MOST of us are too worried about our own health to think about hassling our parents to go to the gym, but it could just save their lives.

Heart disease is Australia's biggest killer, particularly for men and women aged 45-59 years.

But it is possible to lower your risk of being struck down so fitness chain Jetts is calling on Gen X and Gen Y to look out for their parents' health.

Every person who joins a Jetts gym on Open Heart Day this Saturday will be making a donation to the Heart Foundation as well as becoming more heart smart.

Jetts founder Brendon Levenson said more than half of all Australians were not active enough to achieve health benefits.

He said he wanted the nationwide fundraiser to draw attention to the importance of a healthy heart.

"Regular exercise is critical for preventing many conditions, such as heart disease, but the fact is that most Australians are not nearly active enough to prevent those conditions," Mr Levenson said.

"We're calling on all generations to rethink their heart health and see exercise as more than just a way to fit into a pair of jeans but as a part of protecting one's health."

Heart Foundation CEO Dr Lyn Roberts said she hoped the initiative would encourage whole families to be more heart smart.

For every person who joins a Jetts gym on Open Heart Day, the gym will waive the standard $99 joining fee and will also donate $10 to the Heart Foundation.