Quantitative anatomy of the growing psoas major muscle in the human fetus — an anatomical, digital, and statistical study

In terms of morphometric parameters, the psoas major displays growth dynamics diverse to four functions: from a gradual inhibition of growth, which is typical of both natural logarithmic functions (total length and tendon length), and a reverse model (belly width and tendon width) through a linear growth (distance between the origin and the widest belly level, muscle projection surface area, belly projection surface area, tendon projection surface area, and volume) to a hyperbolic growth (belly length).