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Contraction Force (contraction + force)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Investigation of the Relationship Between Stimulus Parameters and a Human Muscle Contraction Force During Stimulation of the Gastrocnemius Muscle

ARTIFICIAL ORGANS, Issue 2 2010
Piotr Kaczmarek
Abstract The article presents the results of investigations on the influence of biphasic stimulus parameters such as duration and stimulus interphase interval (IPI) on a gastrocnemius muscle contraction force. Seven healthy volunteers participated in this experiment, and 24 different stimuli patterns were tested. Special attention was paid to the comfort level of a sensory perception while the electrostimulation was applied. During the test, an optimal stimulus pattern evoking contraction at the level over 15% maximum voluntary contraction force and preserving a good comfort perception reported by all of the participants was investigated. It was found that bursts of pulses with width 175 µs and the IPI from 50 to 1000 µs satisfied these criteria. Moreover, it was observed that the increase of the IPI duration generated a significantly stronger contraction force in comparison with the stimulation with the standard biphasic pulses (IPI = 0 µs) having the same amplitude, frequency, and pulse duration. This shows that the modulation of the IPI might be a potentially useful support for the standard force-control methods and may find an application in neuromuscular electrical stimulation systems. [source]

Preparation and pH-sensitivity of polyacrylonitrile (PAN) based porous hollow gel fibers

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Xinyuan Shen
Abstract Polyacrylonitrile based porous hollow gel fibers were prepared from PAN hollow fibers by oxidation and subsequent alkaline treatment. Fourier-transform infrared (FTIR), X-ray diffraction, and scanning electron microscope (SEM) analyses showed that the PAN porous hollow gel fiber was a kind of amphoteric fiber due to the combination of cationic groups of pyridyl and anionic groups of carboxyl; after gelation the hollow channel and finger-like pores on the fiber walls were conserved. The effects of cyclization reaction degree, alkaline solution concentration, and alkaline treatment time on the mechanical properties or pH-sensitive behavior of the porous hollow gel fibers were investigated. The elongation/contraction behavior was studied in detail. It was found that the gel fiber exhibited a large swelling in an alkaline solution and contracting in an acid solution; the swelling change in length was above 90%; the responsive time of elongation/contraction was less than 20 s; the maximum contraction force was 20 N/cm2; and pH-sensitivity was reversible. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Effect of transcranial magnetic stimulation on voluntary activation in patients with quadriceps weakness

MUSCLE AND NERVE, Issue 2 2005
Dietmar Urbach MD
Abstract Joint disease causes weakness and wasting of adjacent muscles, in part because of inability to fully activate these muscles voluntarily. Previous findings suggest that transcranial magnetic stimulation (TMS) paired with muscle contractions enhances maximal voluntary contraction force (MVC) in healthy subjects by improving voluntary activation (VA). The aim of the present study was to evaluate whether such an effect is also present in subjects suffering from diminished muscle force due to decreased VA. Three single TMS over resting motor threshold were applied in 10 patients with a mean age of 62 years after total-knee arthroplasty either during MVC or during muscle relaxation (control experiment) in a blinded randomized crossover study. MVC and VA were determined using a twitch-interpolation technique at 1, 15, 30, and 60 min after stimulation. There was a significant effect of TMS on MVC if applied in synchrony with muscle contraction, and this persisted for at least 60 min beyond stimulation. In patients suffering from joint disease, TMS might make physiotherapy more effective. Muscle Nerve, 2005 [source]

The effects of clonidine on ropivacaine 0.75% in axillary perivascular brachial plexus block

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2000
W. Erlacher
Introduction: The new long-acting local anesthetic ropivacaine is a chemical congener of bupivacaine and mepivacaine. The admixture of clonidine to local anesthetics in peripheral nerve block has been reported to result in a prolonged block. The aim of the present study was to evaluate the effects of clonidine added to ropivacaine on onset, duration and quality of brachial plexus block. Methods: Patients were randomly allocated into two groups. In group I brachial plexus was performed using 40 ml of ropivacaine 0.75% plus 1 ml of NaCL 0.9%, and in group II brachial plexus was performed using 40 ml of ropivacaine 0.75% plus 1 ml (0.150 mg) of clonidine. Onset of sensory and motor block of radial, ulnar, median and musculocutaneous nerve were recorded. Motor block was evaluated by quantification of muscle force, according to a rating scale from 6 (normal contraction force) to 0 (complete paralysis). Sensory block was evaluated by testing response to a pinprick in the associated innervation areas. Finally, the duration of the sensory block was registered. Data were expressed in mean±SD. For statistical analysis a Student t -test was used. A P -value of ,0.05 was considered as statistically significant. Results: The duration of blockade was without significant difference between the groups. Group I: 718±90 min; Group II: 727±117 min. There was no intergroup difference in sensory and motor onset or in quality of blockade. Conclusion: The addition of clonidine to ropivacaine 0.75% does not lead to any advantage of block of the brachial plexus when compared with pure ropivacaine 0.75%. [source]