Age is nothing but a number, according to a new, rather unusual study. The research, conducted by Spanish researchers at Camilo Jose Cela University, found that marathon runners finish at about the same times when they're 18 years old or between 55 and 60. 

How is this possible? The Spanish researchers described a person's marathon times as a U-shape, which curves as they age. The findings are contrary to what researchers previously thought about marathoners' running times. They used to believe that it was more linear, with times worsening as a runner aged. Instead, they found that a runner's time improved by four percent each year from 18 until men and women reached their peaks at 27 and 29 years old, respectively. After that, their race times increased by about two percent each year.  

"While the rate at which performance drops is moderate until the age of 55, from then on the drop becomes sharper in both male and female runners," said Juan Del Coso Garrigós, a scientist from university and main author of the study, in a press release.  

For their study, the scientists created a database with the finish times of over 45,000 runners who participated in the New York City marathon in 2010 and 2011. The study also included the top 10 men and women between the ages of 18 and 75. "The difference in the amount of time it takes men and women to finish a marathon remains at approximately 20 percent until age 55. But from this age onwards the differences between the sexes are greater, and reach more than 40 percent at 70 years old," Del Coso said.

It's unclear how often the older marathon runners trained or what their diets were. But those factors, along with the amount of sleep they get every night, are critical to optimal performance. Marathon running, or running in general, is a great way to get recommended levels of physical activity, which will help prevent diabetes and cardiovascular disease, among other chronic illnesses. Along with a healthy diet, longevity is almost guaranteed.  

The National Heart, Lung, and Blood Institute suggests starting with at least 30 minutes of physical activity three days a week, and building up to 45 minutes. Walking is a great way to burn those calories, as well as cleaning the car, doing laundry, or other household chores. Get up, take the stairs if you can, and start moving so that you can be fit at any age. 

Source: Lara B, Salinero J, Del Coso J. The relationship between age and running time in elite marathoners is U-shaped. Age. 2014.