Multi-Axis Physiological Classification (MPC): Making Sports More Inclusive, Fair and Safe

With few exceptions, competitive sports organize athletes into male and female categories, yet sex is a proxy for the physiological variables that actually shape performance and safety. This essay argues for organizing competition around measurable physiological states: body mass, height, limb length, bone mineral density, and lean body mass. These would apply to every athlete, regardless of sex assigned at birth, gender identity, or hormonal history. The argument rests on four principles: athletes already submit to body measurement; greater inclusion means more people participating; sorting by the actual variables is fairer than sorting by a proxy; and sports exist for fair and safe competition for everyone, which makes the other three obligatory rather than optional. Drawing on physiological, ethical, and legal literature, the essay frames the proposal as “sports with categories, not categories with sports,” responds to ten counter-arguments, and sets out an implementation path that builds on existing anti-doping systems (Therapeutic Use Exemptions and the Athlete Biological Passport) and low-cost body composition measurement.