Researchers developed a laboratory machine for testing the spherical deformation in textiles and an algorithm for calculating the deformation of flat textiles under dynamic loads. Investigation of the spherical elongation of fabrics under cyclic stresses focused on the parts of a garment exposed to the most stress: the elbow and knee. Results from simulated wear conditions provided data for calculating the elongation of warp yarns and filling yarns in the samples, and established the limits of yarn stress. The deformation of a 100 percent woolen fabric was greater than that of a wool/polyester blend fabric due to structural changes in individual fibers. The deformation of a twill fabric was greater than that of a plain weave fabric due to the lower number of yarn crossings. Relaxation was greater in the woolen fabrics. 9 refs.