Biophysics of Figure Skating: How Physics Powers Quadruple Axles and High-Speed Spins

Science Friday host Flora Lichtman interviews Deborah King about the biomechanics of elite figure skating. They explain how skaters generate up to 4.5 revolutions in the air, the importance of body position and timing, and how mental pressure intersects with physical skill. The discussion covers moment of inertia, angular momentum, and the forces experienced on landing, as well as how off-ice training and energy systems support these feats. The episode also touches on differences across skating disciplines and how physics informs performance and injury prevention.

Overview

In this Science Friday episode, Flora Lichtman sits down with Deborah King, a professor of exercise science and athletic training at Ithaca College, to unpack the physics and biomechanics behind the most demanding moves in Olympic figure skating. The conversation centers on how athletes defy expectations of what the human body can do on ice, balancing aerodynamics, rotation, and landing mechanics with mental focus and training strategies. King emphasizes that physics sets the stage for what skaters can accomplish, but technique, body shape, and cognitive preparation are essential to perform within those physical constraints.

The Hardest Skill: Quadruple Axle

King describes the quadruple axle as a forward takeoff that results in a 4.5 revolution jump, with landings that occur backward. She notes that the skater’s airtime is typically under a second, roughly 0.8 to 0.9 seconds, which makes the rotation speed astonishingly high. Because the jump begins facing forward yet lands facing backward, the skater must complete an extra 0.2 revolution to reorient, effectively creating a 4.5-turn rotation in the air. "In the quadruple axle, you're probably seeing airtime 0.8 to 0.9 seconds." - Deborah King, Professor of Exercise Science and Athletic Training, Ithaca College.

Spin Mechanics and Body Position

Beyond airtime, the way Malinin and other skaters position their bodies mid-air is critical. King highlights how high the jump can be and how quickly the body snaps into a tight rotational configuration, with legs straight, feet close, and arms crossed to reduce inertial resistance. She points out that in fast rotations there is little time for head spotting, which makes internal body awareness and proprioception essential to know where the body is and how to land. "he goes high, then snaps into his rotating position so quickly." - Deborah King.

Body Size, Inertia, and Rotation

Weight, height, and overall body shape influence a skater’s moment of inertia, which dictates how easily they can spin. King explains that a more slender, pencil-like frame minimizes rotational resistance, enabling faster spins. Skaters also face a trade-off: bringing limbs in tight increases spin rate but places greater demands on muscular control to hold the position and maintain balance. She uses a tire-swing analogy to illustrate the concept: "you can make it go faster by pulling your arms in" - Deborah King.

Forces on Landing and Injury Risk

Landing a quad jump subjects the body to extreme forces for only a few milliseconds. King cites estimates that landings can generate 8 to 10 times a skater’s body weight, depending on technique and stiffness of the impact. She contrasts skating with ballet, noting that ballet often distributes impact through a longer range of motion in the ankle, knee, and hip, which can spread forces over time. The discussion also touches on how researchers estimate these forces and how they relate to injury risk, with the recognition that precise in-skate measurements remain challenging but are an active area of study. "8 to 10 times your body weight" - Deborah King.

Endurance, Energy Systems, and Training

Free programs in figure skating demand endurance in addition to explosive power. The host notes that a four-minute free skate sits at the intersection of aerobic and anaerobic energy systems, requiring sustained power, control, and transitions between jumps and glides. King underscores the hybrid energy demands, comparing the length to a miler in track and field, and explaining how skaters train to optimize both aerobic power and anaerobic capacity while maintaining technical precision. "It's a combination of both aerobic power and anaerobic energy systems" - Deborah King.

Mental Side, Pressure, and Performance

The conversation also delves into the psychological dimension: the pressure to perform at the Olympics, the long lead-up to a four-year cycle, and how mental factors must align with physical execution at the critical moment. King notes that even world champions face challenges, and success depends on integrating physical technique with mental readiness at the exact moment of takeoff and landings. "The pressure to perform is absolutely major" - Flora Lichtman.

Training, Off-Ice Preparation, and Cross-Sport Transfer

The discussion considers training strategies and the possibility of skaters applying rotational skills to other sports such as aerials and halfpipe, with transfer depending on the sport’s rotational demands and in-flight mechanics. King also discusses the value of off-ice conditioning, the importance of targeted muscle groups, and how improvements in loading tolerance, proprioception, and balance translate into on-ice performance and injury prevention. The episode closes with reflections on the broader questions scientists seek to answer about figure skating physics, including how to quantify loads, optimize training schedules, and link on-ice techniques to off-ice conditioning.

Key Quotes

"In the quadruple axle, you're probably seeing airtime 0.8 to 0.9 seconds." - Deborah King

"he goes high, then snaps into his rotating position so quickly." - Deborah King

"you can make it go faster by pulling your arms in" - Deborah King

"8 to 10 times your body weight" - Deborah King

"It's a combination of both aerobic power and anaerobic energy systems" - Deborah King