The 87654321 Session is a series of Out & Back runs:
4 mins out, 4 minutes back
3.5 mins out, 3.5 mins back
3 mins out, 3 mins back etc.
As time frames decrease, return speed will hopefully increase (or at least be maintained).
Of course, you’ll run at your own pace throughout.
For those that want a steady run, a looped route of around 4 miles will also be offered.