The Fun of Latin and Ballroom Dancing Explained with Mechanics

Last semester, I picked up Latin and ballroom dancing as a hobby. All through high school I didn’t dance, but thanks to the recommendation of a friend I decided to go to free introductory dance lessons. At first it was just fun to socialize, learn some new steps and practice body coordination, but I soon grew to love it. Our Latin dance teacher has a particular habit of describing dance movements in terms of coordinates and physics; rumba walks require your center of mass over your front foot for balance and look best if you extend the axis running from your shoulder to opposite leg as far as possible. This mentality has slowly creeped its way into my brain, and eventually I realized that, hey, dance really is about physics! You don’t know it while dancing, but every movement is purposeful when viewed through a pair physics-colored safety glasses.

When first starting to dance, everything is about mechanical control of your body and constantly asking the question, where is my center of mass (let's abbreviate it as COM) right now? Of course you wouldn’t consciously ask yourself that, but even without asking your body will give the answer. While posing still, if your COM is not somewhere well supported by your limbs, you’ll fall down because relative to the point of floor contact your bodyweight is generating torque on your COM. On a single limb, your COM needs to be over the supporting limb to stay balanced. On more than one limb, your COM should be somewhere between the limbs based on how your bodyweight is distributed towards each (unless the floor is slippery. Then it’s best to choose a limb to center over otherwise your supports will simply fall apart and you’ll hit the floor). When you begin to move horizontally, core muscles contract in order to support your center of mass on its journey from one place to another through fluid motion.

Spinning generates torque along other axes and accordingly makes you conscious of where your body axes are. Since torque acts along levers originating at your COM, all body axes will include your COM. Torque is defined in parallel to Newton’s second law by the equation

                                                              1.       τ=Iα    (torque equation)

Where τ is torque, I is inertia and a is angular acceleration. Inertia is related to the distribution of your body mass in space around a rotational axis. While spinning on an axis perpendicular to the ground like a ballerina or ice skater, contracting your arms from an extended position can reduce your moment of inertia and increase your angular acceleration based on the existing torque. And expanding your body to increase inertia while tilting your axis slightly can slow your spin and generate a simultaneous forward momentum to get you out of the spin and into horizontal motion. Manipulating the position of your center of mass so that it remains relatively stationary while moving around it by torque is what allows break-dancers to do such complicated flips. Dancing is all a game of mechanics.

Fig. 1: Dancing as an act of balancing forces (University of Illinois at Urbana-Champaign)

What makes Latin and ballroom dance special to me is that all of the dances are partner dances. This means double the complication, but also double the fun! Instead of your COM, your tandem COM is what counts. And all movements and spins are done together accordingly. What’s even more exhilarating is that your tandem COM is without your body, so when you go for a partner spin you’ll both be spinning about an axis between the two of you (assuming equal mass). In Latin and ballroom dance, a concept that is stressed is partner connection. This means making sure both of your bodies push against each other at the point of contact in a way that conveys information about how each of you is moving. What this also does is make the tandem COM more stable. When partner connection is weak, your tandem COM can constantly dissolve and reform. This makes both partners unstable and rely on knowing their own COMs to maintain balance. A strong connection means both partners can fully commit to the unwavering tandem COM and structure each motion together. And believe me, you can feel this. It’s really exciting when you and your partner start to move as one, and not having to worry about your own balance allows you to focus on the art of the dance.

This post is a little less reference and math heavy than some of the past ones, which I thought would be a nice break. I just wanted to share what makes Latin and ballroom dance such a special hobby to me. Dancers out there, please let me know if you think my description does dance justice in the comments below. Other Thinkers, I wanna hear your thoughts too. And check out a few minutes of this video of world-class Latin dancers. Thanks guys!