30. It is the answer to the question what is the square root of 900? As a young boy, I thought that was the age people qualified as being old, but now that I just celebrated my 62nd birthday I don’t think that’s true at all. For fantasy football owners, however, the number 30 has just one meaning – it’s the age, we are told, at which a running back’s production and fantasy value is said to begin to fall.

Is that fact or myth?

With regards to the current batch of 30-year-old running backs, the adage appears to be true. In almost every case, as you will see in the box below, the running back at age 30 were less efficient than in his years up to age 29.

Running Backs - Yards per Touch Player age up to 29 30 31 32 Frank Gore 32 5.15 4.34 4.57 4.19 DeAngelo Williams 32 5.33 5.18 3.92 5.30 Darren Sproles 32 6.91 6.64 7.38 5.10 Steven Jackson 32 4.80 3.86 4.07 3.18 Pierre Thomas 31 5.45 6.66 2.02 Adrian Peterson 30 5.26 4.78 Matt Forte 30 5.05 4.91 Chris Johnson 30 4.91 4.31 Rashad Jennings 30 4.82 5.17 Justin Forsett 30 5.49 4.36 Danny Woodhead 30 6.06 6.12 Mike Tolbert 30 5.06 5.12 Reggie Bush 30 5.16 3.91

Even the 2015 rushing champion, Adrian Peterson, was not immune. Despite a great year after his return from a suspension, Peterson’s “yards-per-touch” was down 9.1 percent. Considering only the fantasy-worthy backs on this list, Rashad Jennings and Danny Woodhead were the only two who improved after they celebrated their 30th birthday.

Another eight running backs will hit the “magic number” during this football season. What should fantasy owners do about the situation? In dynasty leagues should you trade them for cents-on-the-dollar? Should you avoid them altogether in redraft leagues?

Let’s look at each player individually:

Charles won't turn 30 until late this season but after two knee injuries, owners need to be cautious.