The Aging Neuromuscular System and Motor Performance

Age-related changes in the basic functional unit of the neuromuscular system, the motor unit, and its neural inputs have a profound effect on motor function, especially among the expanding number of old (older than ∼60 yr) and very old (older than ∼80 yr) adults. This review presents evidence that age-related changes in motor unit morphology and properties lead to impaired motor performance that includes 1) reduced maximal strength and power, slower contractile velocity, and increased fatigability; and 2) increased variability during and between motor tasks, including decreased force steadiness and increased variability of contraction velocity and torque over repeat contractions. The age-related increase in variability of motor performance with aging appears to involve reduced and more variable synaptic inputs that drive motor neuron activation, fewer and larger motor units, less stable neuromuscular junctions, lower and more variable motor unit action potential discharge rates, and smaller and slower skeletal muscle fibers that coexpress different myosin heavy chain isoforms in the muscle of older adults. Physical activity may modify motor unit properties and function in old men and women, although the effects on variability of motor performance are largely unknown. Many studies are of cross-sectional design, so there is a tremendous opportunity to perform high-impact and longitudinal studies along the continuum of aging that determine 1) the influence and cause of the increased variability with aging on functional performance tasks, and 2) whether lifestyle factors such as physical exercise can minimize this age-related variability in motor performance in the rapidly expanding numbers of very old adults

Methods, systems, and devices for pairing vagus nerve stimulation with motor therapy in stroke patients

A method of treating motor deficits in a stroke patient, comprising assessing a patient's motor deficits, determining therapeutic goals for the patient, based on the patient's motor deficits, selecting therapeutic tasks based on the therapeutic goals, performing each of the selected therapeutic tasks repetitively, observing the performance of the therapeutic tasks, initiating the stimulation of the vagus nerve manually at approximately a predetermined moment during the performance of the therapeutic tasks, stimulating the vagus nerve of the patient during the performance of the selected therapeutic tasks, and improving the patient's motor deficits.Board of Regents, University of Texas Syste

Impact of COPD and anemia on motor and cognitive performance in the general older population: results from the English longitudinal study of ageing

Background: Cognitive and motor-performance decline with age and the process is accelerated by decline in general health. In this study, we aimed to estimate the effects of COPD and HB levels on cognitive and motor performance in the general older population and assess potential interaction. Methods: The English Longitudinal Study of Aging is a population-based cohort study including measurements of lung-function and HB levels together with cognitive and motor performance testing. Data were collected from 5709 participants including three measurement time over eight years. COPD was defined using lung-function-parameters and clinical symptoms. HB was assessed continuously and low HB was defined using clinical anemia cutoffs. Linear mixed-effects regression models were used to quantify the associations of COPD and HB with outcome measures, both individually and in combination. Results: Participants with both low HB and COPD demonstrated worse motor performance compared to individuals with only one exposure, resulting in up to 1 s (95%CI, 0.04–1.8) longer time needed to complete the five times sit to stand task than what would be expected based on purely additive effects. Additionally in individuals with COPD, the time to complete the motor-performance task per unit decrease in continuous HB levels was longer than in participants without COPD after full adjustment for confounding (up to 1.38 s/unit HB level, 95% CI: 0.65–2.11). Conclusion: In persons with COPD low HB levels may contribute to low motor-performance in a supra additive fashion. Further studies should re-evaluate whether earlier treatment of lower HB in these individuals might be beneficial

The General Motor Ability Hypothesis: An old idea revisited

While specific motor abilities have become a popular explanation for motor performance, the older, alternate notion of a general motor ability should be revisited. Current theories lack consensus, and most motor assessment tools continue to derive a single composite score to represent motor capacity. In addition, results from elegant statistical procedures such as higher order factor analyses, cluster analyses, and Item Response Theory support a more global motor ability. We propose a contemporary model of general motor ability as a unidimensional construct that is emergent and fluid over an individual’s lifespan, influenced by both biological and environmental factors. In this article, we address the implications of this model for theory, practice, assessment, and research. Based on our hypothesis and Item Response Theory, our Lifespan Motor Ability Scale can identify motor assessment tasks that are relevant and important across varied phases of lifespan development

Artificial intelligence based direct torque control of induction motor drive system

In this project, a three-phase Induction motor (IM) under the direct torque control (DTC) technique is studied. IM is known for its simple engines and its self-starter feature but it always suffered a setback in the area of torque and speed control as it is a highly coupled nonlinear plant and proves to be most complex and expensive speed drive. The application of direct torque control (DTC) is beneficial for fast torque reaction in IM but provide high torque and ripples due to harmonic effects. Thus, the speed control of induction motor is important to achieve maximum torque and efficiency. The aim of this study is to improve tracking performance of the induction motor drive using artificial intelligence control system. A method for controlling induction motor drive is presented with Proportional-Integral (PI) controller and Artificial Neural Networks (ANNs) for performance comparison. MATLAB/SIMULINK software is used to develop a three-phase 2 pole-cage type induction motor model. Also the performances of the two controllers have been verified in terms of its speed and torque responses. The ANN is trained so that the speed of the drive tracks the reference speed. This study proved that the performance and dynamics of the induction motor are enhanced using ANN controller as compared with PI controller

Impact of the motor magnetic model on direct flux vector control of interior PM motors

The stator-field-oriented, direct-flux vector control has been proven to be effective in terms of linear torque control and model independent performance at limited voltage and current (i.e. in flux weakening) for AC drives of various types. The performance of the direct-flux vector control relies on the accuracy of the flux estimation, as for any field oriented control. The knowledge of the motor magnetic model is critical for flux estimation when the operating at low speed. This paper addresses the effects of a limited knowledge of the motor model on the performance of the control at low speed, for an Interior Permanent Magnet motor drive. Experimental results are give

Brain Activation During Passive and Volitional Pedaling After Stroke

Background: Prior work indicates that pedaling-related brain activation is lower in people with stroke than in controls. We asked whether this observation could be explained by between-group differences in volitional motor commands and pedaling performance. Methods: Individuals with and without stroke performed passive and volitional pedaling while brain activation was recorded with functional magnetic resonance imaging. The passive condition eliminated motor commands to pedal and minimized between-group differences in pedaling performance. Volume, intensity, and laterality of brain activation were compared across conditions and groups. Results: There were no significant effects of condition and no Group × Condition interactions for any measure of brain activation. Only 53% of subjects could minimize muscle activity for passive pedaling. Conclusions: Altered motor commands and pedaling performance are unlikely to account for reduced pedaling-related brain activation poststroke. Instead, this phenomenon may be due to functional or structural brain changes. Passive pedaling can be difficult to achieve and may require inhibition of excitatory descending drive

Apraxia and motor dysfunction in corticobasal syndrome

Background: Corticobasal syndrome (CBS) is characterized by multifaceted motor system dysfunction and cognitive disturbance; distinctive clinical features include limb apraxia and visuospatial dysfunction. Transcranial magnetic stimulation (TMS) has been used to study motor system dysfunction in CBS, but the relationship of TMS parameters to clinical features has not been studied. The present study explored several hypotheses; firstly, that limb apraxia may be partly due to visuospatial impairment in CBS. Secondly, that motor system dysfunction can be demonstrated in CBS, using threshold-tracking TMS, and is linked to limb apraxia. Finally, that atrophy of the primary motor cortex, studied using voxel-based morphometry analysis (VBM), is associated with motor system dysfunction and limb apraxia in CBS.   Methods: Imitation of meaningful and meaningless hand gestures was graded to assess limb apraxia, while cognitive performance was assessed using the Addenbrooke's Cognitive Examination - Revised (ACE-R), with particular emphasis placed on the visuospatial subtask. Patients underwent TMS, to assess cortical function, and VBM.   Results: In total, 17 patients with CBS (7 male, 10 female; mean age 64.4+/2 6.6 years) were studied and compared to 17 matched control subjects. Of the CBS patients, 23.5% had a relatively inexcitable motor cortex, with evidence of cortical dysfunction in the remaining 76.5% patients. Reduced resting motor threshold, and visuospatial performance, correlated with limb apraxia. Patients with a resting motor threshold <50% performed significantly worse on the visuospatial sub-task of the ACE-R than other CBS patients. Cortical function correlated with atrophy of the primary and pre-motor cortices, and the thalamus, while apraxia correlated with atrophy of the pre-motor and parietal cortices.   Conclusions: Cortical dysfunction appears to underlie the core clinical features of CBS, and is associated with atrophy of the primary motor and pre-motor cortices, as well as the thalamus, while apraxia correlates with pre-motor and parietal atrophy

Factors contributing to Australian adolescents’ self-report of their motor skill competence

An adolescents motor skill competence can affect areas such as sports participation, social activities and future academic or employment decisions. The Adolescent Motor Competence Questionnaire (AMCQ) is a 26-item questionnaire that uses a four point Likert response (never, sometimes, frequently, always) to assess motor-related activities during adolescence. This study aims to provide evidence of the construct validity using Principle Component Analysis (PCA) and to identify factors that contributed to Australian adolescent self-reported motor competence. A final aim was to determine whether individual item responses differed between males and females. The AMCQ was completed by 160 adolescents (Mage = 14.45 SD = .75, 12 to 16). The PCA using varimax rotation extracted four factors (Eiqenvalue of 1.21 or above) explaining 52% of variance and representing Participation in Physical Activity and Sports, Activities of Daily Living, Public Performance, and Peer Comparison. Overall males reported higher AMCQ scores compared to females. Females responded negatively (sometimes/never) to all items particularly those on Physical Activity and Sports and Public Performance. Males who responded negatively had lower AMCQ scores than the females. These findings indicate male and female adolescents may judge their motor competence on different factors, which should be considered when planning physical activity interventions

Investigation of Motor Supply Signature Analysis to Detect Motor Resistance Imbalances

The trend to use inverter drives in industry is well established. It is desirable to monitor the condition of the motor/drive combination with the minimum of system intervention and at the same time retaining compatibility with the latest generation of AC PWM vector drives. This paper studies the effect of stator resistance asymmetry on the performance of the motor driven by a latest-generation unmodified AC PWM drive under varying speed conditions. The asymmetry of increased resistance in one phase is intended to simulate the onset of a failing connection between drive and motor but one that is non-critical and will remain undetected in use because the resistance increase is small and does not appear to affect the motor operation significantly. The performance is compared against baseline motor data for the resistance increase. Moreover, it is also examined following an auto-tune on the drive with the asymmetric motor in order to observe if any effects of resistance imbalance can be shown on the sensorless vector control algorithms. Initial results from the motor tests clearly show a difference in values measured from the motor current and voltage signals, which can be a useful indication of the asymmetry of the drive system