Hi, I have been doing (I think) HIIT for the last 3 weeks on the eliptical trainer. From what i’ve read, you need to get your heart rate into the 90% max zone. According to This, my max is 187 which means I need to get the heart rate to 169. As a beginner, I do 30 seconds fast, 90 seconds recovery. I notice that during the 30 second high intensity, my heart rate only gets to about 140 - 145, but I am pushing myself hard. I honestly feel like any faster and I will fall over.

Now, I dont increase the tension on the eliptical, I just run at a steady pace on the easiest setting, then explode as fast as possible during the 30 second interval. Do I also need to increase the tension? What is it I’m doing wrong…?

The problem here is your interval ratio is 1:3. In other words, for every 1 seconds you do at high intensity you’re doing 3 at active rest.

If you are pushing as hard as you say you are during you HI intervals then quite simply, you’re resting for too long.

Try an interval ratio of 1:2 max. Mix it up a bit and try shorter intervals as well. For example you may want to try a 10/20 or 10/15 interval split.

If you still struggle to hit that 95% MHR zone then I suggest trying your HIIT out on the track, sprinting - this way you will definitely get your heart rate up.