Sam Liu

Sam Liu studies in a laboratory the thing most dunkers only feel. He is a biomechanics researcher who calls himself a dunk enjoyer rather than a dunker, and his route to the force plates ran through basketball. The fire caught in 2008 while he watched the Olympics, during a stretch when basketball was a national frenzy in China, and the dream started as the NBA before shrinking to Division I, then to college basketball anywhere.

He did most of his schooling in China before two years in Australia, where by his own account he played too much basketball and not enough of anything else. When his father had a chance to work in the United Kingdom he followed, and found a country with almost no basketball culture and no high school team, so he simply trained. He ran the old internet jump programs, Air Alert and its endless plyometrics, which he says did not help at all, and ran cross country, which helped less. On his best day he could touch the hoop. It got serious at Oxford, where he read engineering science and played under a strength coach for the first time.

Biomechanics turned up there as a third-year elective, and surprised him, because the field leaned toward the mechanical properties of bone and tendon rather than whole-body movement. Sam wanted the movement. When he asked his master’s advisor about a PhD on jumping, she pointed out that a good athlete would put his head through the ceiling of the gait lab, which also had only two small force plates in a straight line, useless for measuring what each leg does. So he came to the United States. By the time he sat down with Dylan Haugen he was in the final year of a PhD at Stevens Institute in New Jersey, under an advisor who let him put an adjustable hoop in the lab. The study took four years of approvals before a single data point existed, and covers 21 male and female athletes jumping with and without a basketball.

His first research question is the one dunkers argue about constantly: how much planting the plant leg actually does, and how much blocking the block leg does. The answer held for essentially everybody in his sample, which almost never happens in movement analysis and points to a feature of the task rather than the person. The plant leg does much of the blocking too, killing most of the body’s forward momentum while also accelerating it upward, which is why it carries the deeper angles and the higher demands. The block leg lands later, once the center of mass is already rising, so every ounce of force it produces goes straight into height. He can also explain why Isaiah Rivera‘s plant-leg hip is always sore: it catches the body at long muscle length, exactly the condition that produces soreness.

Most of his other answers talk people out of their anxieties. Arm swing works indirectly, by changing how the legs push into the ground, and nearly all the published research compares a full swing against hands on hips, which describes nobody’s running jump. Penultimate length is a proxy for the approach rather than a rule, so the short penultimate of a jumper like Travis Reynolds is fine as long as it still delivers speed and a low center of mass. Limb proportions are a non-modifiable trade-off, so ignore them and let the stimulus rather than the weight room number guide the work. He argues the ceiling on women’s dunking is specific practice and not physiology, since elite men and women who jump the same height produce force patterns you cannot tell apart. Sam keeps a stake in his own findings, writing papers, taking breaks from writing about dunking to go dunk, and front-rimming a windmill on a nine-foot hoop at his school.