The Failure Behavior of the Anchorage of Hairs During Slow Extraction

In a study from 2001, researchers investigated the anchorage strength of hairs in pig skin by extracting them at a slow speed of 0.1 mm/s and recording the pulling force and displacement of the tweezers. They found that anagen (growing phase) hairs had a different force-displacement relationship and were easier to extract, with a maximum force of 0.36 N, compared to telogen (resting phase) hairs, which required 1.8 N. Anagen hairs also had a longer extracted hair length of 4.8 mm, versus 3.0 mm for telogen hairs. The study suggested that two phenomena contribute to the anchorage of anagen hairs: failure at the interface between the hair and skin around the inner root sheath (IRS), followed by failure of the hair itself. A model for anagen hair extraction was proposed based on these findings.