More from the article...

... According to research into the molecular changes associated with aging, humans experience two drastic lurches forward, one at the average age of 44 and the other at the average age of 60.

"We're not just changing gradually over time; there are some really dramatic changes," geneticist Michael Snyder of Stanford University said in August when the study was published.

"It turns out the mid-40s is a time of dramatic change, as is the early 60s. And that's true no matter what class of molecules you look at." ...

@#2

Back in the day, I used to ride a bicycle around the area.

20, 30, 40, sometimes 50 miles in a ride (I even did the Golden Apple Century). Up and down (the downhills were awesome :) ) the hills of the area.

Then, around 2000 or so, I hit my late 40's and I noticed a change. My endurance plunged.

So, my experience seems to correlate with what the article cites.

It was not a gradual transition for me, but a ~everything is OK, then... whoa, what happened~ type of experience.