UC Berkeley Engineers Show Hula Hooping Relies on Full Lower Body

Keeping a hula hoop spinning against gravity is not simply "all in the hips" or dependent on an hourglass waist shape, according to a new study by University of California, Berkeley mechanical engineers reported by UC Berkeley News.

Published in the journal Nonlinear Dynamics, the research was led by UC Berkeley Professor of Mechanical Engineering Oliver O’Reilly alongside graduate student Chrystal Chern and former postdoctoral researcher Theresa Honein, now an assistant professor at the American University of Beirut.

Challenging the 2025 NYU Hourglass-Cone Model

The UC Berkeley team began investigating the biomechanics of hula hooping after reading a 2025 New York University physics study that modeled the human body as a rigid, undulating hourglass-shaped cone and concluded that a sloped waist and curvy hips were necessary to keep a hoop from sliding to the floor.

Because human hoopers successfully spin hoops regardless of waist curvature, O’Reilly, Chern, and Honein modeled the lower body as a system of four interconnected pendulums representing the torso and hips, the femur (thighs), the tibia (shins), and the metatarsals (feet).

Coordinated Leg Joint Kinematics and Upward Launch Speed

By analyzing the equations of motion across those four skeletal segments, the researchers showed that vertical oscillations generated by the knees, ankles, and thighs work in concert with horizontal hip rotation to create the upward friction and normal forces needed to counteract gravity.

The team found that waist size and torso slope have a negligible effect on whether a hoop stays up. Instead, successful hula hooping requires launching the hoop at a sufficient initial speed in the same direction as the body’s rotation while synchronizing the subtle up-and-down rhythm of the lower-body joints.