Newbie member. Magazine article question.

[Deleted User]

I coach my son [read my bio if you're someone who hates parent coaches, which in my experience is sometimes justified].   I normally do a field based speed endurance session [5 x 1300m with 150 spints - off the bat/no recoveries] but I read somewhere and I am positive it was Runner's World quite recently about a track based session that involved incrementally increasing the sprint/jog phases by counting strides. 

I have genuinely spent all night so far trying to find the article by going through the last six months of magazine/trawling through twitter feeds and googling the site and have drawn a blank.  Can anyone help?  I wanted to hold the session tomorrow, ahead of next weekends U17 Nationals, where he'll be competing in the 800m.  I wanted to mix it up a bit while tapering his miles - this session, I seem to remember was a finite 9 minutes.

Thanks in advance.