Treadmill HIIT Routine

anachronicles

I just wanted to get some opinions here on sprinting drills.

Is it best to do longer intervals at a slightly lower speed (1 minute at 8.5 with 30 seconds rest) or short intervals at a high intensity (30 seconds at 9.5 with 30 seconds rest)?

Thanks!

meshashesha2012

what are your goals?