good, that's what I've been doing! I've just started what we call interval training, sounds similar to this HIIT thing. Jog 10 seconds, sprint 10 seconds, walk 10 seconds - repeat until death
still experimenting with it but it is a lot harder work than straight running, so must be better exercise. Also I found my muscles aching quite a lot after the first time I did it, and I'm used to running so must have been harder work. Also also, it makes you realize you usually can work harder than you think.