Ankle muscle strength discriminates fallers from non-fallers

Area of Science:

• Biomechanics
• Gerontology
• Neurology

Background:

• Center of pressure (CoP) displacement negatively correlates with maximal isometric torque (MIT) of ankle muscles.
• This relationship has not been studied in elderly fallers (EF).

Purpose of the Study:

• To investigate the relationship between ankle muscle MIT and CoP displacement in a diverse age group, including EF.
• To identify a critical torque threshold below which balance is impaired.

Main Methods:

• Measured MIT of plantar flexors (PFs) and dorsal flexors (DFs) and CoP in 90 volunteers (young adults, middle-aged adults, elderly non-fallers, and EF).
• Normalized MIT (nMIT) and CoP (nCoP) using body weight and height, respectively.
• Summed PF and DF MIT to calculate overall maximal ankle muscle strength.

Main Results:

• A significant negative correlation was found between nCoP and nMIT.
• 90% of EF had an nMIT below 3.1 N·m·kg(-1), while 85% of non-fallers had an nMIT above this threshold.
• Postural stability was significantly reduced below the 3.1 N·m·kg(-1) threshold.

Conclusions:

• Ankle muscle weakness is a contributing factor to postural instability and increased fall risk.
• A threshold of 3.1 N·m·kg(-1) for nMIT can identify individuals with compromised balance.
• Measuring ankle torque may aid in the clinical identification of potential fallers.