Fitness Research Lets Boys Be Boys

The boys barreled through the classroom door, holding up their freshly filled specimen bottles for others to see and relishing the chorus of “Ewwwwwwwwww!”

“OK, grab your cups,” exercise physiologist Tim Scheett told the next gaggle of boys, escorting them to the restroom while a lab technician put the first bottles on ice.

It was urine sample day in a course called Boys Summer Science Challenge, one of the occasional reminders to the 20 students that this is no ordinary summer school class.

The 8- to 11-year-olds have been spending their mornings at Rancho San Joaquin Middle School in Irvine as human guinea pigs. They play football, rugby, basketball, handball and baseball--and sometimes have their heartbeats monitored and their urine sampled--as test subjects for a UCI pediatrician’s research project.

The goal of the research project, now in its ninth year, is to pinpoint the link between exercise and children’s growth, to understand the physiological mechanisms involved, to learn how much is good and how much is bad.

“There are few things you can do to the human body to actually make it grow tissue, but exercise is one of them,” said Dr. Dan Cooper, UCI director of respiratory and critical-care research. Physical activity makes bones grow stronger and more dense, increases muscle mass and generates blood vessels in the tissue, he said.

But less understood, Cooper said, is how and why those changes occur.

It’s especially fascinating to explore these questions with children because the hormones that control much of the growth that naturally occurs during puberty appear to be the same hormones involved during physical activity, he said.

Further, by studying the effects of exercise in the bodies of healthy children, Cooper--whose research is funded by the National Institutes of Health--hopes to be able to determine exercise guidelines for chronically ill children.

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For example, youngsters with cystic fibrosis, a debilitating lung disease, can live longer and improve the quality of their lives by being more physically fit, he said. But how much exercise, and what kind, is best for a child with serious respiratory problems, whose lungs are not properly delivering oxygen to the blood and muscles? Children with chronic heart disease, or who have had cardiac surgery, likewise need guidelines, he said. Kids with rheumatoid arthritis can improve their condition with exercise, but too much actually causes relapses, he said.

“With healthy kids, we probably have a wide window, but with chronic disease, like cystic fibrosis, that window is very small,” he said.

Understanding the science of exercise is especially important these days, Cooper said, because even among healthy children, the nature of sports and physical activity has changed dramatically in recent years.

Gone for many children are unstructured days of bike riding, climbing, hiking and running, which allowed kids to set their own natural pace. Today, play often occurs at parks or on athletic fields, organized by parents and sports leagues, condensed into intense hourlong sessions, with activities and pace dictated by coaches or other adults, he said.

“Kids are naturally more spontaneously physically active than adults. We know that,” said Cooper. “But parents don’t just let kids do their thing anymore, to do spontaneous play.”

And their thing these days often involves only wrist exercise from changing television channels, playing video games or surfing the Internet.

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While physical activity, in general, is healthy for children, scientists also know that too much intense exercise can actually stunt growth, such as with female gymnasts, he said.

Cooper hopes to develop data that could help determine whether the current societal push to start children in soccer, baseball and other organized sports at increasingly younger ages is indeed healthy.

“Are a 6-year-old’s bones built to be optimally stimulated by one to 1 1/2 hours of intense activity? We don’t know. Naturally, kids will have short bursts of activity,” Cooper said. Putting them on soccer fields and basketball courts for nonstop exercise “is the adult model.”

But there are longer-term issues as well. Frailty and osteoporosis among the elderly appears to have roots in childhood, he said. Exercise pumps new calcium into bones only until a person’s mid-20s; from then on, exercise and nutrition only work to maintain bone density, he said.

“You can actually shift yourself up to a level of bone density” through exercise during childhood and teen years, “so that 60 years later, you can reduce the risk of bone fracture,” Cooper said. Likewise, the rising incidence of obesity and heart disease among adults also can stem from the changed nature of childhood exercise, he said.

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Cooper said he regrets that he does not have a grant to study the psychological and sociological issues involving kids and exercise. The current emphasis on winning and excelling in sports appears to have a discouraging effect on teenagers, especially girls who are not the top athletes, he said, and that, in turn, affects their health as adults.

He is writing a grant proposal to study how to better entice teenage girls to exercise, in an effort to stave off osteoporosis in later years. His previous research has shown that during post-pubescent years, bone growth can be stimulated dramatically by exercise.

“It suggested that we have a window of opportunity in late adolescence, so that if we want to target an age range, this is it,” Cooper said.

But for now his attention is focused on the 20 preteens who, five days a week, run around on the athletic fields at Rancho San Joaquin Middle School.

The kids were drawn to the “science challenge” course with promises of lots of sports play, but all had to undergo less-pleasant medical tests before the class began. All had physical exams to determine that they had not yet entered puberty, the age category Cooper is studying this year. (Last year’s study group was prepubescent girls in Hartford, Conn., where Cooper was director of research at Connecticut Children’s Medical Center.)

The boys in Irvine also had their blood drawn--ranked most unpleasant by the kids--so that Cooper could determine their levels of growth hormone and insulin-like growth factor-1. Their body fat percentage was analyzed, and all underwent MRIs (magnetic resonance imaging) to document their muscle mass. For three days, they had to write down every bite of food they ate, giving researchers a clue to their nutritional intake before the exercise program.

The boys said they mostly forget they are research subjects as they run around the bases and shoot hoops. Sometimes, though, the science cannot be ignored.

“Tim, can I take this off?” one boy asked Scheett, Cooper’s research assistant, on a recent morning, pulling up his shirt to reveal a heart rate monitor that had slipped from around his chest down to his waist. Others, including some wearing “accelerators”--devices that record movement--also complained of discomfort.

It was just a hint of what was to come. This day they had to wear them only until the class ended; the next day, the boys would be told to wear them for 24 hours.

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As for the urine specimens, the boys reacted with a characteristic mixture of embarrassment and fascination. And the experience prompted Scheett to suggest a science lesson on hygiene and hand-washing.

The samples were collected three times during the morning’s activities so that Cooper could later test for two types of cytokine, a “cell messenger” that indicates body tissue is inflamed. Cytokines appear to increase after exercise and also appear to influence production of hormones affecting growth, he said.

The boys will undergo another MRI, more blood tests and a repeat nutritional work-up at the end of the five-week program. They also will receive $75 each.

Using children in research is more problematic and less exact than if laboratory animals were involved, Cooper and Scheett acknowledge. Rats can be prodded to run through the exact same maze repeatedly, but there is no way researchers can make sure all 20 boys are running the same distances and at the same exertion level.

“We know everyone is not going to exercise the exact same amount,” said Scheett. But the alternative--putting the boys on treadmills for measured periods--would not have generated the same cooperation, Cooper said.

“Look at them out there,” Scheett said, watching the boys having fun during a rugby drill. “They have no idea they’ve been running for a half-hour.”