HIIT is actually very simple. I didn't know about it before coming here and I haven't read up on it anywhere else but here.
HIIT = High Intensity Interval Training.
"High Intensity": Instead of jogging, you sprint.
"Interval Training": Instead of sprinting the whole distance at one shot (I doubt anyone can do this anyway) you sprint and walk/stop in intervals.
Common sense works wonders.
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