From the "No S**t Sherlock" Department:
"Working men and women across all occupations felt mentally and physically better on the weekends regardless of income, work hours, education, age or marital status, the researchers found."
Though not specifically mentioning it, the study assumes a 7 day week and merely confirms the failed grand social manipulations of centuries gone by.
The French attempted a 10 day week after their Revolution in 1791, and the Soviet Union tried to implement a 5 day week many times, but both were counter productive, and inevitably abandoned for the tried and true 7 day week with an obvious weekend.
Throughout history, archeological records show the 7 day week as the preeminent model for human activity.
The traditional 7 day week could be posited as a social construct or religious edict, but I think it has more to do with our original design and disconnection to the natural cycles of this rock we live upon.
But I’m just silly that way...