... University of Delaware, Newark, DE, USA and 2Department of Mechanical and Aeronautical Engineering, Civil and Environmental Engineering, and Land, Air, and Water Resources, University of California, ... lengthensinstead of shortening. Such contractions are characterizedby higher forces than isometric and shortening contrac-tions and are important parts of many functional activi-ties, such as walking. ... model parameter.Sensitivity analysis showed that under isometric condi-tions at 90° of knee flexion, parameters a, b, A 40, and τ2accounted for ~85% of the total variation of the force-time...