Unloading reaction during sudden ankle inversion in healthy adults

Area of Science:

• Biomechanics
• Human Movement Science

Background:

• Sudden ankle inversion can lead to injuries.
• Understanding the immediate biomechanical response is crucial for injury prevention.

Purpose of the Study:

• To investigate the dynamics of early human response to sudden ankle inversion.
• To compare human responses to a mechanical model simulating inversion.

Main Methods:

• Subjects underwent a 30° ankle tilt via trapdoor release.
• Vertical ground reaction forces (GRFs) were measured.
• Experiments were replicated using a mechanical chair model with and without viscoelastic properties.

Main Results:

• Both humans and the mechanical model showed an initial decrease in vertical GRF under the inverted leg and an increase under the supporting leg.
• Observed changes in vertical GRFs occurred rapidly after trapdoor release.

Conclusions:

• The rapid onset of GRF changes suggests that early dynamic responses to ankle inversion are dominated by mechanical events.
• Neuromuscular reactions appear to have a limited role in the initial phase of response to sudden inversion.