Minimizing the Risk of Injury and Illness in Youth Runners, a Summary of the Evidence

Orthopaedics bone and joint pain

By: Ryan Riggs, MD; Shelli Dills, MD
MUSC Health Sports Medicine

Running has become an increasingly popular sport in youth athletes. Many students in the United States are choosing to participate in cross country or track and field, making running the second most common physical activity in children ages 12-15 years old. Given the increase in participation in running, there has also been an increase in running related injuries in the youth population. The rapid period of growth and development in this age group along with certain intrinsic and extrinsic risk factors all place these athletes at increased risk.

Due to the rapid phase of growth and development, youth runners are particularly susceptible to injury. This is due in part to bones lengthening faster than the muscles and tendons that attach to them. This difference causes increased force to be placed on the muscles and tendons, putting them at greater risk of injury. Typically, children grow the fastest shortly after puberty, around age 12 for girls and age 14 for boys thus the risk is highest for children in this age group. This in addition to incomplete bone minimalization causes a period of bone weakness. During this rapid growth phase, various intrinsic factors (eg, age, height, weight, and gender) and extrinsic factors (eg, training, footwear) impact the risk of injury in youth runners.

Height, weight, and age alone do not seem to carry an increased risk of injury in youth runners; however, body mass index (BMI), both high and low, has been shown to increase risk for stress fractures. For example, a study of 13–18-year-old runners showed that a BMI 20.2- 21.6 was associated with an increased risk of medial tibial stress syndrome when compared to runners with a BMI of 18.8-20.1. Another study showed females with BMI less than 19 were three times more likely to have bone stress injuries than girls with BMI greater than 19.

Female gender is another independent risk factor for injury. Studies shows that female youth runners are more likely than male youth runners to get injured. In addition to this, female runners have greater time loss from participation due to injury. Risk factors for bone stress injury in female youth runners include age of menarche >15, prior fracture, infrequent or absent menstruation after menarche, and participation in gymnastics or dance. Risk factors for bone stress injury in male youth runners include prior fracture and low BMI.

Low bone mineral density has also been associated with an increased risk of injury in runners. Several factors have been shown to be associated with decreased bone mineral density in adolescent runners including BMI less than 17.5, consuming less than 1 serving of dairy per day, and training on average greater than 30 miles per week within a year.

Training plays a major role in injury prevention. Inadequate training has consistently been shown to be a risk factor for injury. A study of adolescent cross-country runners showed that running for less than 8 weeks during the summer months increased the risk for in-season injury. Variability in training is also important and can have a protective effect. Infrequently alternating between short and long running distances and running predominately hills were shown to be risk factors for injury. There does not seem to be a difference in injury rates between running surface type (concrete vs trail) or footwear type, despite several decades of running shoe development. Interventions to change footstrike mechanics have also failed to demonstrate a role in injury prevention.

Other factors to consider in youth runners include the impacts of running on long term heath. Similar to adults, youth athletes undergo exercise induced adaptations to the cardiovascular system. To date there is no long-term data to evaluate the long-term health consequences of these changes to the pre-adolescent heart however the rates of sudden cardiac death in youth runners remains low. The pre-participation physical remains the best tool to screen for risk factors for sudden cardiac death.

Early sport specialization in youth athletes is an independent risk factor for injury throughout all sports, not just running. Overuse injuries increase in those who play their primary sport for more than 8 months a year. Currently there is no guidance on an appropriate age to start sport specialization or whether it actually improves athletic performance.

Evidence supports running as an appropriate sport for adolescent and pre-adolescent children. Children should be encouraged to engage in free play outside of the sport of running to aid in growth and development. There is no evidence to suggest limiting youth runners to specific distances plays a role in injury prevention. Youth runners who engage in supervised training programs were able to compete with low risk of injury regardless of the distances raced.

Running in adolescent and pre-adolescent children is becoming a more popular sport worldwide, especially in the United States. The rapid growth and development experienced in this age group coupled with intrinsic and extrinsic factors places them at an increased risk for running related injuries. It is important to identify these risk factors in order to modify those we can. Understanding the complex interactions of these various factors will help keep running a safe and healthy sport for this age group.