A recent study examined monkey bars through the lens of human evolutionary biology and primate behavior. The research, conducted by Dartmouth College, analyzed playground injuries, primate behavior, and hominin fossils to contextualize climbing’s role in human development.
Monkey bars account for approximately 7% of childhood arm fractures in the U.S. In Canada, they are responsible for 5% of emergency department visits by children, 64% of which result in bone fractures. Another study found monkey bars were responsible for 50% of playground-related extremity fractures and 55% of severe extremity fractures admitted to emergency departments.
Despite these risks, playground injuries rarely result in death. The risk of fatality is 0.15 per 100,000 children or 1 in 30 million. Playground injury rates ranged between 0.26 and 0.59 per 100,000, with nearly 95% of children being treated and released without further hospitalization, according to a study published in Evolution, Medicine, and Public Health.
Fractures of the wrist or forearm account for 6%-21% of childhood bone fractures, with girls slightly more likely to experience fractures from monkey bars despite similar levels of play at "great heights."
U.S. Consumer Product Safety Commission guidelines recommend maximum inter-rung distances of 12 inches for preschoolers and 15 inches for school-aged children, along with height recommendations of 60 inches and 84 inches, respectively. However, a survey of 49 playgrounds in New Jersey found that 100% of monkey bars exceeded 59 inches, with 37% surpassing 78 inches in height.
Treatment trends for playground injuries have evolved. Buckle and greenstick fractures of the distal radius or ulna are now frequently treated with removable splints, wraps, or soft casts for as little as 3 weeks. For children under 10, up to 50% displacement in complete fractures is often deemed acceptable without an orthopedic referral.
The study reported positive long-term outcomes for injured children. In a cohort study, 88% of hospitalized children returned to their baseline quality of life by 4 months, and 92% by 12 months post-injury.
The research also explored the potential developmental benefits of risky play. A randomized control study revealed a 12% increase in moderate-to-vigorous physical activity among children exposed to riskier playground environments. Children with daily access to risky play (1-2 hours per day) demonstrated improved balance and coordination on standardized motor fitness tests. Adding 30 minutes of moderate physical activity per day was associated with a 3%-5% increase in bone strength in 5–11-year-olds, with children who engaged in frequent play showing 6%-14% higher bone mineral content by age 8 and 4%-7% higher by age 11.
"We believe the enduring appeal of monkey bars today is a testament to this evolutionary legacy, and that we must find ways to avoid extreme injuries while also letting children face developmentally appropriate risks," noted study investigators.
Parallels were drawn to primate behavior, where juvenile apes spent significantly more time climbing and arm-swinging than adults. Healed forelimb fractures were found in 21%-36% of wild chimpanzees, gorillas, gibbons, and orangutans. Similar rates of injury were observed in tree-fall incidents among human populations in Papua New Guinea and Fiji.
The researchers analyzed hominin fossils for evidence of climbing-related injuries. The 3.2-million-year-old Australopithecus afarensis skeleton “Lucy” exhibited perimortem fractures consistent with a fall from approximately 13 meters, with fracture patterns comparable to modern pediatric fall injuries.
The authors declared no conflicts of interest related to this study.