Support-specific modulation of grip force in individuals with hemiparesis

The effects of an object's height and weight on force calibration and kinematics when post-stroke and healthy individuals reach and grasp

Impairment in force regulation and motor control impedes the independence of individuals with stroke by limiting their ability to perform daily activities. There is, at present, incomplete information about how individuals with stroke regulate the application of force and control their movement when reaching, grasping, and lifting objects of different weights, located at different heights. In this study, we assess force regulation and kinematics when reaching, grasping, and lifting a cup of two different weights (empty and full), located at three different heights, in a total of 46 participants: 30 sub-acute stroke participants, and 16 healthy individuals. We found that the height of the reached target affects both force calibration and kinematics, while its weight affects only the force calibration when post-stroke and healthy individuals perform a reach-to-grasp task. There was no difference between the two groups in the mean and peak force values. The individuals with stroke had slower, jerkier, less efficient, and more variable movements compared to the control group. This difference was more pronounced with increasing stroke severity. With increasing stroke severity, post-stroke individuals demonstrated altered anticipation and preparation for lifting, which was evident for either cortical lesion side.

Getting a kinematic handle on reach-to-grasp: a meta-analysis

BACKGROUND AND OBJECTIVES

Reach-to-grasp is an essential everyday activity that is often impaired after stroke. The objectives of this review are: (1) identify differences in the kinematic characteristics of reach-to-grasp between individuals with and without stroke, and (2) determine the influence of object location on kinematics.

DATA SOURCES

MEDLINE, AMED, and Embase databases.

ELIGIBILITY CRITERIA

Studies investigating individuals with stroke and neurologically intact control participants completing reach-to-grasp (paretic upper limb) of an object assessed via kinematic assessment (motion analysis).

REVIEW METHODS

Following Cochrane Collaboration guidelines a meta-analysis comparing kinematic characteristics of reach-to-grasp between individuals with and without stroke. Potential risk of bias was assessed using the Down's and Black Tool. Data were synthesised by calculating the standardised mean difference (SMD) in kinematic characteristics between adults with and without stroke.

RESULTS

Twenty-nine studies met the review criteria, mainly of observational design; 460 individuals with stroke and 324 control participants. Kinematic differences in reach-to-grasp were identified in the central and ipsilateral workspace for example, individuals with stroke exhibited significantly lower peak velocity SMD -1.48 (95% CI -1.94, -1.02), and greater trunk displacement SMD 1.55 (95% CI 0.85, 2.25) than control participants. Included studies were assessed as demonstrating unclear or high potential risk-of-bias.

CONCLUSIONS

Differences in kinematic characteristics between individuals with and without stroke were identified which may be different reaching in the ipsilateral and central workspace. Suggesting, that object location may influence some kinematic characteristics and not others which may be pertinent when re-training reach-to-grasp.

PROSPERO

CRD42014009479.

Control of grip force and vertical posture while holding an object and being perturbed

We investigated motor control perspectives of coordinating maintenance of posture and application of grip force when holding an object and being perturbed. Ten subjects stood on the force platform holding an instrumented object in their dominant hand and were exposed to an external perturbation applied to their shoulders. Task demands were manipulated by positioning a slippery cap on top of the instrumented object. Grip force applied to the object, the object acceleration and the center of pressure (COP) were recorded and analyzed during the time intervals typical for the anticipatory (APA) and compensatory (CPA) components of postural control. Onsets of grip force were seen before the onsets of the COP displacement and initiation of movements of the handheld object during the APA phase of postural control, while the onsets of maximum grip force preceded the maximum COP displacement during the CPA phase. When the task demands increased by holding a handheld object with the slippery cap, subjects tended to generate grip force earlier and of a smaller magnitude; also, the COP displacement in the APA phase was smaller as compared to holding a handheld object only. The outcome provides a foundation for future studies of maintenance of vertical posture in people with impairments of balance and grip force control when holding an object and being perturbed.

Age-related changes of grip force control in physically active adults

The age-related changes for controlling grip force in adults who practice regular and supervised physical activity have not been investigated. Fifty-five physically active adults ages 50 years and older and a group of 20 young adults (18-30 years old) performed a task of grasping and lifting an object. The grip force and the object's acceleration were recorded and used to calculate the parameters of grip force control. The levels of daily physical activities were also examined in all age groups. There were no differences in grip force control between the age groups. Conversely, the group over 76 years old used stronger grip force and increased latency (the time from grip force application to the time the object is lifted off the table) to manipulate the object. The results of this study suggest that middle-aged and older adults who exercise regularly can reduce or delay the possible grip force control deficits associated with aging.

The effect of finger joint hypomobility on precision grip force

STUDY DESIGN

Repeated measures experiment.

INTRODUCTION

Traumatic injuries and certain other diseases of the hand typically affect mobility of the finger joints. Decreased mobility may alter grip force control while one is grasping and lifting objects. However, the effect of finger joint hypomobility on grip force control has not yet been systematically investigated.

PURPOSE OF THE STUDY

The aim of this study was to investigate the effects of limited finger joint mobility, without other associated symptoms like pain, or sensory/proprioceptive deficits, on precision grip force control.

METHODS

Fifteen healthy subjects performed a pinching and lifting task of an object equipped with a force sensor and an accelerometer, via opposition of the thumb and index finger, in the following experimental conditions: unrestricted finger joint movement (UJM), restricted finger flexion (RFF), restricted finger extension (RFE), mock restricted flexion (MRF), mock restricted extension (MRE). The following pinch force variables were measured and analyzed: grip force at lift off, grip force peak, load force peak, latency, and static force.

RESULTS

A significant increase in latency (F = 4.41, p < 0.01) was noted during RFE relative to UJM and MRF conditions. There were no statistically-significant differences between the conditions among the other variables of precision grip force control.

CONCLUSIONS

Limited joint mobility of the thumb and index finger may cause temporal changes in precision grip force control, which can lead to reduced manual dexterity. Restoring range of motion might be an important priority to improve thumb-index pinch force control during manipulative tasks.

Occupational Therapy for Upper Limb Post-Stroke Sensory Impairments: A Survey

Purpose:

Upper limb post-stroke sensory impairments have an impact on a significant number of stroke survivors. There is limited research in this area and it is unclear how occupational therapists are addressing sensory impairments in clinical practice. This study aimed to investigate the clinical practice patterns of occupational therapists, perceived barriers to providing interventions and information sources used when addressing upper limb post-stroke sensory impairments.

Methods:

A survey was sent to 500 randomly selected occupational therapists in the United States.

Findings:

The majority of the 145 respondents reported frequently assessing sensation, and half reported providing interventions for sensory impairments. Interventions primarily focused on providing passive sensory stimulation followed by compensatory strategies. Most therapists provided patient/caregiver education about safety. Therapists cited lack of knowledge and skills, patients' short length of stay and lack of time as barriers to utilizing interventions. Most therapists reported not being up to date with current research and requested continuing education to support practice.

Conclusion:

This survey established a profile of American occupational therapists' practice with people with upper limb post-stroke sensory impairments. Therapists have a need for information and training in all aspects of the management of upper limb post-stroke sensory impairment. Further research, evaluating the effectiveness of interventions and exploring therapists' clinical decision making when choosing interventions, is also needed.

A pilot study of sensory feedback by transcutaneous electrical nerve stimulation to improve manipulation deficit caused by severe sensory loss after stroke

Background

Sensory disturbance is common following stroke and can exacerbate functional deficits, even in patients with relatively good motor function. In particular, loss of appropriate sensory feedback in severe sensory loss impairs manipulation capability. We hypothesized that task-oriented training with sensory feedback assistance would improve manipulation capability even without sensory pathway recovery.

Methods

We developed a system that provides sensory feedback by transcutaneous electrical nerve stimulation (SENS) for patients with sensory loss, and investigated the feasibility of the system in a stroke patient with severe sensory impairment and mild motor deficit. The electrical current was modulated by the force exerted by the fingertips so as to allow the patient to identify the intensity. The patient had severe sensory loss due to a right thalamic hemorrhage suffered 27 months prior to participation in the study. The patient first practiced a cylindrical grasp task with SENS for 1 hour daily over 29 days. Pressure information from the affected thumb was fed back to the unaffected shoulder. The same patient practiced a tip pinch task with SENS for 1 hour daily over 4 days. Pressure information from the affected thumb and index finger was fed back to the unaffected and affected shoulders, respectively. We assessed the feasibility of SENS and examined the improvement of manipulation capability after training with SENS.

Results

The fluctuation in fingertip force during the cylindrical grasp task gradually decreased as the training progressed. The patient was able to maintain a stable grip force after training, even without SENS. Pressure exerted by the tip pinch of the affected hand was unstable before intervention with SENS compared with that of the unaffected hand. However, they were similar to each other immediately after SENS was initiated, suggesting that the somatosensory information improved tip pinch performance. The patient’s manipulation capability assessed by the Box and Block Test score improved through SENS intervention and was partly maintained after SENS was removed, until at least 7 months after the intervention. The sensory test score, however, showed no recovery after intervention.

Conclusions

We conclude that the proposed system would be useful in the rehabilitation of patients with sensory loss.

Grip force control in individuals with hand osteoarthritis

Individuals with hand osteoarthritis (OA) experience pain and stiffness that could result in significant limitations in the performance of everyday activities involving upper extremities. The purpose of the study was to evaluate grip force control in individuals with hand OA during the lifting of an object. The study design used was a case-control study. Ten females with hand OA and a group of age-matched females performed two functional tasks: lifting an instrumented object vertically while the load was suddenly changed and lifting and placing the object on a shelf. Load Force Peak, Grip force at liftoff, Grip Force Peak, Time Lag, and Latency were measured and analyzed. Individuals with hand OA were able to modulate the magnitude and temporal parameters of grip force; however, they applied higher grip forces (at liftoff [p=0.002]; Grip Force Peak [p=0.039]) and demonstrated a longer Latency (p=0.015) to manipulate the instrumented object when compared with the control subjects. The Load Force Peak and Time Lag were not significantly different between the two groups. Detailed information about how individuals with hand OA perform prehension activities of daily living will help to better understand the limitations of grip force control in these individuals.

Using touch or imagined touch to compensate for loss of proprioception: a case study

Proprioception is the sense of the position of one's own body. Here, we present a case study of an individual with proprioceptive loss in one limb consequent to stroke. The patient indicated that merely touching his impaired arm with his unimpaired arm temporarily restored his proprioception. We examined this claim and the effects of imagined touch by the unimpaired arm. Assessments were made using three-dimensional tracking of reaching trajectories towards targets in conditions of light and darkness. Both actual and imagined touching significantly reduced movement error and jerk, specifically for targets located in regions that both hands would be able to reach.

Randomized controlled trial of truncal exercises early after stroke to improve balance and mobility

BACKGROUND

Sitting balance and the ability to perform selective truncal movements are important predictors of functional outcome after stroke. However, few clinical trials have evaluated the effect of truncal exercises.

OBJECTIVE

The authors assessed the effect of additional truncal exercises on truncal function, standing balance, and mobility.

METHODS

An assessor-blinded randomized controlled trial was carried out at a stroke rehabilitation hospital. A total of 33 participants (mean 35 days post onset) were randomly assigned to an experimental group (n = 18) or a control group (n = 15). In addition to conventional therapy, the experimental group received 16 hours of truncal exercises. The control group received 16 hours of sham treatment. Truncal function was evaluated by the Trunk Impairment Scale (TIS) and standing balance and mobility by the Tinetti Test. The Romberg with eyes open and eyes closed, Four Test Balance Scale (FTBS), Berg Balance Scale (BBS), Rivermead Motor Assessment Battery (RMAB), Functional Ambulation Categories, and Dynamic Gait Index (DGI) were performed to elucidate the findings of the primary outcome measures.

RESULTS

A treatment effect was found for the experimental group on the TIS (P < .001), Tinetti Test (P < .001), FTBS (P = .014), BBS (P = .007), RMAB (P < .001), and DGI (P = .006).

CONCLUSIONS

In addition to conventional therapy, truncal exercises have a beneficial effect on truncal function, standing balance, and mobility in people after stroke.

Reorganization of multi-muscle and joint withdrawal reflex during arm movements in post-stroke hemiparetic patients

OBJECTIVES

To investigate the behavior of the nociceptive withdrawal reflex (NWR) in the upper limb during reaching and grasping movements in post-stroke hemiparetic patients.

METHODS

Eight patients with chronic stroke and moderate motor deficits were included. An optoelectronic motion analysis system integrated with a surface EMG machine was used to record the kinematic and EMG data. The NWR was evoked through a painful electrical stimulation of the index finger during a movement which consisted of reaching out, picking up a cylinder, and returning it to the starting position.

RESULTS

We found that: (i) the NWR is extensively rearranged in hemiparetic patients, who were found to present different kinematic and EMG reflex patterns with respect to controls; (ii) patients partially lose the ability to modulate the reflex in the different movement phases; (iii) the impairment of the reflex modulation occurs at single-muscle, single-joint and multi-joint level.

CONCLUSIONS

Patients with chronic and mild-moderate post-stroke motor deficits lose the ability to modulate the NWR dynamically according to the movement variables at individual as well as at multi-muscle and joint levels.

SIGNIFICANCE

The central nervous system is unable to use the NWR substrate dynamically and flexibly in order to select the muscle synergies needed to govern the spatio-temporal interaction among joints.

Interventions for sensory impairment in the upper limb after stroke

BACKGROUND

Sensory impairments significantly limit the ability to use the upper limb after stroke. However, little is known about the effects of interventions used to address such impairments.

OBJECTIVES

To determine the effects of interventions that target upper limb sensory impairment after stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched 8 October 2009), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 1), MEDLINE (1966 to January 2009), EMBASE (1980 to January 2009), and six further electronic databases to January 2009. We also handsearched relevant journals, contacted authors in the field, searched doctoral dissertation databases, checked reference lists, and completed citation tracking.

SELECTION CRITERIA

Randomized controlled trials and controlled trials comparing interventions for sensory impairment after stroke with no treatment, conventional treatment, attention placebo or with other interventions for sensory impairment.

DATA COLLECTION AND ANALYSIS

Two review authors selected studies, assessed quality and extracted data. We analyzed study data using mean differences and odds ratios as appropriate. The primary outcome we considered was sensory function and secondary outcomes examined included upper limb function, activities of daily living, impact of stroke and quality of life as well as adverse events.

MAIN RESULTS

We included 13 studies, with a total 467 participants, testing a range of different interventions. Outcome measures included 36 measures of sensory impairment and 13 measures of upper limb function. All but two studies had unclear or high risk of bias. While there is insufficient evidence to reach conclusions about the effects of interventions included in this review, three studies provided preliminary evidence for the effects of some specific interventions, including mirror therapy for improving detection of light touch, pressure and temperature pain; a thermal stimulation intervention for improving rate of recovery of sensation; and intermittent pneumatic compression intervention for improving tactile and kinesthetic sensation. We could not perform meta-analysis due to a high degree of clinical heterogeneity in both interventions and outcomes.

AUTHORS' CONCLUSIONS

Multiple interventions for upper limb sensory impairment after stroke are described but there is insufficient evidence to support or refute their effectiveness in improving sensory impairment, upper limb function, or participants' functional status and participation. There is a need for more well-designed, better reported studies of sensory rehabilitation.

Training grip control with a Fitts' paradigm: a pilot study in chronic stroke

STUDY DESIGN

A clinical measurement study.

PURPOSE

To test the applicability of Fitts' paradigm to grasping tasks in individuals with chronic stroke.

INTRODUCTION

Fitts' Law relates the time of target achievement to task difficulty in repetitive motor tasks.

METHODS

Six male chronic stroke patients performed repetitive actuation of a grip force dynamometer with their affected hands for 12 sessions over four to six weeks.

RESULTS

Movement times followed Fitts' behavior with correlations of R(2)>0.8 for all subjects. Grasp control improved during training, as indicated by an average decrease in Fitts' slope of 26% at high difficulty levels (p<0.05), and decreases in the number of force corrections and in jerkiness, both at p<0.001 level.

CONCLUSIONS

The Fitts' grip force targeting protocol provides an objective standardized instrument for grasp proficiency quantification and a potentially efficacious platform for hand training for persons with stroke.

LEVEL OF EVIDENCE

N/A.

Grip Force Control in Individuals With Multiple Sclerosis

Background. Appropriate regulation of grip force is essential in performance of various activities of daily living such as drinking, eating, buttoning a shirt, and so on. The extent to which individuals with multiple sclerosis (MS) are able to regulate grip forces while performing elements of the activities of daily living is largely unknown. Objective. To investigate how individuals with MS control grip force during performance of functional tasks. Methods. This study evaluated the grip force control in selected individuals with MS (n = 9) and healthy control subjects (n = 9) while they performed the task of lifting and placing an instrumented object on a shelf and the task of lifting the object and bringing it close to the mouth to mimic drinking. The grip forces, object acceleration, force ratio, and time lag were recorded and analyzed. Results. The individuals with MS used significantly larger peak grip force and force ratio than control subjects while performing both tasks and for both hands. In addition, the time lag between the peaks of grip and load forces was significantly longer in individuals with MS. Conclusion. The application of excessive grip force could predispose individuals with MS to additional fatigue and musculoskeletal overuse trauma. Rehabilitation protocols for the MS population may need to account for increased levels of grip force applied during the performance of functional tasks.

Does the location of the touch from the contralateral finger application affect grip force control while lifting an object?

It was recently shown that the magnitude of grip force used to lift and transport a hand-held object decreased if a light finger touch from the contralateral arm was provided to the wrist of the target arm [A.S. Aruin, Support-specific modulation of grip force in individuals with hemiparesis, Arch. Phys. Med. Rehabil. 86 (2005) 768-775]. In this study, we investigated whether the location of the finger touch along the target arm affects the way grip force is reduced. Subjects performed the same task of lifting and transporting an instrumented object with no involvement of the contralateral arm and when an index finger touch of the contralateral arm was provided to the wrist, thumb, mid-forearm, and the hand-held object. Grip force was reduced by approximately the same amount in all conditions with the finger touch compared to the no touch condition suggesting that its reduction was not associated with a particular point of contact of the finger with the target arm. The results of the study provide additional evidence to support of the use of a second arm in the performance of activities of daily living and stress the importance of future studies investigating contralateral arm sensory input on grip force control.

A new perspective in the understanding of hand dysfunction following neurological injury

The human hand is inherently complex and versatile. Its use in everyday activities requires its careful positioning relative to the arm and fine adjustments of the fingers to secure the object in the hand to perform a desired task. Understanding the mechanics of prehension requires an appreciation of the anatomy, biomechanics, kinematics, and control of the hand. This article summarizes these complex mechanisms as well as the central nervous system control of hand movement. We propose a measure to characterize the biomechanics of palmar arch modulation during grasping. We also highlight questions to be investigated in future studies to stimulate further understanding of the motor control of hand function and of the recovery of hand functioning after neurological injury.

Changes in the kinematic structure and non-kinematic features of movements during skilled reaching after stroke: a Laban Movement Analysis in two case studies

The purpose of this study was to adapt a universal language for human movement, Laban Movement Analysis (LMA), to capture the kinematic and non-kinematic aspects of movement in a reach-for-food task by subjects whose movements had been affected by stroke. Two control subjects, one stroke subject with internal capsule damage, and one subject with right posterior parietal stroke were video recorded while performing the reaching task. The movements of limb advancement, grasping the food, and limb withdrawal to place the food in the mouth, were notated using LMA. A scale, the Expressive Reaching Scale (ERS), was derived from the notation. All subjects completed the task; however, the stroke subjects displayed abnormalities in both the kinematic and non-kinematic aspects of movements during reaching with either limb. The most extensive impairments were in the contralateral-to-stroke limb and were most severe in the subject with internal capsule damage. The ERS rating scale may be a useful diagnosis and assessment tool.

Similar motion of a hand-held object may trigger nonsimilar grip force adjustments

The tight coupling between load (L) and grip (G) forces during voluntary manipulation of a hand-held object is well established. The current study is to examine grip-load force coupling when motion of the hand with an object was either self-generated (voluntary) or externally generated. Subjects performed similar cyclic movements of different loads at various frequencies with three types of manipulations: 1) voluntary oscillation, 2) oscillating the right arm via the pulley system by the left leg (self-driven oscillation), and 3) oscillating the arm via the pulley system by another person (other-driven oscillation). During the self-generated movements: 1) the grip forces were larger and 2) grip-load force modulation was more pronounced than in the externally generated movements. The G-L adjustments are not completely determined by the mechanics of object motion; nonmechanical factors related to movement performance, for instance perceptual factors, may affect the G-L coupling.

Impaired anticipatory control of fingertip forces in patients with a pure motor or sensorimotor lacunar syndrome

We examined planning and execution of precision grasp in eight right-handed patients with a right pure motor or sensorimotor lacunar syndrome after a subcortical stroke and eight age-matched controls as they grasped and lifted an instrumented object whose weight could be varied without altering its visual appearance. Grip (normal) and load (tangential) forces at the fingertip-object interface were measured and the grip force rate (GFR) and load force rate (LFR) were derived. Planning of precision grasp was assessed by measurement of anticipatory scaling of peak GFR and peak LFR to object weight. Execution of precision grasp was assessed by measurement of both the timing and efficiency of grip-load force coordination: the pre-load phase duration (PLD) and the load phase duration (LPD) measured timing, whereas the grip force at load force onset (GFO) and the grip force at lift-off (GFL) measured efficiency. Subjects lifted a light and heavy object five times first with the RIGHT hand, then with the LEFT hand, and then once more with the RIGHT AFTER LEFT hand. Patients with stroke did not scale the peak LFR or peak GFR to object weight with the RIGHT hand even with repeated attempts; however, they scaled the peak LFR to object weight on the first lift with the RIGHT AFTER LEFT hand (P = 0.01). Patients also prolonged the PLD and LPD and produced excessive GFO and GFL for RIGHT hand lifts, but decreased the GFL for the heavy object (P = 0.016) with the RIGHT AFTER LEFT hand. Correlation of precision grasp variables from lifts with the RIGHT hand with clinical measures showed that anticipatory scaling of peak LFR and peak GFR did not correlate with clinical measures of hand function, whereas the PLD did (r = 0.88, P = 0.004). The results suggest that patients with right hemiparesis from a subcortical lesion of the corticospinal tract have a higher-order motor planning deficit. This planning deficit is dissociable from deficits in motor execution, is not captured by routine clinical assessment, and is correctable by transfer of information from the unaffected hemisphere. A rehabilitation strategy that involves practice with the left hand prior to practice with the right hand may improve planning of grasping behaviour in patients with right hemiparesis.