You must brush your hair gently and delicately, even when in a rush, because brushing too forcefully stretches the hair fiber to its breaking point and damages it.

noli's read

This recommendation is scientifically sound and validated. In cosmetic science, experimental studies (such as the work of Clarence Robbins and Yash Kamath published in the Journal of Cosmetic Science) confirm that mechanical brushing is a major cause of hair breakage due to friction and tension. When pulling forcefully on a knot, an impact tension is created that exceeds the hair's natural resistance, causing clean fractures along the shaft. Furthermore, aggressive friction lifts and erodes the cuticles (the external protective barrier), making the hair porous, dull, and prone to split ends. The elastic analogy used by the creator is therefore scientifically very accurate: it faithfully illustrates the physical elasticity limits of the fiber. Taking your time to detangle gently, ideally by starting at the ends, is the best method to preserve the aesthetic integrity of your hair.

the sources

No named source held this one up — that absence is part of the verdict.