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Concept: Hand strength

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Hand coordination can allow humans to have dexterous control with many degrees of freedom to perform various tasks in daily living. An important contributing factor to this important ability is the complex biomechanical architecture of the human hand. However, drawing a clear functional link between biomechanical architecture and hand coordination is challenging. It is not understood which biomechanical characteristics are responsible for hand coordination and what specific effect each biomechanical characteristic has. To explore this link, we first inspected the characteristics of hand coordination during daily tasks through a statistical analysis of the kinematic data, which were collected from thirty right-handed subjects during a multitude of grasping tasks. Then, the functional link between biomechanical architecture and hand coordination was drawn by establishing the clear corresponding causality between the tendinous connective characteristics of the human hand and the coordinated characteristics during daily grasping activities. The explicit functional link indicates that the biomechanical characteristic of tendinous connective architecture between muscles and articulations is the proper design by the Creator to perform a multitude of daily tasks in a comfortable way. The clear link between the structure and the function of the human hand also suggests that the design of a multifunctional robotic hand should be able to better imitate such basic architecture.

Concepts: Statistics, Motor control, Task, Hand, Characteristic, Hand strength, Fine motor skill

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Reduced muscular strength, as measured by grip strength, has been associated with an increased risk of all-cause and cardiovascular mortality. Grip strength is appealing as a simple, quick, and inexpensive means of stratifying an individual’s risk of cardiovascular death. However, the prognostic value of grip strength with respect to the number and range of populations and confounders is unknown. The aim of this study was to assess the independent prognostic importance of grip strength measurement in socioculturally and economically diverse countries.

Concepts: Demography, Population, Measurement, Psychometrics, The Independent, Uncertainty, Quantity, Hand strength

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The human hand has so many degrees of freedom that it may seem impossible to control. A potential solution to this problem is “synergy control” which combines dimensionality reduction with great flexibility. With applicability to a wide range of tasks, this has become a very popular concept. In this review, we describe the evolution of the modern concept using studies of kinematic and force synergies in human hand control, neurophysiology of cortical and spinal neurons, and electromyographic (EMG) activity of hand muscles. We go beyond the often purely descriptive usage of synergy by reviewing the organization of the underlying neuronal circuitry in order to propose mechanistic explanations for various observed synergy phenomena. Finally, we propose a theoretical framework to reconcile important and still debated concepts such as the definitions of “fixed” vs. “flexible” synergies and mechanisms underlying the combination of synergies for hand control.

Concepts: Nervous system, Neuron, Energy, Axon, Synapse, Electromyography, Hand, Hand strength

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Muscle attachment sites (entheses) on dry bones are regularly used by paleontologists to infer soft tissue anatomy and to reconstruct behaviors of extinct organisms. This method is commonly applied to fossil hominin hand bones to assess their abilities to participate in Paleolithic stone tool behaviors. Little is known, however, about how or even whether muscle anatomy and activity regimes influence the morphologies of their entheses, especially in the hand. Using the opponens muscles from a sample of modern humans, we tested the hypothesis that aspects of hand muscle architecture that are known to be influenced by behavior correlate with the size and shape of their associated entheses. Results show no consistent relationships between these behaviorally-influenced aspects of muscle architecture and entheseal morphology. Consequently, it is likely premature to infer patterns of behavior, such as stone tool making in fossil hominins, from these same entheses.

Concepts: Human, Evolution, Hominidae, Hand, Hand strength, Prehistory, Homininae, Hominini

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Paresis acquired in the intensive care unit (ICU) is common in patients who are critically ill and independently predicts mortality and morbidity. Manual muscle testing (MMT) and handgrip dynamometry assessments have been used to evaluate muscle weakness in patients in a medical ICU, but similar data for patients in a surgical ICU (SICU) are limited.

Concepts: Medicine, Physician, Illness, Muscular system, Paralysis, Hand strength, Grip strength, Muscle memory

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Objectives. To explore the ability of six outcome measures to capture clinically important changes in patients with rheumatic diseases undergoing hand surgery and to study predictors of changes in activity performance in different patient and surgery strata. Methods. A total of 172 patients (median age 59 years, disease duration 18 years) were stratified into subgroups: diagnosis, age, general function, type of surgery. Performance of daily activities and satisfaction were assessed by the Canadian Occupational Performance Measure (COPM). Clinically important improvement was defined as a two-step improvement in COPM. Hand function was assessed by reference to grip strength (Grippit), pinch strength (pinch gauge), hand pain (visual analogue scale) and grip ability (Grip Ability Test). Responsiveness was calculated as effect size (ES) at 6-month follow-up compared with baseline. Results. Clinically important improvement was reached by 25-69% depending on outcome measure and type of surgery. Improvement was smaller in patients with multiple simultaneous procedures. Regardless of diagnosis, age, general function and type of surgery, patients improved significantly in all measures, with the largest changes in COPM(performance) and COPM(satisfaction) (ES 0.7-1.9). The ES of pain ranged from 0.2 to 0.7, Grippit from 0.1 to 0.5 and pinch gauge from 0.4 to 0.8. Hand pain was the only significant predictor of clinically important improvement of COPM(performance): odds ratio 0.71, 95% CI 0.51, 0.98 (P = 0.041). Conclusion. COPM was the most sensitive instrument to capture clinically important improvement, and hand pain was a significant predictor of improvement, irrespective of diagnosis, age, general functional level and type of surgery.

Concepts: Medicine, Hospital, Rheumatology, Physician, Effect size, Hand strength, Grip strength, Canadian model of occupational performance

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The term ‘exploded hand syndrome’ refers to a specific type of crush injury to the hand in which a high compressive force excessively flattens the hand leading to thenar muscle extrusion through burst lacerations. Out of 89 crushed hands seen over a period of seven years, only five had exploded hand syndrome. They were all male industrial workers ranging in age between 24 and 55 years. All patients had thenar muscle extrusion. Other concurrent injuries included fractures/dislocations, compartment syndrome, and ischaemia. All patients were treated by excision of the extruded intrinsic muscles, as well as primary management of concurrent injuries. All patients had functional assessment including: motor power and sensory testing, range of motion of hand joints, and the quick DASH score. Objective testing showed reduced sensibility in the thumb, reduced grip strength (mean 52% of contralateral hand), reduced pinch strength (mean of 27% of contralateral hand), reduced thumb opposition (the mean Kapandji Score was 5 out of 10), and deficits in the range of motion of the metacarpophalangeal and interphalangeal joints of the thumb. The quick DASH score ranged from 11 to 49 and only two patients were able to go back to regular manual work.

Concepts: Injury, Hand, Median nerve, Hand strength, Grip strength, Thumb, Thenar eminence, Work hardening

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Study Design Descriptive, laboratory based, cross sectional study. Objectives To describe scapular musculature strength, endurance, and change in thickness in individuals with unilateral lateral epicondylalgia (LE) compared to their uninvolved limb and the corresponding limb of a matched comparison group. Background Reported poor long term outcomes for the non-surgical management of individuals with LE suggests a less than optimal rehabilitation process. Knowledge of scapular muscle function in a working population of individuals with LE may help further refine conservative management of this condition. Methods Twenty eight patients with symptomatic LE and 28 controls matched by age and gender were recruited to participate in the study. Strength of the middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) was measured with a hand held dynamometer. A scapular isometric muscle endurance task was performed in prone. Changes in muscle thickness of the SA and LT were measured with ultrasound imaging (USI). ANOVA models were used to determine within and between group differences. Results The involved side of the group with LE had significantly lower values for MT strength (P = .031), SA strength (P<.001), LT strength (P = .006), endurance (P = .003), and change in SA thickness (P = .028) when compared to the corresponding limb of the control group. The involved side of the group with LE had significantly lower strength of the LT (P = .023) and SA (P = .016) when compared to their uninvolved limb, however these differences were small and of potentially limited clinical significance. Conclusion When compared to a matched comparison group, there were impairments of scapular musculature strength and endurance in patients with LE, suggesting that the scapular musculature should be assessed and potentially treated in this population. Cause and effect cannot be established as the weakness of the scapular musculature could be a result of LE. J Orthop Sports Phys Ther, Epub 10 Jan 2015. doi:10.2519/jospt.2015.5290.

Concepts: Causality, Cross-sectional study, Muscle, Muscle contraction, Muscular system, Hand strength, Trapezius muscle, Serratus anterior muscle

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Purpose: The purpose of the study was to examine muscle strength and pain sensitivity in postmenopausal women with and without RA. Methods: Ten women with and ten without early RA were recruited. All were postmenopausal, and did not use hormone replacement therapy. Measurements of isokinetic muscle strength in knee flexors/extensors, hand grip strength, timed standing, pressure pain thresholds (PPT), suprathreshold pressure pain, and segmental and plurisegmental endogenous pain inhibitory mechanisms during muscle contraction were assessed. Results: Participants with early RA were weaker in knee flexors, in hand grip strength and they needed more time for the timed standing. Women with early RA had higher sensitivity to threshold pain and suprathreshold pressure pain compared to women without RA. PPTs increased in the contracting muscle as well as in a distant resting muscle during static contractions in both groups. Conclusions: Our results indicate differences in muscular strength between postmenopausal women with and without RA. Furthermore, women with RA had decreased PPT and hyperalgesia, but no dysfunction of segmental or plurisegmental pain inhibitory mechanisms during static exercise compared to healthy controls. The normal function of endogenous pain inhibitory mechanisms despite chronic pain in women with RA might contribute to the good effects of physical activity previously reported. [Box: see text].

Concepts: Muscle, Physical exercise, Rheumatoid arthritis, Muscle contraction, Muscular system, Strength training, Hand strength, Grip strength

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To assess the immediate effect of a suboccipital muscle inhibition (SMI) technique on: (a) neck pain, (b) elbow extension range of motion during the upper limb neurodynamic test of the median nerve (ULNT-1), and © grip strength in subjects with cervical whiplash; and determine the relationships between key variables.

Concepts: Randomized controlled trial, Psychometrics, Pharmaceutical industry, Nerve, Upper limb, Hand strength, Grip strength