Outcome measures for hand function naturally reveal three latent domains in older adults: strength, coordinated upper extremity function, and sensorimotor processing

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.

Outcome Measures Used to Assess Hand Activity in Amputee and Intact Populations: a Literature Review

BACKGROUND

The human hand is critical in assisting with activities of daily living (ADL). Amputation of the hand can affect a person physically, socially and psychologically. Knowledge of outcome measures used to assess upper limb activity of intact and amputee populations may aid in guiding research to develop applicable measurement tools specific to the amputee population. Tools could aid developments in prosthetic design and prescription, which benefit both users and healthcare researchers.

OBJECTIVES

This literature review examined outcome measurement tools used with non-amputee and amputee populations to assess hand activity. The objectives were to identify which characteristics of hand activity are captured by currently available measurement tools.

METHODOLOGY

Searches were conducted using PubMed, Cochrane and ProQuest for studies investigating hand activity for amputee and non-amputee populations. A total of 15 studies were included. PRISMA guidelines were used to assist with study selection. Data extraction and narrative synthesis were carried out.

FINDINGS

A total of 32 outcome measures were found. Frequently used tools were: Box and Block Test, Swedish Disabilities of the Arm Shoulder and Hand Questionnaire, and range of motion. Studies employed a combination of 2 to 12 tools. Themes extracted were: importance of function and quality of life, the need for realistic tasks, and the need for outcome measures specific of the population.

CONCLUSION

There is a gap in research surrounding outcome measurement tools used to assess hand activity in the amputee population. A combination of outcome measures are required to obtain insight into the hand activities of intact and amputee populations. Function and quality of life are important aspects to consider when describing hand activity.

Association of enlarged perivascular spaces with upper extremities and gait impairment: An observational, prospective cohort study

Background and objective

Gait disturbances are common in the elderly and can lead to the loss of functional independence and even death. Enlarged perivascular space (EPVS) and motor performance may be related, but only few studies have explored this relationship. The aim of our study was to investigate the effects of both the severity and location of EPVS on movement disorders.

Method

Two hundred and six participants aged between 45 and 85 years old with complete magnetic resonance imaging (MRI) data were included in our analysis. EPVS were divided into basal ganglia (BG) and centrum semiovale (CSO), and their grades were measured. Gait was assessed quantitatively using a 4-m walkway and TUG test as well as semi-quantitatively using the Tinetti and SPPB tests. The function of upper extremities was evaluated by 10-repeat pronation–supination, 10-repeat finger-tapping, and 10-repeat opening and closing of the hands.

Results

Both high-grade EPVS, whether in BG and CSO, were independently correlated with gait parameters, the TUG time, Tinetti, and SPPB tests. The EPVS located in BG had a significant association with 10-repeat finger-tapping time (β = 0.231, P = 0.025) and a similar association was also observed between CSO-EPVS and 10-repeat pronation–supination time (β = 0.228, P = 0.014).

Conclusion

Our results indicated that EPVS was associated with gait disturbances, and a further investigation found that EPVS has an association with upper extremities disorder. EPVS should be considered as a potential target for delaying gait and upper extremities damage since CSVD can be prevented to some extent.

Impairments in grip and pinch force accuracy and steadiness in people with osteoarthritis of the hand: A case-control comparison

BACKGROUND

Symptomatic hand osteoarthritis (OA) is severely disabling condition. Limited evidence has focused on force control measures in this population.

OBJECTIVES

It was the aim of the present study to determine whether force matching accuracy and steadiness are impaired in people with hand OA. In addition, the relationship between force control measures (accuracy and steadiness) and measures of hand function and pain in people with symptomatic hand OA was explored.

DESIGN

Case-control study.

METHOD

Sixty-two participants with symptomatic hand OA and 26 healthy pain-free controls undertook an isometric grip and pinch force matching task at 50 % of their maximum voluntary contraction. Average pain hand pain was recorded. In addition, the Disability of the Arm Shoulder and Hand Questionnaire (DASH), and the Functional Index of Hand Osteoarthritis were collected.

RESULTS

Grip force-matching accuracy and steadiness were significantly impaired in the hand OA group compared to controls (P < 0.05). Pinch force-matching error was greater in people with hand OA (P < 0.05), however, pinch force steadiness was not different between groups. There was a learning effect in people with hand OA, with resolution of force matching impairments with task repetition. A small positive correlation was identified between grip force control and the DASH. No association was found between other measures of force control and self-reported measures of function or pain.

CONCLUSIONS

People with hand OA presented with greater impairments in measures of submaximal force control. These were correlated with self-reported hand function but not pain. Future studies may wish to examine whether objective measures of functional performance are related to force-matching error and steadiness.

Clinical evaluation of thumb base osteoarthritis: A scoping review

Introduction

Thumb base osteoarthritis (OA) is a prevalent hand OA phenotype, associated with specific risk factors, treatment strategies, and requiring a distinct subset of evaluative approaches. This paper aimed at surveying our clinical evaluative methods and identifying gaps in our ability to capture the thumb's unique attributes and how they could impact our treatment recommendations.

Methods

A scoping review was conducted in accordance with the Joanna Briggs Institute methodology to gather relevant published and non-published articles regarding clinical tests currently available to assess the physical presentation of thumb base OA with special consideration of its specific multifactorial parameters namely architecture, ligaments, biomechanics, neuromuscular control, and proprioception. A full search strategy of MEDLINE, CINAHL, EMBASE, Scopus, Google Scholar, and Clinical Trials.gov from their inception through May 2020 was performed.

Results

Of 1936 citation identified, 54 met the inclusion criteria. Fifty-two clinical physical tests for the evaluation of thumb base OA were extracted, most of which well suited to address research questions regarding efficacy of clinical intervention, however providing limited information regarding the underlying impairments of ligaments, biomechanics, neuromuscular or proprioceptive components.

Conclusions

The tests and measures specific to the basal thumb OA phenotype, and capable of isolating its multifactorial contributors are scarce. Our limited physical assessment repertoire impedes our ability to describe and answer explicative research questions. Without these we cannot evaluate the effect of conservative management and provide specific treatment recommendations. Further research is needed to develop and validate distinct clinical tools for this debilitating pathology.

Force Steadiness: From Motor Units to Voluntary Actions

Voluntary actions are controlled by the synaptic inputs that are shared by pools of spinal motor neurons. The slow common oscillations in the discharge times of motor units due to these synaptic inputs are strongly correlated with the fluctuations in force during submaximal isometric contractions (force steadiness) and moderately associated with performance scores on some tests of motor function. However, there are key gaps in knowledge that limit the interpretation of differences in force steadiness.

Linking commonly used hand therapy outcome measures to individual areas of the International Classification of Functioning: A systematic review

STUDY DESIGN

Systematic review.

INTRODUCTION

Identifying outcome measures that correspond to the International Classification of Functioning (ICF) provides insight into selecting appropriate outcome tools in hand therapy practice.

PURPOSE OF THE STUDY

The objective of this study is to systematically review patient-reported outcome measures commonly used in hand therapy to determine the extent to which the content represents the biopsychosocial view of the ICF.

METHODS

A comprehensive literature search was conducted. Studies that met inclusion criteria were identified, and outcome measures were extracted. The meaningful concept was determined for each item on the measure and linked to the most specific ICF category. Summary linkage calculations were completed.

RESULTS

Eleven patient-reported outcomes were identified from 43 included studies. Activity and participation had the highest content coverage followed by body functions. There was linking to personal factors and not defined-disability and mental health. Environmental factors were not represented in any of the included outcome measures. The core set representation of unique codes ranged from 8.55% to 18.80% (mean: 11.97%) for the Comprehensive ICF Core Set for Hand Conditions and from 30.43% to 47.83% (mean: 31.40%) for the Brief ICF Core Set for Hand Conditions. The percent representation of the Comprehensive ICF Core Set for Hand Conditions for unique disability ranged from 21.62% to 43.24% (mean: 20.33%) and from 62.50% to 87.50% (mean: 72.22%) for the Brief ICF Core Set for Hand Conditions.

DISCUSSION

None of the included measures represent all categories of the ICF Core Sets for Hand Conditions.

CONCLUSION

Utilizing the most recent refinement rules for the linking process, this study provides comparisons of measures along with clarity of content coverage for the most commonly used tools in the practice of hand therapy.

Relevance of grasp types to assess functionality for personal autonomy

STUDY DESIGN

Cross-sectional research design.

INTRODUCTION

Current assessment of hand function is not focused on evaluating the real abilities required for autonomy.

PURPOSE OF THE STUDY

To quantify the relevance of grasp types for autonomy to guide hand recovery and its assessment.

METHODS

Representative tasks of the International Classification of Functioning, Disability and Health activities in which the hands are directly involved were recorded. The videos were analyzed to identify the grasps used with each hand, and their relevance for autonomy was determined by weighting time with the frequency of appearance of each activity in disability and dependency scales. Relevance is provided globally and distinguished by hand (right-left) and bimanual function. Significant differences in relevance are also checked.

RESULTS

The most relevant grasps are pad-to-pad pinch (31.9%), lumbrical (15.4%), cylindrical (12%), and special pinch (7.3%) together with the nonprehensile (18.6%) use of the hand. Lumbrical grasp has higher relevance for the left hand (19.9% vs 12%) while cylindrical grasp for the right hand (15.3% vs 7.7%). Relevancies are also different depending on bimanual function.

DISCUSSION

Different relative importance was obtained when considering dependency vs disability scales. Pad-to-pad pinch and nonprehensile grasp are the most relevant grasps for both hands, whereas lumbrical grasp is more relevant for the left hand and cylindrical grasp for the right one. The most significant difference in bimanual function refers to pad-to-pad pinch (more relevant for unimanual actions of the left hand and bimanual actions of the right).

CONCLUSIONS

The relative importance of each grasp type for autonomy and the differences observed between hand and bimanual action should be used in medical and physical decision-making.

LEVEL OF EVIDENCE

N/A.

Individuals with sacroiliac joint dysfunction display asymmetrical gait and a depressed synergy between muscles providing sacroiliac joint force closure when walking

Walking is often compromised in individuals with low back and hip disorders, such as sacroiliac joint dysfunction (SIJD). The disorder involves reduced coactivation of the gluteus maximus and contralateral latissimus dorsi, which together provide joint stability during walking. The purpose of our study was to compare the kinematics and contributions of selected muscles to identified synergies during walking between healthy individuals and those with SIJD. Six women with unilateral SIJD and six age-matched healthy controls walked on a force-measuring treadmill at 1 m/s while we recorded kinematics and the activity of 16 muscles with surface EMG. Non-negative matrix factorization was used to identify patterns of EMG activity (muscle synergies). Individuals with SIJD exhibited less hip extension and lower peak vertical ground reaction forces on the affected side than the unaffected side. In contrast to controls, the SIJD group also displayed a depressed muscle synergy between gluteus maximus on the affected side and the contralateral latissimus dorsi. The results indicate that individuals with SIJD exhibited both reduced activation of gluteus maximus during a loading synergy present in walking and greater asymmetry between legs when walking compared with age-matched controls.

Peg-manipulation capabilities of middle-aged adults have a greater influence on pegboard times than those of young and old adults

Declines in manual dexterity are frequently quantified as the time it takes to complete the grooved pegboard test. The test requires individuals to manipulate 25 pegs, one at a time, by removing them from a well and inserting them into a prescribed hole. The manipulation of each peg involves four phases: selection, transport, insertion, and return. The purpose of our study was to compare the times to complete the four phases of peg manipulation and the forces applied to the pegboard during peg insertion as young, middle-aged, and old adults performed the grooved pegboard test. The relative significance of the peg-manipulation attributes for 30 young (24.0 ± 4.4 years), 15 middle-aged (46.5 ± 6.5 years), and 15 old (70.4 ± 4.0 years) adults was assessed with a multiple-regression analysis. The grooved pegboard test was performed on a force plate. Pegboard times for the old adults (81 ± 17 s) were longer than those for young (56 ± 7 s) and middle-aged (58 ± 11 s) adults. Regression analysis indicated that the explanatory variables for the pegboard times of young (R² = 0.33) and middle-aged (R² = 0.78) adults were the times for the peg insertion and return phases, whereas the predictors for old adults (R² = 0.49) were the times for the peg selection and transport phases. The relative influence of peg-manipulation capabilities on a pegboard test of manual dexterity was greater for middle-aged adults than for young and old adults.

A Physical Model Suggests That Hip-Localized Balance Sense in Birds Improves State Estimation in Perching: Implications for Bipedal Robots

In addition to a vestibular system, birds uniquely have a balance-sensing organ within the pelvis, called the lumbosacral organ (LSO). The LSO is well developed in terrestrial birds, possibly to facilitate balance control in perching and terrestrial locomotion. No previous studies have quantified the functional benefits of the LSO for balance. We suggest two main benefits of hip-localized balance sense: reduced sensorimotor delay and improved estimation of foot-ground acceleration. We used system identification to test the hypothesis that hip-localized balance sense improves estimates of foot acceleration compared to a head-localized sense, due to closer proximity to the feet. We built a physical model of a standing guinea fowl perched on a platform, and used 3D accelerometers at the hip and head to replicate balance sense by the LSO and vestibular systems. The horizontal platform was attached to the end effector of a 6 DOF robotic arm, allowing us to apply perturbations to the platform analogous to motions of a compliant branch. We also compared state estimation between models with low and high neck stiffness. Cross-correlations revealed that foot-to-hip sensing delays were shorter than foot-to-head, as expected. We used multi-variable output error state-space (MOESP) system identification to estimate foot-ground acceleration as a function of hip- and head-localized sensing, individually and combined. Hip-localized sensors alone provided the best state estimates, which were not improved when fused with head-localized sensors. However, estimates from head-localized sensors improved with higher neck stiffness. Our findings support the hypothesis that hip-localized balance sense improves the speed and accuracy of foot state estimation compared to head-localized sense. The findings also suggest a role of neck muscles for active sensing for balance control: increased neck stiffness through muscle co-contraction can improve the utility of vestibular signals. Our engineering approach provides, to our knowledge, the first quantitative evidence for functional benefits of the LSO balance sense in birds. The findings support notions of control modularity in birds, with preferential vestibular sense for head stability and gaze, and LSO for body balance control,respectively. The findings also suggest advantages for distributed and active sensing for agile locomotion in compliant bipedal robots.

Validation of a constrained-time movement task for use in rehabilitation outcome measures

Current motor assessment tools can provide numerical indicators of performance but do not provide actionable information to target further improvement in rehabilitation interventions. Psychophysics-based outcome measures show promise to provide more useful information in the laboratory environment but have been limited in clinical implementation. Here we present a constrained-time task to assess paced and non-rhythmic movements. The task's output metrics include trial-by-trial adaptation rate and the just noticeable difference of a perturbation. We show that the task's metrics are reliable (i.e. high test-retest reliability) and are responsive to changes in feedback type and experience. We also discuss the task's versatility to be used for other types of movements including grasping. The consistent, sensitive and flexible time-constrained movement task we present provides a foundation from which to develop advanced outcome measures for prosthesis users and for other rehabilitation contexts.

Observational Evidence of the Association Between Handgrip Strength, Hand Dexterity, and Cognitive Performance in Community-Dwelling Older Adults: A Systematic Review

BACKGROUND

Deterioration of hand motor function is a possible risk factor of cognitive impairment in older adults. Despite a growing body of research, a lack of clarity exists regarding the relationships. This review offers a synthesis of existing observational studies evaluating the associations of handgrip strength and hand dexterity with cognitive performance in community-dwelling older adults.

METHODS

PubMed, PsycINFO, and ScienceDirect were systematically searched (search dates: 1990-2016), and relevant articles were cross-checked for related and relevant publications.

RESULTS

Twenty-two observational studies assessed the association of handgrip strength or hand dexterity with cognitive performance; none evaluated handgrip strength and hand dexterity together. Handgrip strength was associated with global cognition, mostly assessed using the Mini-Mental State Examination, cross-sectionally and longitudinally. Also, one cross-sectional and three longitudinal studies found an association with cognitive domains, such as language, memory, visuospatial ability, working memory, and processing speed. Hand dexterity was only assessed cross-sectionally in four studies. These studies found an association with cognitive domains, such as executive function.

CONCLUSIONS

Although handgrip strength was associated with cognitive performance, it is unclear which variable at baseline affects the other in the long-term. Cross-sectional studies indicate an association between hand dexterity and cognitive performance, yet longitudinal studies are needed to elucidate this association. The interaction effects of both decreased grip strength and hand dexterity on cognitive performance is still unclear; therefore, future studies will need to consider the interaction of the three variables cross-sectionally and longitudinally.

Manual Dexterity and Intralimb Coordination Assessment to Distinguish Different Levels of Impairment in Boccia Players with Cerebral Palsy

Background

Boccia is a paralympic sport played by athletes with severe neurological impairments affecting all four limbs. Impaired manual dexterity (MD) and intralimb coordination (ILC) may limit individuals’ ability to perform certain activities such as grasping, releasing, or manipulating objects, which are essential tasks for daily life or to participate in para sports such as boccia. However, there are currently no specific instruments available to assess hand–arm coordination in boccia players with severe cerebral palsy (CP).

Purpose

To design new sport-specific coordination tests to assess impaired MD and ILC in boccia players; afterward, quantify to what extent their coordination is impaired compared to a control group (CG) without neurological impairments.

Methods

Seventy-three recreational boccia players with severe CP (BC1: age = 34.01 ± 16.43 years; BC2: age = 33.97 ± 14.29 years), and 19 healthy adults (age = 27.89 ± 7.08 years) completed the test battery. The Box and Block test (BBT) and Box and Ball test (BBLT) were used to assess MD and four tapping tests to assess upper ILC.

Results

Both MD tests were able to discriminate between sport classes. Boccia players obtained better scores in the BBLT in comparison to the BBT, showing that the BBLT had more appropriate testing features. On the other hand, only one of the ILC tests was able to discriminate between sport classes, displaying the highest practical significance (d = −1.12). Participants with CP scored significantly worse in all the coordination tests compared to the CG.

Conclusion

Using sport-specific equipment facilitated grasp function during the MD assessment. Regarding the ILC, the type of movement (continuous vs. discrete) seems to be more relevant for classification than the movement direction (vertical vs. horizontal) or the presence of a ball.

A framework for identifying the adaptations responsible for differences in pegboard times between middle-aged and older adults

Time to complete two tests of manual dexterity, the 9-hole Peg Test and Grooved Pegboard Test, increases with advancing age. However, the adaptations responsible for the differences in pegboard times between middle-aged and older adults are largely unknown. Potential mechanisms include neuromuscular characteristics, cognitive function, and cutaneous sensation. To provide a tractable framework to address these gaps in knowledge, the purpose of the current study was to identify the latent variables underlying age-associated differences in time to complete the 9-hole and grooved pegboard tests. The approach involved an independent component analysis that identified associations between the two pegboard times for the two groups of participants with two to six secondary outcomes. The common association across three of the four conditions (two groups and two pegboard tests) was features derived from force-matching tasks requiring submaximal isometric contraction. In addition, there were significant associations for older adults between age, measures of cognitive function, and pegboard times. Nonetheless, the significant associations were unique for each age group and pegboard test. The results provide a framework for subsequent mechanistic studies to identify the adaptations underlying age-associated declines in manual dexterity.

On neuromechanical approaches for the study of biological and robotic grasp and manipulation

Biological and robotic grasp and manipulation are undeniably similar at the level of mechanical task performance. However, their underlying fundamental biological vs. engineering mechanisms are, by definition, dramatically different and can even be antithetical. Even our approach to each is diametrically opposite: inductive science for the study of biological systems vs. engineering synthesis for the design and construction of robotic systems. The past 20 years have seen several conceptual advances in both fields and the quest to unify them. Chief among them is the reluctant recognition that their underlying fundamental mechanisms may actually share limited common ground, while exhibiting many fundamental differences. This recognition is particularly liberating because it allows us to resolve and move beyond multiple paradoxes and contradictions that arose from the initial reasonable assumption of a large common ground. Here, we begin by introducing the perspective of neuromechanics, which emphasizes that real-world behavior emerges from the intimate interactions among the physical structure of the system, the mechanical requirements of a task, the feasible neural control actions to produce it, and the ability of the neuromuscular system to adapt through interactions with the environment. This allows us to articulate a succinct overview of a few salient conceptual paradoxes and contradictions regarding under-determined vs. over-determined mechanics, under- vs. over-actuated control, prescribed vs. emergent function, learning vs. implementation vs. adaptation, prescriptive vs. descriptive synergies, and optimal vs. habitual performance. We conclude by presenting open questions and suggesting directions for future research. We hope this frank and open-minded assessment of the state-of-the-art will encourage and guide these communities to continue to interact and make progress in these important areas at the interface of neuromechanics, neuroscience, rehabilitation and robotics.

Unilateral Eccentric Contraction of the Plantarflexors Leads to Bilateral Alterations in Leg Dexterity

Eccentric contractions can affect musculotendon mechanical properties and disrupt muscle proprioception, but their behavioral consequences are poorly understood. We tested whether repeated eccentric contractions of plantarflexor muscles of one leg affected the dexterity of either leg. Twenty healthy male subjects (27.3 ± 4.0 yrs) compressed a compliant and slender spring prone to buckling with each isolated leg. The maximal instability they could control (i.e., the maximal average sustained compression force, or lower extremity dexterity force, LED_force) quantified the dexterity of each leg. We found that eccentric contractions did not affect LED_force, but reduced force variability (LED_SD). Surprisingly, LED_force increased in the non-exposed, contralateral leg. These effects were specific to exposure to eccentric contractions because an effort-matched exposure to walking did not affect leg dexterity. In the exposed leg, eccentric contractions (i) reduced voluntary error corrections during spring compressions (i.e., reduced 0.5–4 Hz power of LED_force); (ii) did not change spinal excitability (i.e., unaffected H-reflexes); and (iii) changed the structure of the neural drive to the α-motoneuron pool (i.e., reduced EMG power within the 4–8 Hz physiological tremor band). These results suggest that repeated eccentric contractions alter the feedback control for dexterity in the exposed leg by reducing muscle spindle sensitivity. Moreover, the unexpected improvement in LED_force in the non-exposed contralateral leg was likely a consequence of crossed-effects on its spinal and supraspinal feedback control. We discuss the implications of these bilateral effects of unilateral eccentric contractions, their effect on spinal and supraspinal control of dynamic foot-ground interactions, and their potential to facilitate rehabilitation from musculoskeletal and neuromotor impairments.

Robot-assisted and conventional therapies produce distinct rehabilitative trends in stroke survivors

Background

Comparing the efficacy of alternative therapeutic strategies for the rehabilitation of motor function in chronically impaired individuals is often inconclusive. For example, a recent randomized clinical trial (RCT) compared robot-assisted vs. conventional therapy in 77 patients who had had chronic motor impairment after a cerebrovascular accident. While patients assigned to robotic therapy had greater improvements in the primary outcome measure (change in score on the upper extremity section of the Fugl-Meyer assessment), the absolute difference between therapies was small, which left the clinical relevance in question.

Methods

Here we revisit that study to test whether the multidimensional rehabilitative response of these patients can better distinguish between treatment outcomes. We used principal components analysis to find the correlation of changes across seven outcome measures between the start and end of 8 weeks of therapy. Permutation tests verified the robustness of the principal components found.

Results

Each therapy in fact produces different rehabilitative trends of recovery across the clinical, functional, and quality of life domains. A rehabilitative trend is a principal component that quantifies the correlations among changes in outcomes with each therapy.

Conclusions

These findings challenge the traditional emphasis of RCTs on using a single primary outcome measure to compare rehabilitative responses that are naturally multidimensional. This alternative approach to, and interpretation of, the results of RCTs may will lead to more effective therapies targeted for the multidimensional mechanisms of recovery.

Trial registration

ClinicalTrials.gov number NCT00719433. Registered July 17, 2008.

Electronic supplementary material

The online version of this article (doi:10.1186/s12984-016-0199-5) contains supplementary material, which is available to authorized users.

Force steadiness as a predictor of time to complete a pegboard test of dexterity in young men and women

The purpose of the study was to evaluate the capacity of an expanded set of force steadiness tasks to explain the variance in the time it takes young men and women to complete the grooved pegboard test. In a single experimental session, 30 participants (mean ± SD) (24.2 ± 4.0 yr; 15 women) performed the grooved pegboard test, two tests of hand speed, measurements of muscle strength, and a set of submaximal, steady contractions. The steadiness tasks involved single and double actions requiring isometric contractions in the directions of wrist extension, a pinch between the index finger and thumb, and index finger abduction. Time to complete the grooved pegboard test ranged from 41.5 to 67.5 s. The pegboard times (53.9 ± 6.2 s) were not correlated with any of the strength measurements or the reaction time test of hand speed. A stepwise, multiple-regression analysis indicated that much of the variance (R(2) = 0.70) in pegboard times could be explained by a model that comprised two predictor variables derived from the steadiness tasks: time to match the target during a rapid force-matching task and force steadiness (coefficient of variation for force) during a single-action task. Moreover, the pegboard times were significantly faster for women (51.7 ± 6.8 s) than men (56.1 ± 4.9 s). Participants with slower pegboard times seemed to place a greater emphasis on accuracy than speed as they had longer times to match the target during the rapid force-matching task and exhibited superior force steadiness during the single-action task.

Strength, Multijoint Coordination, and Sensorimotor Processing Are Independent Contributors to Overall Balance Ability

For young adults, balance is essential for participation in physical activities but is often disrupted following lower extremity injury. Clinical outcome measures such as single limb balance (SLB), Y-balance (YBT), and the single limb hop and balance (SLHB) tests are commonly used to quantify balance ability following injury. Given the varying demands across tasks, it is likely that such outcome measures provide useful, although task-specific, information. But the extent to which they are independent and contribute to understanding the multiple contributors to balance is not clear. Therefore, the purpose of this study was to investigate the associations among these measures as they relate to the different contributors to balance. Thirty-seven recreationally active young adults completed measures including Vertical Jump, YBT, SLB, SLHB, and the new Lower Extremity Dexterity test. Principal components analysis revealed that these outcome measures could be thought of as quantifying the strength, multijoint coordination, and sensorimotor processing contributors to balance. Our results challenge the practice of using a single outcome measure to quantify the naturally multidimensional mechanisms for everyday functions such as balance. This multidimensional approach to, and interpretation of, multiple contributors to balance may lead to more effective, specialized training and rehabilitation regimens.

Force Variability during Dexterous Manipulation in Individuals with Mild to Moderate Parkinson's Disease

Parkinson’s disease (PD) is a progressive neurodegenerative disease affecting about 1–2% of the population over the age of 65. Individuals with PD experience gradual deterioration of dexterous manipulation for activities of daily living; however, current clinical evaluations are mostly subjective and do not quantify changes in dynamic control of fingertip force that is critical for manual dexterity. Thus, there is a need to develop clinical measures to quantify those changes with aging and disease progression. We investigated the dynamic control of fingertip forces in both hands of 20 individuals with PD (69.0 ± 7.4 years) using the Strength–Dexterity test. The test requires low forces (<3 N) to compress a compliant and slender spring prone to buckling. A maximal level of sustained compression is informative of the greatest instability the person can control, and thus is indicative of the integrity of the neuromuscular system for dexterous manipulation. Miniature sensors recorded fingertip force (F) during maximal sustained compressions. The force variability during sustained compression was quantified in two frequency bands: low (<4 Hz, F_LF) and high (4–12 Hz, F_HF). F_LF characterizes variability in voluntary fluctuations, while F_HF characterizes variability in involuntary fluctuations including tremor. The more-affected hand exhibited significantly lower F and lower F_LF than those in the less-affected hand. The more-affected hand showed significant negative correlations between F_LF and the Unified Parkinson’s Disease Rating Scale motor scores for both total and hand-only, suggesting that greater force variability in the voluntary range was associated with less clinical motor impairment. We conclude the nature of force variability in the voluntary range during this dynamic and dexterous task may be a biomarker of greater motor capability/flexibility/adaptability in PD. This approach may provide a more quantitative clinical assessment of changes of sensorimotor control in individuals with PD.