I was pretty familiar with interval training from decades ago, but HIIT is an intense form of interval training. I read up on a few different websites and decided to just give it a try. My main take away was don't overdo it as you can hurt yourself. I thought I was starting out easy, but I am actually pretty tired this morning.

So I was on the elliptical and did a 5 minute warmup followed by 5 repeats of 15 seconds full out exertion with 45 seconds of recovery. I then did about 5 minutes of steady state cardio because I was feeling surprisingly sweaty and "exerted" by those 5 repetitions (I really went as hard as I could so pushed myself very hard). I followed that by 2 reps of 30 seconds high exertion (I won't say full exertion probably 80-90% because I couldn't do 100% for 30 seconds) with 1 minute of recovery. I finished with 5 minute cooldown.

I felt like I had done a pretty intense workout even though it was short - 20 minutes including warm up and recovery. I was sweating alot.

Because time at the gym is a premium, I followed with a 30 minute strength training workout as I often do. I had a fairly high intensity strength training session too because the gym was empty on halloween night and I basically had one of the weight rooms to myself.

My knees are too shot to do sprint type stuff (running/jogging) so I felt the eliptical was a good place to start as I am used to doing cardio on it. One of my knees feels a little tired this morning so hopefully I didn't over do it - seems like it shouldn't have been!

Anyway, I have been exercising regularly since February and am looking for ways to amp up the intensity without spending lots more time so this seems a good direction. For those of you familiar with HITT, am I on the right track? I read also to only do this maybe 1-2 times a week and do steady cardio the other days. Is that what you all do? Any suggestions how to get the intensity bursts while protecting bad knees?

Thanks!

Sounds like you have it right. If you're trying to save your knees on the elliptical, then opt for going faster as opposed to increasing the resistance during intervals. If your machine will allow a change in incline then do that as well unless it hurts.

I have my own elliptical at home so I do a circuit type workout. I do 5 minutes of steady state cardio on the elliptical and then jump off and do 20 burpees as fast as I can. then back on the elliptical. Doing that for 30 minutes wears me plum out.