Pinch Task Research Articles

Trapeziometacarpal joint movement during pinching measured by ultrasonography

ObjectiveFunctional hand activity induces complex motion of the trapeziometacarpal (TMC) joint. Analyzing the TMC joint motion in vivo can aid in understanding joint behavior and lead to advancements in joint health evaluation. The purpose of this study was to quantify TMC joint motion during pinching using ultrasonography. DesignHealthy participants (n = 10) held a pinch meter in key pinch configuration and pinched to three prescribed force levels. Ultrasonography was used to record the motion of the TMC joint. The position and rotation of the first metacarpal were calculated. Repeated measures one-way ANOVAs were used for comparisons (α = 0.05). ResultsWhen the pinch force was increased from 0 to 10, 20 and 30 N, the first metacarpal translated in the dorsal(+)/volar(-) direction -0.3 mm [95 % CI: (-0.5 mm, -0.1 mm); p = 0.0151], -0.5 mm [95 % CI: (-0.8 mm, -0.1 mm); p = 0.0113] and -0.8 mm [95 % CI: (-1.4 mm, -0.2 mm); p = 0.0146]. Significance was not observed for proximal(+)/distal(-) translation (p = 0.224). The metacarpal rotated in the abduction(+)/adduction(-) direction 0.7° [95 % CI: (-0.8°, 2.1°); p = 0.3239], 2.6° [95 % CI: (0.1°, 5.1°); p = 0.0416] and 3.3° [95 % CI: (0.2°, 6.3°); p = 0.0393], at pinch forces of 10, 20 and 30 N, respectively. ConclusionsThe TMC joint undergoes volar translation and abduction rotation during pinch tasks. Ultrasonography can be used to quantify this motion and aid in the advancement of joint behavioral study.

Enhancing motor skill learning through multiple sessions of online high-definition transcranial direct current stimulation in healthy adults: insights from EEG power spectrum.

The purpose of this study was to evaluate the influence of high-definition transcranial direct current stimulation (HD-tDCS) on finger motor skill acquisition. Thirty-one healthy adult males were randomly assigned to one of three groups: online HD-tDCS (administered during motor skill learning), offline HD-tDCS (delivered before motor skill learning), and a sham group. Participants engaged in a visual isometric pinch task for three consecutive days. Overall motor skill learning and speed-accuracy tradeoff function were used to evaluate the efficacy of tDCS. Electroencephalography was recorded and power spectral density was calculated. Both online and offline HD-tDCS total motor skill acquisition was significantly higher than the sham group (P < 0.001 and P < 0.05, respectively). Motor skill acquisition in the online group was higher than offline (P = 0.132, Cohen's d =1.46). Speed-accuracy tradeoff function in the online group was higher than both offline and sham groups in the post-test. The online group exhibited significantly lower electroencephalography activity in the frontal, fronto-central, and centro-parietal alpha band regions compared to the sham (P < 0.05). The findings suggest that HD-tDCS application can boost finger motor skill acquisition, with online HD-tDCS displaying superior facilitation. Furthermore, online HD-tDCS reduces the power of alpha rhythms during motor skill execution, enhancing information processing and skill learning efficiency.

Site Dependency of Anodal Transcranial Direct-Current Stimulation on Reaction Time and Transfer of Learning during a Sequential Visual Isometric Pinch Task.

Considering the advantages of brain stimulation techniques in detecting the role of different areas of the brain in human sensorimotor behaviors, we used anodal transcranial direct-current stimulation (a-tDCS) over three different brain sites of the frontoparietal cortex (FPC) in healthy participants to elucidate the role of these three brain areas of the FPC on reaction time (RT) during a sequential visual isometric pinch task (SVIPT). We also aimed to assess if the stimulation of these cortical sites affects the transfer of learning during SVIPT. A total of 48 right-handed healthy participants were randomly assigned to one of the four a-tDCS groups: (1) left primary motor cortex (M1), (2) left dorsolateral prefrontal cortex (DLPFC), (3) left posterior parietal cortex (PPC), and (4) sham. A-tDCS (0.3 mA, 20 min) was applied concurrently with the SVIPT, in which the participants precisely controlled their forces to reach seven different target forces from 10 to 40% of the maximum voluntary contraction (MVC) presented on a computer screen with the right dominant hand. Four test blocks were randomly performed at the baseline and 15 min after the intervention, including sequence and random blocks with either hand. Our results showed significant elongations in the ratio of RTs between the M1 and sham groups in the sequence blocks of both the right-trained and left-untrained hands. No significant differences were found between the DLPFC and sham groups and the PPC and sham groups in RT measurements within the SVIPT. Our findings suggest that RT improvement within implicit learning of an SVIPT is not mediated by single-session a-tDCS over M1, DLPFC, or PPC. Further research is needed to understand the optimal characteristics of tDCS and stimulation sites to modulate reaction time in a precision control task such as an SVIPT.

Older and younger adults differ in time course of skill acquisition but not in overall improvement in a bimanual visuomotor tracking task.

Manual motor performance declines with age, but the extent to which age influences the acquisition of new skills remains a topic of debate. Here, we examined whether older healthy adults show less training-dependent performance improvements during a single session of a bimanual pinch task than younger adults. We also explored whether physical and cognitive factors, such as grip strength or motor-cognitive ability, are associated with performance improvements. Healthy younger (n = 16) and older (n = 20) adults performed three training blocks separated by short breaks. Participants were tasked with producing visually instructed changes in pinch force using their right and left thumb and index fingers. Task complexity was varied by shifting between bimanual mirror-symmetric and inverse-asymmetric changes in pinch force. Older adults generally displayed higher visuomotor force tracking errors during the more complex inverse-asymmetric task compared to younger adults. Both groups showed a comparable net decrease in visuomotor force tracking error over the entire session, but their improvement trajectories differed. Young adults showed enhanced visuomotor tracking error only in the first block, while older adults exhibited a more gradual improvement over the three training blocks. Furthermore, grip strength and performance on a motor-cognitive test battery scaled positively with individual performance improvements during the first block in both age groups. Together, the results show subtle age-dependent differences in the rate of bimanual visuomotor skill acquisition, while overall short-term learning ability is maintained.

Dopamine D2 Receptor Modulates Exercise Related Effect on Cortical Excitation/Inhibition and Motor Skill Acquisition.

Exercise is known to benefit motor skill learning in health and neurological disease. Evidence from brain stimulation, genotyping, and Parkinson's disease studies converge to suggest that the dopamine D2 receptor, and shifts in the cortical excitation and inhibition (E:I) balance, are prime candidates for the drivers of exercise-enhanced motor learning. However, causal evidence using experimental pharmacological challenge is lacking. We hypothesized that the modulatory effect of the dopamine D2 receptor on exercise-induced changes in the E:I balance would determine the magnitude of motor skill acquisition. To test this, we measured exercise-induced changes in excitation and inhibition using paired-pulse transcranial magnetic stimulation (TMS) in 22 healthy female and male humans, and then had participants learn a novel motor skill-the sequential visual isometric pinch task (SVIPT). We examined the effect of D2 receptor blockade (800 mg sulpiride) on these measures within a randomized, double-blind, placebo-controlled design. Our key result was that motor skill acquisition was driven by an interaction between the D2 receptor and E:I balance. Specifically, poorer skill learning was related to an attenuated shift in the E:I balance in the sulpiride condition, whereas this interaction was not evident in placebo. Our results demonstrate that exercise-primed motor skill acquisition is causally influenced by D2 receptor activity on motor cortical circuits.

Feasibility of using fNIRS to explore motor-related regional haemodynamic signal changes in patients with sensorimotor impairment and healthy controls: A pilot study.

While functional near-infrared spectroscopy (fNIRS) can provide insight into cortical brain activity during motor tasks in healthy and diseased populations, the feasibility of using fNIRS to assess haemoglobin-evoked responses to reanimated upper limb motor function in patients with tetraplegia remains unknown. The primary objective of this pilot study is to determine the feasibility of using fNIRS to assess cortical signal intensity changes during upper limb motor tasks in individuals with surgically restored grip functions. The secondary objectives are: 1) to collect pilot data on individuals with tetraplegia to determine any trends in the cortical signal intensity changes as measured by fNIRS and 2) to compare cortical signal intensity changes in affected individuals versus age-appropriate healthy volunteers. Specifically, patients presented with tetraplegia, a type of paralysis resulting from a cervical spinal cord injury causing loss of movement and sensation in both lower and upper limbs. All patients have their grip functions restored by surgical tendon transfer, a procedure which constitutes a unique, focused stimulus for brain plasticity. fNIRS is used to assess changes in cortical signal intensity during the performance of two motor tasks (isometric elbow and thumb flexion). Six individuals with tetraplegia and six healthy controls participate in the study. A block paradigm is utilized to assess contralateral and ipsilateral haemodynamic responses in the premotor cortex (PMC) and primary motor cortex (M1). We assess the amplitude of the optical signal and spatial features during the paradigms. The accuracy of channel locations is maximized through 3D digitizations of channel locations and co-registering these locations to template atlas brains. A general linear model approach, with short-separation regression, is used to extract haemodynamic response functions at the individual and group levels. Peak oxyhaemoglobin (oxy-Hb) changes in PMC appear to be particularly bilateral in nature in the tetraplegia group during both pinch and elbow trials whereas for controls, a bilateral PMC response is not especially evident. In M1 / primary sensory cortex (S1), the oxy-Hb responses to the pinch task are mainly contralateral in both groups, while for the elbow flexion task, lateralization is not particularly clear. This pilot study shows that the experimental setup is feasible for assessing brain activation using fNIRS during volitional upper limb motor tasks in individuals with surgically restored grip functions. Cortical signal changes in brain regions associated with upper extremity sensorimotor processing appear to be larger and more bilateral in nature in the tetraplegia group than in the control group. The bilateral hemispheric response in the tetraplegia group may reflect a signature of adaptive brain plasticity mechanisms. Larger studies than this one are needed to confirm these findings and draw reliable conclusions.

Effect of extension of the ulnar fingers on force control and muscle activity of the hand during a precision pinch.

Some individuals extend the three ulnar fingers when performing a precision pinch. The aim of the present study was to investigate the mechanisms and effect of the extension of the ulnar fingers during a pinch. When performing a pulp pinch task with the ulnar fingers in two positions (extension and flexion), 27 participants maintained 5% of their maximum force. The mean pinch force, force variability and time taken to reach the targeted force (reaching time) were calculated. Muscle activity was simultaneously measured, using surface electromyography, for nine muscles: the flexor pollicis brevis; abductor pollicis brevis; flexor pollicis longus; first lumbrical; first dorsal interosseous; flexor digitorum superficialis of the index finger; extensor indicis; and extensor digitorum of the index and ring fingers. No significant differences in the mean pinch force or force variability were found. However, the reaching time was significantly shorter (approximately 20% reduction) in the extension position and the activities in the flexor pollicis brevis, first lumbrical, extensor indicis and extensor digitorum of the ring finger were significantly higher. These findings suggest that extending the ulnar fingers during pinching enhances the activity of key muscles involved in the movement and allows for more rapid force exertion.

Induction of prediction error during memory reconsolidation strengthens recent motor skills.

This study investigated strategies based on the reconsolidation process to promote the strengthening effect of human motor memory. The aim of this study was to evaluate the influence of reactivating the memory of a newly acquired motor skill and performing interventions during its reconsolidation process on motor performance. Sixty healthy participants learned a new Sequential Visual Isometric Pinch Task - SVIPT during the first experimental session. In the second experimental session that was held on the same day, 6 hours after session 1, the participants were divided into 6 different groups. In session 2, there were distinctions between the experimental groups concerning two issues: the presence or absence of a formal memory reactivation session characterized by the execution of repetitions of the learned motor task and the execution of different types of interventions after reactivation (training with the original, slightly modified, or moderately modified motor task). All groups performed the third session to retest the learned motor skill, 24 hours after session 1. The results showed that using training with moderate task variability during memory reconsolidation provides greater motor skill performance gain when compared to repetitive training of the same learned task. Furthermore, performing a session exclusively dedicated to reactivation with the practice of the originally learned task was not a determining condition for recent motor memory reactivation, but rather the induction of prediction error during the reactivation.

Task-dependent alteration of beta-band intermuscular coherence is associated with ipsilateral corticospinal tract excitability.

Beta-band (15-30 Hz) synchronization between the EMG signals of active limb muscles can serve as a non-invasive assay of corticospinal tract integrity. Tasks engaging a single limb often primarily utilize one corticospinal pathway, although bilateral neural circuits can participate in goal-directed actions involving multi-muscle coordination and utilization of feedback. Suboptimal utilization of such circuits after CNS injury can result in unintended mirror movements and activation of pathological synergies. Accordingly, it is important to understand how the actions of one limb (e.g., a less-affected limb after strokes) influence the opposite corticospinal pathway for the rehabilitation target. Certain unimanual actions decrease the excitability of the "unengaged" corticospinal tract, presumably to prevent mirror movement, but there is no direct way to predict the extent to which this will occur. In this study, we tested the hypothesis that task-dependent changes in beta-band drives to muscles of one hand will inversely correlate with changes in the opposite corticospinal tract excitability. Ten participants completed spring pinching tasks known to induce differential 15-30 Hz drive to muscles. During compressions, transcranial magnetic stimulation single pulses to the ipsilateral M1 were delivered to generate motor-evoked potentials in the unengaged hand. The task-induced changes in ipsilateral corticospinal excitability were inversely correlated with associated changes in EMG-EMG coherence of the task hand. These results demonstrate a novel connection between intermuscular coherence and the excitability of the "unengaged" corticospinal tract and provide a springboard for further mechanistic studies of unimanual tasks of varying difficulty and their effects on neural pathways relevant to rehabilitation.

Mixed reality-integrated soft wearable biosensing glove for manipulating objects

Recent advances in flexible sensors and wireless electronics have driven the development of lightweight and ergonomic wearable sensing gloves. Such gloves can be employed in mixed reality (MR) environments to give haptic capabilities during interactions with various objects. However, no prior study shows a quantitative measurement of physical user interactions of object manipulation in MR. Here, we report an MR-integrated soft bioelectronic system on a glove for quantifying the changes in the user's pinching tasks. We use nanomanufacturing techniques to fabricate flexible sensors, wireless circuits, and stretchable interconnectors seamlessly integrated with a wearable glove. The wearable biosensing glove with an integrated capacitive pressure sensor evaluates how users interact directly and indirectly interact with objects. The direct mode describes a user's direct touching and manipulating objects in MR. In contrast, in the indirect mode, objects are located far away and touched via a narrow light beam. The virtual object measurement parameters include mass, movement latency, dynamic friction coefficient, angular drag coefficient, and linear drag coefficient. The experimental results with human subjects show positive, linear relationships between pinching force and dynamic friction coefficient and mass parameters during the direct manipulation mode. Collectively, the MR-enabled wearable biosensing glove system offers unique advantages in detecting physical interactions and sensory feedback for various rehabilitation applications and MR human-machine interfaces.

Using a finite element model of the thumb to study Trapeziometacarpal joint contact during lateral pinch

BackgroundFinite element (FE) analysis is widely used in different fields of orthopaedic surgery, however, its application to the trapeziometacarpal joint has been limited due to the small size, complex biconcave-convex joint geometry, and complex musculature. The goal of this study was to improve upon existing models by creating a muscle-driven FE thumb model and use the model to simulate the biomechanical effect of hand therapy exercises and ligament reconstructive surgeries. MethodsBone and cartilage geometry were based on a CT dataset of a subject performing a static lateral pinch task. A previously validated musculoskeletal model was utilized to extract electromyography (EMG)-driven muscle forces. Five ligaments with biomechanical significance were modeled as springs using literature values and attached according to their anatomical landmarks. FindingsThe biomechanical consequence of various interventions was proxied as a change in the maximum cartilage stress. The result shows tightening the dorsal ligament complex (dorsal radial ligament, dorsal central ligament, posterior oblique ligament) is the most effective, achieving a stress reduction of 4.8%. Five exercises used in hand therapies were modeled, among which thenar eminence strengthening showed the most prominent stress reduction of 4.0%. Four ligament reconstructive surgeries were modeled, with Eaton-Littler reconstruction showed the most significant stress reduction of 25.0%. InterpretationAmong the routinely utilized treatment options for early thumb osteoarthritis, we found that three methods: dorsal ligament imbrication, thenar eminence exercise, and the Eaton-Littler method may confer biomechanical advantages cartilage loading. These advantages align with the clinically observed favorable outcomes.

Children With Cerebral Palsy Show Higher Static-But Not Higher Dynamic-Motor Fatigability in Grip and Pinch Tasks Than Children With Typical Development Do.

The purpose of this study was to investigate differences in static and dynamic motor fatigability during grip and pinch tasks between children with unilateral spastic cerebral palsy (USCP) and children with typical development (TD) and between preferred and nonpreferred hands. Fifty-three children with USCP and 53 age-matched children with TD (mean = 11years 1month; SD = 3years 8months) participated in 30-second maximum exertion sustained and repeated grip and pinch tasks. For sustained tasks, the Static Fatigue Index and the ratio of mean force between the first and last thirds of the curve were calculated. For repeated tasks, the ratio of mean force and the ratio of numbers of peaks between the first and last thirds of the curve were calculated. Higher Static Fatigue Index scores for grip and pinch were found with USCP in both hands and between hands in both groups. Dynamic motor fatigability showed inconsistent results, with higher levels of fatigability in children with TD than in children with USCP for grip in the ratio of mean force between the first and last thirds of the curve in nonpreferred hands and in the ratio of number of peaks between the first and last thirds of the curve in preferred hands. Higher motor fatigability in children with USCP than in children with TD was found for static but not dynamic grip and pinch. Underlying mechanisms may play different roles in static and dynamic motor fatigability. These results highlight that static motor fatigability in grip and pinch tasks should be part of a comprehensive upper limb assessment and that this could be the target of individualized interventions.

Effects of auditory feedback on fine motor output and corticomuscular coherence during a unilateral finger pinch task.

Auditory feedback is important to reduce movement error and improve motor performance during a precise motor task. Accurate motion guided by auditory feedback may rely on the neural muscle transmission pathway between the sensorimotor area and the effective muscle. However, it remains unclear how neural activities and sensorimotor loops play a role in enhancing performance. The present study uses an auditory feedback system by simultaneously recording electroencephalogram (EEG), electromyography (EMG), and exert force information to measure corticomuscular coherence (CMC), neural activity, and motor performance during precise unilateral right-hand pinch by using the thumb and the index finger with and without auditory feedback. This study confirms three results. First, compared with no auditory feedback, auditory feedback decreases movement errors. Second, compared with no auditory feedback, auditory feedback decreased the power spectrum in the beta band in the bimanual sensorimotor cortex and the alpha band in the ipsilateral sensorimotor cortex. Finally, CMC was computed between effector muscle of right hand and contralateral sensorimotor cortex. Analyses reveals that the CMC of beta band significantly decreases in auditory feedback condition compared with no auditory feedback condition. The results indicate that auditory feedback decreases the power spectral in the alpha and beta bands and decreases corticospinal connection in the beta band during precise hand control. This study provides a new perspective on the effect of auditory feedback on behavior and brain activity and offers a new idea for designing more suitable and effective rehabilitation and training strategies to improve fine motor performance.

Modulation of subjective peripheral sensation, F-waves, and somatosensory evoked potentials in response to unilateral pinch task measured on the contractile and non-contractile sides.

Depression of the sensory input during voluntary muscle contractions has been demonstrated using electrophysiological methods in both animals and humans. However, the association between electrophysiological responses of the sensory system and subjective peripheral sensation (SPS) during a voluntary muscle contraction remains unclear. This study aimed to describe the changes in SPS, spinal α-motoneuron excitability (F-wave to M-wave amplitude), and somatosensory evoked potentials (SEPs) during a unilateral pinch-grip task. Outcome variables were measured on the side ipsilateral and contralateral to the muscle contraction and at rest (control). Participants were 8 healthy men aged 20.9±0.8 years. The isometric pinch-grip task was performed at 30% of the maximum voluntary isometric force measured for the right and left hands separately. The appearance rate of the F-wave during the task was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and control condition. Although there was no difference in the F-wave latency between hands and the control condition, the amplitude of the F-wave was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. There was no difference in the amplitude of the SEP at N20. However, the amplitude at P25 was significantly lower for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. The accuracy rate of detecting tactile stimulation, evaluated for 20 repetitions using a Semmes–Weinstein monofilament at the sensory threshold for each participant, was significantly lower during the pinch-grip task for both the ipsilateral (right) and contralateral (left) hands than in the control condition. Overall, our findings show that SPS and neurophysiological parameters were not modulated in parallel during the task, with changes in the subjective sensation preceding changes in electrophysiological indices during the motor task. Our findings provide basic information on sensory-motor coordination.

Increasing motor cortex activation during grasping via novel robotic mirror hand therapy: a pilot fNIRS study

BackgroundMirror therapy (MT) has been used for functional recovery of the affected hand by providing the mirrored image of the unaffected hand movement, which induces neural activation of the cortical hemisphere contralateral to the affected hand. Recently, many wearable robots assisting the movement of the hand have been developed, and several studies have proposed robotic mirror therapy (RMT) that uses a robot to provide mirrored movements of the unaffected hand to the affected hand with the robot controlled by measuring electromyography or posture of the unaffected hand. In some cases of RMT a mirror is placed to allow the person to observe only the unaffected hand but in others users simply observe the robotically assisted hand performing the mirrored movements, as was the case in this study. There have been limited evaluations of the cortical activity during RMT compared to MT and robotic therapy (RT) providing passive movements despite the difference in the modality of sensory feedback and the involvement of motor intention, respectively.MethodsThis paper analyzes bilateral motor cortex activation in nine healthy subjects and five chronic stroke survivors during a pinching task performed in MT, RT, and RMT conditions using functional near infrared spectroscopy (fNIRS). In the MT condition, the person moved the unaffected hand and observed it in a mirror while the affected hand remained still. In RT condition passive movements were provided to the affected hand with a cable-driven soft robotic glove, while, in RMT condition, the posture of the unaffected hand was measured by a sensing glove and the soft robotic glove mirrored its movement on the affected hand.ResultsFor both groups, the RMT condition showed the greatest mean cortical activation on the motor cortex contralateral to the affected (non-dominant for the healthy group) hand compared to other conditions. Individual results indicate that RMT induces similar or greater neural activation on the motor cortex compared to MT and RT conditions. The interhemispheric activations of both groups were balanced in RMT condition. In MT condition, significantly greater activation was shown on the hemisphere ipsilateral to the affected (dominant for the healthy group) hand for both subject groups, while the contralateral side showed significantly greater activation for the healthy group in RT condition.ConclusionThe experimental results indicate that combining visual feedback, somatosensory feedback, and motor intention are important for greater stimulation on the contralateral motor cortex of the affected hand. RMT that includes these factors is hypothesized to achieve a more effective functional rehabilitation due to greater and more balanced cortical activation.

Motor cortex plasticity and visuomotor skill learning in upper and lower limbs of endurance-trained cyclists.

Studies with transcranial magnetic stimulation (TMS) show that both acute and long-term exercise can influence TMS-induced plasticity within primary motor cortex (M1). However, it remains unclear how regular exercise influences skill training-induced M1 plasticity and motor skill acquisition. This study aimed to investigate whether skill training-induced plasticity and motor skill learning is modified in endurance-trained cyclists. In 16 endurance-trained cyclists (24.4 yrs; 4 female) and 17 sedentary individuals (23.9 yrs; 4 female), TMS was applied in 2 separate sessions: one targeting a hand muscle not directly involved in habitual exercise and one targeting a leg muscle that was regularly trained. Single- and paired-pulse TMS was used to assess M1 and intracortical excitability in both groups before and after learning a sequential visuomotor isometric task performed with the upper (pinch task) and lower (ankle dorsiflexion) limb. Endurance-trained cyclists displayed greater movement times (slower movement) compared with the sedentary group for both upper and lower limbs (all P < 0.05), but there was no difference in visuomotor skill acquisition between groups (P > 0.05). Furthermore, endurance-trained cyclists demonstrated a greater increase in M1 excitability and reduced modulation of intracortical facilitation in resting muscles of upper and lower limbs after visuomotor skill learning (all P < 0.005). Under the present experimental conditions, these results indicate that a history of regular cycling exercise heightens skill training-induced M1 plasticity in upper and lower limb muscles, but it does not facilitate visuomotor skill acquisition.

Cortical Re-organization After Traumatic Brain Injury Elicited Using Functional Electrical Stimulation Therapy: A Case Report.

Functional electrical stimulation therapy (FEST) can improve motor function after neurological injuries. However, little is known about cortical changes after FEST and weather it can improve motor function after traumatic brain injury (TBI). Our study examined cortical changes and motor improvements in one male participant with chronic TBI suffering from mild motor impairment affecting the right upper-limb during 3-months of FEST and during 3-months follow-up. In total, 36 sessions of FEST were applied to enable upper-limb grasping and reaching movements. Short-term assessments carried out using transcranial magnetic stimulation (TMS) showed reduced cortical silent period (CSP), indicating cortical and/or subcortical inhibition after each intervention. At the same time, no changes in motor evoked potentials (MEPs) were observed. Long-term assessments showed increased MEP corticospinal excitability after 12-weeks of FEST, which seemed to remain during both follow-ups, while no changes in CSP were observed. Similarly, long-term assessments using TMS mapping showed larger hand MEP area in the primary motor cortex (M1) after 12-weeks of FEST as well as during both follow-ups. Corroborating TMS results, functional magnetic resonance imaging (fMRI) data showed M1 activations increased during hand grip and finger pinch tasks after 12-weeks of FEST, while gradual reduction of activity compared to after the intervention was seen during follow-ups. Widespread changes were seen not only in the M1, but also sensory, parietal rostroventral, supplementary motor, and premotor areas in both contralateral and ipsilateral hemispheres, especially during the finger pinch task. Drawing test performance showed improvements after the intervention and during follow-ups. Our findings suggest that task-specific and repetitive FEST can effectively increase cortical activations by integrating voluntary motor commands and sensorimotor network through functional electrical stimulation (FES). Overall, our results demonstrated cortical re-organization in an individual with chronic TBI after FEST.

A Short-Term Intervention of High-Intensity Exercise and Anodal-tDCS on Motor Learning in Middle-Aged Adults: An RCT.

High-intensity exercise has enhanced motor learning in healthy young adults. Anodal-transcranial direct current stimulation (a-tDCS) may optimize these effects. This study aimed to determine the effects of a short-term high-intensity interval exercise intervention either with or without a-tDCS on the learning and retention of a novel motor task in middle-aged adults. Forty-two healthy middle-aged adults (age = 44.6 ± 6.3, female = 76%) were randomized into three groups: exercise and active a-tDCS, exercise and sham a-tDCS, and a non-exercise and sham a-tDCS control. Participants completed a baseline testing session, followed by three intervention sessions 48-h apart. The exercise groups completed 20-min of high-intensity exercise followed by a novel sequential visual isometric pinch task (SVIPT) while receiving 20-min of 1.5 mA a-tDCS, or sham tDCS. The control group completed 20-min of reading before receiving sham a-tDCS during the SVIPT. Learning was assessed by skill change within and between intervention sessions. Participants returned 5–7 days after the final intervention session and performed the SVIPT task to assess retention. All three groups showed evidence of learning on the SVIPT task. Neither group displayed enhanced overall learning or retention when compared to the control group. High-intensity exercise with or without a-tDCS did not improve learning or retention of a novel motor task in middle-aged adults. The methodological framework provides direction for future research to investigate the potential of differing exercise intensity effects on learning and retention.

Arthrodesis Versus Arthroplasty in Thumb Carpometacarpal Osteoarthritis: Impact on Maximal Voluntary Force, Endurance, and Accuracy of Pinch

To investigate differences in pinch strength recovery among patients with first carpometacarpal joint osteoarthritis treated with either arthrodesis or suspension arthroplasty. Thirty-seven subjects who underwent arthrodesis or suspension arthroplasty for carpometacarpal osteoarthritis were included. Force exerted during maximal voluntary contraction (MVC) in a pinch task was measured. Maximal voluntary contraction was recorded using a haptic device equipped with a load cell from which an analog signal was acquired and digitized for visual feedback. Dynamic force was assessed by a task consisting of 10 repetitions, with a target of 70% of MVC. Endurance was assessed by the length of sustained pinch task at 30% of MVC. Task performance was quantified by mean distance and offset error from the target force as error indices, and standard deviation of force was used as index of force steadiness. The arthrodesis group obtained considerably higher MVC values than the arthroplasty group. No notable differences were found for pinch endurance. The standard deviation for dynamic force was lower for arthroplasty, indicating greater force steadiness. Arthrodesis is associated with greater pinch strength. Arthroplasty is associated with better pinch precision. Therapeutic IV.

Anthropometric scaling of musculoskeletal models of the hand captures age-dependent differences in lateral pinch force

Musculoskeletal models and computer simulations enable non-invasive study of muscle function and contact forces. Hand models are useful for understanding the complexities of hand strength, precision movement, and the dexterity required during daily activities. Yet, generic models fail to accurately represent the entire scope of the population, while subject-specific models are labor-intensive to create. The objective of this study was to assess the efficacy of scaled generic models to represent the broad spectrum of strength profiles across the lifespan. We examined one hundred lateral pinch simulations using a generic model of the wrist and thumb anthropometrically scaled to represent the full range of heights reported for four ages across childhood, puberty, older adolescence, and adulthood. We evaluated maximum lateral pinch force produced, muscle control strategies, and the effect of linearly scaling the maximum isometric force. Our simulations demonstrated three main concepts. First, anthropometric scaling could capture age-dependent differences in pinch strength. Second, a generic muscle control strategy is not representative of all populations. Lastly, simulations do not employ optimal fiber length to complete a lateral pinch task. These results demonstrate the potential of anthropometrically-scaled models to study hand strength across the lifespan, while also highlighting that muscle control strategies may adapt as we age. The results also provide insight to the force–length relationship of thumb muscles during lateral pinch. We conclude that anthropometric scaling can accurately represent age characteristics of the population, but subject-specific models are still necessary to represent individuals.