A component analysis of the generation and release of isometric force in Parkinson's disease

Cortical beta oscillations help synchronise muscles during static posture holding in healthy motor control

How cortical oscillations are involved in the coordination of functionally coupled muscles and how this is modulated by different movement contexts (static vs dynamic) remains unclear. Here, this is investigated by recording high-density electroencephalography (EEG) and electromyography (EMG) from different forearm muscles while healthy participants (n = 20) performed movement tasks (static and dynamic posture holding, and reaching) with their dominant hand. When dynamic perturbation was applied, beta band (15-35 Hz) activities in the motor cortex contralateral to the performing hand reduced during the holding phase, comparative to when there was no perturbation. During static posture holding, transient periods of increased cortical beta oscillations (beta bursts) were associated with greater corticomuscular coherence and increased phase synchrony between muscles (intermuscular coherence) in the beta frequency band compared to the no-burst period. This effect was not present when resisting dynamic perturbation. The results suggest that cortical beta bursts assist synchronisation of different muscles during static posture holding in healthy motor control, contributing to the maintenance and stabilisation of functional muscle groups. Theoretically, increased cortical beta oscillations could lead to exaggerated synchronisation in different muscles making the initialisation of movements more difficult, as observed in Parkinson's disease.

Impaired performance of rapid grip in people with Parkinson's disease and motor segmentation

Bradykinesia, or slow movement, is a defining symptom of Parkinson's disease (PD), but the underlying neuromechanical deficits that lead to this slowness remain unclear. People with PD often have impaired rates of motor output accompanied by disruptions in neuromuscular excitation, causing abnormal, segmented, force-time curves. Previous investigations using single-joint models indicate that agonist electromyogram (EMG) silent periods cause motor segmentation. It is unknown whether motor segmentation is evident in more anatomically complex and ecologically important tasks, such as handgrip tasks. Aim 1 was to determine how handgrip rates of force change compare between people with PD and healthy young and older adults. Aim 2 was to determine whether motor segmentation is present in handgrip force and EMG measures in people with PD. Subjects performed rapid isometric handgrip pulses to 20-60% of their maximal voluntary contraction force while EMG was collected from the grip flexors and extensors. Dependent variables included the time to 90% peak force, the peak rate of force development, the duration above 90% of peak force, the number of segments in the force-time curve, the number of EMG bursts, time to relaxation from 90% of peak force, and the peak rate of force relaxation. People with PD had longer durations and lower rates of force change than young and older adults. Six of 22 people with PD had motor segmentation. People with PD had more EMG bursts compared to healthy adults and the number of EMG bursts covaried with the number of segments. Thus, control of rapid movement in Parkinson's disease can be studied using isometric handgrip. People with PD have impaired rate control compared to healthy adults and motor segmentation can be studied in handgrip.

Involvement of A13 dopaminergic neurons in prehensile movements but not reward in the rat

Tyrosine hydroxylase (TH)-containing neurons of the dopamine (DA) cell group A13 are well positioned to impact known DA-related functions as their descending projections innervate target regions that regulate vigilance, sensory integration, and motor execution. Despite this connectivity, little is known regarding the functionality of A13-DA circuits. Using TH-specific loss-of-function methodology and techniques to monitor population activity in transgenic rats in vivo, we investigated the contribution of A13-DA neurons in reward and movement-related actions. Our work demonstrates a role for A13-DA neurons in grasping and handling of objects but not reward. A13-DA neurons responded strongly when animals grab and manipulate food items, whereas their inactivation or degeneration prevented animals from successfully doing so-a deficit partially attributed to a reduction in grip strength. By contrast, there was no relation between A13-DA activity and food-seeking behavior when animals were tested on a reward-based task that did not include a reaching/grasping response. Motivation for food was unaffected, as goal-directed behavior for food items was in general intact following A13 neuronal inactivation/degeneration. An anatomical investigation confirmed that A13-DA neurons project to the superior colliculus (SC) and also demonstrated a novel A13-DA projection to the reticular formation (RF). These results establish a functional role for A13-DA neurons in prehensile actions that are uncoupled from the motivational factors that contribute to the initiation of forelimb movements and help position A13-DA circuits into the functional framework regarding centrally located DA populations and their ability to coordinate movement.

Moving, fast and slow: behavioural insights into bradykinesia in Parkinson's disease

The debilitating symptoms of Parkinson's disease, including the hallmark slowness of movement, termed bradykinesia, were described more than 100 years ago. Despite significant advances in elucidating the genetic, molecular and neurobiological changes in Parkinson's disease, it remains conceptually unclear exactly why patients with Parkinson's disease move slowly. To address this, we summarize behavioural observations of movement slowness in Parkinson's disease and discuss these findings in a behavioural framework of optimal control. In this framework, agents optimize the time it takes to gather and harvest rewards by adapting their movement vigour according to the reward that is at stake and the effort that needs to be expended. Thus, slow movements can be favourable when the reward is deemed unappealing or the movement very costly. While reduced reward sensitivity, which makes patients less inclined to work for reward, has been reported in Parkinson's disease, this appears to be related mainly to motivational deficits (apathy) rather than bradykinesia. Increased effort sensitivity has been proposed to underlie movement slowness in Parkinson's disease. However, careful behavioural observations of bradykinesia are inconsistent with abnormal computations of effort costs due to accuracy constraints or movement energetic expenditure. These inconsistencies can be resolved when considering that a general disability to switch between stable and dynamic movement states can contribute to an abnormal composite effort cost related to movement in Parkinson's disease. This can account for paradoxical observations such as the abnormally slow relaxation of isometric contractions or difficulties in halting a movement in Parkinson's disease, both of which increase movement energy expenditure. A sound understanding of the abnormal behavioural computations mediating motor impairment in Parkinson's disease will be vital for linking them to their underlying neural dynamics in distributed brain networks and for grounding future experimental studies in well-defined behavioural frameworks.

Are the digit ratio (2D:4D) and hand grip strength related to Parkinson disease in elderly males?

BACKGROUND

Sex hormones affect the pathogenesis of Parkinson patients and it has been suggested that gender is the most important factor in the development and progression of Parkinson's disease. Studies have shown that the second to fourth digit ratio (2D:4D) is affected by the prenatal testosterone and estrogen levels and can predict predisposition to disease. In addition, decreased muscle strength in people with Parkinson's has been repeatedly reported. Hand grip strength (HGS) is a suitable measure to evaluate the musculoskeletal system among the elderly and it is considered as an indicator of the overall strength of the body. This study aimed at investigating the relationship between Parkinson's disease and HGS and 2D:4D ratio.

METHODS

In this study 117 elderly men with Parkinson disease (mean age of 61.66 ± 11.28 years) and 156 healthy control subjects (mean age of 61.86 ± 6.29 years) participated. After determining the level of disability of Parkinson patients by a neurologist (level of disability in the range of 1-4), anthropometric indices (height, weight, length of the second and fourth fingers) and maximum HGS were measured.

RESULTS

Although 2D:4D ratios (right and left hand) of male patients with Parkinson's disease were higher than those of healthy males, this difference was not statistically significant (P = 0.12, P = 0.40; respectively). Conversely, HGS for the right and left hands of Parkinson patients were significantly lower than those of healthy males (P = 0.02, P = 0.03; respectively). The results showed a significant negative relationship between Parkinson disease and the right and left HGS (R = -0.16, P = 0.005; R = -0.17, P = 0.003; respectively). Parkinson disease had no significant relationship with 2D:4D of the right hand, left hand, mean finger ratio and D_R-L 2D:4D (P > 0.05). The regression results showed that the right and left HGS were not able to predict Parkinson disease (P = 0.25, P = 0.16; respectively).

CONCLUSION

We concluded that HGS was negatively associated with the Parkinson disease, but conversely, 2D:4D may not be a valuable biomarker of elevated risk of Parkinson in elderly males.

Rate control deficits during pinch grip and ankle dorsiflexion in early-stage Parkinson's disease

BACKGROUND

Much of our understanding of the deficits in force control in Parkinson's disease (PD) relies on findings in the upper extremity. Currently, there is a paucity of data pertaining to the effect of PD on lower limb force control.

OBJECTIVE

The purpose of this study was to concurrently evaluate upper- and lower-limb force control in early-stage PD and a group of age- and gender-matched healthy controls.

METHODS

Twenty individuals with PD and twenty-one healthy older adults participated in this study. Participants performed two visually guided, submaximal (15% of maximum voluntary contractions) isometric force tasks: a pinch grip task and an ankle dorsiflexion task. PD were tested on their more affected side and after overnight withdrawal from antiparkinsonian medication. The tested side in controls was randomized. Differences in force control capacity were assessed by manipulating speed-based and variability-based task parameters.

RESULTS

Compared with controls, PD demonstrated slower rates of force development and force relaxation during the foot task, and a slower rate of relaxation during the hand task. Force variability was similar across groups but greater in the foot than in the hand in both PD and controls. Lower limb rate control deficits were greater in PD with more severe symptoms based on the Hoehn and Yahr stage.

CONCLUSIONS

Together, these results provide quantitative evidence of an impaired capacity in PD to produce submaximal and rapid force across multiple effectors. Moreover, results suggest that force control deficits in the lower limb may become more severe with disease progression.

Muscle Strength and Power in People With Parkinson Disease: A Systematic Review and Meta-analysis

BACKGROUND AND PURPOSE

No studies have synthesized the literature regarding mechanical muscle function (ie, strength, power, rate of force development [RFD]) in people with Parkinson disease (PD). Here, we aimed to expand our understanding of mechanical muscle function in people with PD (PwPD) by systematically reviewing (1) the psychometric properties of isokinetic/isometric dynamometry in PD, (2) the literature comparing mechanical muscle function in PwPD with healthy controls (HC), and (3) reported associations between muscle mechanical muscle function and functional capacity and/or disease severity.

METHODS

Systematic literature search in 6 databases. Included studies had to (1) enroll and report data on PwPD, (2) include assessment(s) of psychometric properties (ie, validity, reliability, responsiveness) of isokinetic/isometric dynamometry in PD, and/or (3) assess mechanical muscle function in both PwPD and HC using isokinetic/isometric dynamometry.

RESULTS

A total of 40 studies were included. Aim 1 studies (n = 2) showed high reliability for isometric dynamometry (hip-abductor/dorsiflexor/trunk flexor-extensor/handgrip: intraclass correlations coefficients range = 0.92-0.98). Aim 2 studies (n = 40) showed impaired mechanical muscle function (ie, strength, power, RFD) in PwPD compared with HC (effect sizes range = 0.52-1.89). Aim 3 studies (n = 11) showed weak-to-strong associations between overall and lower extremities muscle strength and functional capacity and/or disease severity outcomes (ie, Unified Parkinson Disease Rating Scale).

DISCUSSION AND CONCLUSIONS

Sparse methodological evidence suggests high reliability when using dynamometry in PwPD. Muscle strength, power, and RFD are impaired in PwPD compared with HC. Muscle strength is associated with functional capacity and disease severity.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A403 ).

Quantifying upper limb motor impairment in people with Parkinson's disease: a physiological profiling approach

BACKGROUND

Upper limb motor impairments, such as slowness of movement and difficulties executing sequential tasks, are common in people with Parkinson's disease (PD).

OBJECTIVE

To evaluate the validity of the upper limb Physiological Profile Assessment (PPA) as a standard clinical assessment battery in people with PD, by determining whether the tests, which encompass muscle strength, dexterity, arm stability, position sense, skin sensation and bimanual coordination can (a) distinguish people with PD from healthy controls, (b) detect differences in upper limb test domains between "off" and "on" anti-Parkinson medication states and (c) correlate with a validated measure of upper limb function.

METHODS

Thirty-four participants with PD and 68 healthy controls completed the upper limb PPA tests within a single session.

RESULTS

People with PD exhibited impaired performance across most test domains. Based on validity, reliability and feasibility, six tests (handgrip strength, finger-press reaction time, 9-hole peg test, bimanual pole test, arm stability, and shirt buttoning) were identified as key tests for the assessment of upper limb function in people with PD.

CONCLUSIONS

The upper limb PPA provides a valid, quick and simple means of quantifying specific upper limb impairments in people with PD. These findings indicate clinical assessments should prioritise tests of muscle strength, unilateral movement and dexterity, bimanual coordination, arm stability and functional tasks in people with PD as these domains are the most commonly and significantly impaired.

Brain and Muscle: How Central Nervous System Disorders Can Modify the Skeletal Muscle

It is widely known that nervous and muscular systems work together and that they are strictly dependent in their structure and functions. Consequently, muscles undergo macro and microscopic changes with subsequent alterations after a central nervous system (CNS) disease. Despite this, only a few researchers have addressed the problem of skeletal muscle abnormalities following CNS diseases. The purpose of this review is to summarize the current knowledge on the potential mechanisms responsible for changes in skeletal muscle of patients suffering from some of the most common CSN disorders (Stroke, Multiple Sclerosis, Parkinson’s disease). With this purpose, we analyzed the studies published in the last decade. The published studies show an extreme heterogeneity of the assessment modality and examined population. Furthermore, it is evident that thanks to different evaluation methodologies, it is now possible to implement knowledge on muscle morphology, for a long time limited by the requirement of muscle biopsies. This could be the first step to amplify studies aimed to analyze muscle characteristics in CNS disease and developing rehabilitation protocols to prevent and treat the muscle, often neglected in CNS disease.

Dopamine D2 receptor signaling on iMSNs is required for initiation and vigor of learned actions

Striatal dopamine D2 receptors (D2Rs) are important for motor output. Selective deletion of D2Rs from indirect pathway-projecting medium spiny neurons (iMSNs) impairs locomotor activities in a task-specific manner. However, the role of D2Rs in the initiation of motor actions in reward seeking and taking is not fully understood, and there is little information about how receptors contribute under different task demands and with different outcome types. The iMSN-D2Rs modulate neuronal activity and synaptic transmission, exerting control on circuit functions that may play distinct roles in action learning and performance. Selective deletion of D2Rs on iMSNs resulted in slower action initiation and response rate in an instrumental conditioning task, but only when performance demand was increased. The iMSN-Drd2KO mice were also slower to initiate swimming in a T-maze procedural learning task but were unimpaired in cognitive function and behavioral flexibility. In contrast, in a Pavlovian discrimination learning task, iMSN-Drd2KO mice exhibited normal acquisition and extinction of rewarded responding. The iMSN-Drd2KO mice showed performance deficits at all phases of rotarod skill learning. These findings reveal that dopamine modulation through iMSN-D2Rs influences the ability to self-initiate actions, as well as the willingness and/or vigor with which these responses are performed. However, these receptors seem to have little influence on simple associative learning or on stimulus-driven responding. The loss of normal D2R roles may contribute to disorders in which impaired dopamine signaling leads to hypokinesia or impaired initiation of specific voluntary actions.

Voluntary Muscle Relaxation Can Mitigate Fatigue and Improve Countermovement Jump Performance

Pinto, BL and McGill, SM. Voluntary muscle relaxation can mitigate fatigue and improve countermovement jump performance. J Strength Cond Res 34(6): 1525-1529, 2020-When muscles contract, they create force and stiffness. Thus, muscle activation and relaxation must be strategically sequenced to coordinate and control movement, to enhance athletic variables such as speed and strength. However, research has favored investigation of muscle activation over relaxation. Athletes such as runners, swimmers, and boxers often shake their limbs to allow the muscle to oscillate freely, immediately before a bout. The purpose was to investigate whether shaking the lower limbs with the intention to voluntarily relax the muscles of the limb has an effect on countermovement jump (CMJ) performance. Subjects performed 10 maximal effort CMJs with 30 seconds of rest between each jump. During the rest period, they either performed the relaxation technique or control condition (standing still). Statistical significance was considered at p < 0.05. Subjects significantly improved jump height, compared with their first jump of the day, when performing the relaxation technique. To further investigate the mechanism of enhancement, subjects were grouped into responders and nonresponders. The responder group significantly decreased their jump height and concentric phase impulse (relative to the first jump) during the control condition compared with the nonresponder group, indicating fatigue. When performing the relaxation technique, the responder group improved their jump height and mitigated fatigue by significantly increasing their unweighting impulse and unweighting force. The relaxation technique improved CMJ performance, specifically in those that fatigue with consecutive bouts, by enhancing unweighting, that requires muscle relaxation, rather than propulsion that requires activation. This technique can be useful for training or competition.

Effects of Sub-Chronic MPTP Exposure on Behavioral and Cognitive Performance and the Microbiome of Wild-Type and mGlu8 Knockout Female and Male Mice

Motor dysfunction is a hallmark of Parkinson's disease (PD); however, non-motor symptoms such as gastrointestinal dysfunction often arise prior to motor symptoms. Alterations in the gut microbiome have been proposed as the earliest event in PD pathogenesis. PD symptoms often demonstrate sex differences. Glutamatergic neurotransmission has long been linked to PD pathology. Metabotropic glutamate receptors (mGlu), a family of G protein-coupled receptors, are divided into three groups, with group III mGlu receptors mainly localized presynaptically where they can inhibit glutamate release in the CNS as well as in the gut. Additionally, the gut microbiome can communicate with the CNS via the gut-brain axis. Here, we assessed whether deficiency of metabotropic glutamate receptor 8 (mGlu8), group III mGlu, modulates the effects of the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), on behavioral and cognitive performance in female and male mice. We studied whether these effects are associated with changes in striatal tyrosine hydroxylase (TH) levels and the gut microbiome. Two-week sub-chronic MPTP increased activity of female and male wild-type (WT) and mGlu8 knockout (KO) mice in the open field. MPTP also showed genotype- and sex-dependent effects. MPTP increased the time WT, but not KO, females and males spent exploring objects. In WT mice, MPTP improved sensorimotor function in males but impaired it in females. Further, MPTP impaired cued fear memory in WT, but not KO, male mice. MPTP reduced striatal TH levels in WT and KO mice but these effects were only pronounced in males. MPTP treatment and genotype affected the diversity of the gut microbiome. In addition, there were significant associations between microbiome α-diversity and sensorimotor performance, as well as microbiome composition and fear learning. These results indicate that specific taxa may directly affect motor and fear learning or that the same physiological effects that enhance both forms of learning also alter diversity of the gut microbiome. MPTP's effect on motor and cognitive performance may then be, at least in part, be mediated by the gut microbiome. These data also support mGlu8 as a novel therapeutic target for PD and highlight the importance of including both sexes in preclinical studies.

Use of Jebsen Taylor Hand Function Test in evaluating the hand dexterity in people with Parkinson's disease

OBJECTIVES

To investigate the test-retest reliability of JTT in older patients with Parkinson's disease (PD); and to compare the Jebsen Taylor Hand Function Test (JTT) scores between PD and healthy subjects.

STUDY DESIGN

Cross-sectional comparative study.

METHODS

Fifteen PD and fifteen healthy subjects performed the JTT and the time taken to complete the JTT was recorded.

RESULTS

Test-retest reliabilities of JTT subtests and total score of both dominant and non-dominant hand were good to excellent (ICCs = 0.77-0.97) except J5 checkers which had moderate reliability. PD subjects required significantly longer time to finish subtests and the whole JTT (p < 0.05), except the subtest J1 writing of dominant hand that showed marginal significance (p = 0.059).

CONCLUSION

JTT is a reliable and easily available assessment tool for assessing the hand function of PD subjects. PD subjects took a longer time to complete the JTT, suggesting that they have deficits in gross and fine functional dexterity.

Neuromuscular Impairments Are Associated With Impaired Head and Trunk Stability During Gait in Parkinson Fallers

Background The trunk plays a critical role in attenuating movement-related forces that threaten to challenge the body's postural control system. For people with Parkinson's disease (PD), disease progression often leads to dopamine-resistant axial symptoms, which impair trunk control and increase falls risk. Objective This prospective study aimed to evaluate the relationship between impaired trunk muscle function, segmental coordination, and future falls in people with PD. Methods Seventy-nine PD patients and 82 age-matched controls completed clinical assessments and questionnaires to establish their medical history, symptom severity, balance confidence, and falls history. Gait characteristics and trunk muscle activity were assessed using 3-dimensional motion analysis and surface electromyography. The incidence, cause, and consequence of any falls experienced over the next 12 months were recorded and indicated that 48 PD and 29 control participants fell at least once during this time. Results PD fallers had greater peak and baseline lumbar multifidus (LMF) and thoracic erector spinae (TES) activations than control fallers and nonfallers. Analysis of covariance indicated that the higher LMF activity was attributable to the stooped posture adopted by PD fallers, but TES activity was independent of medication use, symptom severity, and trunk orientation. Furthermore, greater LMF and TES baseline activity contributed to increasing lateral head, trunk, and pelvis movements in PD fallers but not nonfallers or controls. Conclusions The results provide evidence of neuromuscular deficits for PD fallers that are independent of medications, symptom severity, and posture and contribute to impaired head, trunk, and pelvis control associated with falls in this population.

Motor intensive anti-gravity training improves performance in dynamic balance related tasks in persons with Parkinson's disease

Recent studies indicate that the effect of training on motor performance in persons with Parkinson's disease (PDP) is dependent on motor intensity. However, training of high motor intensity can be hard to apply in PDP due to e.g. bradykinesia, rigidity, tremor and postural instability. Therefore, the aim was to study the effect of motor intensive training performed in a safe anti-gravity environment using lower-body positive pressure (LBPP) technology on performance during dynamic balance related tasks. Thirteen male PDP went through an 8-week control period followed by 8 weeks of motor intensive antigravity training. Seventeen healthy males constituted a control group (CON). Performance during a five repetition sit-to-stand test (STS; sagittal plane) and a dynamic postural balance test (DPB; transversal plane) was evaluated. Effect measures were completion time, functional rates of force development, directional changes and force variance. STS completion time improved by 24% to the level of CON which was explained by shorter sitting-time and standing-time and larger numeric rate of force change during lowering to the chair, indicating faster vertical directional change and improved relaxation. DPB completion time tended to improve and was accompanied by improvements of functional medial and lateral rates of force development and higher vertical force variance during DPB. Our results suggest that the performance improvements may relate to improved inter-limb coordination. It is concluded that 8 weeks of motor intensive training in a safe LBPP environment improved performance during dynamic balance related tasks in PDP.

Parkinson disease and exercise

Parkinson disease (PD) is a progressive, neurodegenerative movement disorder. PD was originally attributed to neuronal loss within the substantia nigra pars compacta, and a concomitant loss of dopamine. PD is now thought to be a multisystem disorder that involves not only the dopaminergic system, but other neurotransmitter systems whose role may become more prominent as the disease progresses (189). PD is characterized by four cardinal symptoms, resting tremor, rigidity, bradykinesia, and postural instability, all of which are motor. However, PD also may include any combination of a myriad of nonmotor symptoms (195). Both motor and nonmotor symptoms may impact the ability of those with PD to participate in exercise and/or impact the effects of that exercise on those with PD. This article provides a comprehensive overview of PD, its symptoms and progression, and current treatments for PD. Among these treatments, exercise is currently at the forefront. People with PD retain the ability to participate in many forms of exercise and generally respond to exercise interventions similarly to age-matched subjects without PD. As such, exercise is currently an area receiving substantial research attention as investigators seek interventions that may modify the progression of the disease, perhaps through neuroprotective mechanisms.

Effects of training and weight support on muscle activation in Parkinson's disease

The aim of this study was to investigate the effect of high-intensity locomotor training on knee extensor and flexor muscle activation and adaptability to increased body-weight (BW) support during walking in patients with Parkinson's disease (PD). Thirteen male patients with idiopathic PD and eight healthy participants were included. The PD patients completed an 8-week training program on a lower-body, positive-pressure treadmill. Knee extensor and flexor muscles activation during steady treadmill walking (3 km/h) were measured before, at the mid-point, and after training. Increasing BW support decreased knee extensor muscle activation (normalization) and increased knee flexor muscle activation (abnormal) in PD patients when compared to healthy participants. Training improved flexor peak muscle activation adaptability to increased (BW) support during walking in PD patients. During walking without BW support shorter knee extensor muscle off-activation time and increased relative peak muscle activation was observed in PD patients and did not improve with 8 weeks of training. In conclusion, patients with PD walked with excessive activation of the knee extensor and flexor muscles when compared to healthy participants. Specialized locomotor training may facilitate adaptive processes related to motor control of walking in PD patients.

Force control deficits in individuals with Parkinson's disease, multiple systems atrophy, and progressive supranuclear palsy

Objective

This study examined grip force and cognition in Parkinson’s disease (PD), Parkinsonian variant of multiple system atrophy (MSAp), progressive supranuclear palsy (PSP), and healthy controls. PD is characterized by a slower rate of force increase and decrease and the production of abnormally large grip forces. Early-stage PD has difficulty with the rapid contraction and relaxation of hand muscles required for precision gripping. The first goal was to determine which features of grip force are abnormal in MSAp and PSP. The second goal was to determine whether a single variable or a combination of motor and cognitive measures would distinguish patient groups. Since PSP is more cognitively impaired relative to PD and MSAp, we expected that combining motor and cognitive measures would further distinguish PSP from PD and MSAp.

Methods

We studied 44 participants: 12 PD, 12 MSAp, 8 PSP, and 12 controls. Patients were diagnosed by a movement disorders neurologist and were tested off anti-Parkinsonian medication. Participants completed a visually guided grip force task wherein force pulses were produced for 2 s, followed by 1 s of rest. We also conducted four cognitive tests.

Results

PD, MSAp, and PSP were slower at contracting and relaxing force and produced longer pulse durations compared to controls. PSP produced additional force pulses during the task and were more cognitively impaired relative to other groups. A receiver operator characteristic analysis revealed that the combination of number of pulses and Brief Test of Attention (BTA) discriminated PSP from PD, MSAp, and controls with a high degree of sensitivity and specificity.

Conclusions

Slowness in contracting and relaxing force represent general features of PD, MSAp, and PSP, whereas producing additional force pulses was specific to PSP. Combining motor and cognitive measures provides a robust method for characterizing behavioral features of PSP compared to MSAp and PD.

An evidence-based exercise regimen for patients with mild to moderate Parkinson's disease

Parkinson’s disease (PD) is a neurological disorder that is manifested in the form of both motor and non-motor symptoms such as resting tremor, bradykinesia, muscular rigidity, depression, and cognitive impairment. PD is progressive in nature, ultimately leading to debilitating disruption of activities of daily living. Recently, a myriad of research has been focused on non-pharmacological interventions to alleviate the motor and non-motor symptoms of the disease. However, while there is a growing body of evidence supporting exercise as a viable therapy option for the treatment of Parkinson’s disease, there is a lack of literature enumerating a specific exercise sequence for patients with PD. In this literature review, we analyze the success of specific modalities of exercise in order to suggest an optimal exercise regimen for Parkinson’s disease patients.

Frequency specific activity in subthalamic nucleus correlates with hand bradykinesia in Parkinson's disease

Local field potential recordings made from the basal ganglia of patients undergoing deep brain stimulation have suggested that frequency specific activity is involved in determining the rate of force development and the peak force at the outset of a movement. However, the extent to which the basal ganglia might be involved in motor performance later on in a sustained contraction is less clear. We therefore recorded from the subthalamic nucleus region (STNr) in patients with Parkinson's disease (PD) as they made maximal voluntary grips. Relative to age-matched controls they had more rapid force decrement when contraction was meant to be sustained and prolonged release reaction time and slower rate of force offset when they were supposed to release the grip. These impairments were independent from medication status. Increased STNr power over 5–12 Hz (in the theta/alpha band) independently predicted better performance—reduced force decrement, shortened release reaction time and faster rate of force offset. In contrast, lower mean levels and progressive reduction of STNr power over 55–375 Hz (high gamma/high frequency) over the period when contraction was meant to be sustained were both strongly associated with greater force decrement over time. Higher power over 13–23 Hz (low beta) was associated with more rapid force decrement during the period when grip should have been sustained, and with a paradoxical shortening of the release reaction time. These observations suggest that STNr activities at 5–12 Hz and 55–375 Hz are necessary for optimal grip performance and that deficiencies of such activities lead to motor impairments. In contrast, increased levels of 13–25 Hz activity both promote force decrement and shorten the release reaction time, consistent with a role in antagonising (and terminating) voluntary movement. Frequency specific oscillatory activities in the STNr impact on motor performance from the beginning to the end of a voluntary grip.

Parkinsonian arm movements as altered by task difficulty

A discrete elbow movement to targets with different indexes of difficulty (ID) was used to determine the kinematic organization of arm movements in a young, an elderly and a Parkinson's disease (PD) group (n = 14). Target size and movement amplitude changes led to expected modifications of the kinematics in all three groups according to Fitts' law. Increased task demands by changing target size produced not only differences between the age-groups, but affected the modulation of velocity and acceleration in the parkinsonian patients differentially. For large amplitude movements, the PD patients were less able to increase velocity and acceleration magnitudes when target accuracy constraints were reduced. These findings, when taken together with the observation that speed scaling was preserved for small movement amplitudes, suggest that a reduced capability to initiate and regulate force is the cause for the observed slowness in PD.

Altered pharyngeal muscles in Parkinson disease

Dysphagia (impaired swallowing) is common in patients with Parkinson disease (PD) and is related to aspiration pneumonia, the primary cause of death in PD. Therapies that ameliorate the limb motor symptoms of PD are ineffective for dysphagia. This suggests that the pathophysiology of PD dysphagia may differ from that affecting limb muscles, but little is known about potential neuromuscular abnormalities in the swallowing muscles in PD. This study examined the fiber histochemistry of pharyngeal constrictor and cricopharyngeal sphincter muscles in postmortem specimens from 8 subjects with PD and 4 age-matched control subjects. Pharyngeal muscles in subjects with PD exhibited many atrophic fibers, fiber type grouping, and fast-to-slow myosin heavy chain transformation. These alterations indicate that the pharyngeal muscles experienced neural degeneration and regeneration over the course of PD. Notably, subjects with PD with dysphagia had a higher percentage of atrophic myofibers versus with those without dysphagia and controls. The fast-to-slow fiber-type transition is consistent with abnormalities in swallowing, slow movement of food, and increased tone in the cricopharyngeal sphincter in subjects with PD. The alterations in the pharyngeal muscles may play a pathogenic role in the development of dysphagia in subjects with PD.

Testing the contributions of striatal dopamine loss to the genesis of parkinsonian signs

The diverse and independently-varying signs of Parkinson's disease (PD) are often attributed to one simple mechanism: degeneration of the dopaminergic innervation of the posterolateral striatum. However, growing recognition of the dopamine (DA) loss and other pathology in extra-striatal brain regions has led to uncertainty whether loss of DA in the striatum is sufficient to cause parkinsonian signs. We tested this hypothesis by infusing cis-flupenthixol (cis-flu; a broad-spectrum D1/D2 receptor antagonist) into different regions of the macaque putamen (3 hemispheres of 2 monkeys) while the animal performed a visually-cued choice reaction time task in which visual cues indicated the arm to reach with and the peripheral target to contact to obtain food reward. Following reward delivery, the animal was required to self-initiate release of the peripheral target and return of the chosen hand to its home position (i.e., without the benefit of external sensory cues or immediate rewards). Infusions of cis-flu at 15 of 26 sites induced prolongations of reaction time (9 of 15 cases), movement duration (6 cases), and/or dwell time of the hand at the peripheral target (8 cases). Dwell times were affected more severely (+95%) than visually-triggered reaction times or movement durations (+25% and +15%, respectively). Specifically, the animal's hand often 'froze' at the peripheral target for up to 25-s, similar to the akinetic freezing episodes observed in PD patients. Across injections, slowing of self-initiation did not correlate in severity with prolongations of visually-triggered reaction time or movement duration, although the latter two were correlated with each other. Episodes of slowed self-initiation appeared primarily in the arm contralateral to the injected hemisphere and were not associated with increased muscle co-contraction or global alterations in behavioral state (i.e., inattention or reduced motivation), consistent with the idea that these episodes reflected a fundamental impairment of movement initiation. We found no evidence for an anatomic topography within the putamen for the effects elicited. We conclude that acute focal blockade of DA transmission in the putamen is sufficient to induce marked akinesia-like impairments. Furthermore, different classes of impairments can be induced independently, suggesting that specific parkinsonian signs have unique pathophysiologic substrates.

Quadriceps muscle weakness, activation deficits, and fatigue with Parkinson disease

BACKGROUND

People with Parkinson disease (PD) typically have complaints of weakness. The mechanisms underlying this deficit have not been well established, although many factors may contribute.

OBJECTIVE

This investigation aimed to characterize quadriceps muscle weakness and activation failure in people with PD and explore whether these deficits were related to disease severity. The authors further sought to examine quadriceps muscle fatigability.

METHODS

This was a cross-sectional comparison of 17 people with mild-severe PD and 17 healthy adults matched by age, sex, and body mass index (BMI). The Unified Parkinson's Disease Rating Scale motor score (UPDRS motor) ranged from 9.5 to 61.0. Participants were divided into those with low-PD motor signs (UPDRS motor < 31.7) and high-PD motor signs (UPDRS motor ≥ 31.7). Measures of quadriceps performance included isometric torque, central activation using doublet interpolation, and an isokinetic fatigue test.

RESULTS

Participants with high-PD motor signs had significantly more quadriceps weakness and central activation deficits than those with low-PD motor signs or healthy controls. Strength and activation deficits correlated strongly with UPDRS motor score. Quadriceps muscle fatigue was present in healthy controls and in those with low-PD motor signs but not in those with high-PD motor signs.

CONCLUSIONS

These findings provide additional evidence for lower-extremity strength loss with PD; central activation deficits may account for some of the strength deficits, especially with increased PD motor signs. Also, muscle fatigue did not occur in individuals with a greater degree of PD motor signs, most likely because of insufficient central activation to allow for muscle overload to induce metabolic fatigue.

Young and middle-aged rats exhibit isometric forelimb force control deficits in a model of early-stage Parkinson's disease

Deficits in manual motor control often accompany the early stages of Parkinson's disease (PD), and are often revealed through isometric force tasks. In order to determine whether similar deficits occur in a rat model of early-stage PD, young (8 months) and middle-aged (18 months) rats were trained to produce sustained press-hold-release isometric forelimb responses that allowed for analyses of force output and spectral analysis of forelimb stability and tremor. Rats then received a 6-hydroxydopamine (6-OHDA) infusion into the striatum contralateral to the trained forelimb and were tested for 4 weeks post-lesion. The resulting partial striatal dopamine depletions (which at 41±12% and 43±6% in young and middle-aged rats, respectively, did not differ between the two groups) resulted in isometric forelimb deficits. Specifically, rats exhibited significantly diminished force stability and increased high frequency (10-25Hz) tremor, indicating potential postural disturbances and increased postural tremor, respectively. Durations of press-hold-release bouts were also increased post-lesion, suggesting difficulty in task disengagement. Despite pre-lesion differences in some of the force measures, the effects of partial nigrostriatal DA depletion did not differ between the two age groups. These results support the use of the press-while-licking task in preclinical studies modeling isometric force control deficits in PD.

Rate-dependent impairments in repetitive finger movements in patients with Parkinson's disease are not due to peripheral fatigue

Performance of repetitive finger movements is an important clinical measure of disease severity in patients with Parkinson's disease (PD) and is associated with a dramatic deterioration in performance at movement rates near 2 Hz and above. The mechanisms contributing to this rate-dependent movement impairment are poorly understood. Since clinical and experimental testing of these movements involve prolonged repetition of movement, a loss of force-generating capacity due to peripheral fatigue may contribute to performance deterioration. This study examined the contribution of peripheral fatigue to the performance of unconstrained index finger flexion movements by measuring maximum voluntary contractions (MVC) immediately before and after repetitive finger movements in patients with PD (both off- and on-medication) and matched control subjects. Movement performance was quantified using finger kinematics, maximum force production, and electromyography (EMG). The principal finding was that peak force and EMG activity during the MVC did not significantly change from the pre- to post-movement task in patients with PD despite the marked deterioration in movement performance of repetitive finger movements. These findings show that the rate-dependent deterioration of repetitive finger movements in PD cannot be explained by a loss of force-generating capacity due to peripheral fatigue, and further suggest that mechanisms contributing to impaired isometric force production in PD are different from those that mediate impaired performance of high-rate repetitive movements.

Impaired step up/over in persons with Parkinson's disease

This study explored the functional movement task of stepping up and over an obstacle in individuals with Parkinson's disease to their aged-matched controls. Ten participants with Parkinson's disease and 10 aged matched participants were assessed on the Step Up/Over task completed on a NeuroCom EquiTest long forceplate and analyzed using Group MANOVAs. The results indicate that individuals with Parkinson's disease produce less lifting force and exhibited an increased time to complete the task of stepping up and over an object when compared with their aged matched peers. Considering the substantial risk of falls demonstrated in this population these preliminary finding demonstrate the need for interventions aimed at improving this component of function.

Correlação das escalas de avaliação utilizadas na doença de Parkinson com aplicabilidade na fisioterapia

INTRODUÇÃO: A doença de Parkinson (DP) é uma patologia neurológica crônica e degenerativa do sistema nervoso central que acomete os gânglios da base, cujas características principais são tremor, rigidez e bradicinesia. Com o progresso terapêutico, desenvolveram-se várias escalas visando monitorar a evolução da doença e a eficácia de tratamentos. O objetivo deste estudo de revisão bibliográfica é caracterizar as principais escalas usadas para a avaliação da DP, discutindo sua aplicabilidade à prática fisioterapêutica. MATERIAIS E MÉTODO: Levantamento bibliográfico a partir de bases de dados como Scielo, Medline, Lilacs, PubMed, entre 1990 a 2005. RESULTADOS: Seis escalas são abordadas: Escala dos Estágios de Incapacidade de Hoehn e Yahr; Escala Unificada de Avaliação da DP (UPDRS); Escala de Sydney; Questionário da DP (PDQ-39); Qualidade de vida (PSN); Escala de atividade de Parkinson (PAS). Destacando-se a PDQ-39 pela percepção do paciente sobre sua qualidade de vida. A PAS é a que melhor atende aos objetivos específicos da fisioterapia, pois avalia os principais problemas de mobilidade funcional. Além das escalas de Hoehn e Yahr e a UPDRS, por sua confiabilidade, pois podem ser usadas por fisioterapeutas para melhor avaliação do estado clínico-funcional do paciente. CONCLUSÃO: A necessidade de monitorar a evolução dos pacientes e os resultados de intervenção fisioterapêutica exige do fisioterapeuta o conhecimento para utilizar medidas sistematizadas e de fácil aplicabilidade para avaliar pacientes com DP. Cabe a esse profissional optar pela que permita uma tomada de decisão clínica compatível com seu local de trabalho, com as necessidades do paciente e com o meio em que ele vive.

Is there muscular weakness in Parkinson's disease?

Controversy exists as to whether muscle weakness is present in Parkinson's disease (PD). Computerized literature searches identified clinical trials and reviews about muscular strength assessment in patients with Parkinson's disease, using the following databases: PubMed, Ovid MEDLINE, Ovid EMBASE, the Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature, and Physiotherapy Evidence Database. Seventeen articles fulfilled all criteria for selection. These studies suggested that isokinetic muscle strength was decreased in patients with Parkinson's disease and that muscle weakness was not specifically related to tremor or rigidity. Bilateral asymmetrical muscle weakness was present in Parkinson's disease when presenting with clinical unilateral hemiparkinsonism. Recent studies using sensitive mechanical devices have provided evidence that muscle strength is reduced in patients with Parkinson's disease compared with age-matched controls. The specific cause of this weakness is not known. Questions under debate were whether this weakness was of central or peripheral origin and whether it was intrinsic to the disease or a secondary phenomenon.

Bradykinesia, muscle weakness and reduced muscle power in Parkinson's disease

Muscle power (force x velocity) could clarify the relationship between weakness and bradykinesia in Parkinson's disease (PD). The aims of this study were to determine if patients with PD were weaker and/or less powerful in their leg extensor muscles than a neurologically normal control group and to determine the relative contributions of force and movement velocity/bradykinesia to muscle power in PD. Forty patients with PD and 40 controls were assessed. Strength in Newtons (N) was measured as the heaviest load the participant could lift. Power in Watts (W) was measured by having the participant perform lifts as fast as possible. The PD group were 172 N weaker (95% CI 28-315) and 124 W less powerful at peak power (95% CI 32-216) than controls. However, velocity at maximal power was only reduced compared with controls when lifting light to medium loads. When lifting heavy loads bradykinesia was no longer apparent in the PD group. These results suggest that reduced muscle power in PD at lighter loads arises from weakness and bradykinesia combined, but at heavier loads arises only from weakness. The absence of bradykinesia in the PD group when lifting heavy loads warrants further investigation.

Parkinson's disease and resistive exercise: rationale, review, and recommendations

Individuals with Parkinson's disease (PD) are not only burdened with disease-specific symptoms (i.e., bradykinesia, rigidity, and tremor), but are also confronted with age-associated progressive loss of physical function, perhaps to a greater extent than neurologically normal adults. Suggestions for the inclusion of resistive exercise into treatment to attenuate these symptoms were made over 10 years ago, yet very few well controlled investigations are available. The objective of this review is to establish a clear rationale for the efficacy of resistance training in individuals with PD. Specifically, we highlight musculoskeletal weakness and its relationship to function as well as potential training-induced adaptive alterations in the neuromuscular system. We also review the few resistance training interventions currently available, but limit this review to those investigations that provide a quantitative exercise prescription. Finally, we recommend future lines of inquiry warranting further attention and call to question the rationale behind current exercise prescriptions. The absence of reports contraindicating resistive exercise, the potential for positive adaptation, and the noted benefits of resistance training in other populations may provide support for its inclusion into a treatment approach to PD.

Correlates of movement initiation and velocity in Parkinson's disease: A longitudinal PET study

Limited data exist concerning the mechanisms that underlie the different motor features of Parkinson's disease (PD) and their course over time. Our aims were (1) to identify longitudinal changes in PD patients and (2) to determine the neural correlates of the changes in movement initiation and velocity that occur in the course the disease. Thirteen early stage PD patients were scanned twice off antiparkinsonian medication with H(2)15O PET. Imaging was performed at baseline and again after 2 years while the subjects performed a motor task that was kinematically controlled across time. Paced reaching movements were made towards targets that were presented in a predictable order. Measures of movement onset time (OT) and mean velocity (MV) were recorded during PET. OT and MV decreased significantly from baseline to follow-up. With advancing disease, increasing subcortical activation was detected in the pallidum bilaterally and in the left putamen. In the cortex, motor-related activation increased in the right pre-SMA, anterior cingulate cortex and the left postcentral gyrus. Progressive delays in movement initiation (OT) correlated with increases in the right dorsal premotor cortex (dPMC). Slowing of movement (MV) was associated with declining activation in the left dorsolateral prefrontal cortex and dPMC. Our data suggest that with advancing PD, motor performance is associated with the recruitment of brain regions normally involved in the execution of more complex tasks.

Rate of force production and relaxation is impaired in patients with focal hand dystonia

One factor, which may contribute to slowed movement in dystonia, is impairment in controlling the voluntary rate of motor output. This study examined the ability of patients with focal hand dystonia to rapidly turn force on and off at the wrist and elbow joints. Dystonic patients were slower than controls in rapidly turning on force from rest at both joints, passively relaxing force and rapidly reversing force output from a steady-state flexion contraction. Adding a preload did not improve the ability of dystonic subjects to rapidly turn on force. These results support the idea that dystonia is a disorder of impaired motor cortical activation, possibly due to basal ganglia dysfunction.

Force related activations in rhythmic sequence production

Brain imaging studies have implicated the basal ganglia in the scaling of movement velocity. Basal ganglia activation has also been reported for movement timing. We investigated the neural correlates of scaling of force and time in the production of rhythmic motor sequences using functional magnetic resonance imaging (fMRI) of the human brain. Participants (N = 13) were imaged while squeezing a rigid force transducer in a near isometric manner between thumb and index finger, to reproduce four different rhythmic sequences. The responses were separated by either equal (600 ms) or alternating (400, 800 ms) intervals, and produced with either equal (12 N) or alternating (8, 16 N) forces pulses. Intervals and force levels were balanced across each condition. The primary motor cortex (M1), supplementary motor area (SMA), basal ganglia, thalamus, and cerebellum were activated during the production of sequences marked by equal interval and force. There was no reliable main effect of alternating interval. In contrast, greater activation of these regions was associated with the extra demands of responding with alternating force pulses. We interpret the data as identifying a significant role of the BG in the control of force. In addition, the results indicate the importance of monitoring force when studying brain activation associated with motor timing.

Paradoxical modulation of tendon tap reflex during voluntary contraction in Parkinson's disease

OBJECTIVE

Inadequate supraspinal modulation of spinal motor control mechanisms such as alpha-gamma coactivation is supposed to cause difficulty in maintaining proper voluntary contraction in Parkinson's disease (PD).

METHODS

Subjects were 42 patients with PD and 20 normal volunteers. Soleus H-reflex and tendon tap reflex (T-reflex) were recorded. The maximal reflexes (H(max) and T(max)) at rest were recorded first. Next, the stimulus intensities were fixed to obtain a reflex size of around 25% of M(max) at rest for both H- and T-reflexes, and the reflexes were recorded at rest, during tonic plantarflexion (TPF), and at the onset of plantarflexion.

RESULTS

H(max) at rest was 55% and T(max) 30% in normal subjects, while they were 36 and 31%, respectively, in PD. The size ratio of T(max) and H(max) at rest in PD was larger than normal. In PD, the size of H-reflex increased with TPF as in normal subjects, but T-reflex decreased. These changes in T-reflex were correlated with the grade of rigidity, bradykinesia, and time for 10 m gait. H-reflex had no such correlations.

CONCLUSIONS

T-reflex was abnormally modulated in PD especially during tonic contraction.

SIGNIFICANCE

Inappropriate supraspinal modulation of the spinal reflex pathways disturbs motor performance in PD.

The speed of sit-to-stand can be modulated in Parkinson's disease

OBJECTIVE

To evaluate whether Parkinsonian patients could modify the speed of a sit-to-stand (STS) task to the same extent as that of healthy subjects.

METHODS

Twenty Parkinsonian patients and 20 control subjects were instructed to stand up at a natural and fast speed. Kinematic data and kinetic data were recorded.

RESULTS

Parkinsonian patients were significantly slower than healthy individuals during STS at a natural speed. When required to perform STS task at a fast speed, these patients could increase both peak horizontal and vertical velocities of the task, by significantly increasing hip and ankle dorsiflexion torques and the rate of torque production, just as the control subjects did. In fact, no difference was found for the percentage changes in both peak velocities and movement time between the two groups, though similar between-group differences during STS at a natural speed still existed at a fast speed.

CONCLUSIONS

Parkinsonian patients had problems in generating adequate lower limb joint torques and in the rate of torque production when performing STS at a natural speed. However, these patients were capable of increasing the speed of their STS with the same percentage changes as those of healthy subjects.

SIGNIFICANCE

The capability of Parkinsonian patients for increasing movement speed gives new insights to rehabilitation strategy.

Force control and disease severity in Parkinson's disease

Several measures of isometric contractions reflect motor impairments in subjects with Parkinson's disease (PD), including long relaxation times and greater power in the 5 to 15 Hz electromyographic (EMG) bandwidth during the holding phase of contractions compared to those measures in healthy subjects. We sought to determine whether the impairments observed in subjects with PD in the performance of isometric contractions reflect disease severity. Twenty-eight subjects with PD performed isometric contractions at a torque level equal to 50% of the torque generated during a maximum voluntary contraction while off medication. Subjects were instructed to reach the target torque as fast as possible upon hearing the auditory "go" signal and to relax their muscles when a second auditory cue signaled the end of the hold phase. There was a significant positive correlation between torque relaxation time and Unified Parkinson's Disease Rating Scale (UPDRS)-Motor score. A significant positive correlation was also observed between the proportion of power in the 5 to 15 Hz frequency bin of the agonist EMG signal and UPDRS-Motor score, and a significant negative correlation between the proportion of power in the 15 to 30 Hz frequency bin and UPDRS-Motor score. These measures provide objective quantification of the severity of motor impairment that can be used to investigate the efficacy of different interventions in individuals with PD.

Load force during manual transport in Parkinson's disease

OBJECTIVES

To search for a physiological method for the measurement of upper extremity dexterity during activities of daily life in Parkinson's disease (PD).

MATERIALS AND METHODS

We examined load force output during manual transport in seven patients with PD and 10 healthy controls. PD patients were measured in both the non-medicated and medicated states. The test movement included two continuous sub-movements: an upward-forward transport of an object from the table to the stand, and a downward-backward transport of the object from the stand to the table. Hand movements were recorded using an optoelectronic camera, and load force was measured using a force sensor installed in the test object.

RESULTS

Compared with the controls, PD patients had a different pattern of load force output characterized by slower force development and release, lower peak force, and less dynamic force generation during movement. After medication, the speed of force development and the level of peak force increased in the patients.

CONCLUSIONS

These findings suggest that PD impairs the production of preprogrammed movements. The movements observed in the PD patients may result from compensatory strategies relying more on feedback mechanisms.

Visuo-motor coordination is normal in patients with major depression

Depression and Parkinson's disease (PD) are strongly associated with each other. Similarly, deficient visuo-motor coordination (VMC) accompanies PD from its earliest clinical stages. This double association suggests that a VMC dysfunction would be found in patients with major depression. Previous reports are ambiguous on this matter. Therefore, the present study was undertaken in order to determine whether MD patients pass or fail a VMC test on which PD patients are known to be deficient.Sixty-five MD patients were tested. Fifty-four (83%) had normal VMC. VMC was found to be independent of age, disease duration, severity of depression, or treatment. A deficit was found in 12 patients (17%). In this group too, VMC capabilities did not correlate with depression, or its treatment.These results negate an effect of depression, its accompanying frontal cortical changes, or its treatment on VMC. We propose that abnormal VMC in depression indicates coexisting illness, including possible preclinical PD.

The effects of balance training and high-intensity resistance training on persons with idiopathic Parkinson's disease

OBJECTIVE

To assess immediate and near-term effects of 2 exercise training programs for persons with idiopathic Parkinson's disease (IPD).

DESIGN

Randomized control trial.

SETTING

Public health facility and medical center.

PARTICIPANTS

Fifteen persons with IPD.

INTERVENTION

Combined group (balance and resistance training) and balance group (balance training only) underwent 10 weeks of high-intensity resistance training (knee extensors and flexors, ankle plantarflexion) and/or balance training under altered visual and somatosensory sensory conditions, 3 times a week on nonconsecutive days. Groups were assessed before, immediately after training, and 4 weeks later.

MAIN OUTCOME MEASURES

Balance was assessed by computerized dynamic posturography, which determined the subject's response to reduced or altered visual and somatosensory orientation cues (Sensory Orientation Test [SOT]). Muscle strength was assessed by measuring the amount of weight a participant could lift, by using a standardized weight-and-pulley system, during a 4-repetition-maximum test of knee extension, knee flexion, and ankle plantarflexion.

RESULTS

Both types of training improved SOT performance. This effect was larger in the combined group. Both groups could balance longer before falling, and this effect persisted for at least 4 weeks. Muscle strength increased marginally in the balance group and substantially in the combined group, and this effect persisted for at least 4 weeks.

CONCLUSION

Muscle strength and balance can be improved in persons with IPD by high-intensity resistance training and balance training.

The functional anatomy of parkinsonian bradykinesia

To investigate the difficulty that patients with Parkinson's disease (PD) have in performing fast movements, we used H(2)(15)O PET to study regional cerebral blood flow (rCBF) associated with performance of a simple predictive visuomanual tracking task at three different velocities. Tracking movements in PD patients (versus tracking with the eyes alone) were associated with a general underactivation of the areas normally activated by the task (sensorimotor cortex contralateral to the moving arm, bilateral dorsal premotor cortices, and ipsilateral cerebellum). Presupplementary motor cortex (pre-SMA) ipsilateral to the moving arm had greater than normal movement-related activations. Increasing movement velocity led to increased rCBF in multiple premotor and parietal cortical areas and basal ganglia in the patients as opposed to the few cerebral locations that are normally velocity-related. The functional correlates of PD bradykinesia are: (1) impaired recruitment of cortical and subcortical systems that normally regulate kinematic parameters of movement such as velocity; and (2) increased recruitment of multiple premotor areas including both regions specialized for visuomotor control (ventral premotor and parietal cortices) and some that are not (pre-SMA). The overactivation of cortical regions observed in patients may be functional correlates of compensatory mechanisms and/or impaired suppression as a facet of the primary pathophysiology of PD.

Joint torques during sit-to-stand in healthy subjects and people with Parkinson's disease

OBJECTIVES

To compare lower limb joint torques during sit-to-stand in normal elderly subjects and people with Parkinson's disease, using a developed biomechanical model simulating all phases of sit-to-stand.Design. A cross-sectional study utilizing a Parkinsonian and a control group.

BACKGROUND

Subjects with Parkinson's disease were observed to experience difficulty in performing sit-to-stand. The developed model was used to calculate the lower limb joint torques in normal elderly subjects and subjects with Parkinson's disease, to delineate possible causes underlying difficulties in initiating sit-to-stand task.

METHODS

Six normal elderly subjects and seven age-matched subjects with Parkinson's disease performed five sit-to-stand trials at their self-selected speed. Anthropometric data, two-dimensional kinematic and foot-ground and thigh-chair reactive forces were used to calculate, via inverse dynamics, the joint torques during sit-to-stand in both before and after seat-off phases. The difference between the control and Parkinson's disease group was analysed using independent t-tests.

RESULTS

Both control and Parkinson's disease groups had a similar joint kinematic pattern, although the Parkinson's disease group demonstrated a slower angular displacement. The latter subjects produced significantly smaller normalized hip flexion torque and presented a slower torque build-up rate than the able-bodied subjects (P<0.05).

CONCLUSION

Slowness of sit-to-stand in people with Parkinson's disease could be due to a reduced hip flexion joint torque and a prolonged rate of torque production.

Leg muscle strength is reduced in Parkinson's disease and relates to the ability to rise from a chair

Individuals with Parkinson's disease (PD) have difficulties rising from a chair; however, factors contributing to this inability have never been investigated. We compared lower extremity strength between individuals with PD and healthy controls and quantified the relationships between strength and the ability to rise from a chair. Ten men with mild PD and 10 sex- and age-matched controls performed maximal concentric, isokinetic knee and hip extensor torque on an isokinetic dynamometer to quantify muscle strength. Subjects also rose from a chair at their comfortable pace without the use of their arms and the duration of this task provided a measure of sit-to-stand (STS) ability. Subjects with PD were tested in an on- and off-medication state on different days. Mean hip and knee extensor torques were lower in subjects with PD, with greater deficits found at the hip. Greater hip strength was related to better STS ability in subjects with PD while greater knee strength was related to better STS ability in controls. These results show that individuals with mild PD generate smaller extremity forces compared to controls. Reduced strength, particularly at the hip, may be one factor that contributes to the difficulty of persons with PD to rise from a chair.

Switching of movement direction is central to parkinsonian bradykinesia in sit-to-stand

Patients with Parkinson's disease (PD) are known to manifest slowness in movements. We sought to identify the particular kinematic and kinetic disorders that contribute to the slowness in performing sit-to-stand in these patients. Two inter-related studies were carried out. In the first study, 20 patients with PD and 20 control subjects were instructed to perform sit-to-stand at a natural speed. In the second study, 15 control subjects were instructed to simulate the slower speed of sit-to-stand of the patients identified in the first study. Kinematic and kinetic data were recorded by a PEAK motion analysis system and two force platforms. The results showed that patients with PD generated smaller peak horizontal and vertical velocities during the task. They took a longer time to complete each individual phase as well as the whole movement of sit-to-stand. Patients also produced smaller peak hip flexion and ankle dorsiflexion joint torques and had prolonged time-to-peak torques from sit-to-stand onset. When control subjects simulated the patients' speed of sit-to-stand, there was no difference in all the kinematic and kinetic data between groups. The only exception was that they exhibited a shorter transition time between peak horizontal velocity (flexion phase) and seat-off (extension phase) than the patients. This study demonstrated that the slowness of PD patients during sit-to-stand at a natural speed could be attributed to inadequate peak hip flexion and ankle dorsiflexion torques, a prolonged torque production, as well as a difficulty in switching from the flexion to extension direction during sit-to-stand. As the latter difficulty persisted when the control subjects performed the task at a speed similar to that of the patients, our findings suggest that a fundamental problem of patients with Parkinson's disease could be a switch between movement directions.