Use it or lose it? Effects of age, experience, and disuse on crawling

Videos of typical adults crawling, which can be compared to videos of experienced infants crawling. What happens to early acquired but later abandoned motor skills? To investigate ef‐ fects of disuse on early‐developing motor skills, we examined crawling in two groups of habitual crawlers (34 6–12-month-old infants and five adults with Uner Tan Syndrome) and two groups of rusty crawlers (27 11–12-year-old children and 13 col‐ lege‐aged adults). Habitual crawlers showed striking similarities in gait patterns, limbs supporting the body, and crawling speed, despite dramatic differences in crawling practice, posture, and body size. Habitual crawlers trotted predominantly, whereas rusty crawlers showed a variety of gait patterns. Within sequences, habitual crawlers and children showed more switches in gait patterns than young adults. Children crawled faster and kept fewer limbs on the grounds than the other groups. Old crawl‐ ing patterns were retained despite disuse, but new ones were also added. Surprisingly, results indicate that nothing was lost with disuse, but some features of crawling were gained or altered.