A really interesting study just came out on PLOS One that should be of particular interest to those of us who say they just don’t have enough time to exercise. The study took a bunch of sedentary guys and divided them into three groups: regular exercise, interval training and lazy controls. The guys in the exercise group had to continuously exercise for 50 minutes, the lazy controls did nothing, and the interval training group did three 20-second ‘all-out’ cycle sprints interspersed with two minutes of low speed cycling (just ten minutes of alternating intensities of exercise). 
After twelve weeks the researchers noted “that brief intense interval exercise improved indices of cardiometabolic health to the same extent as traditional endurance training in sedentary men, despite a five-fold lower exercise volume and time commitment.”
It’ll be interesting to see if anyone measures the effects of such brief interval exercise on mood and anxiety disorders (see a 2014 blog post I wrote about the antidepressant effects of exercise).