ABSTRACT
A simple instrument has been developed for quantitative measurement of stiffness (elasticity) and maximum force of the fingers and was tested in a series of 122 out-patients with RA and 101 healthy controls. Values measured for stiffness were higher in RA patients and were scattered more widely than in controls and the mean values for force in the RA patients were lower than in controls. RA patients with an elevated ESR have significantly less strength than those with low ESR. We evaluated the influence of the time of day and weather (humidity and air temperature on the wards and outside the hospital, barometer pressure) on stiffness and force. In 13 in-patients with definite or classical RA and 12 controls, measurements were performed in the morning and afternoons, over periods of 3 weeks. In RA patients, both stiffness and force increased with outside air humidity (p less than 0.05), confirming the clinical experience that stiffness increases in damp weather. In the controls, force decreased with a higher air humidity on the wards (p = 0.05) and increased with higher barometer pressure (p less than 0.05). In the controls joint stiffness was higher in the morning than in the afternoon (p less than 0.05). In the RA group, rather unexpectedly, the reverse was found (p = 0.06), possibly explained by the time of the day the investigation was done. Only in the controls was a significant increase in force noted during the 3 weeks of investigation (p less than 0.005). No correlation was seen between force and stiffness. No correlation was found between disease activity as expressed in ESR, Hb, Rose titre, ARA grading and stiffness or force.
Subject(s)
Arthritis, Rheumatoid/physiopathology , Weather , Atmospheric Pressure , Circadian Rhythm , Elasticity , Female , Finger Joint/physiopathology , Humans , Humidity , Male , Methods , Motor Skills/physiology , Temperature , Tensile Strength , Time FactorsSubject(s)
Electromyography/methods , Muscles/innervation , Neural Conduction , Electrodes , Humans , Time FactorsSubject(s)
Electromyography , Muscles/innervation , Neural Conduction , Neuromuscular Junction/physiology , HumansSubject(s)
Muscles/physiology , Animals , Electric Conductivity , Electrodes , Electromyography/methods , Male , Models, Biological , Rabbits , Rats , Rats, Inbred StrainsABSTRACT
In order to increase insight into the electrical phenomena of active motor units, a computer simulation model has been developed. With this model motor unit action potentials (MUAPs) have been calculated. The model has been based on the superposition of the muscle fibre potentials of the fibres of one motor unit. For verification, calculated MUAPs have been compared with the matching recorded MUAPs. During experiments one motor unit was stimulated and the MUAP of this unit was measured with intramuscular wire electrodes. After the experiments the positions of the activated fibres of this unit and of the electrodes were determined by means of histochemical techniques. Other parameters were derived from other experiments or the literature. Using the obtained set of parameters in the model MUAPs were calculated. These MUAPs were compared with the measured MUAPs. From this comparison it has been concluded that the model predicts the MUAP to an appreciable degree. The results clearly show the dominating effect of muscle fibres in close vicinity of the electrode and the important effect of the activation moment of those fibres on the shape of the MUAP.
Subject(s)
Electromyography , Muscles/physiology , Action Potentials , Animals , Electric Conductivity , Mathematics , Motor Endplate/anatomy & histology , Motor Neurons/physiology , Muscles/anatomy & histology , Neural Conduction , Rats , Rats, Inbred Strains , Time FactorsABSTRACT
It is known that the behavior of fast and slow skeletal muscles differs, but a comparison between fast and slow muscles with different stimulation patterns at various muscle lengths is lacking. The twitch, tetanus, and double pulse responses with a number of interval times have been investigated for a fast (EDL) and a slow (soleus) muscle of the rat at three muscle lengths (in vivo, at 37 degrees C, pentobarbital sodium anesthesia). The twitches of EDL and soleus change with muscle length, but the relative form of the ascending phase is independent of muscle length. The tetanus amplitude is independent of the muscle length over a considerable length range below the optimum twitch length. The form of the ascending phases of EDL-tetanus and double pulse responses (with certain interval times between the stimuli) varies with muscle length in contrast with the comparable soleus force patterns. The maximum slope in the descending phase of all contraction patterns decreases with increasing muscle length above the optimum twitch length.
Subject(s)
Muscle Contraction , Muscle Tonus , Muscles/anatomy & histology , Action Potentials , Animals , Electric Stimulation , In Vitro Techniques , Male , Muscles/physiology , Rats , Time FactorsABSTRACT
In order to study the motor unit action potential a computer stimulation model was developed. It is based on the superposition of single muscle fibre potentials of the fibres belonging to the motor unit. The parameters which characterize each fibre (spatial position, diameter, and a dispersion of arrival time of the potential at the electrode) are chosen from statistical distributions which can be derived from anatomical and physiological data. The electrode type, position and dimensions can be specified. Simulated motor unit action potentials are presented in the time and frequency domain. The stimulation results refer to (1) the influence of the electrode position and dimensions with respect to the motor unit territory, (2) the meaning of this model for the study of pathological phenomena, (3) the variability of some parameters characterizing the motor unit, (4) the selectivity of uni- and bipolar electrodes and finally (5) the influence of the geometrical situation of the motor end-plates within the muscle, on the shape of motor unit action potentials.
