One of the 5 foundations of Lean Six Sigma is a concept called 'Flow' ...when a process moves in a steady, balanced and sustainable rate of throughput which matches as close as possible the customer demand, without stress or overburdening of the resources ( workers or machinery).  The concept of Flow also applies to a state of mind, action  and behavior of an individual worker.  In this context 'flow' is defined by behavioral psychologists and cultural anthropologists, such as professor Natasha Dow Schull from the Massachusetts Institute of Technology (MIT) and author Mihaly Csikszentmihalyi, who in 1990 crystallized the idea of "flow" in his best selling book of the same name.
Prof Schull says 'To achieve flow your worker activity needs to match your worker ability'.  

Ahhh ! This is directly analogous to the lean six sigma understanding of flow.

References to Prof Schull  and her studies of flow in this BBC article. http://www.bbc.co.uk/news/business-32628753