Daily Motor Tasks Research Articles

Improvements in hand functions and changes in proximal muscle activities in myoelectric prosthetic hand users at home: a case series.

Adaptation in proximal muscles for daily motor tasks after sustained use of a prosthetic hand has not been fully understood. This study aimed to investigate changes in hand functions and activities of proximal muscles after multiple weeks of using a myoelectric prosthetic hand at home. Repeated measures. Four people with traumatic upper-limb loss used a myoelectric prosthetic hand (bebionic) at home over the 6- to 8-week period. A user survey, Orthotics and Prosthetics User Survey for Upper Extremity Functional Status 2.0, was used to measure upper-limb functions and the degree of using the prosthetic hand each week. Their hand functions, muscle activities, and grip-specific neuromuscular effort were evaluated by the Southampton Hand Assessment Procedure at the preassessment and postassessment sessions (PRE and POST, respectively). All subjects increased Southampton Hand Assessment Procedure scores at PRE compared with POST with subject-specific changes in muscle activations. In a detail, at POST, subject 1 reduced the shoulder muscle activity compared with PRE, while at POST, subject 2 reduced biceps activity compared with PRE. At POST, greater pectoralis activity and reduced trapezius activity were observed in subject 3, and greater activity in those two muscles was found in subject 4 compared with PRE. After multiple weeks of using the myoelectric prosthetic hands, their hand functions during ADL tasks were improved and changes in the muscle activities were found.

Obesity-related alterations in anticipatory postural mechanisms associated with gait initiation.

Obesity is known to have a detrimental effect on balance and motor performance during daily motor tasks. However, it remains unclear whether these obesity-related impairments are due to deficient anticipatory postural adjustments (APA) that precede voluntary movement. The objective of this study was to examine the effects of obesity on APA and the impacts related on motor performance and mediolateral postural stability during gait initiation. Fifteen obese and ten normal-weight young participants performed a series of gait initiation at their preferred speed. Our results showed that the durations and amplitudes of APA along both anteroposterior and mediolateral directions did not differ between the two groups (P > 0.05). In contrast, compared to normal-weight participants, mechanical effectiveness of APA was reduced in obese participants (P < 0.05). As a result, we observed a decreased motor performance (P < 0.05), in terms of peak anteroposterior center-of-mass velocity at the end of the first step, and a reduced mediolateral stability at swing foot contact in obese participants compared to normal-weight participants (P < 0.05). These findings suggest that APA effectiveness during gait initiation is reduced in obese adults, resulting in a decrease of both mediolateral stability and motor performance compared to their lean counterparts.

Relationship Between Lower Extremity Muscle Function And Gait Variability In Individuals With PD

PURPOSE: Increased variability in motor function can significantly impair performing activities of daily living. The difficulty in performing daily motor tasks is increased in pathological populations, e.g., Parkinson’s disease (PD). The muscular capabilities, e.g., torque production and force control, in PD, are reduced compared to older adults. It is unclear if the reduced muscular capabilities in PD are related to increased difficulty performing regular movements, i.e., gait. This study examined the relationship between muscular capabilities of the lower extremity and gait variability in persons with PD. METHODS: 12 PD and 11 age-matched controls underwent gait and lower extremity muscle testing. Gait was evaluated by having the subjects perform ten over-ground walking trials over a 9-m walkway at a self-selected speed using an 8-camera motion capture system. Linear measures of gait, including stride length, stride time, step width, and velocity, were calculated. Gait variability and force variability were examined using the coefficient of variation (CV = standard deviation/mean × 100%). Lower extremity testing consisted of 1) maximal isometric torque production and 2) submaximal force control using a tracing paradigm at 5, 10, and 20% of their maximal torque production in multiple directions at the hip and ankle. Pearson's correlations were applied to analyze associations between gait variability and force variability. RESULTS: In the PD group, stride time was positively correlated with 20% of ankle dorsiflexion CV (r(21)=.62, p<.05) and velocity was positively correlated with 10 and 20% of ankle plantarflexion CV (r(21)=.59, p<.05) and 20% of hip extension CV (r(21)=.63, p<.05). Maximal torque production of the dorsiflexors (r(21)=.75, p<.05) and plantar flexors (r(21)=.67, p<.05) were positively correlated stride time variability in the PD group. CONCLUSION: The results highlight an association between lower-extremity muscle function and gait function in PD. Interestingly, in those with PD, both maximal strength and control of muscle strength were found to be related to the temporal parameters of gait variability. These results suggest that gait dysfunction could be the result of specific pathological impairments and provide unique opportunities for specialized interventions.

Sensor-Motor Maps for Describing Linear Reflex Composition in Hopping.

In human and animal motor control several sensory organs contribute to a network of sensory pathways modulating the motion depending on the task and the phase of execution to generate daily motor tasks such as locomotion. To better understand the individual and joint contribution of reflex pathways in locomotor tasks, we developed a neuromuscular model that describes hopping movements. In this model, we consider the influence of proprioceptive length (LFB), velocity (VFB) and force feedback (FFB) pathways of a leg extensor muscle on hopping stability, performance and efficiency (metabolic effort). Therefore, we explore the space describing the blending of the monosynaptic reflex pathway gains. We call this reflex parameter space a sensor-motor map. The sensor-motor maps are used to visualize the functional contribution of sensory pathways in multisensory integration. We further evaluate the robustness of these sensor-motor maps to changes in tendon elasticity, body mass, segment length and ground compliance. The model predicted that different reflex pathway compositions selectively optimize specific hopping characteristics (e.g., performance and efficiency). Both FFB and LFB were pathways that enable hopping. FFB resulted in the largest hopping heights, LFB enhanced hopping efficiency and VFB had the ability to disable hopping. For the tested case, the topology of the sensor-motor maps as well as the location of functionally optimal compositions were invariant to changes in system designs (tendon elasticity, body mass, segment length) or environmental parameters (ground compliance). Our results indicate that different feedback pathway compositions may serve different functional roles. The topology of the sensor-motor map was predicted to be robust against changes in the mechanical system design indicating that the reflex system can use different morphological designs, which does not apply for most robotic systems (for which the control often follows a specific design). Consequently, variations in body mechanics are permitted with consistent compositions of sensory feedback pathways. Given the variability in human body morphology, such variations are highly relevant for human motor control.

Electromyographic Pattern during Gait Initiation Differentiates Yoga Practitioners among Physically Active Older Subjects.

During gait initiation, postural adjustments are needed to deal with balance and movement. With aging, gait initiation changes and reflects functional degradation of frailty individuals. However, physical activities have demonstrated beneficial effects of daily motor tasks. The aim of our study was to compare center of pressure (COP) displacement and ankle muscle co-activation during gait initiation in two physically active groups: a group of walkers (n = 12; mean age ± SD 72.6 ± 3.2 years) and a yoga group (n = 11; 71.5 ± 3.8 years). COP trajectory and electromyography of leg muscles were recorded simultaneously during five successive trials of gait initiation. Our main finding was that yoga practitioners had slower COP displacements (p < 0.01) and lower leg muscles % of coactivation (p < 0.01) in comparison with walkers. These parameters which characterized gait initiation control were correlated (r = 0.76; p < 0.01). Our results emphasize that lengthy ankle muscle co-activation and COP path in gait initiation differentiate yoga practitioners among physically active subjects.

Influence of temporal pressure constraint on the biomechanical organization of gait initiation made with or without an obstacle to clear.

Many daily motor tasks have to be performed under a temporal pressure constraint. This study aimed to explore the influence of such constraint on motor performance and postural stability during gait initiation. Young healthy participants initiated gait at maximal velocity under two conditions of temporal pressure: in the low-pressure condition, gait was self-initiated (self-initiated condition, SI); in the high-pressure condition, it was initiated as soon as possible after an acoustic signal (reaction-time condition, RT). Gait was initiated with and without an environmental constraint in the form of an obstacle to be cleared placed in front of participants. Results showed that the duration of postural adjustments preceding swing heel-off ("anticipatory postural adjustments", APAs) was shorter, while their amplitude was larger in RT compared to SI. These larger APAs allowed the participants to reach equivalent postural stability and motor performance in both RT and SI. In addition, the duration of the execution phase of gait initiation increased greatly in the condition with an obstacle to be cleared (OBST) compared to the condition without an obstacle (NO OBST), thereby increasing lateral instability and thus involving larger mediolateral APA. Similar effects of temporal pressure were obtained in NO OBST and OBST. This study shows the adaptability of the postural system to temporal pressure in healthy young adults initiating gait. The outcome of this study may provide a basis for better understanding the aetiology of balance impairments with the risk of falling in frail populations while performing daily complex tasks involving a whole-body progression.

Effect of light and vigorous physical activity on balance and gait of older adults

This study aims to quantitatively assess the effects of vigorous and light physical activity (VPA, LPA) on static balance, gait and sit-to-stand (STS) tasks in a cohort of healthy older adults.To this end, 34 individuals of age >65 years were divided into two groups (n=17 each) who underwent 36 sessions (3×12 weeks) of PA characterized by different levels of intensity, assessed through continuous heart rate monitoring during the training session. Their balance and mobility were objectively evaluated on the basis of postural sway and time of STS measurements performed using a force platform. The main spatiotemporal parameters of gait (i.e. speed, stride and gait cycle duration, stance, swing and double support phase duration) were also acquired using a wearable inertial measurement unit.The results show that most gait parameters and STS time significantly improve in the VPA group but not in the LPA one. For the latter group a reduction only of swing phase duration was detected. PA also induced a generalized reduction of postural sway in both groups in the case of absence of visual input.These findings suggest that PA programs characterized by superior levels of intensity might be more suitable in generally improving static and dynamic daily motor tasks, while in terms of static balance acceptable results can be achieved even when only light activity is performed.

Design and Evaluation of NEUROBike: A Neurorehabilitative Platform for Bedridden Post-Stroke Patients

Over the past decades, a large number of robotic platforms have been developed which provide rehabilitative treatments aimed at recovering walking abilities in post-stroke patients. Unfortunately, they do not significantly influence patients' performance after three months from the accident. One of the main reasons underlying this result seems to be related to the time of intervention. Specifically, although experimental evidences suggest that early (i.e., first days after the injury) and intense neuro-rehabilitative treatments can significantly favor the functional recovery of post-stroke patients, robots require patients to be verticalized. Consequently, this does not allow them to be treated immediately after the trauma. This paper introduces a new robotic platform, named NEUROBike, designed to provide neuro-rehabilitative treatments to bedridden patients. It was designed to provide an early and well-addressed rehabilitation therapy, in terms of kinesiology, efforts, and fatigue, accounting for exercises functionally related to daily motor tasks. For this purpose, kinematic models of leg-joint angular excursions during both walking and sit-to-stand were developed and implemented in control algorithms leading both passive and active exercises. Finally, a set of pilot tests was carried out to evaluate the performance of the robotic platform on healthy subjects.

Design and Evaluation of a new mechatronic platform for assessment and prevention of fall risks

BackgroundStudying the responses in human behaviour to external perturbations during daily motor tasks is of key importance for understanding mechanisms of balance control and for investigating the functional response of targeted subjects. Experimental platforms as far developed entail a low number of perturbations and, only in few cases, have been designed to measure variables used at run time to trigger events during a certain motor task.MethodsThis work introduces a new mechatronic device, named SENLY, that provides balance perturbations while subjects carry out daily motor tasks (e.g., walking, upright stance). SENLY mainly consists of two independently-controlled treadmills that destabilize balance by suddenly perturbing belts movements in the horizontal plane. It is also provided with force sensors, which can be used at run time to estimate the ground reaction forces and identify events along the gait cycle in order to trigger the platform perturbation. The paper also describes the customized procedures adopted to calibrate the platform and the first testing trials aimed at evaluating its performance.ResultsSENLY allows to measure both vertical ground reaction forces and their related location more precisely and more accurately than other platforms of the same size. Moreover, the platform kinematic and kinetic performance meets all required specifications, with a negligible influence of the instrumental noise.ConclusionA new perturbing platform able to reproduce different slipping paradigms while measuring GRFs at run time in order to enable the asynchronous triggering during the gait cycle was designed and developed. Calibration procedures and pilot tests show that SENLY allows to suitably estimate dynamical features of the load and to standardize experimental sessions, improving the efficacy of functional analysis.

Joint kinematics following bi-compartmental knee replacement during daily life motor tasks

Joint kinematics following bi-compartmental knee replacement during daily life motor tasks

Adaptability of anticipatory postural adjustments associated with voluntary movement

The control of balance is crucial for efficiently performing most of our daily motor tasks, such as those involving goal-directed arm movements or whole body displacement. The purpose of this article is twofold. Firstly, it is to recall how balance can be maintained despite the different sources of postural perturbation arising during voluntary movement. The importance of the so-called "anticipatory postural adjustments" (APA), taken as a "line of defence" against the destabilizing effect induced by a predicted perturbation, is emphasized. Secondly, it is to report the results of recent studies that questioned the adaptability of APA to various constraints imposed on the postural system. The postural constraints envisaged here are classified into biomechanical (postural stability, superimposition of motor tasks), (neuro) physiological (fatigue), temporal (time pressure) and psychological (fear of falling, emotion). Overall, the results of these studies point out the capacity of the central nervous system (CNS) to adapt the spatio-temporal features of APA to each of these constraints. However, it seems that, depending on the constraint, the "priority" of the CNS was focused on postural stability maintenance, on body protection and/or on maintenance of focal movement performance.

Towards Interdisciplinarity for Better Insight into Postural Disorders

The control of balance is crucial if we are to perform efficiently most of our daily motor tasks such as those involving goal-directed arm movements or whole-body displacements. Like all terrestrial species, humans move in a gravity field that permanently tends to induce postural destabilization through its attracting effect towards the centre of the Earth. In addition, movements themselves perturb our balance, and can be considered as a self-inflicted perturbation [1]. Alteration of the balance control system may therefore result in postural instability and increase the risk of falls with well-known associated morbid consequences (physical, psychological, social etc).

The human proximal femur behaves linearly elastic up to failure under physiological loading conditions

It has not been demonstrated whether the human proximal femur behaves linearly elastic when loaded to failure. In the present study we tested to failure 12 cadaveric femurs. Strain was measured (at 5000Hz) on the bone surface with triaxial strain gages (up to 18 on each femur). High-speed videos (up to 18,000frames/s) were taken during the destructive test. To assess the effect of tissue preservation, both fresh-frozen and formalin-fixed specimens were tested. Tests were carried out at two strain-rates covering the physiological range experienced during daily motor tasks. All specimens were broken in only two pieces, with a single fracture surface. The high-speed videos showed that failure occurred as a single abrupt event in less than 0.25ms. In all specimens, fracture started on the lateral side of the neck (tensile stress). The fractured specimens did not show any sign of permanent deformation. The force–displacement curves were highly linear (R2>0.98) up to 99% of the fracture force. When the last 1% of the force–displacement curve was included, linearity slightly decreased (minimum R2=0.96). Similarly, all force–strain curves were highly linear (R2>0.98 up to 99% of the fracture force). The slope of the first part of the force–displacement curve (up to 70% fracture force) differed from the last part of the curve (from 70% to 100% of the fracture force) by less than 17%. Such a difference was comparable to the fluctuations observed between different parts of the curve. Therefore, it can be concluded that the proximal femur has a linear-elastic behavior up to fracture, for physiological strain-rates.

Efeitos do uso de órtese na mobilidade funcional de crianças com paralisia cerebral

Objetivo:Comparar o desempenho motor de crianças com paralisia cerebral (PC) em duas condições: com órtese e sem órtese. Métodos:Vinte crianças PC foram avaliadas utilizando-se o teste Gross Motor Function Measure (GMFM), a versão modificada da avaliação da marcha Physicians Rating Scale (PRS) e entrevista com os pais para avaliar o uso de órteses na rotina diária. Resultados:O teste ANOVA que foi utilizado para avaliar o efeito do uso órtese na mobilidade das crianças revelou médias significantemente superiores na condição com órtese durante o desempenho motor grosso e na marcha. Entrevistas informaram que o uso de órteses estava inserido na rotina diária e os pais demonstraram percepção positiva com relação ao uso desse dispositivo. Conclusão: As órteses promoveram o desempenho de tarefas motoras da rotina diária de crianças com PC, podendo orientar os processos de avaliação e de intervenção dos profissionais que trabalham com essa clientela.

Réentraînement a l'effort chez le blesse médullaire

Introduction. – Individualised exercise training programs in spinal cord injury (SCI) individuals are considered highly effective for improving and maintaining capacity for physical activity, as well as for reducing cardiovascular risk. However, no consensus exists on the type, intensity, and frequency of the training programs for SCI. Objective. – To review the literature about training program characteristics for SCI and describe their efficacy, limits, and results, with the aim of proposing specific recommendations. Methods. – Query using Medline and Embase databases. Ninety-nine references were found, including the following: Clinical studies examining physical endurance capacity of individuals with SCI, physiological responses to maximal exercise, or cardiovascular differences between sedentary and wheelchair-trained subjects; Articles? investigating the effects of training programmes for SCI. Results. – Various combinations of training intensity, duration, frequency, type, and ergometers have been proposed for SCI. Whatever the characteristics of the training program, a review of 25 cardiorespiratory training studies involving SCI subjects revealed an average improvement of 9% to 99% in VO 2max, 19% to 118% in power output, and a decrease in submaximal values after 4 to 36 weeks of training. Discussion – Conclusion. – Wheelchair ergometers seems to be interesting for SCI because it mimics closely the daily motor tasks of wheelchair users and allows for adjustment of the wheelchair. Both continuous and interval training programmes are appropriate, but intermittent exercise intensities may be more beneficial since they mimic the intermittent nature of daily activity patterns. Furthermore, on the basis of the results of these studies, we recommend that training at or above 70% of maximum heart rate, for 30 minutes of rhythmic exercise, three days per week during eight weeks, will provide a sound of basis for design of an endurance exercise programme for people with SCI.

Muscle strength, disability and mortality.

The aims of this review are to address (1) the role of muscle strength in the disablement process and (2) muscle strength as a predictor of length of life using data from prospective studies. Functional limitations, such as slow walking speed, predispose older people to disabilities. How much strength is needed for daily motor tasks such as walking varies according to other impairments present. For example, when postural balance is good, only minimum amount of strength is needed for walking. However, in the presence of balance impairment, having good level of strength may help to compensate for the deficit. Having strength well above the required level indicates reserve capacity. It was studied using data from the Honolulu Heart Program launched in 1965 among 8006 men initially aged 45-68 years, whether reserve of strength would be protective of development of future disability. All men with documented diseases at baseline were excluded from the analyses. Those men who were in the lowest third of the distribution of grip strength at baseline were at two to three times greater risk of developing disabilities assessed 25 years later compared to the highest third. It is possible that before they reach the disability level, those with greater reserve of strength may afford to lose more strength, for example following bed rest and inactivity associated with an illness. Midlife grip strength was also found to predict long-term total mortality: those with poorer strength at baseline were more likely to die over the follow-up period of 30 years. The association between muscle strength and disability is largely explained by biomechanical mechanisms. However, the mechanism explaining the association between muscle strength and mortality risk still remains to be explored.