Jerk Response Research Articles

Theoretical investigation of the free fall of a spherical particle in a viscous fluid using continuous piecewise linearization method

This article presents a theoretical investigation of the problem of free fall of a spherical particle in a viscous fluid. The classic Boussinesq-Basset-Oseen (BBO) model for particle motion in laminar flow was modified for generalized flow by using a drag law that is applicable for 0<Re≤2.0×105. By assuming that the acceleration in the Basset force integral is constant, the Basset force effect was approximated to form an integrated added mass coefficient. Consequently, the integro-differential equation of the BBO model was transformed to a first-order nonlinear ordinary differential equation that accounts for the Basset force effect and was solved using the continuous piecewise linearization method (CPLM). The CPLM algorithm was developed based on the jerk-velocity relationship and is applicable to zero and non-zero initial conditions, steady motion, increasing or decreasing velocities and the corresponding acceleration and jerk responses. The CPLM algorithm was shown to predict published experimental results accurately and compared very well with numerical solutions and existing analytical solutions. Examination of the fall response under varying parameters showed that the fall distance, fall time and terminal velocity depend strongly on the sphere diameter, sphere density, and the density and viscosity of the fluid medium. Also, an analytical solution for the power dissipated in the fluid medium as the sphere falls to reach its terminal velocity was derived. The power dissipated was found to increase exponentially as the initial velocity deviates positively from the terminal velocity.

Dynamics of fiber optic airgun bubbles for micropropulsion

While extensive research on pressure wave emissions from meter-scale airgun bubbles, the dynamics at the microscale, particularly regarding fiber laser-induced bubble generation, remains less explored. In this Letter, we investigate the dynamic properties of a fiber optic airgun that fires bubbles to propel polystyrene particles in a two-dimensional plane. A linear dependence of particle propulsion on energy distribution with respect to length is observed. The temporal ejection behavior of the particles is attributed to the abrupt jerk response caused by the expansion diminishes of the bubble. We identify two hydrodynamic regimes governing the liquid–solid interaction, i.e., the axial bubble pressure along the fiber is determined by the bubble-particle length, yielding a boundary coefficient of 0.65. We find the dimensionless maximum axial displacement of the particle approximately follows fourth-power scaling laws and aligns with the experimental results in their respective regimes. Such a study offers potential avenues for micromechanical configurations to manipulate interactions among disparate microsystems, especially in the field of microbubble-driven mechanical actuators.

Atypical knee jerk responses in high-risk children: A longitudinal EMG-study.

We previously found that atypical responses to the knee jerk reflex, i.e., tonic responses (TRs), clonus and contralateral responses in very high-risk (VHR) infants were associated with cerebral palsy (CP) at 21 months. The current study aimed for a better understanding of pathophysiology of atypical knee jerk responses by evaluating whether infant atypical knee jerk responses are associated with CP and atypical knee jerk responses at school-age. 31 VHR-children, who had also been assessed longitudinally during infancy, and 24 typically developing children, were assessed at 7-10 years (school-age). We continuously recorded surface EMG of thigh muscles during knee jerk responses longitudinally during infancy and once at school-age. Neurological condition was assessed with age-appropriate neurological examinations. It included the diagnosis of CP at 21 months corrected age and school-age. CP's type and severity (Gross Motor Function Classification System (GMFCS)) were reported. Persistent TRs in infancy were associated with CP at school-age. TR prevalence decreased from infancy to childhood. At school-age it was no longer associated with CP. Clonus prevalence in VHR-children did not change with increasing age; it was significantly higher in children without than those with CP. Reflex irradiation was common in all school-age children, and its prevalence in contralateral muscles in VHR-children decreased between infancy and childhood. In infancy, TRs indicated an increased risk of CP, but at school-age TRs were not associated with CP. In general, spinal hyperexcitability, expressed as reflex irradiation and TRs, decreased between infancy and school-age.

Abstract- Poster

Background:The onset of asymptomatic or symptomatic MS may result in specific psychiatric symptoms, as well as the long-term evolution of psychiatric disorders. Psychiatric illnesses that develop several years before MS diagnosis have been documented in the literature, although the phenomena remains poorly understood.Case description:Mrs. YB, a 32-year-old housewife, visited the LGBRIMH OPD. For the previous five years, she had a recurrent history of worry and mild physical complaints. Sleep disturbances, panic episodes, ruminative worries, muscle tension, physical weakness, and chest discomfort were among her complaints. Her mood had also deteriorated, and she was concerned that she was suffering from an incurable medical condition. There is no past psychiatric history or history of suicidal or homicidal ideation. She sought the advice of several doctors and underwent a thorough neurological evaluation and investigation, which included a physical examination and investigations such as MDCT chest and MRI-LS spine, which indicated no significant abnormalities. Following it, she was diagnosed with an anxiety disorder. Her symptoms significantly improved after she was treated appropriately. She relapsed and noted that the tingling sensation had gotten worse over 2 years. She acquired clinical signs of excessive knee jerk response on her right side of her lower limb. Repeated contrast Enhanced magnetic resonance imaging (MRI) demonstrated T2 Hyperintensities at D2 and minimal post contrast enhancement suggestive of transverse myelitis. The oligoclonal IgG immunoglobulin level in her CSF was 48.70, indicating multiple sclerosis. The patient had methylprednisolone and azathioprine treatment, which significantly relieved her symptoms.Discussion:Even if all previous tests have been done, unusual psychiatric symptoms necessitate a full neurological examination at each subsequent visit. Long-term monitoring will aid in appropriate diagnosis and provide better care for patients, resulting in a higher quality of life. INTRODUCTION: Obsessions: unwanted intrusive thoughts, lead to significant distress.Compulsions: repetitive behaviours or mental acts to neutralize obsessions.Prevalence:2to3% Onset usually in second or third decade of life.15% after the age of 35. Onset after age 50 is rare & more likely to have an organic aetiology (frontal lobes, basal ganglia).[4]Thyroid diseases may be associated with OCD (1.4 times). Studies show dysregulation of the hypothalamic-pituitary-thyroid axis in OCD.Papillary thyroid carcinoma has subthreshold OCD. [6.7.8] CASE REPORT: 54-yr/F with OCD symptoms for 4 months.OBSESSIONS: being contaminated by dirt & something terrible would happen to her family, if she sees lizard or dogs & didn't take bath.COMPULSIONS: counting till 5, bathing >10 times/day (>30 minutes), washing vessels 5 times.Avoids going out of home, taking bath for past 2 months.Sleeplessness, anxiety,worry about her illness, depressive mood.MEDICAL H/O: thyroid surgery 10 years ago. On T.THYROXINE 300mcg,raised TFT 4 months back,Now on T. THYROXINE 50 mcgNo other significant h/o.Y-BOCS:34.MRI BRAINHyperintensities B/L subcortical white matter Small ischemic changes predominant in frontal lobeTFTT3-125ng/dL T4-22.35Ug/dL TSH<0.05MIU/mLOTHERSWNL MANAGEMENT: SSRI +TCA + Psychotherapy +Thyroxine DISCUSSION: secondary OCD: accompany or follow systemic/neurologic illness.functional neuroimaging studies highlighted differences in regional blood flow.Patients with Thyroid abnormalities also develop OCD.So, always rule out organicity in late onset OCD.

Design of low jerk automatics transmission for vehicle using fuzzy control to improve gear shifting quality and low fuel consumption

Vehicle driveline is the system used transfer engine traction to the wheels. An automatics transmission is the essential and has high role of the driveline. This research was designing a automatic transmission plant and gear shifting logic base on jerk sensing. Which exploit fuzzy mamdani controller. Input variable were throttle-Up and Down position and rate, desired vehicle speed and speed error and even Jerk sensor, while the output of the control was a eight gear shifting actuator. Shifting algorithm was implemented by state machine, which controlled by fuzzy.Based on discussion of simulation result, the proposed automatic transmission control system produce lower vehicle jerk response, smoother drive comfort and fuel consumption.

A newer approach for quantitative assessment of patellar tendon reflex response using biomechanical data of foot movement by a digital method

Summary Background Assessment of deep tendon reflexes such as patellar tendon reflex (PTR) is the vital diagnostic procedure executed routinely by clinicians which can provide valuable information about the reflex arc. Despite common acceptance, the reflex rating scales remain subjective and qualitative, creating an opportunity for the development of objective measures to improve the reliability and efficacy of these clinical tools. Material and methods The proposed study presents with reflex quantification system for knee jerk response using electrogoniometer and accelerometer. These sensors are capable of detecting dynamic changes occurring in the movement of an object and they can convert biomechanical information of movement into digital signals. The proposed system utilizes this technology to assess knee jerk response and provide quantitative data on various aspects of the knee jerk. Results The dynamic action of the leg during knee jerk response created movement patterns which were captured by the utilization of the data acquisition system. Based on the reflex response of the leg, the frequency of analog signals from biomechanical sensors as well as the amplitude of the graph was changed. Components of knee jerk response such as Reflex Movement latency (RL), Jerk time (JT), Total reflex response time (TRT) and Reflex amplitude was recorded from the data obtained. Conclusion This study presents the method of patellar tendon reflex response measuring system based on computational data acquisition system using wearable sensors. This methodology can be used as a additional tool in clinical assessment of deep tendon reflexes. The main advantages of the proposed system are its portability, user-friendly and non-invasive nature.

Real-Time Tracking of Structural Stiffness Reduction with Unknown Inputs, Using Self-Adaptive Recursive Least-Square and Curvature-Change Techniques

In this paper, a new computationally efficient algorithm is developed for online and real-time identification of time, location, and severity of abrupt changes in structural stiffness as well as the unknown inputs such as earthquake signal. The proposed algorithm consists of three stages and is based on self-adaptive recursive least-square (RLS) and curvature-change approaches. In stage 1 (intact structure), a simple compact RLS is hired to estimate the unknown parameters and input of the structure such as stiffness and earthquake. Once the damage has occurred, its time and location are identified in stage 2, using two robust damage indices which are based on the structural jerk response and the error between measured and estimated responses of structure from RLS. Finally, the damage severity as well as the unknown excitations are identified in the third stage (damaged structure), using a self-adaptive multiple-forgetting-factor RLS. The method is validated through numerical and experimental case studies including linear and nonlinear buildings, a truss structure, and a three-story steel frame with different excitations and damage scenarios. Results show that the proposed algorithm can effectively identify the time-varying structural stiffness as well as unknown excitations with high computational efficiency, even when the measured data is contaminated with different levels of noise. In addition, as no optimization method is used here, it can be applied to real-time applications with computational efficiency.

The tonic response to the infant knee jerk as an early sign of cerebral palsy

BackgroundEarly identification of infants at risk of cerebral palsy (CP) is desirable in order to provide early intervention. We previously demonstrated differences in knee jerk responses between 3-month-old high risk and typically developing infants. AimsTo improve early identification by investigating whether the presence of tonic responses (continuous muscle activity occurring after the typical phasic response), clonus or contralateral responses to the knee jerk during infancy is associated with CP. Study designLongitudinal EMG-study. SubjectsWe included 34 high-risk infants (median gestational age 31.9 weeks) who participated in the LEARN2MOVE 0–2 years trial. Outcome measuresVideo-recorded knee jerk EMG-assessments were performed during infancy (1–4 times). Developmental outcome was assessed at 21 months corrected age (CA). Binomial generalized estimating equations models with repeated measurements were fitted using predictor variables. ResultsInfants who later were diagnosed with CP (n = 18) showed more often than infants who were not diagnosed with CP i) tonic responses – from 4 months CA onwards, ii) clonus - from 13 months CA onwards, and iii) contralateral responses - from 15 months CA onwards. LimitationsThe main limitation is the relatively small sample size. ConclusionsThe assessment of tonic responses to the knee jerk using EMG may be a valuable add-on tool to appraise a high risk of CP.

Rebalancing Regulation of Speech: Hyper-Local Content on Global Web-Based Platforms

Public and private discourse online is mediated through global web-based platforms. The platforms hold, enable and carry local and hyper-local conversations between local actors with local consequences. Although online harmful speech has local dimensions, the usual local modes of intervention for harmful speech are no longer viable. Global intervention is difficult since context is often a significant factor in identifying harmful speech. The internet has disrupted regulation of harmful speech and regulators are pushing back. This has an unfortunate effect on freedom of expression while failing to address the problem of harmful speech adequately. This essay highlights the problems that arise from companies' knee jerk responses to the consequences of harmful speech. It offers a way forward.

Improved sliding-mode control for servo-solenoid valve with novel switching surface under acceleration and jerk constraints

The nonlinear sliding-mode (SLM) controller based on the maximum jerk and time-optimal step response has been developed for the control of servo-solenoid valves, which exhibits its performance advantages when compared to traditional PID controller. However, the experiments shows the responses of the SLM control under only jerk constraint will largely vary with different damping and loads, leading to the large overshoot and breakdown under some working conditions (e.g., large viscous damping coefficient). Thus, an improved SLM controller is developed in this paper to deal with the existing drawbacks, where a novel nonlinear SLM surface is proposed by taking into account both spool’s acceleration and jerk limitation. Firstly, the nominal model of servo-solenoid valve is built by linearizing the dynamics on the null position, and the system identification is carried out to achieve the model parameters and their variation ranges. Subsequently, the valve constraints under the power limitation are analyzed through the frequency response of the identified model, which comes out the maximum available velocity, acceleration and jerk. Finally, the improved SLM control algorithm is proposed, where the novel SLM surface considers the maximum plus jerk, the maximum minus jerk and the maximum acceleration. Experimental studies are conducted and the results show that the improved SLM controller under both acceleration and jerk constraints can achieve the continuous and stable sliding mode state, realize the time-optimal step response of the valve, and exhibit strong disturbance rejection abilities.

结构动力响应中急动度的计算

Jerk is of great significance in engineering practice. A numerical method for solving jerk responses was constructed through combination of the radial basis function (RBF) approximation and the collocation method. The proposed method was used to calculate the jerk and the 3rd-order jerk equations, and the RBF interpolation was adopted to approximate the real motion rule, which made good the defect that the traditional methods can’t be used to calculate the jerk. Aimed at the numerical characteristics of the dynamic differential equations, an improved RBF expression of multivariable joint interpolation combining the all-order derivatives of the variable was presented. The initial-value condition of the same order with the differential equation was added to obviously decrease the numerical oscillation. The results of the numerical examples indicate that the proposed method has the advantages of a simple calculation process, high accuracy and high applicability to jerk equations.

Knee jerk responses in infants at high risk for cerebral palsy: an observational EMG study.

Following our clinical observation of tonic responses in response to the knee jerk in infants at very high risk for cerebral palsy (VHR infants), we systematically studied tonic responses, clonus, and reflex irradiation. We questioned (i) whether these responses occurred more often in VHR infants than in typically developing (TD) infants, and (ii) whether they were associated with abnormal general movement quality. Twenty-four VHR and 26 TD infants were assessed around 3 mo corrected age. Surface electromyograms of leg, trunk, neck, and arm muscles were recorded while eliciting the knee jerk. All assessments were video-recorded. VHR infants more often than TD infants showed tonic responses in the ipsilateral quadriceps and hamstring (Mann-Whitney U; P = 0.0005 and P = 0.0009), clonus (Chi-square; P = 0.0005) and phasic responses in the contralateral quadriceps and hamstring (Mann-Whitney U; P = 0.002 and P = 0.0003, respectively). Widespread reflex irradiation occurred in VHR and TD infants. Definitely abnormal general movements and stiff movements were associated with tonic responses (Mann-Whitney U; P = 0.0005, P = 0.007, respectively) and clonus (Mann-Whitney U; P = 0.003 and P = 0.0005) in the ipsilateral quadriceps. Similar to clonus, tonic responses may be regarded as a marker of a loss of supraspinal control. Reflex irradiation primarily is a neurodevelopmental phenomenon of early ontogeny.

Jerks and conductivity anisotropy of lower mantle

Conductivity anisotropy of the lower mantle presumably caused by phase change of dielectric magnesiowustite at depths of 1500–2000 km is detectable from jerks. Jerks are induced by currents in the fluid outer core, propagate upward from the CMB through anisotropic conducting mantle, and appear on the Earth’s surface. The surface jerk patterns are studied theoretically from the potential of the geomagnetic field presented as a sum of magnetic and electric modes. Equations for the fields of both modes and their relationship in a weakly anisotropic earth are obtained by the perturbation method. The field potential is expanded into a series of spherical harmonics, and the equations are solved in the frequency and time domains. The surface jerk responses can be inverted to retrieve anisotropy parameters; the goal function in the inversion may correspond to misfit between the model and experimental values either along the horizontal or vertical components.

Characteristics of Jerk Response Spectra for Elastic and Inelastic Systems

Jerk is the time rate of acceleration and mainly represents the nonstationary component in high frequency band of the earthquake wave. The study on jerk and its response spectra can enhance the recognition of the nonstationary ground motion. The mechanical meaning and research value of jerk are described. Jerk is recommended to be solved by establishing state-space equations and Runge-Kutta method. The solution method of elastic and inelastic jerk response spectra under ground motion is established, and the accurate jerk spectrum should be calculated directly according to numerical computing instead of pseudo-acceleration spectrum. The characteristics of jerk response spectra are studied according to the influencing factors, such as site condition, amplification factor, ductility factor, and reduction factor. The concept of impact reduction factor is presented. The statistical results show that the jerk spectrum has similar rules as the acceleration spectrum, and the amplitude is relative to the predominant period, especially for structures with short or medium period. If the ductility is improved, the effective jerk will reduce obviously, and the impact reduction factor will be enhanced. Different from the strength reduction factor, the impact reduction factor is nearly not relevant to the period.

Acute ataxic neuropathy with hyperreflexia

Dear Editor, The ataxic form of Guillain-Barre syndrome (GBS), characterized by acute profound ataxia with negative Romberg sign and no (or minimal) ophthalmoplegia [1], is considered as an incomplete form of Fisher syndrome [2]. However, its nosological relationship to acute sensory ataxic neuropathy was not discussed [3]. A recent comprehensive study shows how ataxic GBS and acute sensory ataxic neuropathy share similar clinical and laboratory features, forming a continuous spectrum under the term: acute ataxic neuropathy without ophthalmoplegia (AAN) [4]. AAN typically presents with areflexia or hyporeflexia. Preserved or brisk reflexes are seen in GBS or Bickerstaff brainstem encephalitis [5, 6], but not in AAN. We report the first case of AAN with hyperreflexia. A 45-year-old male developed unsteady gait, 5 days after experiencing fever and sore throat. He had no prior medical history and abstained from alcohol. On day 2, he developed diplopia at all extremes of gaze, with left hand and foot numbness, and a broad-based gait. He demonstrated bilateral dysmetria, and abnormal left heel-shin test. Eye pursuit, vertical and horizontal eye movements were full, except for convergence. He had no nystagmus. Pupils were 5 mm bilaterally with normal light and accommodation reflexes. Cranial nerves were otherwise intact with no facial or oropharyngeal weakness. Limb power and tone were normal. He had hyperreflexia in all 4 limbs, but with normal jaw jerk and down-going plantar responses. Despite complaining of left-sided distal dysesthesias, objective sensory testing of all modalities was normal, other than an abnormal Romberg’s test. There was no autonomic involvement. His brain MRI showed no abnormalities or Wernicke’s encephalopathy. MRI spine had no myelopathy or ventral nerve root enhancement. His vitamin B1 levels were normal and lumbar puncture on day 3 was slightly traumatic with 181 red blood cells/lL, protein 1.2 g/dL (normal, \0.6 g/dL) and 45 cells/lL of predominantly lymphocytic white blood cells. We diagnosed AAN with unusually brisk reflexes. As he was ambulatory, we treated him conservatively. Median, ulnar, tibial and peroneal nerve conduction studies on day 4 showed normal amplitudes of the compound motor action potentials and normal distal motor latencies. Sensory nerve action potential amplitudes and latencies were normal. F-waves had normal latencies and were not dispersed. However, his somatosensory evoked potentials, recording from bilateral median and posterior tibial nerves, showed prolonged cerebral evoked N18 and P37 latencies (Table 1). Nerve conduction studies, including peripheral sensory nerve potentials on day 10 remained normal, whereas N18 and P37 latencies normalized by day 15. Anti-GQ1b antibodies were absent, but IgG anti-GM1b antibodies were positive in his serum. Upon discharge on day 12, eye convergence and gait had improved while hyperreflexia and left-sided limb dysmetria remained. His dysesthesia had resolved but Romberg’s test remained positive. He remained alert throughout the illness and his reflexes normalized on day 45. L. L. L. Yeo K. Ng Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore

The Mole: A hard time in social services

It is quite understandable that the impact of the recent tragic child deaths due to abuse at the hands of parents and carers has resulted in a knee jerk response to a critical look at children’s services from all professional perspectives.

Design and evaluation of a reactive and deliberative collision avoidance and escape architecture for autonomous robots

We present the design and evaluation of an architecture for collision avoidance and escape of mobile autonomous robots operating in unstructured environments. The approach mixes both reactive and deliberative components. This provides the vehicle's behavior designers with an explicit means to design-in avoidance strategies that match system requirements in concepts of operations and for robot certification. The now traditional three layer architecture is extended to include a fourth Scenario layer, where scripts describing specific responses are selected and parameterized on the fly. A local map is maintained using available sensor data, and adjacent objects are combined as they are observed. This has been observed to create safer trajectories. Objects have persistence and fade if not re-observed over time. In common with behavior based approaches, a reactive layer is maintained containing pre-defined knee jerk responses for extreme situations. The reactive layer can inhibit outputs from above. Path planning of updated goal point outputs from the Scenario layer is performed using a fast marching method made more efficient through lifelong planning techniques. The architecture is applied to applications with Autonomous Underwater Vehicles. Both simulated and open water tests are carried out to establish the performance and usefulness of the approach.

Primary lateral sclerosis mimicking atypical parkinsonism

Primary lateral sclerosis (PLS), the upper motor neurone variant of motor neurone disease, is characterized by progressive spinal or bulbar spasticity with minimal motor weakness. Rarely, PLS may present with clinical features resembling parkinsonism resulting in occasional misdiagnosis as one of the atypical parkinsonian syndromes. Here we describe five patients initially referred with a diagnosis of levodopa-unresponsive atypical parkinsonism (n = 4) or primary progressive multiple sclerosis (n = 1), but subsequently found to have features consistent with PLS instead. Onset age varied from 49 to 67 years. Unilateral limb slowness or clumsiness was the initial complaint in four, and bulbar symptoms in one. Repeated finger/foot tapping was slow in all five, but without fatiguing or decrement. Spasticity with hyperreflexia, exaggerated jaw jerk and extensor plantar responses were eventually seen in all patients. Anterior horn cell involvement developed in three cases. Early gait disturbances resulting in falls were seen in all patients and none of them responded to dopaminergic medications. Two patients underwent dopamine transporter (DaT) SPECT scanning with normal results. Other features included emotional lability (n = 5) and cognitive impairment involving frontal subcortical systems (n = 1). In conclusion, these cases represent a subgroup of PLS patients in whom pyramidal slowness may be mistaken for akinesia, and spasticity misconstrued as rigidity, leading to an erroneous diagnosis of atypical parkinsonism. However, the absence of fatiguing and decrement on repeated finger/foot tapping should help to distinguish these patients from the true atypical parkinsonian syndromes.

Prolonged Vibration of the Biceps Brachii Tendon Reduces Time to Failure When Maintaining Arm Position With a Submaximal Load

Vibration reduces the amplitudes of the tendon jerk response and the Hoffmann and stretch reflexes in the muscle exposed to the vibration, yet does not alter the time to task failure when the task involves exerting a submaximal force against a rigid restraint. Because the amplitude of the stretch reflex is greater when a limb acts against a compliant load than a rigid restraint, the purpose was to determine the influence of prolonged tendon vibration on the time to failure when maintaining limb position with the elbow flexor muscles. Twenty-five healthy men performed the fatiguing contraction by maintaining elbow angle at 1.57 rad until failure while supporting a load equal to 20% of maximal voluntary contraction (MVC) force. The fatiguing contraction was performed on 3 separate days with different levels of vibration applied to the biceps brachii tendon: no vibration, subthreshold for a tonic vibration reflex (TVR), and suprathreshold for a TVR. MVC force before the fatiguing contraction was similar across the three sessions (mean of 3 sessions: 313 +/- 54 N, P = 0.83). Despite a similar decline in MVC force after the fatiguing contraction across conditions (-18.0 +/- 8.0%, P > 0.05), the time to task failure was 3.7 +/- 1.4 min for the suprathreshold TVR condition, 4.3 +/- 2.1 min for the subthreshold TVR condition, and 5.0 +/- 2.2 min for the no-vibration condition (P < 0 0.001). The average EMG of the elbow flexor muscles was similar (P = 0.22) during the fatiguing contractions. However, the fluctuations in limb acceleration at task onset were greater for the suprathreshold TVR condition (P < 0.01), but were not different between the subthreshold TVR and no-vibration conditions (P > or = 0.22). Furthermore, the difference in the SD of limb acceleration between the no-vibration and vibration conditions was correlated with the difference in time to failure for the no-vibration and subthreshold TVR conditions (P = 0.03; r2 = 0.22), but not for the no-vibration and suprathreshold TVR conditions (P = 0.90; r2 = 0.001). These findings indicate that prolonged vibration reduced the time to failure of a sustained contraction when subjects maintained limb position, suggesting that peripheral inputs to the motor neuron pool play a significant role in sustaining a contraction during tasks that require active control of limb position.

Erb and Westphal: simultaneous discovery of the deep tendon reflexes.

Although the deep tendon reflexes (DTRs) were first introduced simultaneously into the medical literature by Erb and Westphal (1875), there is some evidence that the knee jerk response was well known to laymen prior to that time. Erb wrote that while he was not calling attention to anything new, he realized the utility of the phenomenon in diagnosing certain disease states. Erb viewed the phenomenon more clearly as a true reflex arc, whereas Westphal interpreted it as a local muscle phenomenon. By 1885, the maneuver was used in Europe and across the Atlantic in America. By then, the DTRs had become one of the cardinal features of the neurological examination.