I recently find out that these short classes are actually "Pilates for procrastinating PhD students". I am writing my PhD and therefore I am sitting the whole day in front of the computer. I usually do an aerobic-workout every morning that heats me up but still I start to freeze after a few hours sitting and typing (Israeli winters are cold, too). So I realized that doing one of these challenging 20 minute workouts every 2 hours really works for me - not only heating me up but also let's me get back to work with much more energy. Thank you!