If you haven't been exercising lately, a recent study may give you some incentive to do so. It found that keeping just slightly fit cuts your risk of dying over the next nine years in half. This is compared to those who aren't keeping fit at all. And the difference seems to be due to how much exercise you've been getting recently.

When it comes to exercise, your body has a short memory. It wants to know what you've done for it lately.

Nine years after having their fitness measured, one−quarter of the least fit group had died...

The New Zealand researchers looked at 4,584 middle−aged or older adults between 1986 and 2006. None of the subjects had symptoms of cardiovascular disease. The subjects' fitness was measured by their performance on a treadmill. They were then placed into five groups based on their fitness level. Nine years after having their fitness measured, one−quarter of the least fit group had died, compared to 13% of the next−to−least fit group. That's nearly double.

Even when the results were adjusted for the age of the subjects, the relative risk of mortality was still twice as great for the least fit, compared to next−to−least fit. To see an effect that size again, you'd have to jump to the fittest group, where only 6% died within nine years.

All five groups showed little difference in their lifelong exercise habits. Where they did differ was in their exercise habits over the last few years. The least fit group had been getting much less exercise recently. This appears to have been responsible for their poor fitness level and had a greater effect on mortality than even having diabetes or high blood pressure did.

This is a reminder that no matter how you've lived your life, it's important to make some effort to keep in shape in the here and now.

The good news is that no matter how sedentary you've become, it doesn't take much exercise to boost the odds in your favor. Current guidelines recommend a minimum of 150 minutes of exercise a week for good health. If that seems overwhelming, you can always start slowly. The study suggests that practically any exercise will pay off in the long run. Of course more is better, but some is better than none at all.

And the researchers point out that the findings don't only apply to those who are out of shape; the results suggest that exercise is just as important if you're thin and in generally good health.

An article detailing the study was published in the August 2009 issue of Medicine and Science in Sports and Exercise.