Jan 29, 2015
The Bigger They Are…

dawncomstock-head.jpgBy Dawn Comstock

The Center for Injury Research and Policy at The Research Institute at Nationwide Children’s Hospital in Cincinnati shares its analysis of injury patterns of high school athletes as they relate to those athletes’ body mass index.

The U.S. is undergoing an obesity epidemic, and unfortunately our youth are not immune. Recent estimates suggest that as many as one-third of U.S. adolescents may be overweight or obese. Encouraging participation in sports and other physical activities is an important way to promote a healthy lifestyle that in turn can lead to decreased risk of overweight and obesity, and a higher quality of life.

One interesting effect of the increased prevalence of overweight and obesity in the U.S. is a change in sports team demographics. More than ever before, it is now becoming increasingly likely that smaller adolescents in team contact sports such as football, soccer, and basketball may be pitted against a much larger defender. Thus, these changing demographics may be influencing injury rates and patterns.

Recently, the National High School Sports-Related Injury Surveillance Study analyzed injury patterns by body mass index (BMI), which is calculated as kilograms of body mass divided by the square of an athlete’s height in meters. For example, if a 170-pound (77 kg) athlete is six feet tall (2 m), their BMI would be calculated as 77/4 = 19.

It is important to note that BMI is not always a good indicator of body fat percentage for very muscular athletes because a higher than average amount of muscle will translate into an increased BMI. However, an athlete’s BMI is still indicative of their size and body mass and thus can provide us with useful information.

Using criteria provided by the Centers for Disease Control and Prevention,1 we used an athlete’s BMI, age, and gender to categorize them as underweight, normal weight, overweight, or obese. Here is a summary of our findings:

Prevalence of overweight and obesity

• On average, for every 100 injured high school athletes, 60 are considered normal weight, 20 are overweight, 16 are obese, and 4 are underweight.

• The prevalence of overweight and obesity among injured athletes is highest in football (54 percent). Alarmingly, two-thirds of injured defensive tackles, offensive tackles, and centers were obese.

• After football, injured wrestlers had the next highest prevalence of overweight and obesity (32 percent).

• Although this study did not directly measure injury rates by BMI, there appears to be a similar prevalence of overweight and obesity among injured athletes and non-injured athletes, and thus there is no indication that injury rates are affected by BMI.

Injured body site by body mass index

• Overall, the most commonly injured body sites were the ankle/foot (23 percent), knee (15 percent), head/face/neck (15 percent), and shoulder/upper arm/elbow (13 percent).

• Compared to normal weight athletes, injured obese athletes were almost 30 percent more likely to sustain a knee injury. One potential reason for this may be that heavier athletes have less stability.

Injury diagnosis by body mass index

• Overall, the most common diagnoses were incomplete ligament sprains (28 percent), incomplete muscle strains (14 percent), contusions (13 percent), fractures (10 percent), and concussions (9 percent).

• Compared to normal weight athletes, injured underweight athletes were almost 50 percent more likely to sustain a fracture.

• Potential reasons for this increased risk of fracture include underweight athletes having decreased bone mass or decreased muscle or adipose tissue, resulting in less cushion to absorb impact from collisions. Also, underweight athletes may be faster than heavier athletes and thus they may be more likely to be involved in high-speed, high-impact collisions.

Injury severity by body mass index

• Although half of all injured players resumed participating in their sport within 1-2 days (23 percent) or 3-6 days (28 percent) following injury, the remainder missed 7-9 days (15 percent), 10-21 days (15 percent), or 22 or more days (17 percent).

• Compared to normal weight athletes in football, injured obese athletes were 25 percent more likely to sustain an injury resulting in 1-2 days time loss.

Injury mechanism by body mass index

• Obese athletes were 30 percent more likely to sustain injury following contact with another player.

• Underweight athletes were 60 percent more likely to sustain an injury during a play ruled as illegal activity.

Being aware of BMI-specific injury patterns can help coaches and athletic trainers prevent future injury. Here are some potential ways to decrease injury:

• Promote the long-term health of your athletes by encouraging physical fitness and healthy eating, and discouraging athletes from purposely gaining unhealthy weight.

• Screen all underweight athletes, particularly females, to determine whether any disordered eating habits may exist.

• Focus on developing balance, flexibility, and strength in all athletes, particularly those who may be overweight or obese. References 1) Centers for Disease Control and Prevention. National Center for Health Statistics. CDC growth charts: United States. 2000. www.cdc.gov/growthcharts. Accessed August 26, 2007.

Dawn Comstock, PhD, is a principle investigator at the Center for Injury Research and Policy at The Research Institute at Nationwide Children’s Hospital. She is also an assistant professor at Ohio State University in the College of Medicine and the College of Public Health. Her research interests include the epidemiology of sports, recreation, and leisure activity-related injuries among children and adolescents as well as the life-long health benefits associated with an active childhood. She can be reached at [email protected].

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