It is recommended to carry out uni- and biaxial elongation experiments applying tensile stress controlled experiments, including subsequent stress relaxation measurements and determine the recoverable strain.
This should be done at various transient stress ramps equivalent to related elongation/stretch rates.
This is expected to enable you to derive (i) stress- and (ii) deformation energy related fatiguing characteristics of your material. From (i) and (ii) different characteristic maximum stresses can result which depend on the material/tissue structure and it’s re-healing/repair mechanisms, in case such exist.