American journal of physical medicine
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In collaboration with the College of Engineering the author has developed a laboratory, or clinic, based, battery operated "universal" control system, designed to improve disabled gait in upper motor neuron disabilities, especially stroke, hemiplegia, and cerebral palsy, by applying several channels of FES (Functional Electrical Stimulation) to the lower limb muscles while the patient is walking. The timing of the FES pulses, which can be applied to as many as six of the patient's muscles, is determined by potentiometer controlled one-shot timers, which are triggered by any of three switches in the sole of either shoe. Combinations of inverters, flip flops, AND gates and OR gates in the externally connected logic circuits determine the sequence of delays and pulses applied to the patient's muscles. ⋯ The author concludes that the gait characteristics of some hemiplegic patients will improve as they become adapted over a period of weeks or months to a control logic, which lessens their functional limitations by the use of a properly timed and amplified sequence of FES pulses. He suggests that the FES control requirements for individual patients should be determined experimentally with a control system "universally" adaptable to a wide range of disabilities, and that these control parameters could then determine the design of portable units, which may be used on a long term basis. These units would include only the operational options needed to duplicate the gait corrections found to be practicable for each individual patient, by the testing procedure, through a universal logic unit as described in this paper.
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The plateau of tetanic tension in a lengthening contraction of muscle at any given length is always greater than that in an isometric contraction at the same given length. To account for this excess of tension, it is suggested that the contractile machinery is "locked" in a strained condition that might make the muscle capable of bearing a greater tension in a lengthening contraction than it can develop in an isometric contraction. It is proposed that this strained condition also occurs in a lengthening contraction of the twitch response. ⋯ To account for the plateau of tension observed after quick lengthening in the early phase of twitch contraction indirect evidence is presented favoring the view that the quick lengthening during stretch is followed by slow lengthening and stress relaxation (decrease of tension) in series elastic elements and simultaneous shortening and increase of tension in the contractile component. When the original concept of active state tension in the twitch response is interpreted in the light of lengthening contraction, it is concluded that the labeled or implied Po for the plateau of the active state tension is unwarranted and confusing. It seems that the primary source of confusion is the assumption that the tension a muscle is capable of bearing in a lengthening contraction is equatable with the tension it can develop in an isometric contraction.