HIIT on the treadmill

so today i tried my first treadmill HIIT. i was trying to find out what was a good sprinting speed that i was comfortable with. i was conservative in the beginning and then went a little faster bc i thought i could take it. this is what i did:

first
5 minute jog at 5.5 mph

then
1 minute run 7 mph

2 minute walk 3.5 mph

1 minute run 7.5mph

2 minute walk 3.5 mph

1 minute run 7.7 mph

2 minute walk 3.5 mph

1 minute run 7.7 mph

2 minute walk 3.5 mph

1 minute run 7.7 mph

2 minute walk 3.5 mph

1 minute run 7.8 mph

2 minute walk 3.5 mph

1 minute run 7.8 mph

2 minute walk 3.5 mph

1 minute run 8 mph

2 minute walk 3.5 mph

do you think this is good? should i change the time intervals? should i try to do all 8mph next time for the sprints?

Re: HIIT on the treadmill

Your first time Id say thats pretty awesome.

You can try and push for 8 if you feel like your 7's were a bit slow for you. At your very last eighth interval, you should physically feel you cant do one more even if you tried. Thats how you will know your max speed.

Because of the intensity, just make sure you give your body at least 24-48 hrs of rest before doing it again.