ligament

I have two basic questions for the experts in the soft tissue biomechanics community. 

a) I am interested in the biomechanics of a specific tendon in a specific high-speed deformation. How plausible is it for me to assume strain-rate independence, and therefore, the existence of a strain energy function? In other words, how accurate is the assumption of pseudoelasticity for tendons under high strain-rate? I feel comfortable with the assumption (evidence would help a lot, however) for tissues such as mesentery, skin and, I guess, even muscle.