Waiting for the weekend can often seem unbearable, a whole seven days between Saturdays. Having seven days in a week has been the case for a very long time, and so people don’t often stop to ask why.

Just over half the states in the U.S. have schools that operate on a 4 day/per week schedule. Their numbers continue to climb. It's an effort by schools to attract and retain teachers.

In TODAY.com's Expert Tip of the Day, a trainer explains how incorporating HIIT into a weekly workout routine can boost one's ...