All-Terrain Vehicles (ATVs) are a leading cause of youth injury in the USA, resulting in over 170 deaths and 40,000 reported injuries per year; these figures have steadily increased over the last decade. To reduce injury risk and severity, small-frame, limited power vehicles are made available for youths. The ATV industry’s Safety Institute recommends the following restrictions: engine volumes < 70cc for children < 12 years; engines < 90cc for children 12-15 years; no restrictions for children 16 years and older. However, little scientific evidence is available with regards to the anthropometric relationship between young riders and vehicle frame size in determining an appropriate fit, much less the ability to control the ATV.
The objective of this study was to quantify the biomechanical relationship between the size of young riders and ATV type in a static condition with the hypothesis that age alone is not a suitable measure of rider-vehicle frame fit.
Male children (6-11 years, n=8 and 12-15 years, n=11) were recruited to sit upon adult and youth-sized ATVs inclined and declined between 0° and 30° in 5° increments while anthropometric markers were recorded at 50 Hz using twelve digital motion capture cameras. Fit was categorized by five measures adapted from 4-H recommendations to improve rider fit: standing seat clearance, hand size, foot vs. foot-brake position, elbow angle, and handlebar-to-knee distance.
Results indicate the age 12-15 group fit the adult ATV better than the age-appropriate youth model (63% of subjects fit all categories on adult vs. 20% on youth). The age 6-11 group fit poorly on both bikes (0% on adult versus 12% on youth).
Despite prevailing rules, age alone is not a good predictor of vehicle fit; new recommendations for ATV size, redesign, or new intermediate ATV size categories may be needed.