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A fully automated system is described for estimating the numbers and relative sizes of functioning motor units in proximal and distal muscles of the arm and leg. In this system, a computer controls the motor nerve stimulation, and analyzes the potentials evoked from the muscles; a subprogram searches for instances of "alternation." In 33 healthy volunteers, aged 21 to 56 years, the median-innervated thenar muscles of one hand were tested 2 to 3 times; the mean motor unit estimate was 228 +/- 93 SD. For similar numbers of biceps brachii, extensor digitorum brevis, and vastus medialis muscles, the respective mean values were 113 +/- 40, 131 +/- 45, and 229 +/- 108 units. The reproducibility of the method was such that the overall coefficient of variation, for the normalized results from the 121 muscles studied, was 22%. The reliability of the automated method was doubled if 3 estimates, rather than one, were performed on each muscle. Comparisons of the results obtained by automated and "manual" methods indicated that the computer-derived values tended to be lower by approximately 33%.

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Avaibbb at k t ! Previously offered only through AFTAS risk management workshop, this hefty guide to risk management issues shares information every PT professional needs to know. ..on preventive recording ... malpractice and other bases of potential liabiliq..the judicial process when dealing with malpractice ... informed consent ... and more! In a handy, usable format. Numerous expert contributors. (21 7 pages, tabbed 3-ring binder, 1990) Order No. P-95 s.

There have been theoretical studies presented that postulate a change in the stimulus current amplitude required to recruit nerve fibers with different stimulus current pulse widths. Based on these theoretical predictions, it has been suggested that the stimulus pulse width parameter may be used to selectively recruit fibers of different sizes and that this selectivity should increase with increasing distance from the stimulus electrode. In this paper, a simulation study of the recruitment patterns of a population of motor nerve fibers with a histologically accurate fiber diameter distribution is presented. Nerve fiber excitation simulations coupled with a time varying field simulation suggest that, for surface stimulation, there is only a marginal selectivity achievable in the average nerve fiber diameter that is recruited across the range of commonly used stimulus pulse widths but this selectivity also increases with increased electrode distance. Experimental evidence consisting of estimates of nerve fiber diameter based on motor unit latency studies is also presented that is consistent with the predictions made by the electromagnetic field and nerve fiber excitation simulations.