For most of us the fact we can walk, talk and breathe all at the same time might not strike us as a miracle, but for researcher Enzo Cafarelli it's one of life's mysteries. How do we do that? How does the brain and central nervous system know what strings to pull and how hard to pull them?

    It's a puzzle to which Cafarelli, a professor in York's Kinesiology and Health Science Program, has devoted more than 20 years of research.

    One of the mysteries of muscle control Cafarelli is exploring is how our muscles are affected by fatigue. Can training them make a difference in performance? Finding answers to these questions would be important for "real-world" applications for senior citizens or people recovering from muscular injuries.

    His research concerns two primary aspects of muscle control by the nervous system. The first is how we compensate for fatigue (for example, during muscular or sport activity). Whenever a muscle is used forcefully and repeatedly it begins to lose its ability to generate force. "There is some evidence that the brain says, no, I'm not going to do this action any more. It's called 'central fatigue'," Cafarelli says.

    He and his colleagues record the neurally-generated electrical activity in muscle and record its force output under a variety of conditions that reflect fatigue and adaptation to training.

    The second is how we adapt to chronic use ? for example, when muscles grow larger because of weight training. "When muscle is used repeatedly over weeks and months, say, by lifting weights, it gets bigger and stronger," says Cafarelli.

    "I'm interested in how your motor system adapts to this much larger engine. With bigger muscles, if the system didn't compensate, every time you picked up the phone you'd bash yourself in the head."

    By manipulating muscles electrically and measuring their responses in the lab, Cafarelli says he hopes to understand more about their control in everyday activities.

Photo: Nik Sarros