I tried that HIIT 2 weeks ago for the first time. That has got to be the most intense workout I ever had. I'm not gonna lie here and say I did the workout perfectly though. I tried 20sec sprint and 10sec rest, after the 5th sprint I couldn't do more
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Last week I switched it up a bit. Did 20sec sprint and 20sec jogging, this way I lasted 8 sets. The last 2 sets weren't close to full sprint though. I'll keep doing it, it's one hell of a workout.