Ian Cathers

Physicists and engineers have some great tools. When these tools are used to examine living things it is possible to tease open a little of their complex workings. Ian has a background in maths, physics and engineering, and his research and teaching has focussed on applying these tools to health sciences and the human body.

Ian’s teaching spans many of the undergraduate programs within the Faculty of Health Sciences and includes introductory science, radiation physics, hearing physics and sound instrumentation. While valuing face-to-face contact with students, he has also been involved in the development of a variety of independent-learning materials. You can look at one of these on-line packages (homeostasis). Ian is the Year 1 co-ordinator for the Bachelor of Health Sciences program and is the Faculty’s Associate Director for Information and Communication Technology in Teaching and Learning. The quality of his teaching has been recognised with a Faculty Excellence in Teaching Award.

When a muscle is stretched, it responds by shortening (this is the basis of a "knee-jerk" reaction). While this reaction is sometimes described in books as a simple and stereotyped response, it seems we have a great deal of conscious control over its action. Ian has conducted experiments with colleagues and students which clearly prove that we can alter the stiffness of a limb by consciously controlling these reflex responses. The graph shows the results from some of these experiments. So, are reflex responses really “reflex”?

The stretch reflex response depends on the frequency content and size of the stretch to muscles. While this may not be so surprising, other experiments have shown that the reflex response actually adapts to different types of muscle stretch. It seems that we can make use of the mathematical predictability of muscle stretches to enhance the timing of our response to them and so obtain greater benefit from the reflex responses.

This short video (160 kb) shows a computer-controlled servomotor stretching Ian’s wrist muscles while their electrical activity is recorded.

You cannot voluntarily move any part of your body at a greater frequency than about 8 Hz. However, movements involving impacts contain frequencies higher than this. Ian has undertaken a study with colleagues to map out the frequency spectra of normal human movement.

This study used miniature accelerometers (shown in the photo) that were attached to the wrist and ankle while subjects performed a range of activities. The study found that there were frequencies beyond 100 Hz in high impact movements!

Ian has recently begun work on this with another colleague and the aim of the research is to determine whether there is a correlation between physical activity levels – particularly associated with travel - and cardiovascular disease risk factors in young adults.

If you would like to discuss the possibility of undertaking a postgraduate research degree in any of these areas, please contact Ian (i.cathers@fhs.usyd.edu.au).

E-mail	I.Cathers@fhs.usyd.edu.au
Phone	+61 2 935 19287
Fax	+61 2 935 19520
Office	L231
Address	Faculty of Health Sciences Cumberland campus, C42 The University of Sydney PO Box 170 Lidcombe NSW 1825 Australia