Ground Reaction Force
The force exerted by the ground upon the body in reaction to the force the body exerts on the ground, as described by Newton's Third Law; a central concept in orthotic biomechanics.
Full Definition
Ground reaction force (GRF) is the vector force produced by the ground in response to the load applied through the foot during standing and locomotion. In orthotic practice, understanding the direction and magnitude of the GRF relative to joint centres is essential for designing devices that create appropriate extension or flexion moments at the knee and ankle. Editors will encounter the term in biomechanical assessment reports, research papers, and clinical justification documents. 'Ground reaction force' is not hyphenated. It is commonly abbreviated GRF after first use. Editors must distinguish GRF from 'ground reaction AFO' (GRAFO), which is a device designed to harness GRF to extend the knee.
Usage
Usage note: Do not hyphenate. Abbreviate to GRF after first definition. Ensure editors do not confuse this biomechanical concept with the device category 'ground reaction AFO,' which exploits this force therapeutically.
In Context
- "The biomechanical report showed that the ground reaction force passed posterior to the knee centre, producing a flexion moment that the orthosis was designed to counteract." — Biomechanical assessment report
- "Distinguish GRF (ground reaction force) from GRAFO (ground reaction ankle foot orthosis) if both terms appear in the same clinical document." — Editorial checklist