So-called "silent strokes" may be hard to detect, but can cause permanent, irrevocable damage. Now a new study shows that something as simple as breaking a sweat can help fend them off.

Silent strokes are blood vessel blockages that usually do not have any accompanying physical symptoms. The injury occurs in areas of the brain that control a person's mood or temperament as opposed to motor functions or the ability to speak. Often, silent strokes foreshadow more serious, obvious ones.

While the damage from silent strokes is usually permanent, their occurrence can be lessened through exercise, according to Columbia University researchers, who studied the exercise habits of elderly people over a six-year span.

But to see any benefits, seniors may just have to put down their golf clubs and jump into a swimming pool, play a round of tennis or go biking.

That's because the protection only kicks in when seniors get their heart rates up. The study found that engaging in moderate or intense exercise on a regular basis reduced the risk of silent stroke by 40%.

Unfortunately, light exercise doesn't bestow the same benefits, which is a problem for seniors with physical and mental limitations.

Nevertheless, any form of exercise promotes good health, and can help prevent other problems like heart disease. The American Heart Association prescribes a weekly minimum of 150 minutes of moderate or 75 minutes of intense exercise. For seniors who are out of shape, walking is an easy place to begin.

And if even that's too strenuous, don't give up: Ask a doctor or exercise specialist to come up with a personalized plan.