There's a saying in rehab: Proximal stability = distal mobility. In plain terms, if you want the far ends of your body to grab and kick stuff, then you best have a good foundation from which to work. As a hospital occupational therapist, I can't really well expect a person to be able to eat a grape off a spoon if the shoulder (and subsequently, the trunk...and subsequently the hips...) have the structural integrity of green hospital jell-O.
The distal/far reaches of a drummer are assigned seemingly impossible tasks for concurrent execution. For left-AND-right-arms-AND-legs-AND-hands-AND-feet, each limb has specific assignments independent of one another at any given time. And our foundation for all this octopus-like mobility starts at the Throne.
In a sitting position, we think of our "buns" on that seated - those gluteal muscles absorbing the seat and the seat supporting the glutes. That's the way I always thought of it in my pre-therapy life. But in reality, it's the pelvis we're balancing on from the throne. The left and right pelvis form the shape of a bowl, with our sacrum and coccyx (tailbone) at the base of the spine from the back of our body. It holds and protects organs and structures involved in our digestion and breathing. The pelvis is also our shock-absorbers in when we're walking around so the spine stays safe from the jarring of stair climbing and jogging. So in reality, the "butt" that contacts my Roc-n-Soc is actually two bony nubs at the bottom of the left and right pelvis called the ischial tuberosities (also known as IT or sitbone). The sitbones are good to be acquainted with if you do any amount of sitting in your day, and as drummers we sit... A LOT! And all that sitting can be a lot more stressful to the body than one would think.