Maximum Force Capacity of Back Extensor Muscles in Healthy Women and Men: Not Different, if Anthropometrically...

Area of Science:

• Biomechanics
• Human Physiology
• Comparative Anatomy

Background:

• Trunk extension strength is a key functional measure.
• Understanding sex-based differences in strength is crucial for various applications.
• Previous research has not fully elucidated sex-based differences in normalized trunk strength.

Purpose of the Study:

• To compare absolute and relative trunk extension strength between healthy men and women.
• To investigate the influence of upper body weight on sex-based strength differences.
• To determine the clinical relevance of observed strength variations.

Main Methods:

• Isometric maximal voluntary contraction (MVC) testing was performed by 115 women and 124 men.
• Maximal torque, upper body weight (expressed as torque), and the MVC-to-upper-body-weight ratio were primary outcomes.
• Results were evaluated for statistical significance, effect size (ES), and difference in mean values (DMV) relative to minimal important difference (MID).

Main Results:

• Men demonstrated significantly higher absolute MVC values and upper body torque than women (p < 0.0001).
• After normalizing for upper body weight, the difference in relative trunk extension strength between sexes was not considered clinically relevant (p = 0.0055, ES = 0.364).
• Both sexes showed a physiological strength reserve of approximately 100% relative to upper body weight.

Conclusions:

• Absolute trunk extension strength is markedly greater in men compared to women.
• Relative trunk extension strength, adjusted for upper body weight, is comparable between sexes.
• Sex-based differences in trunk strength are largely explained by variations in absolute body mass.