How often are you doing HIIT ? In general, a person shouldn't be doing HIIT more than once, maybe twice a week.
HIIT is a great way to increase your level of fitness, but doing it too often can really tax a person's body. thus the reason they should only do it once, maybe twice a week. max.
If you're looking for a low impact, high intensity workout, try spinning or Zumba. Zumba is a Latin dance based aerobics workout. Step aerobic can be low impact too as long as you don't do it without the jumps or hops.
And don't knock a daily walk. Walking is wonderful low impact cardiovascular exercise. You shouldn't be doing too much high intensity exercise. It really will wear your body down. Take this slow and easy AND add in some low intensity forms of exercise.
Some of the wear and tear on your joints could be coming from the excess HIIT workouts.
Edited by: ARCHIMEDESII at: 4/26/2011 (12:31)