Sex differences in quadriceps strength in OA.

Area of Science:

• Orthopedics
• Sports Medicine
• Human Physiology

Background:

• Knee osteoarthritis (OA) is a prevalent condition affecting joint function.
• Sex differences in muscle strength are well-documented but less understood in OA populations.
• Muscle volume is a key determinant of muscle force production.

Purpose of the Study:

• To investigate sex differences in quadriceps torque and power, normalized for muscle volume, in individuals with knee OA.
• To identify factors contributing to any observed sex differences in muscle function.

Main Methods:

• Assessed isometric torque, isotonic power, and maximal unloaded velocity in men and women with knee OA.
• Normalized torque and power to quadriceps muscle volume.
• Utilized the interpolated twitch technique for voluntary activation (VA) assessment.
• Measured evoked twitch and torque-frequency characteristics to evaluate muscle fiber properties.

Main Results:

• Women exhibited significantly lower torque and power across all tested loads compared to men.
• Normalizing for muscle volume reduced sex differences in power by 50%, though significant differences remained at lower contraction intensities (10-40% MVC).
• No significant sex differences were found in voluntary activation, torque-frequency properties, or twitch contractile characteristics.

Conclusions:

• Minor sex differences in quadriceps torque and power persist in knee OA patients when muscle volume is considered.
• Voluntary activation and intrinsic muscle contractile properties do not appear to explain these remaining sex differences.
• Other unmeasured factors likely contribute to the observed sex disparities in muscle function in this population.