Effects of incremental ambulatory-range loading on arch height index parameters

Area of Science:

• Biomechanics
• Orthopedics
• Human Locomotion

Background:

• The medial longitudinal arch's deformation under body weight is crucial for foot function.
• Current assessment methods, like the Arch Height Index, use static sitting and standing postures (10% and 50% body weight).
• These static loads underestimate the forces experienced during ambulation, limiting understanding of arch behavior under dynamic conditions.

Purpose of the Study:

• To compare arch height changes under static (sitting, standing) and incremental body weight loading (10%-120%).
• To evaluate the linearity of arch stiffness across a range of ambulatory loads.
• To refine our understanding of foot biomechanics during walking.

Main Methods:

• 25 healthy subjects underwent arch height measurements using a force target-matching procedure.
• Measurements were taken at incremental body weight loads from 10% to 120% in 10% steps.
• Static sitting and standing arch heights were compared to specific load conditions.

Main Results:

• Arch deformation was less in the sitting position compared to the 10% body weight condition.
• No significant difference was found between standing and 50% body weight conditions.
• Arch deformation showed both linear and curvilinear trends across the ambulatory load range, with most deformation occurring within this range.

Conclusions:

• Static arch height measurements may not fully represent deformation under typical ambulatory loads.
• Arch stiffness is not strictly linear throughout the ambulatory load range.
• The majority of healthy foot arch deformation occurs during the dynamic loading of ambulation.