A Commentary on Kugler,Turvey, Schmidt,and Rosenblum's Ecological Approach to Motor Systems

I argue that Kugler, Turvey, Schmidt, and Rosenblum's (1990) attempt to find adiabatic invariants is premature and describes several prior considerations that must be taken into account to properly understand a motor system. I maintain that Kugler et al. can and should be much more direct in taking the thermody- namic dissipative systems perspective on motor activity. For example, performance in a true comfort mode should be something that can be maintained indefinitely in practice for at least 3 to 5 hr. Then, it can be expected that thermodynamic equilibrium or near equilibrium has been established. Even if this is done, however, the fact that animals have alternative optimizations available to them and choose what they optimize in a given performance raises problems that Kugler et al. have not addressed. In a second part of this article, I outline more specific issues concerning flow that Kugler et al. should confront and suggest how they might proceed. Finally, I explain why I am especially eager to see them investigate locomotion as against upper body activities and describe the sequences of experiments that should be performed.