Understanding the J-Curve and Its Physical Forces at Work

The Geometry of the Hybrid Approach

Modern high jump, dominated by the Fosbury Flop, differs from the other jumps because of its nonlinear approach run. We use what is known as a [J-shaped curve.]

This hybrid path combines two phases with distinct biomechanical purposes. The first part is a straight run (generally 3 to 5 steps) designed to generate pure horizontal speed and rhythm, similar to sprint acceleration.

The second part is a tight curve (4 to 5 steps) leading toward the bar. This transition from straight to curved is the secret of the jump.

The goal is not simply to reach the landing mat, but to generate physical forces that the athlete could not produce by running in a straight line.

The coach must ensure that the athlete does not [cut] the curve (making it too flat) or start it too early, since the integrity of this geometric path is what allows the necessary rotation in the air without conscious muscular effort

Generating Centrifugal Force

The magic of the curve lies in the physics of centrifugal force. When a body moves at speed along a curved path, a force is generated that pushes it outward.

To avoid being flung off tangentially, the jumper must lean toward the inside of the curve. This lean creates an angle between the body and the ground.

The faster the athlete runs and the tighter the curve, the greater the lean required. This leaning position stores potential energy.

At takeoff, when the foot plants and brakes the horizontal movement, that centrifugal force is released, acting like a catapult that helps launch the athlete vertically and, crucially, facilitates the back-first rotation over the bar.

Without the curve, there is no fluid rotation; the athlete would have to [force] the turn with the shoulders, losing height

Maintaining the Integrity of the Body Lean

A common technical error is leaning by bending at the waist or lowering the inside shoulder. The coach must insist that the lean comes [from the ankle.]

The body should behave like a rigid board, leaning as one unit toward the center of the curve’s imaginary circle. This correctly aligns the center of mass.