Grip Force Control In Patients Research Articles

Relative contribution of sensory and motor deficits on grip force control in patients with chronic stroke

ObjectiveThis study aimed to characterize grasping behavior in static (weight-dependent modulation and stability of control) and dynamic (predictive control) aspects specifically focusing on the relative contribution of sensory and motor deficits to grip force control in patients with chronic stroke. MethodsTwenty-four chronic stroke patients performed three manipulative tasks: five trials of 5-s grasp-lift-holding, 30-s static holding, and vertical dynamic/cyclic oscillation of holding the object. ResultsExerted static grip force on the paretic side exhibited statistically greater than that on the non-paretic side. Spearman's rank correlation coefficient revealed that the contribution to static grip force control was larger in sensory deficits than in motor deficits. In addition, the sensory deficit is related to the reduced coupling between grip force and load force, suggesting difficulty in predictive control due to the absence of sensory feedback. ConclusionsGiven that grip force control involves predictive feedforward and online feedback control, the evaluation of grip force might be an important and feasible evaluation manner for the assessment of sensorimotor control in patients post-stroke. SignificanceDetailed evaluation of grip force control would help to understand the mechanisms underlying hand dysfunction in stroke patients.

Anticipatory and Reactive Grip Force Control in Patients with Alzheimer's Disease: A Pilot Study.

Alzheimer's disease (AD) affects several cognitive functions and causes altered motor function. Fine motor deficits during object manipulation are evident in other neurological conditions, but have not been assessed in dementia patients yet. Investigate reactive and anticipatory grip force control in response to unexpected and expected load force perturbation in AD. Reactive and anticipatory grip force was investigated using a grip-device with force sensors. In this pilot study, fifteen AD patients and fourteen healthy controls performed a catching task. They held the device with one hand while a sandbag was dropped into an attached receptacle either by the experimenter or by the participant. In contrast to studies of other neurological conditions, the majority of AD patients exerted lower static grip force levels than controls. Interestingly, patients who were slow in the Luria's three-step test produced normal grip forces. The timing and magnitude of reactive grip force control were largely preserved in patients. In contrast, timing and extent of anticipatory grip forces were impaired in patients, although anticipatory control was generally preserved. These deficits were correlated with decreasing Mini-Mental State Examination scores. Apraxia scores, assessed by pantomime of tool-use, did not correlate with performance in the catching task. We interpreted the decreased grip force in AD in the context of loss of strength and lethargy, typical for patients with AD. The lower static grip force during object manipulation may emerge as a potential biomarker for early stages of AD, but more studies with larger sample sizes are necessary.

Effects of cervical manipulation on pain, grip force control, and upper extremity muscle activity: a randomized controlled trial

Objectives: Individuals with neck pain experience disrupted grip force control when performing manipulative tasks. Manipulative physical therapy might decrease pain and change the activity of surrounding muscles; however, its effect on upper limb motor control remains undetermined. This study aims to analyze the effects of cervical manipulation on pressure pain threshold (PPT), upper extremity muscle activity along with grip force control in individuals with neck pain.Methods: Thirty subjects with neck pain were instructed to grasp and lift an object before and after cervical (n = 15) or sham (n = 15) manipulation. The patients’ PPT, electromyographic (EMG) activity of the upper extremity/scapular muscles, and grip force control were analyzed before and after one session of manipulation.Results: No significant differences were found in the grip force control, PPT and EMG activity variables between groups.Discussion: These results suggest that a single session of cervical manipulation may not modify upper limb motor control, more specifically grip force control and EMG activity, in patients with cervical pain. Future studies should investigate potential changes in grip force control in patients with different features of neck pain and/or by applying long-term treatment.Level of Evidence: 1b.

Effects of transcranial direct current stimulation on grip force control in patients with cerebellar degeneration

BackgroundThe control of grip forces when moving a hand held object is impaired in patients with cerebellar degeneration. We asked the question whether after-effects of anodal transcranial direct current stimulation (tDCS) applied to the lateral cerebellum or M1 improved grip force control in cerebellar patients.MethodsGrip force control while holding an object during cyclic arm movements was assessed in patients with pure cerebellar degeneration (n = 14, mean age 50.2 years ± SD 8.8 years) and age- and sex-matched control participants (n = 14, mean age 50.7 years ± SD 9.8 years). All subjects were tested before and after application of tDCS (2 mA, 22 min) in a within-subject design. Each subject received anodal tDCS applied to the cerebellum, anodal tDCS applied to M1 or sham-stimulation with a break of 1 week between the three experimental sessions.ResultsThere were no clear after-effects of tDCS on grip force control neither in control participants nor in cerebellar patients. Cerebellar patients showed typical impairments with higher grip forces, a higher variability of movements.ConclusionIn the present study, deficits in grip force control were neither improved by tDCS applied over the cerebellum nor M1 in cerebellar degeneration.

P174. Effects of left and right brain damage on anticipatory motor behavior during grasping and lifting with the ipsilesional hand

Behavioral studies in patients with left and right brain damage revealed the specialized function of both hemispheres in motor control. Recently, we investigated anticipatory grip force control in patients with stroke affecting the left or the right hemisphere during object lifting with the ipsilesional non-paretic hand. We found imprecise anticipation of grip force to the weight of everyday objects (like a carton with milk or a package of paper tissues) in patients with left brain damage while patients with right brain damage performed closer to normal. This finding suggests a particular role of the motor-dominant left brain in predicting object properties based on knowledge about the object identity. By contrast, we found no deficit of anticipatory grip force control in stroke patients when the initial weight information was provided by the size of the object. Also the perceptual size-weight-illusion was the same in patients and control subject. In the present study we tested material as the critical variable determining object weight. We hypothesized that the anticipation of material information as well as the so-called material-weight illusion may be reduced in patients with left brain damage, as material information about object characteristics may be a less direct cue to weight compared to size. Twelve patients with left brain damage (LBD), ten patients with right brain damage (RBD) and fourteen control subjects (CTR) lifted two pairs of identically-weighted objects which differed in size in the size-weight-illusion paradigm and in apparent material (polystyrene and aluminum) in the material-weight-illusion paradigm. In an additional control pair, the size and weight of two wooden blocks differed in the natural way. Participants’ grip forces and the lift forces were measured with a sensor (170 g) attached to the objects’ top surfaces. Subjects had to indicate which object in a pair is felt heavier before and after 6 lifts of each cube in a pair. Participants of all three groups experienced the size–weight–illusion. The material–weight–illusion was perceived less clearly without a clear difference between patients and control subjects. During the first lift of each object, the steepness of the grip force increase (quantified as the peak grip force rate) reflected the objects’ apparent weight as indicated by size. However variability was substantial in both patients groups. Different materials induced less clear differences in grip force rate. In particular, patients with left brain damage failed to scale their grip force profile according to the material. Also for the wooden object pair, data of LBD patients revealed a weaker anticipation of object properties than observed in the other groups. Our results confirm the normal processing of object size information for the scaling of grip forces and for the perception of the size-weight illusion in patients with brain damage, indicating that size processing is resistant to a wide range of brain damage. LBD patients in particular showed no consistent scaling of grip forces according to variations in material properties. Performance variability was however large in patients, suggesting that deficits depend on the specific lesion pattern which varied a lot across patients. In conclusion, the motor-dominant left hemisphere seems to play a prominent role in the processing of material information for object manipulation. However the responsibility seems to be less selective than when information is derived from object identity.

Abnormal capacity for grip force control in patients with congenital insensitivity to pain

Congenital insensitivity to pain (CIP), which is an extremely rare sensory neuropathy, is defined as the absence of normal responses to noxious stimuli. Although motor function is not directly impaired in CIP patients, it is likely that the sensory deficit affects the motor control system. In order to characterize motor capacity in CIP patients, we here measured grip force and acceleration of a held object in 12 patients with CIP and 12 age-matched able-bodied subjects. The results demonstrated that the grip force during the object grasp-lift-holding task was significantly greater, less reproducibility and greater fluctuation in the acceleration of the object in CIP patients than in normal subjects. Moreover, some patients showed absence of temporal coupling between the grip and load force, suggesting that anticipatory modulation of the grip force was at least partly impaired. As far as the authors know, this is the first study to characterize motor control ability in patients with CIP. The observed abnormal motor capacity can be at least partly attributed to a lack of sensory inputs mediated by Aδ and unmyelinated C-, specifically C-tactile, fibers. The present results may provide information useful for the prevention of secondary injury and education for patients during the developmental stage.

Role of Movement Velocity on the Magnitude of Grip Force while Lifting an Object with Touch from the Contralateral Finger

We investigated whether slower velocity of arm movement affects grip-force generation in conditions with the finger touch provided to the wrist of the target arm. Nine subjects performed the task of lifting and transporting an object at slow, intermediate, and fast velocities with a light finger touch from the contralateral arm and without it. There was an effect of velocity of arm movement on grip-force generation in both conditions. However, when the no touch and touch trials performed with similar velocity were matched, the effect of touch on grip-force reduction was statistically significant (p < .001). The observed decrease in grip force could not be explained by slower movement execution in the touch conditions and underlines the importance of using a contralateral touch in the performance of activities of daily living. It also points to a possibility of the development of therapeutic advances for the enhancement of grip-force control in patients with neurological impairments.

Grip force control in patients with neck and upper extremity pain and healthy controls

ObjectiveTo investigate whether sensory and motor problems in patients with non-specific neck and upper extremity pain can be ascribed to a deficit of sensory–motor integration. MethodsGrip force control and adaptation were measured in 81 cases, 32 former cases and 39 healthy controls, during repetitive lifting and holding of an object. The object (300g) was lifted vertically over 20cm and held for 5s, using the dominant arm (the affected arm in all cases). The object was novel to the subjects when lifted for the first time, and was lifted five times consecutively. Grip forces orthogonal to the object’s surface and its vertical acceleration were measured. ResultsCases used significantly higher grip forces than both other groups, while vertical acceleration was not different. After the initial lift, all groups significantly reduced the maximum grip force. ConclusionsSubjects with neck and upper extremity pain consistently use higher grip forces than controls, but adjust grip forces by a similar amount after the first lift. Compensation of impaired sensory information rather than a general deficit in sensory–motor integration seems to account for these findings. SignificanceNon-specific neck and upper extremity pain coincides with objectifiable changes in control of grip force.

Force tracking system for the assessment of grip force control in patients with neuromuscular diseases

Background. The majority of hand functionality assessment methods consist of the maximal voluntary grip force measurement. Additional knowledge on sensory-motor control can be obtained by capturing functional grip force in a time frame. Tracking methods have been successfully used for the assessment of grip force control in stroke patients and patients with Parkinson’s disease. Methods. A novel tracking system for the evaluation of grip force control is presented. The system consists of a grip-measuring device with the end-objects of different shapes which was used as input to a tracking task where the patient applied the grip force according to the visual feedback. The grip force control was assessed in 20 patients with neuromuscular diseases and 9 healthy subjects. The performance of two tracking tasks was analysed in five grips. The ramp-tracking task was designed to assess the grip strength and muscle fatigue. The sinus-tracking task was used to evaluate grip force control during periodic muscle activation. Findings. The results suggest that in some patients the disease did not affect their grip force control despite evident muscular weakness. Most patients produced larger tracking errors in precision grip while the healthy subjects showed less significant differences in performance among the grips tested. Interpretation. The current study investigated force control in patients with neuromuscular diseases where detection of small changes in motor performance is important when following the progress of disease. The presented evaluation method can provide additional information on muscle activation and fatigue as compared to traditional grip strength testing.

Grip force control during object manipulation in cerebral stroke

To analyze impairments of manipulative grip force control in patients with chronic cerebral stroke and relate deficits to more elementary aspects of force and grip control. Nineteen chronic stroke patients with fine motor deficits after unilateral cerebral lesions were examined when performing 3 manipulative tasks consisting of stationary holding, transport, and vertical cyclic movements of an instrumented object. Technical sensors measured the grip force used to stabilize the object in the hand and the object accelerations, from which the dynamic loads were calculated. Many patients produced exaggerated grip forces with their affected hand in all types of manipulations. The amount of finger displacement in a grip perturbation task emerged as a highly sensitive measure for predicting the force increases. Measures of grip strength and maximum speed of force changes could not account for the impairments with comparable accuracy. In addition to force economy, the precision of the coupling between grip and load forces was impaired. However, no temporal delays were typically observed between the grip and load force profiles during cyclic movements. Impaired sensibility and sensorimotor processing, evident by delayed reactions in the perturbation task, lead to an excessive increase of the safety margin between the actual grip force and the minimum force necessary to prevent object slipping. In addition to grip force scaling, cortical sensorimotor areas are responsible for smoothly and precisely adjusting grip forces to loads according to predictions about movement-induced loads and sensory experiences. However, the basic feedforward mechanism of grip force control by internal models appears to be preserved, and thus may not be a cortical but rather a subcortical or cerebellar function, as has been suggested previously.

Moving objects with clumsy fingers: how predictive is grip force control in patients with impaired manual sensibility?

Anticipatory grip force adjustments to movement-induced load fluctuations of a hand-held object suggest that motion planning is based on an internal forward model of both the external object properties and the dynamics of the own motor apparatus. However, the central nervous system also refers to real time sensory feedback from the grasping digits in order to achieve a highly economical coupling between grip force and the actual loading requirements. We analyzed grip force control during vertical point-to-point arm movements with a hand-held instrumented object in 9 patients with moderately impaired tactile sensibility of the grasping digits due to chronic median nerve compression (n = 3), axonal (n = 3) and demyelinating sensory polyneuropathy (n = 3) in comparison to 9 healthy age- and sex-matched control subjects. Point-to-point arm movements started and ended with the object being held stationary at rest. Load force changes arose from inertial loads related to the movement. A maximum of load force occurred early in upward and near the end of downward movements. Compared to healthy controls, patients with impaired manual sensibility generated similar static grip forces during stationary holding of the object and similar force ratios between maximum grip and load force. These findings reflect effective grip force scaling in relation to the movement-induced loads despite reduced afferent feedback from the grasping digits. For both groups the maxima of grip and load force coincided very closely in time, indicating that the temporal regulation of the grip force profile with the load profile was processed with a similar high precision. In addition, linear regression analyses between grip and load forces during movement-related load increase and load decrease phases revealed a similar precise temporo-spatial coupling between grip and load forces for patients and controls. Our results suggest that the precise and anticipatory adjustment of the grip force profile to the load force profile arising from voluntary arm movements with a hand-held object is centrally mediated and less under sensory feedback control. As suggested by previous investigations, the efficient scaling of the grip force magnitude in relation to the movement-induced loads may be intact when deficits of tactile sensibility from the grasping fingers are moderate.

Feedback-based training of grip force control in patients with brain damage

Objective: Feedback-based training of grip force control in patients with various brain lesions was evaluated. Design: Patients were instructed to hold a force transducer in a precision grip and to track with their grip force a moving target, which was presented together with the feedback signal on a monitor. Training performance was evaluated during a maximum of 10 sessions. Before and after the training, performance in two transfer tasks, which differed in target characteristics from the training task, was examined. Patients: Ten patients with impaired grip force control, after brain lesions of different origin, were selected on the basis of a clinical examination of hand function. Main Outcome Measures: Tracking accuracy in training tasks and transfer tasks was evaluated by calculating the conventional root-mean-square error. Results: Nine out of the 10 patients reduced their tracking error considerably during a maximum of 10 subsequent sessions ( t test, p < 0.05), and most of them reached normal or near-normal performance. In addition, they improved in both transfer tasks ( t test, p < 0.05). Detailed analysis showed that impaired initial performance and improvement was not uniform among patients and could be attributed to individual aspects of force control. Conclusions: In view of these results, a feedback-based training of grip force may be a useful enrichment of motor therapy.