Greg Taylor will never forget the day his life almost ended. It was summer and he started feeling nauseous while umpiring a softball match in the Hutt Valley.

"I sat there with a cold towel around my neck for 10 minutes. It was only when my arm started aching and I found myself wondering if it had been hit by a softball during a game, that I realised this might be more serious."

Yet even after he was rushed to Hutt Hospital and the doctor told him that he was having a heart attack, Greg was in denial.

"No mate, I've just got heat stroke," he said. "I'm only 42."

That was three years ago, but Greg's case is not an isolated one. The number of males aged 40-plus who are dropping dead while exercising now has councils looking at getting defibrillators for their gyms and pools.

In the past few months two men have died at council-run facilities: one a 48-year-old swimmer and the other a 44-year-old squash player.

Manukau City Council is looking at whether to buy the heart equipment for all leisure centres, while Auckland City Council is also considering whether such equipment is needed. The move coincides with new Heart Foundation research that shows death rates from heart disease - which at one time were steadily decreasing - may plateau and even rise in coming years. The foundation says the most alarming aspect of this is that the biggest leap in reported cases of heart disease is for men between the ages of 25 and 34.

Professor Norman Sharpe, medical director of the National Heart Foundation, said: "This is very serious for New Zealand."

He said one of the main problems was that disease of the heart muscle could occur over many years without people being aware of it.

Several indicators raise the risk profile for people - high blood pressure, raised cholesterol, smoking or a family history of heart problems.

Healthy living was the key and that meant no smoking, a nutritious diet and moderate exercise.

People like Greg, were often not aware they were at risk, said Professor Sharpe.

"If people have heart disease and exercise, particularly if they exercise vigorously, then they do have increased risk of a heart attack."

Auckland University's Dr Bruce Arroll, an associate professor in primary health care, said while exercise was beneficial, many people were not aware that to be safe from a heart attack, long walks were actually better than extreme aerobic bouts. "The best thing is not to exercise at those vigorous levels. It would definitely be safer if people walked a lot instead," he said.

But he understands that there is a definite feel-good factor to aerobic workouts. "That just makes it so important for everyone to know their heart risk before exercising because although it's a rare event when someone dies at 48, that really is too young when most people can expect to live to 78 in our society."