The more you know, the less you grow.

That’s certainly true if you use the word as people sometimes do, not to mean “to have knowledge of” or “to be aware of” but “to be convinced or certain of.” Statements like “I know the Earth is flat” show you’ve stopped considering other possibilities.

But it’s in the consideration of other possibilities that you learn and grow.

This is particularly true in your pursuit of optimal health and fitness.

Conversely, there are times in your pursuit when you need to stop considering and start acting. Times when the evidence and your prior experiences are so overwhelming that you can be certain.

So by now you should know - in every possible way to use the word - to exercise nearly every day and ambitiously once or twice a week.

It’s called “a miracle cure,” in a Medical News Today article about the 2018 Physical Activity Guidelines for Americans, since “scientific evidence has shown, whatever your age, being physically active makes you happier and healthier.” Bear in mind that governmental health advice tends to be conservative, yet PAGA states that 150 minutes per week of moderate-intensity aerobic exercise reduces your risk of premature death, coronary heart disease, stroke, high blood pressure, type 2 diabetes, and depression.

Double that exercise time and you also reduce the risk of two of the more feared cancers, colon and breast.

PAGA also calls for “muscle-strengthening activities of moderate or greater intensity and that involve all major muscle groups on two or more days a week, as these activities provide additional health benefits.” Though not directly cited in the document, part of that recommendation resulted from a 2016 study that appeared in BMC Public Health associating muscle strength with a reduced rate of cancer mortality.

Moreover, since the publication of the 2018 edition of PAGA, a review published online in October 2109 by CA: A Cancer Journal for Clinicians has found “a strong level of evidence” that exercise also reduces the risk of endometrial, kidney, bladder, esophageal, and stomach cancers, as well as “moderately lowers” the risk of lung cancer.

Despite all the aforementioned information, only 20.9 percent of American adults meet both guidelines for aerobic and muscle-strengthening activity, according to the CDC - and a lack of the latter is the primary culprit. While slightly more than half of adults walk or run or bike enough to meet the aerobic exercise time requirement, less than a third lift weights or something equivalent twice a week.

So while most U.S. adults certainly “have knowledge of” and “are aware of” the benefits of exercise, they still don’t “know” of them in the way that engenders action.

Just in case you’re not already convinced - or have been slacking off a bit and could use a dose of motivation - here’s information on a relatively new theory about why exercise reduces the risk of cancer.

It’s offered in an opinion piece by Peter Biro of Deaken University and two colleagues and published in a 2019 issue of Trends in Cancer. The theory begins simply enough: Those in shape and exercising regularly, use more energy than those who do not.

This use of energy does more than improve strength and endurance when you run, lift weights, or work around the house; it also adds strength and endurance to your immune system.

Factor into this the cell mutations that occur in your body and can lead to tumors, the destruction of normal body tissue, and the creation of cancer. Your immune system usually battles these mutations and defeats them before cancer manifests.

It’s a battle that requires more energy than normal, even more so if tumors do indeed develop. When the energy required is more than the body can produce for this fight, the battle is lost and cancer results.

You increase what Biros calls “energetic capacity,” however, by being in shape , exercising ambitiously, and using more energy than the sedentary or half-hearted exercisers.

Increased “energetic capacity” is why Biros believes study upon study finds exercise reduces the risk of many cancers by as much as 25 percent, as well as why regular exercisers have a better risk of surviving many cancers than sedentary people do.

Often in past articles and twice in today’s, I have used “ambitious” or “ambitiously” to describe exercise. It means that for part of a workout (or even all on occasion besides the warmup and the cooldown) you leave your comfort zone.

Your breathing becomes labored to the point where you can’t finish a full sentence in one breath. Your muscles feel taxed, and if you worked them harder, they would begin to burn.

Occasional periods of exercise this intense, according to a study using male subjects and published in the British Journal of Sports Medicine in 2011, further reduce the risk of cancers because exercise intensity has been found to be “inversely associated with the risk of premature death from cancer.”