You should first also look at this very impressive Video of the Virtual Soldier, featuring realistic digital humans (and Virtools ;). The point is to create a virtual human, with all muscles, joints, and behavior. They already simulate effort minimisation, comfort maximisation, all things we do naturally. Eventually they will simulate muscle fatigue and heart beat modification during effort !! All this to be able to prototype ergonomics of work environment, clothes etc.
“Santos, an intelligent avatar with realistic biomechanical abilities, functions in a powerful human modeling and simulation environment, the Santos environment.
Santos conducts human factors studies in design relevant to training, production, or performance needs of real-world realistic system addresses rigorous biomechanics, gait, motion prediction, and related issues. Santos, like not other digital human simulation solution, acts intelligently and autonomously to allow humans to safely and effectively understand human performance in and response to many scenarios.”