The guidelines, issued by the American Academy of Pediatrics (AAP), are based on recent research into pediatric blood pressure and the latest recommendations on defining and treating high blood pressure in adults.

According to the AAP, children and teens with "pre-hypertension" -- blood pressure that is elevated but not high enough for a diagnosis of high blood pressure -- should be eligible for all competitive sports. They should also, however, make any needed lifestyle changes to lower their blood pressure, and continue to have their numbers checked every six months.

Those lifestyle changes include regular exercise, a well-balanced diet and, if necessary, weight loss, the AAP writes in its journal, Pediatrics.

The recommendations are similar for kids who have what is known as stage 1 hypertension. According to the academy, they should be eligible for all competitive sports as long as they have no major organ damage related to their blood pressure -- such as enlargement in the heart's main pumping chamber or any other form of heart disease.

Children and teenagers with stage 1 high blood pressure should also have the diagnosis confirmed with a repeat measurement one to two weeks later, according to the AAP. Lifestyle changes are recommended as treatment, while some kids may need to be referred to a pediatrician who specializes in cardiovascular problems -- particularly those with heart problems or who have consistently high numbers on several blood-pressure measurements over time.

The AAP does recommend sports restrictions for kids with the most serious cases of high blood pressure, or stage 2 hypertension. They should not participate in sports likely to cause sharp temporary spikes in blood pressure; those include weightlifting, gymnastics, martial arts, wrestling, cycling, snowboarding and field events that involve throwing.

Children and teenagers with stage 2 high blood pressure need to get their numbers down to normal levels before they can participate in those sports, according to the AAP. All kids with the condition should be referred to a specialist and treated with lifestyle changes and/or medication.

When a child has co-existing heart problems, the AAP says, decisions on sports need to be made on a case-by-case basis, depending on the severity of the heart problem and the type of sport.

Diagnosing high blood pressure in children is more complicated than in adults, for whom hypertension is defined as a systolic blood pressure higher than 140 mm/Hg or a diastolic pressure of 90 mm/Hg or higher. Pre-hypertension is a systolic pressure between 120 and 139 mm/Hg or a diastolic level between 80 and 89.

In children and teens younger than 18, doctors compare the child's blood pressure with the published norms for other kids of the same age, sex and height.

High blood pressure is diagnosed when a child has three or more readings that are at or above the 95th percentile -- meaning that his or her blood pressure is higher than that of at least 95 percent of kids the same age, sex and height.

Stage 2 hypertension refers to blood pressure that is more than 5 mm/ Hg above the 99th percentile. Pre-hypertension is diagnosed in kids whose levels put them at or above the 90th percentile but below the 95th.

According to the AAP, all athletes with pre-hypertension or high blood pressure should limit substances that could cause blood-pressure spikes -- including caffeine, certain medications (like common over-the-counter painkillers and decongestants), tobacco and stimulants.

The academy also points out that obese youngsters are at particular risk of high blood pressure, and while extra weight is valued in certain sports, such as football, young athletes should not be encouraged to bulk up.

SOURCE: Pediatrics, June 2010 (online May 31, 2010).