Interpreting Charts

Force-time chart

The primary chart shows vertical ground reaction force (vGRF) over time.

Series

Colour	Series	Y-axis
Green	Total force (L + R)	Left (N)
Orange	Left plate only	Left (N)
Blue	Right plate only	Left (N)
Yellow	Velocity	Right (m/s)
Purple dashed	Displacement	Right (m)

Phase bands

Coloured shading marks the automatically detected phases:

Phase	What it means
Unweighting	Force drops below bodyweight — eccentric initiation
Braking	Force below bodyweight, downward velocity decelerating
Propulsion	Force above bodyweight, upward acceleration
Flight	Force ≈ 0, airborne
Landing	Impact spike on landing

See Jump Phase Definitions for full detail.

Bodyweight line

A dashed horizontal line at the athlete’s estimated bodyweight. Anything above = net upward force; below = net downward (unweighting / flight).

Velocity and displacement

Velocity is computed by trapezoidal integration of net force ÷ mass. Displacement is a second integration of velocity. Both reset to zero at takeoff.

• Peak negative velocity = end of braking phase
• Velocity = 0 at takeoff
• Peak positive displacement = jump height (matches impulse-momentum method)

F-V and F-D loops

Below the main chart are two scatter sub-charts:

• F-V loop — force vs velocity throughout the propulsive phase. Area = propulsive work.
• F-D loop — force vs displacement. Slope at origin ≈ stiffness.

Left-right asymmetry

When two plates are connected, the metrics panel shows an Asymmetry Index (AI):

AI = (|L − R|) / max(L, R) × 100%

Values >15% may warrant attention depending on the metric and athlete context.