STATURESTATURE Mechanics
STATURE / Science
Every number STATURE shows — demand factor, work per rep, range of motion — is computed from the same published biomechanical models used in sports science research. This page explains the core concepts; the sub-pages go deeper.
Every strength exercise is a physics problem. A barbell applies a downward force (load × gravity), and your muscles must produce enough torque at each joint to overcome it. The geometry of your skeleton — the lengths of your bones and how they connect — determines how much torque is required.
Biomechanical analysis models this geometry. Given your height and body proportions, it computes the length of each limb segment, the angle of each joint at each phase of a lift, and the resulting moment arms. A moment arm is the perpendicular distance from a joint to the line of force — longer moment arms require more muscle torque to move the same external load.
Two lifters of identical height and weight can have measurably different femur lengths, arm lengths, and torso dimensions. Those differences translate directly into different amounts of mechanical work per rep. STATURE makes those differences visible.
Three factors dominate biomechanical advantage in the barbell lifts:
ROM is the vertical distance the barbell travels from start to lockout. Taller lifters generally have larger ROM in the squat and deadlift; shorter arms produce smaller ROM in the bench press and overhead press. Because mechanical work equals force times displacement, a smaller ROM directly reduces the joules required per rep at any given load.
A longer femur increases the horizontal distance from the hip joint to the barbell in the squat — the hip moment arm. Every extra centimeter of femur length adds roughly 19–20 Nm of required hip extensor torque at a 200 kg squat. In the deadlift, a shorter torso and longer arms together reduce the moment arm at the lumbar spine, a major source of injury risk in heavy pulling.
Not all of your bodyweight moves against gravity in every lift. In the squat, roughly 80% of body mass travels vertically with the barbell (McBride et al., 2009). In the bench press, body mass is fully supported — only the barbell moves. STATURE applies sex-differentiated effective mass factors so that work estimates account for total system load, not just the barbell alone.
STATURE’s core output is the demand factor: a single number that captures how much harder or easier a lift is for a given body type, relative to an average-proportioned person at the same height and weight.
A demand factor of 1.00 means the lift is exactly as mechanically demanding as it would be for someone with population-average proportions. A demand factor of 1.15 means it is 15% more demanding — you must be 15% stronger, in absolute terms, to match the performance of an average-proportioned lifter at the same bodyweight.
The demand factor combines three components:
Because demand factors are ratios, they are independent of the absolute load used. The same demand factor applies whether you are lifting 60 kg or 200 kg — it is a property of your geometry, not your strength.
The demand factor feeds into every adjusted metric STATURE computes:
These metrics are computed at build time for programmatic pages and in real time on the interactive tools. The physics engine runs entirely client-side — no data leaves your device.