Here are some of my usual HIIT workouts:
1. Track sprints - I know you said you can't do this, but just listing it. I do this very sparingly. It causes a lot of muscle damage and seems to interfere with my leg workouts. I have also gotten injuried on these several times.
2. Bike and elliptical sprints - I do these most often
3. HIIT variable cardio - I will go to the gym and do 5-10 minutes worth of sprints on a variety of machines, and intersperse sprints with 10-15 minutes low II cardio. I.E. 5 mins sprints stair master, 10 minutes walking, 10 mins sprints elliptical, 10 mins low intensity rowing.
Thanks a lot!! I did some sprints a few weeks back and they really fried my legs, but were great b/c I was short on time. I might try them again today and just see how I feel.
Tomorrow I'll aim for 5-10 minutes of sprinting on the elliptical and then do the rest slow and steady.
As always, I really appreciate the feedback!