The failure behavior of the anchorage of hairs during slow extraction
March 2001
in “Journal of biomechanics”
TLDR Growing hairs are easier to pull out than resting hairs due to different anchorage strengths.
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.
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