In the renowned 1993 study of young violinists, performance researcher Anders Ericsson found that the best ones all practiced the same way: in the morning, in three increments of no more than 90 minutes each, with a break between each one. Ericcson found the same pattern among other musicians, athletes, chess players and writers.
For Real Productivity, Less is Truly More: http://blogs.hbr.org/schwartz/2010/05/for-real-productivity-...
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I don't expect 'managers' to understand this... Mythical Man Month is nearing on 40 years old, and apparently the current crop of tech leaders haven't bothered to read it.