A Systematic Review of the Effect of Physical Rehabilitation on Balance in People with Diabetic Peripheral Neuropathy Who are at Risk of Falling.

Background: Falls are a significant issue in people with diabetic peripheral neuropathy. Balance interventions have been broadly administered in individuals with diabetic peripheral neuropathy, but the effects on static and dynamic balance in those who are at risk of falling have not yet been comprehensively reviewed. Objective: To provide a synthesis of the literature regarding the effectiveness of physical rehabilitation interventions to improve balance in people with diabetic peripheral neuropathy who are at risk of falling. Methods: Four databases (PubMed, Embase, the Cochrane Central Register of Controlled Trials, Cumulated Index in Nursing and Allied Health Literature) were systematically searched from inception to July 2022. Articles meeting the eligibility criteria (ie, participants with diabetic peripheral neuropathy and at risk of falling based on validated fall balance outcome risk cut off scores; inclusion of physical rehabilitation intervention) underwent a quality assessment using the Physiotherapy Evidence Database scale. Data regarding fall risk was extracted. Results: Sixteen studies met the eligibility criteria. Participants in six studies improved balance such that their fall risk was reduced from a moderate-high risk of falls to no or low risk of falls from pre- to post-intervention. Interventions within these six studies were variable and included balance exercise, gait training, endurance, tai-chi with mental imagery, proprioceptive training, aerobic training, and yoga. Participants in seven of the remaining studies showed no improvement and participants in three studies showed mixed results regarding improved balance and reduced fall risk status by post-intervention. Conclusion: While physical rehabilitation is sufficient to improve balance in individuals with diabetic peripheral neuropathy who are at risk of falling, few interventions led to improved balance and reduced fall risk. Interventions involving intentional weight shifting, manipulation of the base of support, and displacement of the center of mass such as tai-chi and yoga appear to provide the most consistent results in terms of decreasing fall risk. To better understand the effectiveness of rehabilitation on balance and fall risk, future studies should examine the impact of physical interventions on prospective fall rates.

Age-Related Differences in Motor Skill Transfer with Brief Memory Reactivation.

Motor memories can be strengthened through online practice and offline consolidation. Offline consolidation involves the stabilization of memory traces in post-practice periods. Following initial consolidation of a motor memory, subsequent practice of the motor skill can lead to reactivation and reconsolidation of the memory trace. The length of motor memory reactivation may influence motor learning outcomes; for example, brief, as opposed to long, practice of a previously learned motor skill appears to optimize intermanual transfer in healthy young adults. However, the influence of aging on reactivation-based motor learning has been scarcely explored. Here, the effects of brief and long motor memory reactivation schedules on the retention and intermanual transfer of a visuomotor tracing task are explored in healthy older adults. Forty older adults practiced a virtual star-tracing task either three ("brief reactivation") or ten ("long reactivation") times per session over a two-week period. Comparison with a previously reported group of younger adults revealed significant age-related differences in the effect of the motor memory reactivation schedule on the intermanual transfer of the motor task. In older adults, unlike younger adults, no significant between-group differences were found by practice condition in the speed, accuracy, or skill of intermanual task transfer. That is, motor task transfer in healthy younger, but not older, adults appears to benefit from brief memory reactivation. These results support the use of age-specific motor training approaches and may inform motor practice scheduling, with possible implications for physical rehabilitation, sport, and music.

Neuromechanical control of impact absorption during induced lower limb loading in individuals post-stroke.

Decreased loading of the paretic lower limb and impaired weight transfer between limbs negatively impact balance control and forward progression during gait in individuals post-stroke. However, the biomechanical and neuromuscular control mechanisms underlying such impaired limb loading remain unclear, partly due to their tendency of avoiding bearing weight on the paretic limb during voluntary movement. Thus, an approach that forces individuals to more fully and rapidly load the paretic limb has been developed. The primary purpose of this study was to compare the neuromechanical responses at the ankle and knee during externally induced limb loading in people with chronic stroke versus able-bodied controls, and determine whether energy absorption capacity, measured during induced limb loading of the paretic limb, was associated with walking characteristics in individuals post-stroke. Results revealed reduced rate of energy absorption and dorsiflexion velocity at the ankle joint during induced limb loading in both the paretic and non-paretic side in individuals post-stroke compared to healthy controls. The co-contraction index was higher in the paretic ankle and knee joints compared to the non-paretic side. In addition, the rate of energy absorption at the paretic ankle joint during the induced limb loading was positively correlated with maximum walking speed and negatively correlated with double limb support duration. These findings demonstrated that deficits in ankle dorsiflexion velocity may limit the mechanical energy absorption capacity of the joint and thereby affect the lower limb loading process during gait following stroke.

Beyond pain in the brain: A clinician's guide to interpreting the spinal cord's role in the pain experience.

INTRODUCTION: Physical therapy practice has greatly improved in providing a biopsychosocial approach when considering persistent pain. However, the spinal cord is often overlooked as a structure with an important role in modulating nociceptive information. PURPOSE: This article highlights the role of the dorsal horn (DH) in nociceptive processing and its impact on persistent pain conditions as they appear clinically. Key processes occurring in the spinal cord are described, including cellular changes and local spinal network responses to nociceptive stimuli. Additionally, associated clinical symptoms are discussed and some aspects of physical therapy evaluation are challenged based on the mechanisms of nociceptive processing presented in this commentary. IMPLICATIONS: The spinal cord is an active participant in nociceptive processing, directly impacting the intensity, spread, and recurrence of pain, including within the context of central sensitization. Changes in the behavior of DH neurons are possible with sufficient stimulation and may occur after injury. Additionally, spinal cord activation patterns may lead to bilateral symptoms given adequate strength and duration despite a single peripheral driver. Viewing the spinal cord as a dynamic structure capable of up or down regulating its response to stimuli gives the clinician a better understanding of the nervous system's complex response to prolonged nociceptive input.

Perturbation-Induced Protective Arm Responses: Effect of Age, Perturbation-Intensity, and Relationship with Stepping Stability: A Pilot Study.

During balance recovery from slip perturbations, forward flexion (elevation) of the arms serves to counterbalance the posteriorly displaced center of mass (CoM). We aimed to investigate whether aging affects modulation of arm responses to various intensities of unpredictable slip perturbations and whether arm responses are related to compensatory stepping stability. Ten healthy young adults and ten healthy older adults participated. Participants were asked to react naturally to three randomly administered levels of slip-like surface perturbations (intensity 1 (7.75 m/s2), intensity 2 (12.00 m/s2) and intensity 3 (16.75 m/s2), which occurred by means of forward acceleration of the treadmill belt while standing. Kinematic data were collected using a motion capture system. Outcomes included arm elevation displacement, velocity, and margin of stability (MoS) of compensatory stepping. The results reveal no modulation of arm elevation velocity in older adults from perturbation intensity 1 to 2, whereas younger adults demonstrated progressive increases from intensity 1 to 2 to 3. At intensity 3, older adults demonstrated reduced maximal arm elevation velocity compared to younger adults (p = 0.02). The results in both groups combined reveal a positive correlation between maximal arm elevation velocity and first compensatory step MoS at intensity 3 (p = 0.01). Together, these findings indicate age-related decreases in arm response modulation and the association of arm elevation response with protective stepping stability, suggesting that fall prevention interventions may benefit from an emphasis on arm elevation velocity control in response to greater perturbation intensities.

Development and Psychometric Testing of the Bimanual Assessment Measure for People With Chronic Stroke.

IMPORTANCE: Few tools are available to assess bimanual deficits after stroke. OBJECTIVE: To develop the Bimanual Assessment Measure (BAM), which assesses a person's hand coordination in both preferred and prestroke roles (i.e., stabilizer or manipulator). DESIGN: Development and psychometric testing of the BAM. SETTING: Research laboratory. PARTICIPANTS: People with chronic stroke (n = 24), age-matched controls (n = 23), and occupational therapists (n = 40). OUTCOMES AND MEASURES: We assessed the BAM's internal consistency, reliability, and face and known-groups validity. RESULTS: Items were selected as meaningful tasks that represented a range of bimanual coordination requirements (e.g., symmetrical forces and timing, asymmetrical forces and timing, time-limited reactive movement). Focus groups of people with stroke and occupational therapists provided input into BAM development. The BAM was found to have excellent reliability and internal consistency and face and known-groups validity. CONCLUSIONS AND RELEVANCE: The BAM is a valid, reliable measure for people with chronic stroke that identifies bimanual coordination deficits beyond unimanual impairments and the potential capacity for people to return to prestroke hand roles (i.e., as a manipulator). What This Article Adds: This article introduces the BAM as a new assessment measure of bimanual functioning with the potential capacity to restore prestroke hand roles as either a manipulator or a stabilizer among people with chronic stroke.

Enhancing motor learning in people with stroke via memory reactivation during sleep.

PURPOSE: Investigate the use of repetitive delivery of task-related auditory cues, known as targeted memory reactivation (TMR), throughout a 1-hour daytime nap to enhance motor learning in individuals with chronic stroke. RESEARCH METHOD: Participants with a history of stroke at least 6 months prior were recruited to perform a novel overhand throwing task to randomly appearing target locations using the nonparetic upper extremity immediately before and after a 1-hour daytime nap. Half of the participants received TMR during the nap. RESULTS: Participants who received TMR demonstrated a greater overall reduction in absolute and variable spatial errors relative to the NoTMR control group. Both groups demonstrated similar generalization of skill to 2 untrained variants of the trained task, but not to a novel untrained task. CONCLUSIONS: This study suggests that TMR may enhance motor learning after stroke. Future studies should investigate whether TMR can lead to improvements of the paretic upper extremity during clinically based rehabilitation interventions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Examining the influence of mental stress on balance perturbation responses in older adults.

BACKGROUND: Reach-to-grasp responses following balance perturbations are important to fall prevention but are often ineffective in older adults. The ability to shift attention from an ongoing cognitive task to balance related processes has been shown to influence reach-to-grasp effectiveness in older adults. However, the added influence of stress and anxiety - known to negatively affect attention shifting ability - has not yet been explored in relation to recovery from balance perturbations. Given that fear and anxiety over falling is a key fall risk factor, an understanding of how such a negative mental state may affect postural reactions is important. This study aimed to investigate the effect of varied induced emotional states on reach-to-grasp balance responses in older adults. METHODS: Healthy older adults (mean age 70.5 ± 5.38 years) stood laterally between 2 handrails with contact sensors. A safety harness with an integrated loadcell was worn to prevent falls and measure the amount of harness assistance (expressed as percent body weight). With instructions to grasp one rail to restore balance, participants' balance was laterally disturbed using surface translations under three randomized conditions: no cognitive task, neutral (verb generation) task, and mental stress task with negative prompts (paced auditory serial addition). The primary outcome was frequency of protective grasps. Secondary outcomes included frequency of harness assistance during trials with grasp errors as well as wrist movement time, trajectory distance, and peak velocity. RESULTS: Perceived level of distress was highest for the mental stress task compared to no task (p < 0.001) and neutral task conditions (p = 0.008). The mental stress task resulted in the lowest percentage of protective grasps (p < 0.001) in response to balance perturbations. Closer examination of trials that resulted in grasp errors (i.e., collisions or overshoots), revealed increased harness assistance and reduced peak velocity of wrist movement (p < 0.001) under the mental stress condition compared to grasp errors that occurred under the no task or neutral task condition. DISCUSSION AND CONCLUSION: Distressing mental thoughts immediately prior to a balance perturbation lead to reduced effectiveness in reach-to-grasp balance responses compared to no or neutral cognitive tasks and should be considered as a possible fall risk factor.

Trunk kinematics and muscle activation patterns during stand-to-sit movement and the relationship with postural stability in aging.

BACKGROUND: Stand-to-sit (StandTS) movement is an important functional activity that can be challenging for older adults due to age-related changes in neuromotor control. Although trunk flexion, eccentric contraction of the rectus femoris (RF), and coordination of RF and biceps femoris (BF) muscles are important to the StandTS task, the effects of aging on these and related outcomes are not well studied. RESEARCH QUESTION: What are the age-related differences in trunk flexion, lower extremity muscle activation patterns, and postural stability during a StandTS task and what is the relationship between these variables? METHODS: Ten younger and ten older healthy adults performed three StandTS trials at self-selected speeds. Outcomes included peak amplitude, peak timing, burst duration, and onset latency of electromyography (EMG) activity of the RF and BF muscles, trunk flexion angle and angular velocity, whole body center of mass (CoM) displacement, center of pressure (CoP) velocity, and ground reaction force (GRF). RESULTS: There were no age-related differences in weight-bearing symmetry, StandTS and trunk flexion angular velocity, or BF activity. In both groups, EMG peak timing of RF was preceded by BF. Compared to younger adults, older adults demonstrated shorter RF EMG burst duration, reduced trunk flexion, and reduced stability as indicated by the longer duration in which CoM was maintained beyond the posterior limit of base of support (BoS), greater mean anterior-posterior CoP velocity and larger standard deviation of CoM vertical acceleration during StandTS with smaller vertical GRF immediately prior to StandTS termination. Trunk flexion angle and RF EMG burst duration correlated with stability as measured by the duration in which the CoM stayed within the BoS. SIGNIFICANCE: Decreased trunk flexion and impaired eccentric control of the RF are associated with StandTS instability in aging and suggest the importance of including StandTS training as a part of a comprehensive balance intervention.

Chronic Poststroke Deficits in Gross and Fine Motor Control of the Ipsilesional Upper Limb.

OBJECTIVES: Individuals with stroke often experience contralesional and ipsilesional arm motor deficits. The aim of this study was to compare fine and gross motor hand dexterity of the ipsilesional hand post-stroke with controls, normative values, and the contralesional hand. DESIGN: Data were collected from right-handed individuals with chronic stroke (n = 20), age-/sex-matched controls (n = 10), and normative values (n = 20) performing the Nine-Hole Peg Test and the Box and Blocks Test. RESULTS: Individuals with stroke demonstrated poorer performance with the ipsilesional arm relative to both the control group (mean difference [95% confidence interval]: Nine-Hole Peg Test [seconds], 3.4 [-0.5 to 7.3]; Box and Blocks Test [number of blocks], -12.3 [-20.3 to -4.2]) and normative values (mean difference [95% confidence interval]: Nine-Hole Peg Test [seconds], 6.5 [4.0-9.1]; Box and Blocks Test (number of blocks), -15.3 [-20.1 to -10.5]). Ipsilesional arm performance was significantly better than performance with the contralesional arm (mean difference [95% confidence interval]: Nine-Hole Peg Test [seconds], -9.4 [-20.2 to 1.4]; Box and Blocks Test (number of blocks), 33.2 [20.9-45.5]). CONCLUSION: These findings identify residual deficits in fine and gross dexterity of the ipsilesional hand in commonly used outcome measures of hand manipulation among individuals with chronic stroke. Possible underlying mechanisms and clinical relevance are discussed.

A systematic review of upper extremity responses during reactive balance perturbations in aging.

BACKGROUND: Balance responses to perturbations often involve the arms in an attempt to either restore balance or protect against impact. Although a majority of research has been dedicated to understanding age-related changes in lower limb balance responses, there is a growing body of evidence supporting age-related changes in arm responses. This systematic review aimed to summarize differences in arm responses between older and younger adults under conditions requiring counterbalancing, reaching to grasping, and protection against impact. METHODS: Following a systematic review and critical appraisal of the literature, data regarding the arm response in studies comparing young and older adults was extracted. The resulting articles were also assessed for quality to determine risk of bias. RESULTS: Fifteen high quality studies were identified. The majority of these studies reported delayed onsets in muscle activation, differences in arm movement strategies, delayed movement timing, increased impact forces, and greater grasp errors in older compared to young adults. These differences were also identified under varied visual and cognitive conditions. CONCLUSIONS: The studies included in this review demonstrate age-related differences in arm responses regardless of the direction and nature of the perturbation. These differences could provide insight into developing more targeted rehabilitation and fall prevention strategies. More research is needed to assess whether the identified age-related differences are a necessary compensation or a contributory factor to balance impairments and fall risk in older adults.

Age-Related Differences in Arm and Trunk Responses to First and Repeated Exposure to Laterally Induced Imbalances.

The objective of this study was to examine age-related differences in arm and trunk responses during first and repeated step induced balance perturbations. Young and older adults received 10 trials of unpredictable lateral platform translations. Outcomes included maximum arm and trunk displacement within 1 s of perturbation and at first foot lift off (FFLO), arm and neck muscle activity as recorded using electromyography (EMG), initial step type, balance confidence, and percentage of harness-assisted trials. Compared to young adults, older adults demonstrated greater arm and trunk angular displacements during the first trial, which were present at FFLO and negatively associated with balance confidence. Unlike young adults, recovery steps in older adults were directed towards the fall with a narrowed base of support. Over repeated trials, rapid habituation of first-trial responses of bilateral arm and trunk displacement and EMG amplitude was demonstrated in young adults, but was absent or limited in older adults. Older adults also relied more on harness assistance during balance recovery. Exaggerated arm and trunk responses to sudden lateral balance perturbations in older adults appear to influence step type and balance recovery. Associations of these persistently amplified movements with an increased reliance on harness assistance suggest that training to reduce these deficits could have positive effects in older adults with and without neurological disorders.

Aging, Vestibular Function, and Balance: Proceedings of a National Institute on Aging/National Institute on Deafness and Other Communication Disorders Workshop.

Balance impairment and falls are among the most prevalent and morbid conditions affecting older adults. A critical contributor to balance and gait function is the vestibular system; however, there remain substantial knowledge gaps regarding age-related vestibular loss and its contribution to balance impairment and falls in older adults. Given these knowledge gaps, the National Institute on Aging and the National Institute on Deafness and Other Communication Disorders convened a multidisciplinary workshop in April 2019 that brought together experts from a wide array of disciplines, such as vestibular physiology, neuroscience, movement science, rehabilitation, and geriatrics. The goal of the workshop was to identify key knowledge gaps on vestibular function and balance control in older adults and develop a research agenda to make substantial advancements in the field. This article provides a report of the proceedings of this workshop. Three key questions emerged from the workshop, specifically: (i) How does aging impact vestibular function?; (ii) How do we know what is the contribution of age-related vestibular impairment to an older adult's balance problem?; and more broadly, (iii) Can we develop a nosology of balance impairments in older adults that can guide clinical practice? For each of these key questions, the current knowledge is reviewed, and the critical knowledge gaps and research strategies to address them are discussed. This document outlines an ambitious 5- to 10-year research agenda for increasing knowledge related to vestibular impairment and balance control in older adults, with the ultimate goal of linking this knowledge to more effective treatment.

Sensorimotor performance is improved by targeted memory reactivation during a daytime nap in healthy older adults.

Sensorimotor consolidation occurs during sleep. However, the benefit of sleep-based consolidation decreases with age due to decreased sleep quality and quantity. This study aimed to enhance sensorimotor performance through repetitive delivery of task-based auditory cues during sleep, known as targeted memory reactivation (TMR). Healthy older adults performed a non-dominant arm throwing task before and after a 1 h nap. While napping, half of participants received TMR throughout the hour. Participants who received TMR during sleep demonstrated a greater overall change in throwing accuracy from the start of the first to the end of the second throwing task session. However, there was no generalization of throwing accuracy to variants of the task or to a novel dart throwing task. Findings support the use of TMR during sleep to enhance task-specific sensorimotor performance in healthy older adults despite age-related decreases in sleep quality and quantity. Future research is needed to evaluate the effects of TMR on rehabilitation protocols.

Competition for limited neural resources in older adults leads to greater asymmetry of bilateral movements than in young adults.

We previously demonstrated that lateralization in the neural control of predictive and impedance mechanisms is reflected by interlimb differences in control of bilateral tasks. Aging has been shown to reduce lateralization during unilateral performance, presumably due to greater recruitment of the ipsilateral hemisphere. We now hypothesize that aging-related reduction in the efficiency of neural resources should produce greater behavioral asymmetry during bilateral actions that require hemispheric specialization for each arm. This is because simultaneous control of dominant and nondominant arm function should induce competition for hemisphere-specific resources. To test this hypothesis, we now examine the effect of aging (young, n = 20; old, n = 20) on performance of a mechanically coupled task, in which one arm reaches toward targets while the other arm stabilizes against a spring that connects the two arms. Results indicate better dominant arm reaching performance and better nondominant arm stabilizing performance for both groups. Most notably, limb and joint compliance was lower in the dominant arm, leading to dominant arm deficits in stabilizing performance. Group analysis indicated that older adults showed substantially greater asymmetry in stabilizing against the spring load than did the younger adults. We propose that competition for limited neural resources in older adults is associated with reduced contributions of right hemisphere mechanisms to right-dominant arm stabilizing performance, and thus to greater asymmetry of performance.NEW & NOTEWORTHY We provide evidence for greater asymmetry of interlimb differences in bilateral coordination for stabilizing and preserved asymmetry of reaching with aging. These results provide the first evidence for increased lateralization with aging within the context of a complementary bilateral task.

Systematic Review Investigating the Effects of Nonpharmacological Interventions During Sleep to Enhance Physical Rehabilitation Outcomes in People With Neurological Diagnoses.

OBJECTIVE: Conduct a systematic review of nonpharmacological interventions applied during sleep to enhance physical rehabilitation outcomes of individuals with a neurological diagnosis. DATA SOURCES: Three online databases were searched for original research. STUDY SELECTION: Intervention studies were included that used outcome measures of impairment, activity, and/or participation. DATA EXTRACTION: Two reviewers independently screened 2287 titles and abstracts, reviewed 101 full texts, extracted data, and assessed study quality and risk of bias for 9 included studies. DATA SYNTHESIS: All included studies were randomized controlled trials involving continuous positive airway pressure (CPAP) with inpatient individuals with stroke and sleep apnea. Several studies also included long-term outpatient follow-ups. Results in terms of outcomes based on impairment, activity, and participation were mixed. However, several studies found that the use of CPAP following stroke and sleep apnea during early stroke recovery had benefits relative to no CPAP. CONCLUSIONS: The only nonpharmacological intervention to be administered during sleep in a neurological population to improve physical rehabilitation outcomes was found to be CPAP. This review was complicated by the variety of outcome measures used, lack of physical rehabilitation description, and CPAP compliance. In general, participants who had acceptable to good CPAP compliance saw the largest improvements in physical rehabilitation outcomes. Several other promising methods of brain stimulation during sleep are discussed.

Use of targeted memory reactivation enhances skill performance during a nap and enhances declarative memory during wake in healthy young adults.

Sleep is an important component of motor memory consolidation and learning, providing a critical tool to enhance training and rehabilitation. Following initial skill acquisition, memory consolidation is largely a result of non-rapid eye movement sleep over either a full night or a nap. Targeted memory reactivation is one method used to enhance this critical process, which involves the pairing of an external cue with task performance at the time of initial motor skill acquisition, followed by replay of the same cue during sleep. Application of targeted memory reactivation during sleep leads to increased functional connectivity within task-related brain networks and improved behavioural performance in healthy young adults. We have previously used targeted memory reactivation throughout the first two slow-wave sleep cycles of a full night of sleep to enhance non-dominant arm throwing accuracy in healthy young adults. Here, we aimed to determine whether application of targeted memory reactivation throughout a 1-hr daytime nap was sufficient to enhance performance on the same non-dominant arm throwing task in healthy young adults. Participants were allocated to either nap or no nap, and within those groups half received targeted memory reactivation throughout a 1-hr between-session period, leading to four groups. Only participants who slept between sessions while receiving targeted memory reactivation enhanced their throwing accuracy upon beginning the second session. Future studies will aim to use this technique as an adjunct to traditional physical rehabilitation with individuals with neurologic diagnoses such as stroke.

Handedness results from complementary hemispheric dominance, not global hemispheric dominance: evidence from mechanically coupled bilateral movements.

Two contrasting views of handedness can be described as 1) complementary dominance, in which each hemisphere is specialized for different aspects of motor control, and 2) global dominance, in which the hemisphere contralateral to the dominant arm is specialized for all aspects of motor control. The present study sought to determine which motor lateralization hypothesis best predicts motor performance during common bilateral task of stabilizing an object (e.g., bread) with one hand while applying forces to the object (e.g., slicing) using the other hand. We designed an experimental equivalent of this task, performed in a virtual environment with the unseen arms supported by frictionless air-sleds. The hands were connected by a spring, and the task was to maintain the position of one hand while moving the other hand to a target. Thus the reaching hand was required to take account of the spring load to make smooth and accurate trajectories, while the stabilizer hand was required to impede the spring load to keep a constant position. Right-handed subjects performed two task sessions (right-hand reach and left-hand stabilize; left-hand reach and right-hand stabilize) with the order of the sessions counterbalanced between groups. Our results indicate a hand by task-component interaction such that the right hand showed straighter reaching performance whereas the left hand showed more stable holding performance. These findings provide support for the complementary dominance hypothesis and suggest that the specializations of each cerebral hemisphere for impedance and dynamic control mechanisms are expressed during bilateral interactive tasks. NEW & NOTEWORTHY We provide evidence for interlimb differences in bilateral coordination of reaching and stabilizing functions, demonstrating an advantage for the dominant and nondominant arms for distinct features of control. These results provide the first evidence for complementary specializations of each limb-hemisphere system for different aspects of control within the context of a complementary bilateral task.