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Subject-specific mathematical muscle models could prove valuable for predicting the forces necessary to achieve therapeutic loading conditions in individuals with paralyzed limbs. Although numerous muscle models are available, three modeling approaches were chosen that can accommodate a variety of stimulation input patterns. To our knowledge, no direct comparisons between models using paralyzed muscle have been reported. The three models include 1) a simple second-order linear model with three parameters and 2) two six-parameter nonlinear models (a second-order nonlinear model and a Hill-derived nonlinear model). Soleus muscle forces from four individuals with complete, chronic SCI were used to optimize each model's parameters (using an increasing and decreasing frequency ramp) and to assess the models' predictive accuracies for constant and variable (doublet) stimulation trains at 5, 10, and 20 Hz in each individual. Despite the large differences in modeling approaches, the mean predicted force errors differed only moderately (8\u201315 % error; P = 0.0042), suggesting physiological force can be adequately represented by multiple mathematical constructs. The two nonlinear models predicted specific force characteristics better than the linear model in nearly all stimulation conditions, with minimal differences between the two nonlinear models. Either nonlinear mathematical model can provide reasonable force estimates; individual application needs may dictate the preferred modeling strategy.<\/jats:p>","DOI":"10.1152\/japplphysiol.00935.2005","type":"journal-article","created":{"date-parts":[[2005,11,24]],"date-time":"2005-11-24T01:44:38Z","timestamp":1132796678000},"page":"1027-1036","source":"Crossref","is-referenced-by-count":27,"title":["Predicting human chronically paralyzed muscle force: a comparison of three mathematical models"],"prefix":"10.1152","volume":"100","author":[{"given":"Laura A.","family":"Frey Law","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard K.","family":"Shields","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"R1","unstructured":"Aaron SLand Stein RB.Comparison of an EMG-controlled prosthesis and the normal human biceps brachii muscle.Am J Phys Med55: 1\u201314, 1976."},{"key":"R2","doi-asserted-by":"publisher","DOI":"10.1007\/BF02441424"},{"key":"R3","doi-asserted-by":"publisher","DOI":"10.1152\/jn.1976.39.4.788"},{"key":"R4","doi-asserted-by":"publisher","DOI":"10.1016\/S1050-6411(97)00029-1"},{"key":"R5","doi-asserted-by":"publisher","DOI":"10.1109\/10.704869"},{"key":"R6","doi-asserted-by":"publisher","DOI":"10.1109\/10.247798"},{"key":"R7","doi-asserted-by":"publisher","DOI":"10.1038\/sj.sc.3100364"},{"key":"R8","doi-asserted-by":"publisher","DOI":"10.1007\/s004210050606"},{"key":"R9","doi-asserted-by":"publisher","DOI":"10.1007\/PL00013785"},{"key":"R10","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1999.86.1.350"},{"key":"R11","doi-asserted-by":"publisher","DOI":"10.1007\/BF00204116"},{"key":"R12","unstructured":"Close CMand Frederick DK.Modeling and Analysis of Dynamic Systems. 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