I'm totally confident in the good faith of the authors and their genuine commitment to provide a reliable, and probably ambitious, piece of research. I may be wrong but there should be a couple of flaws that can be hard to find in the maze of these 3 pages containing complex formulas and equations.
Wherever they may be, there are obviously major flaws that led to a mathematical model that is totally divergent from the real-life data. And that sole fact is sufficient to discard the model first, and more obviously the values it is supposed to generate.
In this case, the simulation errors take on dramatic proportions (never seen in my short but nevertheless actual experience as an industrial engineer graduate). In brief, the formulas predict that it would be necessary to put a load higher than 8000 N just to stretch the plantar fascia by about 1%, when the real-life data tell us, quite bluntly that :
1- about 100 N would do the work
2- no plantar fascia exist anymore beyond 880 N of traction
The second point is by far the most comical : it is physically impossible to reach the recommended 8000 N for the simple reason that the plantar fascia would have broken way before.
In this case the simulated and actual values diverge from a factor 80.
Just to give you an idea of how huge this divergence is, imagine a reckoning that is supposed to give a rather accurate estimation of your body weight, given other body data. If you weight 70 kg, an equation system that goes wrong by a factor 80 would predict à theoretical body weight of about 5600 kg !!!