Kids' play may assist adult bone strength

by Stephen Forgacs
Staff writer

More than 200 Richmond school children are participating in a UBC study to determine how growing bones can benefit from increased levels of physical activity.

The study, led by Human Kinetics Asst. Prof. Heather McKay, involves 210 Grade 3 and 4 children aged eight or nine and will determine to what extent an active lifestyle can contribute to bone density -- an important factor in preventing osteoporosis and brittle bones later in life.

While a control group of children is continuing with the normal school physical education program, a larger group is participating in a curriculum which incorporates higher impact exercises specially designed for the study by Human Kinetics student Lindsay Waddell.

"Much of the research money in this fascinating area has been directed at treatment of osteoporosis," says McKay. "My thinking is that it's time to take a good look at prevention. Historically, projects that address prevention are overlooked by medical research granting agencies. They don't always have the foresight within our health-care system to invest that way."

While McKay's principal focus is the effect of loading, weight-bearing or impact exercises on bone density, she is also looking at differences in diet, and cultural and genetic factors in the Caucasian and Asian children in the study group.

Some of these factors include a higher incidence of lactose intolerance in the Asian population, as well as a possible genetic predisposition to osteoporosis. Despite these factors, McKay says fractures among Asians with osteoporosis appear to be less common than in the Caucasian population, possibly because of a different physical geometry or bone dimensions.

McKay, whose earlier research at the University of Saskatchewan looked at genetic factors in bone density and osteoporosis risk in consecutive generations of Saskatchewan grandmothers, mothers and daughters, believes present generations of children are growing up at risk for osteoporosis later in life because of their sedentary lifestyles, often dominated by television and video games.

The diminished importance of physical education in elementary schools and the gradual elimination of mandatory physical education programs in high schools are factors McKay cites as possibly contributing to the threat of osteoporosis-prone generations.

"Children by nature are extremely active, yet for some reason we seem to be socializing our children away from movement," says McKay.

McKay and Human Kinetics doctoral student Moira Petit launched the Richmond study in October and found it considerably easier to set up than McKay's University of Saskatchewan study. While the Saskatchewan study required a year to recruit and set up, McKay was able to recruit the children, with parental permission, within six weeks thanks to the co-operation of the Richmond School Board. School board members, principals and teachers are helping administer the program.

The children are also surveyed on their diet, particularly calcium intake, and their normal activities. As well, vertical jumps and calf circumference are measured to gauge changes in muscle strength. Bone density is measured using a standard diagnostic tool for osteoporosis called bone densitometry.

McKay says teachers involved in the study are already commenting on what they perceive to be an increase in strength and co-ordination among children participating. And, after visiting some participating groups, McKay noticed that a few students have enthusiastically embraced their new activities such as skipping rope, one of the exercises introduced as part of the study.

Initial results of the study, which involves UBC researchers from a number of departments on campus, should be compiled by June this year.

Although this is the first study in which schools have been randomly assigned as control or experimental groups, previous research suggests that the activities of early prepubescent childhood have the greatest influence on adult bone status.

"One of the strengths of this project is that it is multi-disciplinary. We're working with people in nutrition, education, medicine, radiology, and leisure and sport management," says McKay.

McKay and colleagues' earlier research into bone growth of children has shown that childhood and teenage years are very important for the development of bones that will remain healthy. Although much of the way a body's skeleton develops is determined by genetics, her research group found that during a three-year period around the time of greatest height gain, or the so-called growth spurt, the greatest percentage of bone mass is accrued. In fact, both boys and girls accrue 30 per cent of their total bone mineral during this time. This amount roughly represents the amount of bone mineral that women will lose over time after menopause.

The year following the greatest growth spurt, which occurs later in boys, is viewed as a period of "relative fragility," because bone density lags behind the rapid linear growth of bones. A higher incidence of wrist fractures have been reported in both boys and girls during this period.

"It's very important that children, and particularly girls, have diets and lifestyles that support the development of healthy bones if they are to have strong bones and avoid problems later in life," says McKay, adding that it doesn't take much in terms of weight-bearing activity to build and maintain bone density in children and adults alike.