MUSCLE bound

The pride of our nation, the finely honed men and women who bring home the kudos from international sports arenas, may soon be calling a halt mid-stride to the way they push their bodies.

And the towering stars of the country's beloved Aussie Rules could in future seasons find a way to protect themselves against the dreaded hamstring injuries -- the scourge of every player and every coach's nightmare.

The growing evidence through seven years, research at Monash University on the behaviour of the body's key muscles during heavy exercise is pointing to a need for new training techniques to protect athletes, as well as assist sufferers of muscular disorders.

Professor Uwe Proske of Monash's Physiology department has been working with the research director of the Centre for Biomedical Engineering Dr David Morgan and postgraduate students on Dr Morgan's theory on the causes of muscle soreness.

Stressful exercise

They have found that under some forms of stressful or eccentric exercise, the muscle fibres are stretched.

"We've known for a long time that eccentric contractions produce soreness, and in more recent years that there might be some damage associated with it,'' explains Professor Proske.

Muscles generally contract during exercise, but during eccentric exercise muscles are stretched as they contract. Common forms of eccentric exercise include horseriding, skiing and downhill walking.

"Walking up a mountain makes you tired, but walking down again makes you not only tired but also sore the next day,'' explains Professor Proske. "Downhill walking, when the muscles in your legs are acting as breaks and prevent you from falling, is associated with lengthening contractions."

Professor Proske says there are three kinds of muscle contractions -- concentric, where the muscle contracts and shortens; eccentric, where the muscle contracts and is stretched at the same time; and isometric, where the muscle contracts while held at a fixed length..

"We know that just one bout of lengthening contractions will encourage the muscle to adapt and protect itself against the next potential round of eccentric contraction. The muscle adapts by repairing not just the damaged areas but by changing the entire structure of the damaged muscle fibres and incorporating extra bits on the end," Professor Proske explained.

"The remarkable muscle will protect itself for up to six weeks, and it is this knowledge that could have enormous impact on athletic training."

The next step is incorporating this into an exercise regime, says Professor Proske.

"We have also shown that if you intentionally make someone undergo a regular period of concentric or shortening exercises, then they become more vulnerable to the damage from lengthening contractions in eccentric exercise."

Sportspeople hamstrung

The impact for sportspeople is going to be far-reaching, and emphasises the importance of training to protect muscles during exercise, he says.

"But it requires a careful analysis of each sport and of the kinds of contractions involved in that particular activity."

In football, for example, hamstring injuries are common.

"As the player kicks, he is using the extensor muscles to straighten the leg and push the ball up, but he may well be contracting his flexor muscles at the same time, which would then be lengthened as they contracted, which we suspect is the case".

Professor Proske says it's possible that if footballers routinely did mild eccentric exercise, the incidence of hamstring injury would drop. "We can't prove it yet, but we are pursuing it.''

The training issue promises to be a big deal for athletes, says Professor Proske, and the work at Monash is now being recognised interna-tionally. But perhaps the greatest hurdle is the conservative sports community.

"These are new ideas. Much of the emphasis on training to date has been on metabolic aspects such as diet, sugars and drinks. Our approach is more from a mechanical viewpoint and it is more fundamental.

"In the long term you want to know more about both aspects, but the implications of what we have seen are very serious and may lead to the design of new exercise regimes to provide maximum performance under all conditions."