Thirty minutes of exercise is a day a breath of fresh air for asthma sufferers, not enough for everyone else, according to new studies

Half an hour a day can keep the asthma doctor away. But if you want to steer clear of the cardiologist, you may want to quadruple that.

Two separate studies published this week addressed the idea of exercising 30 minutes a day. The asthma report said that’s ideal; the other, examining heart failure, pointed to the need for far more exercise.

Adults with asthma who exercised for 30 minutes a day, regardless of the specific activity, were 2.5 times more likely to have control over their symptoms than those who did not exercise.

Traditionally, asthma patients were wary of exercise.

“There is growing evidence showing people can do exercise on a consistent basis and more than being safe, it is good for you and it helps with your asthma,” Dr. Simon Bacon, author of the study, told the News Thursday. “For people with asthma the biggest problem is the symptoms — breathlessness and waking up in the middle of the night.”

“Historically it has been the mindset of: you have asthma, no exercise,” says Bacon, a professor in the Department of Exercise Science at Concordia University, Montreal, Canada.

He studied 643 people over the course of a year. Of these, 250 did absolutely no physical activity.

“What we found was the more physical activity you do, the better off you are,” Bacon says. “About 100 people did the guideline levels of activity and they had the very best results.”

The survey was just published in BMJ Open Respiratory Research, a medical journal, but its author doesn’t exactly sound shocked.

“Exercise generally tends to be good for you, so I am not surprised it is good for people with asthma,” Bacon says.

What surprised Dr. Clifford W. Bassett, medical director of Allergy and Asthma Care of New York, most was how many people do absolutely no physical activity.

“We already know from other studies that sports and exercise can reduce asthma symptoms — period,” Bassett says. “They should be under supervision and they have less symptoms.”

Adding that “there is a tremendous benefit in the ability to strengthen the lungs in people with asthma,” Bassett says, “Pick the right exercise for you.”

But another study released earlier this week found that the daily 30 minutes of exercise people have been doing is simply not enough to ward off heart failure.

Those who did four times that amount — yes, two hours a day — had far less chance of heart failure, at 35 percent, than those who stuck to the half hour a day, according to a study published in the journal Circulation.

Researchers reviewed 12 studies and analyzed data from 370,460 people.

Over 15 years, the participants reported their exercise and daily activities — and there were 20,203 heart failures. The government-recommended half-hour a day simply was not enough to keep the heart, a muscle, strong.

Those who exercise two and four times as much as the recommended half hour had a substantial risk reduction of 20 and 35 percent. The findings held true for men and women, all ages and races.