This paper presents results of experimental and computational analysis of the artificial muscle (in form of coiled spring) made of nylon fishing line. By experimental measurement, the elasticity modules of chosen untwisted and twisted fishing line as well the spring constant of the coiled spring are found The prestressing force in the twisted line and the coiled spring is measured as well. The measured parameters are put into the analytical and Finite Element Method (FEM) computational model of the coiled spring to calculate the elongation that results from the applied mechanical load. Linear and non-linear numerical elastostatic analysis is performed. An expression is established for analytical calculation for the thermoelastic stroke of the muscle. A good agreement of the measured and calculated results is obtained. Contrary to analytical methods, FEM enables modeling and simulating complex mechanical structures that occur in biomechanical and mechatronic applications of the artificial muscles in a form of nylon springs.