptor agonists that may possess neuroprotective effects, and agents of antioxidation, antiinflammation, and antiapoptosis. The results of these studies will shed new light to our hope that PD can be cured in the future.     

普拉克索在帕金森病中的应用

正>帕金森病(Parkinson′s disease)是一种常见的发生于中老年人的缓慢进展的神经系统变性性疾病,临床以静止性震颤、肌强直和运动障碍为主要特征。随着人口老年化的进程,其患病率逐年增高,已成为仅次于脑血管病的神经系统常见病。长期以来,以左旋多巴为主的药物替代治疗是帕金     

Neuromuscular disease and extubation dysphagia

Post-extubation dysphagia is a common and serious problem. The presence of neuromuscular disease at the time of intubation is likely to increase this. Until recently, the prevalence and the association with length of intubation had not been clarified. Results published in this journal suggest that 93% of extubated patients with neuromuscular disease had post-extubation dysphagia, which in 33% of cases was considered severe. The number of days ventilated was the single predictor of severe dysphagia and a consequent prolonged hospital stay. Further work to build on these results to unravel the complex interplay between disease, trauma, and other unknown factors will be required.     

Physiological and methodological aspects of rate of force development assessment in human skeletal muscle

Rate of force development (RFD) refers to the ability of the neuromuscular system to increase contractile force from a low or resting level when muscle activation is performed as quickly as possible, and it is considered an important muscle strength parameter, especially for athletes in sports requiring high‐speed actions. The assessment of RFD has been used for strength diagnosis, to monitor the effects of training interventions in both healthy populations and patients, discriminate high‐level athletes from those of lower levels, evaluate the impairment in mechanical muscle function after acute bouts of eccentric muscle actions and estimate the degree of fatigue and recovery after acute exhausting exercise. Notably, the evaluation of RFD in human skeletal muscle is a complex task as influenced by numerous distinct methodological factors including mode of contraction, type of instruction, method used to quantify RFD, devices used for force/torque recording and ambient temperature. Another important aspect is our limited understanding of the mechanisms underpinning rapid muscle force production. Therefore, this review is primarily focused on (i) describing the main mechanical characteristics of RFD; (ii) analysing various physiological factors that influence RFD; and (iii) presenting and discussing central biomechanical and methodological factors affecting the measurement of RFD. The intention of this review is to provide more methodological and analytical coherency on the RFD concept, which may aid to clarify the thinking of coaches and sports scientists in this area.     

Nonmotor complications of Parkinson disease

Nonmotor manifestations are integral components of Parkinson disease (PD), and they often have a greater impact on disability and quality of life than the motor features that currently define the illness. Nonmotor features of PD, such as dementia, may be an intrinsic feature of the disorder and persist regardless of the medication state (ie, they continue to manifest in the "on" or "off" state); some nonmotor features, such as psychotic symptoms, may be iatrogenic complications of pharmacologic intervention for the treatment of the motor manifestations of PD. Iatrogenic complications, such as psychosis and impulse control disorders, may respond to modification of the PD treatment regimen at the risk of worsening motor symptoms. Thus, a balance must be struck between controlling nonmotor manifestations and motor features of the disease.     

Neuromuscular neutral zones sensitivity to lumbar displacement rate

OBJECTIVES: To determine the displacement and tension thresholds (developed during anterior lumbar flexion) which trigger reflexive muscular activity in the multifidus muscles; their variability with the velocity of flexion; and the pattern of threshold variability across the lumbar spine.Design. An in-vivo study of the feline during passive lumbar flexion applied via the L-4/5 supraspinous ligament. METHOD: EMG from six pairs of intramuscular electrodes inserted in the L-1/2 to L-6/7 multifidus muscles was recorded while the lumbar spine was passively flexed to 75% of the physiological strain of the supraspinous ligament at rates of 17-100%/s. Three-dimensional models of tension threshold, flexion rate and lumbar levels were developed from the experimental data. RESULTS: Displacement and tension thresholds were the lowest at the fastest flexion rate and gradually increased as flexion rates decreased. Electromyographic activity was detected at low thresholds at the center of the flexion and at gradually increasing thresholds at higher and lower lumbar segments. CONCLUSION: Multifidus reflexive muscular activity, which stabilize the spine, is triggered at a displacement and tension thresholds of 5-15% of the physiological range. Earlier activation of muscular activity occurs as the velocity of flexion increases. Earlier activation also occurs near the center of flexion. RELEVANCE: Sensory-motor neurological feedback maintains spine stability and is responsive to the velocity of lumbar motion. A neuromuscular silence exists in small lumbar movements in which spine stability is not protected by the musculature. Spine models constructed to predict risk factors could benefit from incorporating this new information.     

Thumb force deficit after lower median nerve block

PURPOSE: The purpose of this study was to characterize thumb motor dysfunction resulting from simulated lower median nerve lesions at the wrist. METHODS: Bupivacaine hydrochloride was injected into the carpal tunnel of six healthy subjects to locally anesthetize the median nerve. Motor function was subsequently evaluated by measuring maximal force production in all directions within the transverse plane perpendicular to the longitudinal axis of the thumb. Force envelopes were constructed using these measured multidirectional forces. RESULTS: Blockage of the median nerve resulted in decreased force magnitudes and thus smaller force envelopes. The average force decrease around the force envelope was 27.9%. A maximum decrease of 42.4% occurred in a direction combining abduction and slight flexion, while a minimum decrease of 10.5% occurred in a direction combining adduction and slight flexion. Relative decreases in adduction, extension, abduction, and flexion were 17.3%, 21.2%, 41.2% and 33.5%, respectively. Areas enclosed by pre- and post-block force envelopes were 20628 +/- 7747 N.N, and 10700 +/- 4474 N.N, respectively, representing an average decrease of 48.1%. Relative decreases in the adduction, extension, abduction, and flexion quadrant areas were 31.5%, 42.3%, 60.9%, and 52.3%, respectively. CONCLUSION: Lower median nerve lesion, simulated by a nerve block at the wrist, compromise normal motor function of the thumb. A median nerve block results in force deficits in all directions, with the most severe impairment in abduction and flexion. From our results, such a means of motor function assessment can potentially be applied to functionally evaluate peripheral neuropathies.     

帕金森病伴发抑郁的研究进展

帕金森病伴发抑郁是帕金森病最常见的非运动症状之一,越来越受到研究者的关注。本文将就近年来关于帕金森病伴发抑郁的发病机制、临床表现、诊断及治疗等进展进行概述。     

帕金森病吞咽障碍的临床特点

帕金森病吞咽各阶段均可出现功能障碍,临床主要表现为吞咽模式不稳定,吞咽时间延长、残留、误吸等。研究发现咽横纹肌存在异常的肌纤维蛋白转化及反复去神经损伤,支配咽的周围神经存在α-突触核蛋白沉积,调节吞咽过程的高级中枢存在功能异常,这些变化构成了吞咽障碍的结构基础。另外,呼吸运动和吞咽过程可相互影响,帕金森病异常的呼吸模式也参与了吞咽障碍的发生。在治疗方面,鉴于帕金森病进行性加重和异质性的特点,选择个体化、早期、长期、多学科治疗更有利于延缓吞咽障碍进展。     

揭示帕金森病患者运动迟缓的相关因素

目的:运动迟缓是造成帕金森病的主要特征,而肌无力、强直、震颤、运动多变、思维缓慢是其主要影响因素,而产生这些现象的机制是非常复杂的。资料来源:应用计算机检索“Medline”1980-01/2004-04的关于帕金森病运动迟缓的病理生理学机制的文章,检索词“Parkinsondisease,bradyki-nesia,pathophysiology”,限定文章语言种类为“English”。资料选择:对资料进行初审,选取旨在探讨帕金森病运动迟缓相关影响因素的随机对照试验的文献,对选取的文献进行查找全文,排除重复研究。资料提炼:共选取36篇探讨帕金森病运动迟缓的相关文献,其中32篇文献与之相关,排除4篇重复研究。资料综合:总结所选文献中关于帕金森病运动迟缓的发病机制的内容,按照影响运动迟缓因素等几方面进行归类分析。其中6篇文献分析了运动迟缓的5种因素,15篇文献对帕金森病的发病机制及其他疾病做了比较,7篇文献对动物模型及手术机制做了探讨,支持手术可以改善帕金森病患者的运动功能。结论:运动迟缓的主要缺陷是运动减慢,在运动起始时肌力的反射强度不足,结果运动时偏离了所要达到的目的,而要采用多个小步来达到,由于在主动运动时运动命令设定的阈值低下而引起。     

经颅超声诊断帕金森病

目的 探讨经颅超声(TCS)诊断帕金森病(PD)的临床应用价值。方法 随机选取478例临床确诊的神经变性疾病患者(病例组),根据诊断标准分为PD、帕金森叠加综合征、继发性帕金森综合征及原发性震颤亚组;另选取同期124名正常志愿者作为对照组。应用TCS盲法测量黑质(SN)高回声面积,比较各组SN高回声阳性率及SN高回声面积差异,计算TCS诊断PD的敏感度及特异度。对PD亚组患者进行急性多巴反应试验,比较SN高回声阳性率与多巴反应试验阳性率的差异。结果 TCS的中脑显示率为81.72%(492/602),剔除中脑显示不清者后,病例组入组389例,其中PD患者170例,对照组103名。PD亚组SN高回声阳性率和SN高回声面积均明显高于其余各组(P均<0.01)。TCS诊断PD的敏感度为81.76%(139/170),特异度为77.64%(250/322)。PD亚组多巴反应阳性率与SN高回声阳性率差异无统计学意义(P>0.01)。结论 SN高回声为PD的典型TCS特征,对于诊断PD具有重要应用价值。     

简明帕金森病评分量表/帕金森病致残量表评估帕金森病患者运动功能的信度和效度

目的:应用简明帕金森病评分量表/帕金森病致残量表(简称为简明帕金森病评分量表)评价帕金森病患者运动损伤情况,并对其信度和效度进行分析。方法:于2005-07/11选择天津医科大学总医院神经内科门诊68例帕金森病患者,用简明帕金森病评分量表及统一帕金森病评分量表对其进行临床评价。评价均在上午进行,如患者有症状波动,则在“开”期进行。简明帕金森病评分量表分为运动评价、日常生活活动及运动并发症3部分,共21项内容,每个项目的计分值按程度分为0～3分4个等级。采用Cronbachα系数、每个项目得分与剩余项目总分间的相关系数评价量表的内部一致性,采用结构效度评价量表的效度。结果:所有患者全部进入结果分析。①简明帕金森病评分量表各部分Cronbachα系数均在0.85以上,除运动评分部分外,其余部分均高于统一帕金森病评分量表。统一帕金森病评分量表第20项(静止性震颤)与其他项目的相关性最小(相关系数为0.10),其他相关系数低于0.30的还有统一帕金森病评分量表第17项(感觉症状),简明帕金森病评分量表的第1项(静止性震颤)及第10项(吞咽),相关系数分别为0.12、0.25和0.29。②简明帕金森病评分量表各部分与统一帕金森病评分量表各分量表之间均呈正相关,Pearson相关系数在0.47～0.96。③简明帕金森病评分量表各部分与Hoehn&Yahr分期呈正相关(rs=0.89)。单因素方差分析显示,不同Hoehn&Yahr分期帕金森病患者简明帕金森病评分量表评分显著不同。post-hoct检验显示,除Hoehn&Yahr1～1.5期(P=0.17)外,其余各期间差异均存在显著性意义(P<0.05)。结论:简明帕金森病评分量表/帕金森病致残量表具有较高的信度和效度,值得临床推广。     

The role of heart rate in the development of cardiovascular disease

Heart rate is an independent risk factor for patients with cardiovascular disease, in particular with arterial hypertension, myocardial infarction, coronary artery disease and heart failure. This relation is supported by a large number of animal studies as well as clinical trials which are summarized in this article. These studies demonstrated detrimental effects of increased heart rate on the function and structure of the cardiovascular system. Heart rate can be easily detected during physical examination of the patient and therefore allows a simple conclusion on prognosis and efficiency of therapy.