Some years ago I was shocked when a colleague of mine complained about having to walk from her car to the office building. Since I knew where she parked her car, which was in the street right in front of the building, I asked, why?

“I hate walking,” she said.

Would you rather be stuck in a wheelchair, I wondered, but didn’t say it out loud. The street where we parked our cars was lined with old plane trees, such a pretty sight, year round. Such a lovely walk if you happened to be parked some distance from the office building.

That walk was a great opportunity for daily aerobic exercise.

I did myself some good by walking, according to the authors of an article in the Harvard Medical School blog: “Regular aerobic exercise will bring remarkable changes to your body, your metabolism, your heart, and your spirits. It has a unique capacity to exhilarate and relax, to provide stimulation and calm, to counter depression and dissipate stress.”

These psychological rewards have a neurochemical basis. Exercise reduces levels of the body’s stress hormones, such as adrenaline and cortisol. It also stimulates the production of endorphins, the body’s natural painkillers and mood elevators, that’s why it’s not your imagination if you feel great after a long hike.

But, there is more. There are important mental rewards as well. Exercise changes the brain in ways that protect memory and thinking skills.

In a study done at the University of British Columbia, researchers found that regular aerobic exercise, the kind that gets your heart and your sweat glands pumping, appears to boost the size of the hippocampus, the brain area involved in verbal memory and learning, according to this Harvard Medical School blog post.

Experts agree that exercise offer many health benefits, but how long we should sweat and puff to get the optimal benefits from aerobic exercise is a question that has not been answered definitively yet.

An article in Business Insider refers to numerous studies that put the optimal time down to between 30 and 45 minutes for four days per week.

Common sense could be a good enough guideline here. Most people who live active lives and are not athletes who earn their living through sport, have limited time to devote to exercise. It makes sense to include activities like walking, cycling, gardening or housework – that are already part of a daily routine – as part of an informal exercise regime. Once or twice a week get off at an earlier bus stop or make it a habit not to park right in front of the nearest entrance to the mall.

It’s possible to get in enough exercise and reap the health benefits without having an official aerobics exercise schedule.