[NiteHawk]

Here is the reason to keep them seperated...

Now the reason I say to keep your HIIT sessions seperate from your weight training days is that both use glycogen for their main fuel source. Also your body's hormonal responses to both weight lifting and HIIT are the same. So I always keep them seperate.

Not necessary but most beneficial if you keep them seperate. I recommend treating them the same.

If you are on a machine, they should have a timer or clock on there that you could watch or set for the times you want. Also on a track, just wear a watch or stopwatch to do it correctly.