Forearm muscle activation during power grip and release

Impaired performance of rapid grip in people with Parkinson's disease and motor segmentation

Bradykinesia, or slow movement, is a defining symptom of Parkinson's disease (PD), but the underlying neuromechanical deficits that lead to this slowness remain unclear. People with PD often have impaired rates of motor output accompanied by disruptions in neuromuscular excitation, causing abnormal, segmented, force-time curves. Previous investigations using single-joint models indicate that agonist electromyogram (EMG) silent periods cause motor segmentation. It is unknown whether motor segmentation is evident in more anatomically complex and ecologically important tasks, such as handgrip tasks. Aim 1 was to determine how handgrip rates of force change compare between people with PD and healthy young and older adults. Aim 2 was to determine whether motor segmentation is present in handgrip force and EMG measures in people with PD. Subjects performed rapid isometric handgrip pulses to 20-60% of their maximal voluntary contraction force while EMG was collected from the grip flexors and extensors. Dependent variables included the time to 90% peak force, the peak rate of force development, the duration above 90% of peak force, the number of segments in the force-time curve, the number of EMG bursts, time to relaxation from 90% of peak force, and the peak rate of force relaxation. People with PD had longer durations and lower rates of force change than young and older adults. Six of 22 people with PD had motor segmentation. People with PD had more EMG bursts compared to healthy adults and the number of EMG bursts covaried with the number of segments. Thus, control of rapid movement in Parkinson's disease can be studied using isometric handgrip. People with PD have impaired rate control compared to healthy adults and motor segmentation can be studied in handgrip.

A Musculoskeletal Model of the Hand and Wrist Capable of Simulating Functional Tasks

OBJECTIVE

The purpose of this work was to develop an open-source musculoskeletal model of the hand and wrist and to evaluate its performance during simulations of functional tasks.

METHODS

The current model was developed by adapting and expanding upon existing models. An optimal control theory framework that combines forward-dynamics simulations with a simulated-annealing optimization was used to simulate maximum grip and pinch force. Active and passive hand opening were simulated to evaluate coordinated kinematic hand movements.

RESULTS

The model's maximum grip force production matched experimental measures of grip force, force distribution amongst the digits, and displayed sensitivity to wrist flexion. Simulated lateral pinch strength replicated in vivo palmar pinch strength data. Additionally, predicted activations for 7 of 8 muscles fell within variability of EMG data during palmar pinch. The active and passive hand opening simulations predicted reasonable activations and demonstrated passive motion mimicking tenodesis, respectively.

CONCLUSION

This work advances simulation capabilities of hand and wrist models and provides a foundation for future work to build upon.

SIGNIFICANCE

This is the first open-source musculoskeletal model of the hand and wrist to be implemented during both functional kinetic and kinematic tasks. We provide a novel simulation framework to predict maximal grip and pinch force which can be used to evaluate how potential surgical and rehabilitation interventions influence these functional outcomes while requiring minimal experimental data.

Do the Testing Posture and the Grip Modality Influence the Shoulder Maximal Voluntary Isometric Contraction?

Assessing and monitoring shoulder strength is extremely important during rehabilitation. A fixed dynamometer represents a valid and inexpensive assessment method. However, it has not been studied whether posture and grip modality influence shoulder muscle strength. The aim of this study was to compare shoulder strength values between sitting and standing positions and between the handle and cuff grip modalities. A total of 40 volunteers were divided into a posture (PG) and a handle-cuff group (HCG). Participants in the PG were asked to perform a maximum voluntary isometric contraction (MVIC) for shoulder flexion, extension, ab-adduction, and intra-extra rotation in standing and sitting positions. The HCG participants were tested in a standing position while holding a handle or with a cuff around their wrist. PG showed higher forces in the standing position for shoulder flexion (p = 0.009); internal rotation showed higher values in the sitting position (p = 0.003). ER/IR ratio was significantly higher in the standing position (p < 0.001). HCG showed higher significant forces during cuff modality in all positions and grip modalities, including the ER/IR ratio (p < 0.05). Different body positions and grip modalities influenced the assessment of shoulder strength as recorded by a fixed dynamometer; therefore, these factors should be carefully considered when carrying out a shoulder strength assessment, and we encourage the development of assessment guidelines to make future clinical trial results comparable.

A1 pulley stretching treats trigger finger: A1 pulley luminal region under digital flexor tendon traction

BACKGROUND

A1 pulley stretching is recognized as a clinically beneficial treatment for trigger finger. It is thought to lead to an increase in the cross-sectional area of the A1 pulley luminal region, thus improving trigger finger symptoms. The purpose of the present study was thus to evaluate the resultant forces during stretching that increase the CSA of the A1 pulley luminal region using fresh-frozen cadavers.

METHODS

Using seven fingers from three fresh-frozen cadavers to replicate A1 pulley stretching, we investigated the resultant forces during stretching that increase the cross-sectional area of the A1 pulley luminal region. The traction forces of the flexor digitorum profundus tendons were increased in steps to 150 N, and the cross-sectional area and height of the A1 pulley luminal region were measured using ultrasonography.

FINDINGS

The cross-sectional area of the A1 pulley luminal region increased with step-wise increases in the flexor digitorum profundus traction. On average, the cross-sectional area and height of the A1 pulley luminal region showed increases of 31.4% and 43.6%, respectively, compared to the unloaded condition.

INTERPRETATION

These results confirmed that A1 pulley stretching increases the cross-sectional area of the A1 pulley luminal region. A1 pulley stretching has the potential to reduce the severity of trigger finger in patients facing surgery.

Get a grip: individual variations in grip strength are a marker of brain health

Demonstrations that grip strength has predictive power in relation to a range of health conditions-even when these are assessed decades later-has motivated claims that hand-grip dynamometry has the potential to serve as a "vital sign" for middle-aged and older adults. Central to this belief has been the assumption that grip strength is a simple measure of physical performance that provides a marker of muscle status in general, and sarcopenia in particular. It is now evident that while differences in grip strength between individuals are influenced by musculoskeletal factors, "lifespan" changes in grip strength within individuals are exquisitely sensitive to integrity of neural systems that mediate the control of coordinated movement. The close and pervasive relationships between age-related declines in maximum grip strength and expressions of cognitive dysfunction can therefore be understood in terms of the convergent functional and structural mediation of cognitive and motor processes by the human brain. In the context of aging, maximum grip strength is a discriminating measure of neurological function and brain health.

Is synergistic organisation of muscle coordination altered in people with lateral epicondylalgia? A case-control study

BACKGROUND

Lateral epicondylalgia is a common musculoskeletal disorder and is associated with deficits in the motor system including painful grip. This study compared coordination of forearm muscles (muscle synergies) during repeated gripping between individuals with and without lateral epicondylalgia.

METHODS

Twelve participants with lateral epicondylalgia and 14 controls performed 15 cyclical repetitions of sub-maximal (20% maximum grip force of asymptomatic arm), pain free dynamic gripping in four arm positions: shoulder neutral with elbow flexed to 90° and shoulder flexed to 90° with elbow extended both with forearm pronated and neutral. Muscle activity was recorded from extensor carpi radialis brevis/longus, extensor digitorum, flexor digitorum superficialis/profundus, and flexor carpi radialis, with intramuscular electrodes. Muscle synergies were extracted using non-negative matrix factorisation.

FINDINGS

Analysis of each position and participant, demonstrated that two muscle synergies accounted for >97% of the variance for both groups. Between-group differences were identified after electromyography patterns of the control group were used to reconstruct the patterns of the lateral epicondylalgia group. A greater variance accounted for was identified for the controls than lateral epicondylalgia (p=0.009). This difference might be explained by an additional burst of flexor digitorum superficialis electromyography during grip release in many lateral epicondylalgia participants.

INTERPRETATION

These data provide evidence of some differences in synergistic organisation of activation of forearm muscles between individuals with and without lateral epicondylalgia. Due to study design it is not possible to elucidate whether changes in the coordination of muscle activity during gripping are associated with the cause or effect of lateral epicondylalgia.

De Quervain’s syndrome: It may not be an isolated pathology

Introduction

This paper details a retrospective review of patients’ records diagnosed with de Quervain’s syndrome following a traumatic event but no history of repetitive strain.

Methods

Data analysis of 41 patients was performed. The inclusion criteria were pain over first dorsal compartment, pain on resisted extensor pollicis brevis and/or abductor pollicis longus, and a positive Finkelstein’s test. The assessment included a subjective history to establish a repetitive activity or a traumatic incident and diagnostic tests to establish possible instability or osteoarthritis.

Results

There were 13 men and 28 women with an age range from 20 to 72 years. Statistical analysis was undertaken using Fisher’s Exact tests. 46.3% ( n = 19) of 41 patients had a ligament injury diagnosed after the de Quervain’s. 94.7% ( n = 18) of 19 patients with ligament instability had a history of trauma, and this was statistically significant. Clinically significant was that 82.9% ( n = 34) of 41 patients demonstrated extensor carpi ulnaris (ECU) muscle weakness, but there was no statistical significant correlation between ECU weakness and ligament instability. Patients could have ECU weakness without ligament instability; however, patients with ligament instability appeared more likely to have ECU weakness.

Conclusions

The results would suggest that de Quervain’s syndrome, in a proportion of patients, could be secondary to underlying wrist pathology due to previous trauma. If the patient does not report a true repetitive strain history, a more thorough assessment may need to be undertaken to establish if there is any underlying pathology.

Influence of volar and dorsal static orthoses in different wrist positions on muscle activation and grip strength in healthy subjects

Introduction

Orthoses are indicated for injuries of the wrist, although there is weak evidence for its influence on extensor muscle activation patterns. The purpose of this study was to compare two designs of volar and dorsal wrist orthoses in several positions, from flexion to extension, by surface electromyography wrist extensor muscle activation and grip strength in healthy subjects.

Methods

We analysed extensor carpi radialis brevis and longus, extensor carpi ulnaris and extensor digitorum comunis muscle activity by surface electromyography. The volunteers performed maximum and submaximum (50%) isometric grips, which were evaluated with a Jamar™ dynamometer using volar and dorsal orthoses with several positions of the wrist (0°, 15° and 30°), both in flexion and extension ( p < 0.05).

Results

Our results showed a significant decrease in extensor muscle activation at 15° and 30° of wrist extension in both volar and dorsal orthoses at 100% and 50% of maximum task. A decrease was also found at rest at 15° of wrist flexion volar orthoses. Decreased grip strength was found at 15° and 30° of wrist flexion in both volar and dorsal orthoses.

Conclusions

Based on the results of this sample, we would suggest, as orthotic prescriptions, 15° or 30° wrist extension orthoses as a supporting therapeutic modality for performance in new studies with lateral epicondylitis in association with low-intensity grip activity; or 15° of wrist flexion volar orthoses for rest, depending on the chronicity of the disease and individual assessment. Future studies with symptomatic patients are needed to confirm these findings.

Functional outcomes following single-event multilevel surgery of the upper extremity for children with hemiplegic cerebral palsy

BACKGROUND

Outcomes following single-event multilevel surgery of the upper extremity for children with cerebral palsy have not been well described in the literature. Since 1996, all children with hemiplegic cerebral palsy at our institution thought to be candidates for upper extremity surgery have had serial Shriners Hospital for Children Upper Extremity Evaluation performed for both clinical decision making and outcome assessment. The goal of the current study was to determine the functional outcomes, as described by the Shriners Hospital for Children Upper Extremity Evaluation, following single-event multilevel surgery of the upper extremity in children with hemiplegic cerebral palsy.

METHODS

The study design was a retrospective, case-control series. The case group consisted of forty children with hemiplegic cerebral palsy who underwent upper-extremity single-event multilevel surgery. The control group consisted of twenty-six children with hemiplegic cerebral palsy who had not received any upper-extremity interventions. The spontaneous functional analysis, dynamic positional analysis, and grasp-release analysis sections of the Shriners Hospital for Children Upper Extremity Evaluation were compared between the two groups.

RESULTS

The operative and nonoperative groups were comparable with respect to age (p = 0.09), sex (p = 0.97), initial spontaneous functional analysis scores (p = 0.37), dynamic positional analysis scores (p = 0.73), and grasp-release analysis scores (p = 0.16). For the single-event multilevel surgery group, significant improvements were noted for the mean spontaneous functional analysis score (p < 0.0001) and the mean dynamic positional analysis score (p < 0.0001), but not the mean grasp-release analysis score (p = 0.75). For the nonoperative control group, no significant changes were noted for the mean spontaneous functional analysis score (p = 0.89), the mean dynamic positional analysis score (p = 0.98), or the mean grasp-release analysis score (p = 0.36). Significant differences were noted between the single-event multilevel surgery and nonoperative control groups for the mean changes in the spontaneous functional analysis score (p = 0.01) and the mean change in the dynamic positional analysis score (p < 0.0001), but not the mean changes in the grasp-release analysis score (p = 0.56).

CONCLUSIONS

Children with hemiplegic cerebral palsy showed significantly improved dynamic segmental alignment and, to a lesser degree, spontaneous use of the upper extremity following single-event multilevel surgery compared with a comparable nonoperative control group. However, the grasp-release ability did not significantly improve in either the operative or nonoperative group.

Motion coordination patterns during cylinder grip analyzed with a sensor glove

PURPOSE

To determine whether the grip of a healthy subject's hand shows certain universal characteristics. To accomplish this, we examined the complex interactions of the fingers during gripping of different-size cylindrical objects.

METHODS

A total of 48 subjects (11 women, 37 men) performed 5 cylinder grips with different object sizes. The 14 joint angular profiles of the 5 digits were measured dynamically with a Technische Universität Berlin sensor glove.

RESULTS

Frequently, initial movement was detected before the actual grip. This movement consisted of passive flexion of the fingers the moment the hand rose from the table, followed by active extension of the fingers before gripping the object. Along with the type of joint, the size of the object gripped influenced the frequency of these initial movements (p<.001). During actual grip, the proximal interphalangeal joints' flexion was significantly greater than the flexion of the metacarpophalangeal and distal interphalangeal joints (p<.001). The mean flexion of the proximal interphalangeal joints was 43 degrees , that of the metacarpophalangeal joints was 28 degrees , and that of the distal interphalangeal joints was 26 degrees. Apart from these findings, the larger the flexion angle was, the more time tended to be needed to fulfil the motion.

CONCLUSIONS

The results show that there is a universal motion pattern with the cylinder grip in healthy individuals concerning the range of movement of the finger joints. However, to fully understand the cylinder grip in healthy individuals, our next step will be to analyze the dynamics of the cylinder grip as well. For that purpose, we examine the dynamic interactions between the fingers--that is, their chronological sequence during the cylinder grip.

Surgical management of thumb deformity in children with hemiplegic-type cerebral palsy

BACKGROUND

Evidence-based clinical decision-making for the surgical management of thumb deformities in children with cerebral palsy is difficult, primarily because of a lack of consensus with respect to assessment of thumb alignment and function. We have used the Shriners Hospital Upper Extremity Evaluation, a validated assessment tool, to determine the outcome after thumb reconstruction surgery in these children. The goals of this study were to determine the relationship between static and dynamic assessments of the thumb before surgery, the outcomes with respect to static and dynamic alignments of the thumb after soft tissue and skeletal surgery, and the relationship between preoperative spontaneous functional use of the involved extremity (indicative of the magnitude of neurologic impairment) and the change in thumb dynamic alignment after surgery.

METHODS

A retrospective case series was performed, consisting of 33 children with hemiplegic-type cerebral palsy who had undergone surgical reconstruction of the thumb between 1998 and 2006. All children had preoperative and postoperative Shriners Hospital Upper Extremity Evaluation analyses performed (mean time to follow-up was 2 y and 2 mo). Static modified House scale of thumb alignment, dynamic thumb positional analysis, and the spontaneous functional use of the involved extremity were compared and contrasted.

RESULTS

Dynamic thumb alignment was significantly worse than static thumb alignment (P=0.0005). Comparable improvements were achieved in both static and dynamic thumb alignment after surgical thumb reconstruction (P=0.6242). Optimal outcome was achieved more frequently in the static alignment (82% of cases) than in the dynamic alignment (61% of cases). There was poor correlation between the spontaneous use of the involved extremity before surgery and the changes in thumb dynamic alignment after surgery (Pearson correlation coefficient 0.1554, P=0.39).

CONCLUSIONS

Static thumb alignment is not a good predictor of dynamic function, and interventions designed to improve function should focus on the assessment of dynamic thumb alignment. Improvements in both static and dynamic alignment of the thumb are possible after reconstructive surgery (consisting of muscle release, tendon transfer, and skeletal stabilization), regardless of the degree or density of underlying neurologic impairment.

The Immediate Effects of Manual Massage on Power-Grip Performance After Maximal Exercise in Healthy Adults

OBJECTIVE

Research into the effects of manual massage on physical performance has proved inconclusive, with studies primarily examining the major muscle groups of the lower extremities. Grip performance is essential for object manipulation, as well as for many grip-dependent activities and sports; but there have been no studies to determine the effects of manual massage on immediate grip performance in healthy subjects. The purpose of this study was to assess the effects of using manual massage to improve power-grip performance immediately after maximal exercise in healthy adults.

STUDY DESIGN

This was a pretest/post-test study.

SETTING

The study took place in a suburban allied health school.

SUBJECTS

Fifty-two (52) volunteer massage-school clients, staff, faculty, and students participated.

INTERVENTIONS

Subjects randomly received either a 5-minute forearm/hand massage of effleurage and friction (to either the dominant hand or nondominant hand side), 5 minutes of passive shoulder and elbow range of motion, or 5 minutes of nonintervention rest.

OUTCOME MEASURES

Power-grip measurements (baseline, postexercise, and postintervention) were performed on both hands using a commercial hand dynamometer. These measurements preceded and followed 3 minutes of maximal exercise using a commercial isometric hand exerciser that produced fatigue to 60% of baseline strength.

RESULTS

After 3 minutes of isometric exercise, power grip was consistently fatigued to at least 60% of baseline, with recovery occurring over the next 5 minutes. Statistical analyses involving single-factor repeated-measures analyses of variance (p = 0.05) with Bonferroni a priori tests (p = 0.0083) demonstrated that massage had a greater effect than no massage or than placebo on grip performance after fatigue, especially in the nondominant-hand group.

CONCLUSIONS

Manual massage to the forearm and hand after maximal exercise was associated with greater effects than nonmassage on postexercise grip performance. The present data do support the use of a 5-minute manual massage to assist immediate grip performance after fatigue in healthy subjects.

Quantitative assessment of upper limb muscle fatigue depending on the conditions of repetitive task load

The aim of this study was to discriminate fatigue of upper limb muscles depending on the external load, through the development and analysis of a muscle fatigue index. Muscle fatigue is expressed by a fatigue index based on an amplitude parameter (calculated in the time domain) and a fatigue index based on a frequency parameter (a parameter calculated in the frequency domain). The fatigue index involves a regression function that describes changes in the EMG signal parameter, time elapsing before muscle fatigue and the probability of specific trends in changes in EMG parameters for the population under study. The experimental study covered a group of 10 young men. During the study, they exerted force at a specific level and for a specific time in 12 load variants. During the study, EMG signals from four muscles of the upper limb were recorded (trapezius pars descendents, biceps brachii caput breve, extensor carpi radialis brevis, flexor carpi ulnaris). For each variant and for each examined muscles, the value of the fatigue index was calculated. Values of that index quantitatively expressed fatigue of a specific muscle in a specific load variant. A statistical analysis indicated variation in the fatigue of the biceps brachii caput breve, extensor carpi radialis brevis, and flexor carpi ulnaris muscles depending on the external load (load variant) according to the task performed with the upper limb. The study demonstrated usefulness of the fatigue index in expressing quantitatively muscle fatigue and in discriminating muscle fatigue depending on the external load.

Treatment of Dynamic Scaphoid Instability

BACKGROUND

Chronic wrist pain attributable to scaphoid instability without fixed deformity (dynamic instability) presents a treatment dilemma. The diagnosis usually is delayed, missing the opportunity for direct repair. The intercarpal fusion, tenodesis, and capsulodesis procedures create a fixed deformity. This report presents an outcome study of a new treatment for dynamic scaphoid instability that spanned more than 5 years.

METHODS

Arthroscopic evaluation was used to confirm the diagnosis for 105 wrists of 102 patients who had experienced wrist pain for an average of 24.4 months. The treatment for these patients involved transferring two thirds of the extensor carpi radialis longus through the distal pole of the reduced scaphoid volarly to the intact flexor carpi radialis. The postoperative follow-up period averaged 63 months.

RESULTS

The average grip strength increased by 65%. The average active wrist extension-flexion increased by 9%, with an average radial deviation loss of 6 degrees. The overall results, as measured by the modified Green and O'Brien clinical wrist scale, were as follows: excellent (49%), good (24%), and fair (26%). Good to excellent results were reported by 85% of the patients. Pain relief was reported by 94% of the patients, and 93% of the patients would recommend the procedure to others.

CONCLUSIONS

Scaphoid instability without fixed deformity is a complex problem. Conventional treatments have drawbacks. The new technique produced positive results that are quite promising for the management of dynamic scaphoid instability.

The effect of wrist orthoses on forearm muscle activity

A general hypothesis is that a wrist orthosis reduces the wrist extensor muscle load. The aim of this study was to investigate the effects of a completely stiff wrist orthosis (SO) and a commercially available wrist orthosis (CO) on flexor and extensor electromyographic (EMG)-activity in a standardised intermittent gripping task and during standardised manual work tasks. Surface EMG from two forearm flexor and two extensor muscles was recorded. The target grip forces were 5%, 20% and 40% of maximal voluntary contraction (MVC). During the grip contraction phase CO had no effect on the EMG-readings. SO resulted in higher EMG activity than when gripping with CO and with no orthosis (NO), especially when gripping with 40% MVC. During the relaxation phase neither CO nor SO had any effect on the extensors. For the flexors the SO gave higher EMG-readings than when gripping with CO and NO, especially at 40% MVC. In conclusion the wrist orthoses tested did not reduce the EMG-activity from the flexors or the extensors during gripping or manual tasks.