Ok, so I decided to try HIIT out this morning at they gym. I stretched, then jogged for 5 minutes on the treadmill going 6.5 miles an hour. At the 5 minute mark, I increased the speed to 12.5mph and sustained that speed for 30 seconds. then I slowed back down to 6.5....well, the machine automatically stopped and on the display it said "Check Speed Functions".....I tried pressing clear, cancel, start, resume....no buttons would unlock the machine.
I then jumped over to the next machine, ran for 30 seconds at 11mph this time, then back down to 6.5mph. Well, same thing happened....I broke the second machine too!
I don't know if these treadmills can't handle that kind of speed or have some sort of control device built in or what....but bottom line, I don't think I can do HIIT on the treadmill.
What would my next best choice be for HIIT, at the gym? The ellipse machine, the bike???