The pleasure to create, adapt or combine equations according to a physiological rationale (e.g. maximizing metabolic energy saving, minimizing mechanical work), then find out that nature follows the obtained predictions in terms of control variables. Sometimes, particularly when facing complex problems in physics, mechanical simulation software has been used to explore potential solutions in a wide variable space. In some cases, models had to be incorporated into customly writen programs (Mathematica®, LabView).

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