It involves sitting - something we are good at - but we're taking away the seat so that your seat and legs work hard.
Lean your shoulders down to your tailbone against a sturdy flat surface, like the fridge or a wall, until your hips are even with your knees or close to that position.
You want your foot weight in the heels, not your toes, with a focus on squeezing your glutes, stomach and legs.
The four main muscles in your thighs, called the quadriceps, will feel the burn.
It you want to work harder, grab something with weight to it and do some slow front raises, some chest presses, which not only help sculpt your shoulders and upper body, it will also take your mind off the steam coming off your legs.
Try to hold the pose for 60 seconds. But if you aren't even close, practice lowering down and coming up a little, and then lowering again to get the muscles used to the load.