The evidence is there.  You can participate in elite level marathoning at any age.  The former notions of athletes being obsolete after 30 have been completely discredited.

This article:

http://www.cnn.com/2009/HEALTH/07/16/athletes.comeback.endurance/index.html

from CNN discusses athletes in many sports remaining or reaching elite level in their 30’s and 40’s.  Here are some examples from the article:

• Lance Armstrong is competing in the Tour de France at age 37
• Dana Torres won the Silver in the 2008 Olympics at age 41
• Haile Gebrselassie broke the world record for the fastest marathon in September 2008 at the age of 35
• Quarterback, Kurt Warner at 37, led the Arizona Cardinals to the Super Bowl in January 2009
• Oksana Chusovitina, 33, won a silver medal for the vault in the 2008 Olympics

They didn’t mention it in the article, but I remember being inspired when Constantina Tomescu-Dita won the women’s marathon in the 2008 Olympics at age 38.  I am 31 now–that night (for a couple of hours, anyways) I felt like I could train hard and win the Olympics, too!  While winning anything may not be in the cards for me, I definitely see these examples as inspiration that I have many years ahead of me to improve my performance in the marathon.

Even if you are not elite and not planning to be, this evidence is inspiring.  Being an athlete is not synonymous with being under 30.  The flipside is being athlete at any age can clearly keep you feeling youthful.

If you have never run a marathon, do not let concerns about age hamper your goals.  There is an amazing spread of ages at marathons.  It is very inspiring–especially when someone at least twice your age buzzes past you.  I want to be one of those people someday.