Muscle power
A UVic exercise physiologist sheds new light on muscle metabolism in children

by Margaret Milne

Tag, dodge ball, red rover... much of children’s play involves high-power, high-intensity, short-duration activities. This sort of exercise is known as anaerobic exercise, but until recently, the research evidence suggested that children’s muscles were not mature enough for anaerobic activities.

This seemed counter-intuitive to Dr. Kathy Gaul of UVic’s school of physical education. “If you watch children play spontaneously,” she says, “it’s very anaerobic!”

To investigate questions about anaerobic abilities, Gaul is using an innovative technique to “see” inside children’s muscles while they exercise. The results she’s finding are helping to build up a comprehensive picture of muscle metabolism in healthy children.

Studying muscle metabolism— the chemical reactions that occur in working muscles—is notoriously difficult in children. Traditional methods involve techniques such as muscle biopsies, where a large-bore needle is used to remove a small section of muscle. Invasive procedures like this are generally not permitted on children. Even in adult research, the use of muscle biopsies is limited, because they can only be done after the subject stops exercising, Gaul explains. “They only tell us the net effect of what has happened in the muscle.”

To solve this problem, Gaul uses a technique known as magnetic resonance spectroscopy (MRS). “This is a new technology for pediatric exercise physiology that allows us to see what’s happening in the muscle while the muscle is working,”she says.

In MRS, a large magnet is used to align the molecules inside the subject’s muscle. A gentle pulse of energy is then sent through the muscle to try to knock the molecules out of alignment. By looking at the response to this pulse, the researcher can tell what sort of chemical environment is present in the muscle. All of this is performed while the subjects are actively using their muscle. The only thing they feel is the fatigue setting in.

To see if maturity and anaerobic ability are truly linked, Gaul recruited 18 female child athletes aged nine to 16 and divided them into prepubescent and post-pubescent groups. The children were chosen from a competitive synchronized swimming team. “They needed to be active and motivated,” says Gaul, “because we were asking them to work very hard.” To exercise anaerobically, the girls pushed repeatedly for two minutes against a foot pedal to raise a heavy weight until their muscles were exhausted.

If anaerobic ability was dependent on maturity, Gaul’s MRS results should have shown that, at the end of the exhaustive exercise, the older girls’ muscles had a more acidic chemical environment than the younger girls’ muscles. Instead, she found no significant differences between the two groups throughout the two minutes of hard work—both groups had similar anaerobic metabolic characteristics. “The anaerobic systems in children are much better than we thought,” says Gaul.

Gaul’s results are important because they increase our understanding of how normal children’s muscles work. She sees many more places the MRS technique could be used to add to the pool of knowledge. For example, can a child’s anaerobic ability be improved through training?

She has recently completed a project to compare the anaerobic abilities of 7–9 year-old gymnasts with their inactive peers and is currently conducting another with prepubescent and pubescent hockey players.

If Gaul discovers that children’s anaerobic abilities are responsive to training, the findings will be important to coaching and rehabilitation programs for children. Perhaps the most fundamental consequence of Gaul’s research, though, is that children are being treated as a distinct and unique population in this type of research.

“In the past, adult concepts have been applied to pediatric populations,” says Gaul. “We don’t do that with anything else, so why would we do it with muscles?”

Margaret Milne wrote this as a participant in the SPARK program (Students Promoting Awareness of Research Knowledge), funded by UVic, the Natural Sciences and Engineering Research Council, and the Social Sciences and Humanities Research Council.