Sex Differences in Human Ankle Stiffness During Standing Balance

Area of Science:

• Biomechanics
• Human Movement Science
• Orthopedics

Background:

• Ankle stiffness is crucial for maintaining upright balance and preventing injuries.
• Understanding sex differences in ankle mechanics is vital for tailored rehabilitation and injury prevention strategies.

Purpose of the Study:

• To quantify sex differences in 2-dimensional (2D) ankle stiffness during various upright standing balance tasks.
• To investigate the underlying anthropometric and neuromuscular mechanisms contributing to observed sex differences in ankle stiffness.

Main Methods:

• Utilized a dual-axis robotic platform to measure ankle torques and quantify 2D ankle stiffness.
• Healthy young adults performed balance tasks including co-contraction, weight-bearing, and torque generation.
• Ankle stiffness was analyzed in both sagittal and frontal planes.

Main Results:

• Males consistently demonstrated significantly greater ankle stiffness than females across most tested conditions and planes.
• Sex differences in sagittal plane ankle stiffness were explained by both anthropometric and neuromuscular factors.
• Frontal plane ankle stiffness differences were primarily attributed to anthropometric factors.

Conclusions:

• Significant sex differences exist in 2D ankle stiffness during upright balance, with males being stiffer.
• Anthropometric and neuromuscular factors play differential roles in explaining these sex differences across movement planes.
• Findings provide a basis for understanding sex-specific locomotion stability and ankle injury risk.