Wrist flexion and extension torques measured by highly sensitive dynamometer in healthy subjects from 5 to 80 years

Low-Cost Dynamometer for Measuring and Regulating Wrist Extension and Flexion Motor Tasks in Electroencephalography Experiments

A brain-computer interface could control a bionic hand by interpreting electroencephalographic (EEG) signals associated with wrist extension (WE) and wrist flexion (WF) movements. Misinterpretations of the EEG may stem from variations in the force, speed and range of these movements. To address this, we designed, constructed and tested a novel dynamometer, the IsoReg, which regulates WE and WF movements during EEG recording experiments. The IsoReg restricts hand movements to isometric WE and WF, controlling their speed and range of motion. It measures movement force using a dual-load cell system that calculates the percentage of maximum voluntary contraction and displays it to help users control movement force. Linearity and measurement accuracy were tested, and the IsoReg's performance was evaluated under typical EEG experimental conditions with 14 participants. The IsoReg demonstrated consistent linearity between applied and measured forces across the required force range, with a mean accuracy of 97% across all participants. The visual force gauge provided normalised force measurements with a mean accuracy exceeding 98.66% across all participants. All participants successfully controlled the motor tasks at the correct relative forces (with a mean accuracy of 89.90%) using the IsoReg, eliminating the impact of inherent force differences between typical WE and WF movements on the EEG analysis. The IsoReg offers a low-cost method for measuring and regulating movements in future neuromuscular studies, potentially leading to improved neural signal interpretation.

Comparison of strength profile representations using musculoskeletal models and their applications in robotics

Musculoskeletal models provide an approach towards simulating the ability of the human body in a variety of human-robot applications. A promising use for musculoskeletal models is to model the physical capabilities of the human body, for example, estimating the strength at the hand. Several methods of modelling and representing human strength with musculoskeletal models have been used in ergonomic analysis, human-robot interaction and robotic assistance. However, it is currently unclear which methods best suit modelling and representing limb strength. This paper compares existing methods for calculating and representing the strength of the upper limb using musculoskeletal models. It then details the differences and relative advantages of the existing methods, enabling the discussion on the appropriateness of each method for particular applications.

Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations

ABSTRACT

Nuzzo, JL. Narrative review of sex differences in muscle strength, endurance, activation, size, fiber type, and strength training participation rates, preferences, motivations, injuries, and neuromuscular adaptations. J Strength Cond Res 37(2): 494-536, 2023-Biological sex and its relation with exercise participation and sports performance continue to be discussed. Here, the purpose was to inform such discussions by summarizing the literature on sex differences in numerous strength training-related variables and outcomes-muscle strength and endurance, muscle mass and size, muscle fiber type, muscle twitch forces, and voluntary activation; strength training participation rates, motivations, preferences, and practices; and injuries and changes in muscle size and strength with strength training. Male subjects become notably stronger than female subjects around age 15 years. In adults, sex differences in strength are more pronounced in upper-body than lower-body muscles and in concentric than eccentric contractions. Greater male than female strength is not because of higher voluntary activation but to greater muscle mass and type II fiber areas. Men participate in strength training more frequently than women. Men are motivated more by challenge, competition, social recognition, and a desire to increase muscle size and strength. Men also have greater preference for competitive, high-intensity, and upper-body exercise. Women are motivated more by improved attractiveness, muscle "toning," and body mass management. Women have greater preference for supervised and lower-body exercise. Intrasexual competition, mate selection, and the drive for muscularity are likely fundamental causes of exercise behaviors in men and women. Men and women increase muscle size and strength after weeks of strength training, but women experience greater relative strength improvements depending on age and muscle group. Men exhibit higher strength training injury rates. No sex difference exists in strength loss and muscle soreness after muscle-damaging exercise.

Sex differences in wrist torque and endurance-Biomechanical factors associated with developing lateral epicondylitis of the humerus

Since eccentric contractions contribute to the development of tendinopathy, sex differences in wrist torque and endurance may be involved in the pathophysiology of lateral epicondylitis and its refractoriness. Therefore, the present study investigated sex differences in wrist torque and endurance. The wrist extension and flexion torques of the 100 wrists of 25 males and 25 females were measured. The following parameters were assessed: muscle strength at the starting- and end point for the measurement, Δ muscle strength, that is, the amount of a loss over time, and the muscle endurance ratio, that is, the decrease rate over time. Each parameter in males and females was statistically analyzed. In wrist extension, muscle strength at the starting point was 6.1 Nm for males and 3.3 Nm for females (p < 0.001); Δ Muscle strength was -0.052 Nm/s for males and -0.038 Nm/s for females (p = 0.036); The muscle endurance ratio was 99.1%/s for males and 98.8%/s for females (p = 0.015). In wrist flexion, muscle strength at the starting point and absolute value of Δ muscle strength were significantly larger in males than in females; No significant difference was observed in the muscle endurance ratio in wrist flexion between males and females. These results revealed sex differences in wrist torque and endurance. The muscle endurance ratio of the wrist extensors was lower in females than in males, which suggests that females need to exert more effort to maintain the wrist extension position under resistance. This may predispose the wrist extensor muscles in females to eccentric contractions.

Does Trans-radial Longitudinal Compression Influence Myoelectric Control?

BACKGROUND

Existing trans-radial prosthetic socket designs are not optimised to facilitate reliable myoelectric control. Many socket designs pre-date the introduction of myoelectric devices. However, socket designs featuring improved biomechanical stability, notably longitudinal compression sockets, have emerged in more recent years. Neither the subsequent effects, if any, of stabilising the limb on myoelectric control nor in which arrangement to apply the compression have been reported.

METHODOLOGY

Twelve able-bodied participants completed two tasks whilst wearing a longitudinal compression socket simulator in three different configurations: 1) compressed, where the compression strut was placed on top of the muscle of interest, 2) relief, where the compression struts were placed either side of the muscle being recorded and 3) uncompressed, with no external compression. The tasks were 1) a single-channel myoelectric target tracking exercise, followed by 2), a high-intensity grasping task. The wearers' accuracy during the tracking task, the pressure at opposing sides of the simulator during contractions and the rate at which the limb fatigued were observed.

FINDINGS

No significant difference between the tracking-task accuracy scores or rate of fatigue was observed for the different compression configurations. Pressure recordings from the compressed configuration showed that pressure was maintained at opposing sides of the simulator during muscle contractions.

CONCLUSION

Longitudinal compression does not inhibit single-channel EMG control, nor improve fatigue performance. Longitudinal compression sockets have the potential to improve the reliability of multi-channel EMG control due to the maintenance of pressure during muscle contractions.

Design of a compliant, stabilizing wrist mechanism for a pediatric hand exoskeleton

Children affected by hand impairment due to cerebral palsy or stroke experience serious difficulties when performing activities of daily life (ADL), which reduces their quality of life and development. Wearable robots such as hand exoskeletons have been proposed to support people with hand impairment in therapy as well as daily tasks. While numerous actuated wearable robots have been developed, few designs support both fingers and wrist function, despite being mutually relevant for reach-to-grasp tasks. A recent feasibility study investigating the use of PEXO, a lightweight and fully wearable pediatric hand exoskeleton, showed that a wrist fixed in a slightly extended position may limit the user's ability to reach and grasp during ADL and restrict the user group. These insights and further interactions with clinicians inspired a novel design of PEXO that features an additional degree of freedom in the wrist. In this paper, we present a compliant wrist mechanism extending the existing leaf spring finger mechanism of the device. The novel design provides both wrist motion capability of 60° in flexion and extension and wrist stabilization at the same time while actively supporting finger motion. Preliminary results suggest that the adjustability in the wrist enables a larger variety of grasping gestures. The implemented wrist support has the potential to allow for a more versatile use of PEXO and increase the potential target user group.

Anthropometrics and electromyography as predictors for maximal voluntary isometric wrist torque: Considerations for ergonomists

The purpose of this study was to evaluate anthropometry and forearm muscle activity as predictors of maximal isometric wrist torque. Thirteen anthropometric measures, forearm electromyography from flexor carpi radialis (FCR) and extensor carpi radialis (ECR), and maximal isometric wrist flexion/extension torque were obtained from 25 male participants. Pearson correlation coefficients assessed relationships between peak isometric torque and: (1) anthropometrics, (2) FCR and ECR activation, (3) FCR/ECR antagonist/agonist coactivation ratios. Based on significant correlations, linear regression equations were developed (SPSS v.25; p < 0.05). Hand thickness, forearm circumference and ECR activation or hand thickness, elbow circumference, FCR activation and body weight were most highly correlated with extension or flexion torque, respectively. Hand thickness, forearm circumference, and ECR activation (R² = 54.5%; p = 0.001) and hand thickness, elbow circumference, FCR activation (R² = 68.3%; p < 0.001) explained similar variance in torque regressions as did the addition of body weight to extension (R² = 58.0%; p = 0.001) and flexion (R² = 69.9%; p < 0.001) torque regression equations, respectively. Circumference measurements, a pseudo for muscle size, and activation amplitude influenced wrist force output more than limb length or coactivation.

Voluntary and magnetically evoked muscle contraction protocol in males with Duchenne muscular dystrophy: Safety, feasibility, reliability, and validity

INTRODUCTION/AIMS

Clinical trials addressing treatments for Duchenne muscular dystrophy (DMD) require reliable and valid measurement of muscle contractile function across all disease severity levels. In this work we aimed to evaluate a protocol combining voluntary and evoked contractions to measure strength and excitability of wrist extensor muscles for safety, feasibility, reliability, and discriminant validity between males with DMD and controls.

METHODS

Wrist extensor muscle strength and excitability were assessed in males with DMD (N = 10; mean ± standard deviation: 15.4 ± 5.9 years of age), using the Brooke Upper Extremity Rating Scale (scored 1-6), and age-matched healthy male controls (N = 15; 15.5 ± 5.0 years of age). Torque and electromyographic (EMG) measurements were analyzed under maximum voluntary and stimulated conditions at two visits.

RESULTS

A protocol of multiple maximal voluntary contractions (MVCs) and evoked twitch contractions was feasible and safe, with 96% of the participants completing the protocol and having a less than 7% strength decrement on either measure for both DMD patients and controls (P ≥ .074). Reliability was excellent for voluntary and evoked measurements of torque and EMG (intraclass correlation coefficient [ICC] over 0.90 and over 0.85 within and between visits, respectively). Torque, EMG, and timing of twitch-onset measurements discriminated between DMD and controls (P < .001). Twitch contraction time did not differ significantly between groups (P = .10).

DISCUSSION

Findings from this study show that the protocol is a safe, feasible, reliable, and a valid method to measure strength and excitability of wrist extensors in males with DMD.

Development of new outcome measures for adult SMA type III and IV: a multimodal longitudinal study

OBJECTIVE

The aim of this study was the comprehensive characterisation of longitudinal clinical, electrophysiological and neuroimaging measures in type III and IV adult spinal muscular atrophy (SMA) with a view to propose objective monitoring markers for future clinical trials.

METHODS

Fourteen type III or IV SMA patients underwent standardised assessments including muscle strength testing, functional evaluation (SMAFRS and MFM), MUNIX (abductor pollicis brevis, APB; abductor digiti minimi, ADM; deltoid; tibialis anterior, TA; trapezius) and quantitative cervical spinal cord MRI to appraise segmental grey and white matter atrophy. Patients underwent a follow-up assessment with the same protocol 24 months later. Longitudinal comparisons were conducted using the Wilcoxon-test for matched data. Responsiveness was estimated using standardized response means (SRM) and a composite score was generated based on the three most significant variables.

RESULTS

Significant functional decline was observed based on SMAFRS (p = 0.019), pinch and knee flexion strength (p = 0.030 and 0.027), MUNIX and MUSIX value in the ADM (p = 0.0006 and 0.043) and in TA muscle (p = 0.025). No significant differences were observed based on cervical MRI measures. A significant reduction was detected in the composite score (p = 0.0005, SRM = -1.52), which was the most responsive variable and required a smaller number of patients than single variables in the estimation of sample size for clinical trials.

CONCLUSIONS

Quantitative strength testing, SMAFRS and MUNIX readily capture disease progression in adult SMA patients. Composite multimodal scores increase predictive value and may reduce sample size requirements in clinical trials.

Contraction Phase and Force Differentially Change Motor Evoked Potential Recruitment Slope and Interhemispheric Inhibition in Young Versus Old

Interhemispheric interactions are important for arm coordination and hemispheric specialization. Unilateral voluntary static contraction is known to increase bilateral corticospinal motor evoked potential (MEP) amplitude. It is unknown how increasing and decreasing contraction affect the opposite limb. Since dynamic muscle contraction is more ecologically relevant to daily activities, we studied MEP recruitment using a novel method and short interval interhemispheric inhibition (IHI) from active to resting hemisphere at 4 phases of contralateral ECR contraction: Rest, Ramp Up [increasing at 25% of maximum voluntary contraction (MVC)], Execution (tonic at 50% MVC), and Ramp Down (relaxation at 25% MVC) in 42 healthy adults. We analyzed the linear portion of resting extensor carpi radialis (ECR) MEP recruitment by stimulating at multiple intensities and comparing slopes, expressed as mV per TMS stimulation level, via linear mixed modeling. In younger participants (age ≤ 30), resting ECR MEP recruitment slopes were significantly and equally larger both at Ramp Up (slope increase = 0.047, p < 0.001) and Ramp Down (slope increase = 0.031, p < 0.001) compared to rest, despite opposite directions of force change. In contrast, Active ECR MEP recruitment slopes were larger in Ramp Down than all other phases (Rest:0.184, p < 0.001; Ramp Up:0.128, p = 0.001; Execution: p = 0.003). Older (age ≥ 60) participants’ resting MEP recruitment slope was higher than younger participants across all phases. IHI did not reduce MEP recruitment slope equally in old compared to young. In conclusion, our data indicate that MEP recruitment slope in the resting limb is affected by the homologous active limb contraction force, irrespective of the direction of force change. The active arm MEP recruitment slope, in contrast, remains relatively unaffected. Older participants had steeper MEP recruitment slopes and less interhemispheric inhibition compared to younger participants.

Effect of Age and Body Size on the Wrist's Viscoelasticity in Healthy Participants From 3 to 90 Years Old and Reliability Assessment

Excessive or insufficient levels of passive musculoarticular stiffness (PMAS) can lead to joint impairment or instability. Quantifying the PMAS may provide a better understanding of neurological or musculoskeletal disorders. The aims of the present study were multiple: first, to assess the reliability of quantifying PMAS and to collect normative data on the wrist in healthy participants, and second, to assess the effect of age and body size on PMAS. For this purpose, a total of 458 participants from 3 to 90 years old were analyzed with an electromechanical oscillation device (EOD). Passive sinusoidal movements were induced in a flexion/extension pattern in the participants' wrists, enabling an objective measurement of elastic stiffness (EL) and viscous stiffness (VI). Both the dominant and non-dominant wrists were assessed. Two-way repeated-measures ANOVA revealed a sex differentiation from puberty (12-18 years old) and an increase of EL and VI from childhood to adulthood and a decrease of stiffness at old age. EL and VI values were associated with body size characteristics and age. After body size normalization, EL was no longer influenced by the variables measured. On the other hand, VI remained moderately influenced by age and body size. The current study was able to provide normative data of PMAS in the wrist of healthy participants.

Test-Retest Reliability of Isokinetic Wrist Strength and Proprioception Measurements

CONTEXT

The evaluation of the wrist strength and proprioception gives clinicians and researchers information about effectiveness of their rehabilitation protocol or helps diagnosis of various neuromuscular and somatosensorial disorders. Isokinetic dynamometers are considered the gold standard for these evaluations. However, the studies about test-retest reliability of isokinetic dynamometer are inadequate.

OBJECTIVE

The purpose of this study was to determine the test-retest reliability of isokinetic wrist strength and proprioception measurements using the Cybex isokinetic dynamometer.

DESIGN

Test-retest reliability study.

SETTING

University laboratory.

PARTICIPANTS

Thirty participants were enrolled (age 23.2 [2.8] y, height 171.1 [7] cm, weight 66.6 [11.6] kg) in this study.

INTERVENTION

Cybex isokinetic dynamometer was used for strength and proprioception measurements.

MAIN OUTCOME MEASURES

Concentric flexion-extension strength test was performed at 90°/s angular velocity, and eccentric flexion-extension strength test was performed at 60°/s angular velocity. The proprioception of the wrist was assessed via active joint position sense. The 30° extension of the wrist, which is accepted as the functional position of the wrist, was selected as the targeted angle. The intraclass correlation coefficient (ICC2,1) method was used for test-retest analysis (P < .05).

RESULTS

The active joint position sense measurements of dominant (ICC2,1: .821) and nondominant (ICC2,1: .763) sides were found to have good test-retest reliability. Furthermore, with the exception of dominant eccentric extension strength (moderate reliability) (ICC2,1: .733), eccentric and concentric flexion (dominant: ICC2,1 = .890-.844; nondominant: ICC2,1 = .800-.898, respectively), and extension (dominant: ICC2,1 = .791 [concentric], nondominant: ICC2,1 = .791-.818, respectively) strength measurements of both sides were found to have good reliability.

CONCLUSIONS

This study shows that the Cybex isokinetic dynamometer is a reliable method for measuring wrist strength and proprioception. Isokinetic dynamometers can be used clinically for diagnosis or rehabilitation in studies which contain wrist proprioception or strength measurements.

A suite of automated tools to quantify hand and wrist motor function after cervical spinal cord injury

BACKGROUND

Cervical spinal cord injury (cSCI) often causes chronic upper extremity disability. Reliable measurement of arm function is critical for development of therapies to improve recovery after cSCI. In this study, we report a suite of automated rehabilitative tools to allow simple, quantitative assessment of hand and wrist motor function.

METHODS

We measured range of motion and force production using these devices in cSCI participants with a range of upper limb disability and in neurologically intact participants at two time points separated by approximately 4 months. Additionally, we determined whether measures collected with the rehabilitative tools correlated with standard upper limb assessments, including the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) and the Jebsen Hand Function Test (JHFT).

RESULTS

We find that the rehabilitative devices are useful to provide assessment of upper limb function in physical units over time in SCI participants and are well-correlated with standard assessments.

CONCLUSIONS

These results indicate that these tools represent a reliable system for longitudinal evaluation of upper extremity function after cSCI and may provide a framework to assess the efficacy of strategies aimed at improving recovery of upper limb function.

Interlimb transfer and generalisation of learning in the context of persistent failure to accomplish a visuomotor task

Transfer, in which capability acquired in one situation influences performance in another is considered, along with retention, as demonstrative of effectual learning. In this regard, interlimb transfer of functional capacity has commanded particular attention as a means of gauging the generalisation of acquired capability. Both theoretical treatments and prior empirical studies suggest that the successful accomplishment of a physical training regime is required to bring about generalised changes that extend to the untrained limb. In the present study, we pose the following question: Does interlimb transfer occur if and only if the training movements are executed? We report findings from JG-an individual recruited to a larger scale trial, who presented with (unilateral) deficits of motor control. We examined whether changes in the performance of the untrained right limb arose following practice undertaken by the impaired left limb, wherein the majority of JG's attempts to execute the training task were unsuccessful. Comparison was made with a group of "control" participants drawn from the main trial, who did not practice the task. For JG, substantial gains in the performance of the untrained limb (registered 3 days, 10 days and 1 year following training) indicated that effective learning had occurred. Learning was, however, expressed principally when the unimpaired (i.e. untrained) limb was utilised to perform the task. When the impaired limb was used, marked deficiencies in movement execution remained prominent throughout.

The motor unit number index (MUNIX) profile of patients with adult spinal muscular atrophy

OBJECTIVE

Objective of this study is the comprehensive characterisation of motor unit (MU) loss in type III and IV Spinal Muscular Atrophy (SMA) using motor unit number index (MUNIX), and evaluation of compensatory mechanisms based on MU size indices (MUSIX).

METHODS

Nineteen type III and IV SMA patients and 16 gender- and age-matched healthy controls were recruited. Neuromuscular performance was evaluated by muscle strength testing and functional scales. Compound motor action potential (CMAP), MUNIX and MUSIX were studied in the abductor pollicis brevis (APB), abductor digiti minimi (ADM), deltoid, tibialis anterior and trapezius muscles. A composite MUNIX score was also calculated.

RESULTS

SMA patients exhibited significantly reduced MUNIX values (p < 0.05) in all muscles, while MUSIX was increased, suggesting active re-innervation. Significant correlations were identified between MUNIX/MUSIX and muscle strength. Similarly, composite MUNIX scores correlated with disability scores. Interestingly, in SMA patients MUNIX was much lower in the ADM than in the ABP, a pattern which is distinctly different from that observed in Amyotrophic Lateral Sclerosis.

CONCLUSIONS

MUNIX is a sensitive measure of MU loss in adult forms of SMA and correlates with disability.

SIGNIFICANCE

MUNIX evaluation is a promising candidate biomarker for longitudinal studies and pharmacological trials in adult SMA patients.

Reference values for muscle strength: a systematic review with a descriptive meta-analysis

BACKGROUND

Muscle strength is an important component of health.

OBJECTIVE

To describe and evaluate the studies which have established the reference values for muscle strength on healthy individuals and to synthesize these values with a descriptive meta-analysis approach.

METHODS

A systematic review was performed in MEDLINE, LILACS, and SciELO databases. Studies that investigated the reference values for muscle strength of two or more appendicular/axial muscle groups of health individuals were included. Methodological quality, including risk of bias was assessed by the QUADAS-2. Data extracted included: country of the study, sample size, population characteristics, equipment/method used, and muscle groups evaluated.

RESULTS

Of the 414 studies identified, 46 were included. Most of the studies had adequate methodological quality. Included studies evaluated: appendicular (80.4%) and axial (36.9%) muscles; adults (78.3%), elderly (58.7%), adolescents (43.5%), children (23.9%); isometric (91.3%) and isokinetic (17.4%) strength. Six studies (13%) with similar procedures were synthesized with meta-analysis. Generally, the coefficient of variation values that resulted from the meta-analysis ranged from 20.1% to 30% and were similar to those reported by the original studies. The meta-analysis synthesized the reference values of isometric strength of 14 muscle groups of the dominant/non-dominant sides of the upper/lower limbs of adults/elderly from developed countries, using dynamometers/myometer.

CONCLUSIONS

Most of the included studies had adequate methodological quality. The meta-analysis provided reference values for the isometric strength of 14 appendicular muscle groups of the dominant/non-dominant sides, measured with dynamometers/myometers, of men/women, of adults/elderly. These data may be used to interpret the results of the evaluations and establish appropriate treatment goals.

Neuromechanical Simulation of Hand Pronation and Supination Task in Parkinson's disease

Parkinson's disease is a prevalent and debilitating neurological disorder, where the severity of motor symptoms are frequently monitored using clinical tests that include a hand pronation and supination task. Objective quantification of motor symptoms in persons with Parkinson's disease and detection of dopamine-induced dyskinesias during treatment is important for the management of the most common symptoms in persons with Parkinson's disease. Thus, the development of a neuromechanical model of rhythmic hand pronation and supination may further our understanding of the mechanisms underlying motor symptoms during rhythmic upper extremity tasks in persons with Parkinson's disease. The aim of this study was to create a model for a rhythmic hand pronation and supination task. This was done to create a simulation of a popular diagnostic task used in determining the severity of motor impairments in persons with Parkinson's disease. It is imperative to understand the neural dynamics as well as the physiological constraints placed on a system such as this in both the creation of a usable model as well as understanding the neuromechanical interactions occurring during this diagnostic task. This model of either normal or slowed, clinical behavior, can then serve as a springboard for the creation of models that characterize disordered motor movement and perhaps even the creation of models that could be incorporated into the diagnostic process.

Skeletal Muscle Quantitative Nuclear Magnetic Resonance Imaging and Spectroscopy as an Outcome Measure for Clinical Trials

Recent years have seen tremendous progress towards therapy of many previously incurable neuromuscular diseases. This new context has acted as a driving force for the development of novel non-invasive outcome measures. These can be organized in three main categories: functional tools, fluid biomarkers and imagery. In the latest category, nuclear magnetic resonance imaging (NMRI) offers a considerable range of possibilities for the characterization of skeletal muscle composition, function and metabolism. Nowadays, three NMR outcome measures are frequently integrated in clinical research protocols. They are: 1/ the muscle cross sectional area or volume, 2/ the percentage of intramuscular fat and 3/ the muscle water T2, which quantity muscle trophicity, chronic fatty degenerative changes and oedema (or more broadly, “disease activity”), respectively. A fourth biomarker, the contractile tissue volume is easily derived from the first two ones. The fat fraction maps most often acquired with Dixon sequences have proven their capability to detect small changes in muscle composition and have repeatedly shown superior sensitivity over standard functional evaluation. This outcome measure will more than likely be the first of the series to be validated as an endpoint by regulatory agencies. The versatility of contrast generated by NMR has opened many additional possibilities for characterization of the skeletal muscle and will result in the proposal of more NMR biomarkers. Ultra-short TE (UTE) sequences, late gadolinium enhancement and NMR elastography are being investigated as candidates to evaluate skeletal muscle interstitial fibrosis. Many options exist to measure muscle perfusion and oxygenation by NMR. Diffusion NMR as well as texture analysis algorithms could generate complementary information on muscle organization at microscopic and mesoscopic scales, respectively. ³¹P NMR spectroscopy is the reference technique to assess muscle energetics non-invasively during and after exercise. In dystrophic muscle, ³¹P NMR spectrum at rest is profoundly perturbed, and several resonances inform on cell membrane integrity. Considerable efforts are being directed towards acceleration of image acquisitions using a variety of approaches, from the extraction of fat content and water T2 maps from one single acquisition to partial matrices acquisition schemes. Spectacular decreases in examination time are expected in the near future. They will reinforce the attractiveness of NMR outcome measures and will further facilitate their integration in clinical research trials.

Robot-assisted mirroring exercise as a physical therapy for hemiparesis rehabilitation

The paper suggests a therapeutic device for hemiparesis that combines robot-assisted rehabilitation and mirror therapy. The robot, which consists of a motor, a position sensor, and a torque sensor, is provided not only to the paralyzed wrist, but also to the unaffected wrist to induce a symmetric movement between the joints. As a user rotates his healthy wrist to the direction of either flexion or extension, the motor on the damaged side rotates and reflects the motion of the normal side to the symmetric angular position. To verify performance of the device, five stroke patients joined a clinical experiment to practice a 10-minute mirroring exercise. Subjects on Brunnstrom stage 3 had shown relatively high repulsive torques due to severe spasticity toward their neutral wrist positions with a maximum magnitude of 0.300kgfm, which was reduced to 0.161kgfm after the exercise. Subjects on stage 5 practiced active bilateral exercises using both wrists with a small repulsive torque of 0.052kgfm only at the extreme extensional angle. The range of motion of affected wrist increased as a result of decrease in spasticity. The therapeutic device not only guided a voluntary exercise to loose spasticity and increase ROM of affected wrist, but also helped distinguish patients with different Brunnstrom stages according to the size of repulsive torque and phase difference between the torque and the wrist position.

Measurement of wrist flexion and extension torques in different forearm positions

Background

Forceful activities of the wrist were considered to be a risk factor for the epicondylitis. However, there are still conflicting evidence concerning work-relatedness of epicondylitis. The main problem is that there is little information about which forearm postures are capable of withstanding higher torque loads and the extent of the differences in the torques generated by different forearm postures. The objective of this study was to investigate the differences in wrist flexion and extension torques among different forearm positions in healthy subjects.

Methods

Twenty wrists of 10 asymptomatic volunteers were evaluated. The apparatus to measure the wrist torque consisted of a handle with a force sensor and a table to place the forearm in different positions. The direction of the handle can change when measuring different forearm positions. The forearm of the examinee was secured to the table. The participants were asked to exert themselves in maximal isometric contraction for wrist flexion or extension, and to maintain it for 5 s. Each evaluation of the flexion and extension torque was conducted twice. Three forearm positions were evaluated: neutral, pronation, and supination. The intra-class correlation coefficients between first and second measurements were evaluated for the maximum torque. The maximum torques and flexion/extension ratio were compared among the positions. In addition, the agility and endurance for the wrist extension/flexion torques were compared among the positions.

Results

The intra-class correlation coefficients between first and second measurements were 0.928 and 0.866 for the wrist flexion and extension measurements, respectively. The highest torques for the wrist flexion and extension were observed in the supination and pronation positions, respectively (P < 0.01). There was a higher extension/flexion ratio in the supination position compared to the other positions (P < 0.05). There was a superior agility for the wrist flexion in the supination position compared to the pronation position.

Conclusions

The normal balance of the wrist flexion–extension torques in different forearm positions were characterized. This information might aid the provision of advice regarding the optimal positions for performing specific tasks and could help to elucidate the pathophysiology of epicondylitis.