Middle-aged men playing recreational hockey may be risking a heart attack if they push themselves too hard on the rink, a new Canadian study suggests.

More than 500,000 men and 70,000 women play recreational hockey in Canada, and there are about 10 deaths each year from heart attacks on the rink.

But even that small risk can be lowered if men who play hockey on the weekends have regular exercise, the researchers say.

The study looked at 113 men in Cape Breton over the age of 35 who play recreational hockey. The researchers monitored their heart activity before, during and after their games. The average age of the men was 42.

In every case, the men exceeded their target heart rate during the game. On average, the men spent 30 minutes per game above their target heart rate.

The upper limit of the target heart-rate range is defined as 85 per cent of a person's maximum heart rate, which is 220 beats per minute minus a person's age.

Most of the men in the study exceeded their calculated maximum heart rate during their games.

"Very vigorous exercise predisposes you to risk of heart attacks or sudden death. And that risk is much higher if you don't exercise regularly," says Paul MacDonald, a Sydney, N.S. cardiologist and co-author of the study.

But that's no reason to stop playing pickup, says Murray Mittleman, of Harvard University's Institute for Prevention of Cardiovascular Disease.

He recommends instead that men who play hockey during the winter also exercise regularly throughout the year. That's the best way to lower your risk of a heart attack during vigorous exercise.

Both the study and Mittleman's commentary appear in Tuesday's issue of the Canadian Medical Association Journal.