vendex and Cerebrovascular-Disorders

We evaluated a method for measuring abnormal upper-limb motor performance in post-stroke hemiparetic subjects. A servomechanism (MIME) moved the forearm in simple planar trajectories, directly controlling hand position and forearm orientation. Design specifications are presented, along with system performance data during an initial test of 13 stroke subjects with a wide range of impairment levels. Performance of subjects was quantified by measuring the forces and torques between the paretic limb and the servomechanism as the subjects relaxed (passive), or attempted to generate force in the direction of movement (active). During passive movements, the more severely impaired subjects resisted movement, producing higher levels of negative work than less-impaired subjects and neurologically normal controls. During active movements, the more severely impaired subjects produced forces with larger directional errors, and were less efficient in producing work. These metrics had significant test-retest repeatability. These motor performance metrics can potentially detect smaller within-subject changes than motor function scales. This method could complement currently used measurement tools for the evaluation of subjects during recovery from stroke, or during therapeutic interventions.

Topics: Activities of Daily Living; Aged; Algorithms; Bias; Case-Control Studies; Cerebrovascular Disorders; Forearm; Hemiplegia; Humans; Middle Aged; Models, Neurological; Motor Activity; Range of Motion, Articular; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Torque

Takeuchi N, Kuwabara T, Usuda S. Development and evaluation of a new measure for muscle tone of ankle plantar flexors: the Ankle Plantar Flexors Tone Scale.. To develop and evaluate the reliability and concurrent validity of a clinically feasible measure for muscle tone of the ankle plantar flexors.. Cross-sectional reliability and validity study of the Ankle Plantar Flexors Tone Scale.. Department of rehabilitation in a general hospital.. Patients (N=74) with cerebrovascular disease.. Not applicable.. Muscle tone of the ankle plantar flexors was measured using the Ankle Plantar Flexors Tone Scale, the Modified Ashworth Scale (MAS), quality of muscle reaction with the Modified Tardieu Scale, and passive resistive joint torque with a handheld dynamometer. Intrarater and interrater reliabilities were assessed using the Cohen kappa coefficient (kappa). Internal consistency was assessed using the Cronbach alpha (alpha). Concurrent validity was assessed with the Spearman rank correlation coefficient (rho).. The Ankle Plantar Flexors Tone Scale included 3 items: stretch reflex, middle range resistance, and final range resistance. Intrarater and interrater reliabilities and internal consistency of the Ankle Plantar Flexors Tone Scale showed moderate to excellent agreement (kappa=.63-.94; alpha=.81). Concurrent validity of the Ankle Plantar Flexors Tone Scale was low to very high among the 3 items of the Ankle Plantar Flexors Tone Scale and existing measures. The Spearman rank correlation coefficient showed high to very high correlation between stretch reflex and quality of muscle reaction as indices of the central component (rho=.85-.94). Middle range resistance and final range resistance as indices of the peripheral component had low to moderate correlation with passive resistive joint torque using a handheld dynamometer and MAS (rho=.44-.68).. The Ankle Plantar Flexors Tone Scale allows measurement of ankle plantar flexor tone in greater detail than existing subjective measures and provides a reliable and valid method for research and clinical use.

Topics: Aged; Aged, 80 and over; Ankle; Cerebrovascular Disorders; Cross-Sectional Studies; Disability Evaluation; Female; Humans; Male; Middle Aged; Movement; Muscle Strength Dynamometer; Muscle Tonus; Reflex, Stretch; Reproducibility of Results; Torque

To examine weakness after stroke, in terms of both level and rate of torque generation.. Descriptive. T tests for dependent and independent samples and Pearson's product moment correlation coefficients were performed.. A rehabilitation unit.. Ten stroke subjects, aged 56 to 81 years, undergoing rehabilitation. Ten neurologically normal subjects aged 55 to 78 years were the controls.. Peak isometric elbow flexor and extensor torque and time to 90% peak elbow flexor and extensor torque at 6 weeks and at 25 weeks after stroke.. At 6 weeks after stroke, subjects were only half as strong and took two to three times longer to produce torque compared to controls (p < or = .05). By 25 weeks after stroke, significant improvements in peak torque (p < or = .02) and time to 90% peak flexor torque (p < or = .05) were seen so that values were within normal limits.. Decreased rate of torque development compounds the problem of reduced peak torque, which may have significant implications for stroke patients, especially in situations where muscles are very weak or where force needs to be generated quickly.

Topics: Aged; Aged, 80 and over; Arm; Cerebrovascular Disorders; Exercise; Female; Functional Laterality; Humans; Male; Middle Aged; Muscle Weakness; Reference Values; Torque

Stiff-legged gait, characterized by limited knee flexion during the swing period, is a common consequence of upper motor neuron injury. The purpose of this investigation was to determine whether the rectus femoris and hamstrings muscles (which act at both the hip and knee) contribute to stiff-legged gait if active during the swing period of the gait cycle. Ten subjects with unilateral stiff-legged gait due to stroke were evaluated. Swing period free gait data were obtained. A biomechanical model of the affected limb was developed for each subject. Muscle and tendon lengths were scaled to individual subjects while constant nominal values for maximum muscle forces were used for all subjects. Torque driven forward dynamic simulations were employed to determine the sensitivity of swing period maximum knee flexion angle to changes in hip and knee torques. Combined torque and muscle driven simulations were used to access the action of specific two-joint muscles. Both hip flexion torque and knee extension torque were found to influence knee angle, but knee angle was more sensitive to changes in torque at the knee joint. The actions of the rectus femoris and long hamstrings are most marked at the knee, although their action at the hip opposes their action at the knee. Rectus femoris activity during early swing acts to limit knee flexion and contributes to stiff-legged gait. Long hamstring activity in early swing contributes to knee flexion.

Topics: Adult; Aged; Biomechanical Phenomena; Cerebrovascular Disorders; Computer Simulation; Female; Gait; Hip; Humans; Knee; Knee Joint; Leg; Male; Middle Aged; Models, Biological; Muscle, Skeletal; Range of Motion, Articular; Torque

Topics: Cerebrovascular Disorders; Ergometry; Functional Laterality; Humans; Motor Cortex; Muscle Contraction; Muscle Weakness; Physical Exertion; Torque

It is hypothesized that, depending on the motor task, the angular range of a joint may be subdivided into zones in which agonist and antagonist muscles are coactive, only one group of muscles is active or neither group is active. It is further hypothesized that central commands may change the size and location of these spatial zones. We investigated whether spatial zones are used by the nervous system and how they may be changed to provide postural stability of the elbow. We compared responses to sudden unloading of the elbow flexors in neurologically normal subjects with those in patients with postural control deficits due to unilateral hemispheric and/or subcortical lesions. By studying responses in patients, we sought to determine whether the specification of zones of agonist/antagonist muscle coactivation ("coactivation zones") may be essential for postural stability. At an initial elbow angle (130 degrees; full extension is 180 degrees), flexors were pre-activated by compensating an initial load which was equal to approximately 30% of the subject's maximal isometric voluntary contraction effort. Subjects were instructed not to correct the arm displacement elicited by a sudden decrease in the load. Data from 10 trials were collected at each of 4-6 final load levels (separated by 1.5-2 Nm) in order to map out the relationship between torque and angle in each subject. The procedure was repeated from a more flexed initial position of the elbow (100 degrees). EMG activity from two elbow flexors and two elbow extensors, as well as torque, velocity and joint position were recorded. Healthy control subjects and patients with mild clinical symptoms had coactivation zones or small silent zones around the final positions established after unloading. In these subjects, final positions of the limb were stable. Voluntary movement, i.e., transition of the limb from one initial position to another, was associated with a change in the location of the zone in articular space. The presence of large silent zones in patients with moderate or severe symptoms was correlated with postural instability and oscillations about the final position of the arm after unloading. The comparison of results from healthy and hemiparetic subjects implies that the central specification of the size and the location of a coactivation zone may be fundamental for the control of posture and movement.

Topics: Adult; Aged; Cerebrovascular Disorders; Electromyography; Female; Forearm; Hand; Hemiplegia; Humans; Isometric Contraction; Male; Middle Aged; Motor Activity; Movement; Muscle, Skeletal; Posture; Reference Values; Torque