Stiffness of Human Hair Correlates with the Fractions of Cortical Cell Types

The study investigated the relationship between hair stiffness and its microstructure in 156 Japanese women. It found that hair stiffness, measured by bending modulus, was significantly higher in hair rich in para-like cortical cells. The bending modulus correlated with the fraction of para-like cortical cells, while the elastic moduli inside macrofibrils were similar for both para- and ortho-like cortical cells. The differences in hair stiffness were attributed to the intermacrofibrillar materials associated with the different cortical cell types.