Here it is, the HIIT theory I mentioned above. It was a Dr. Tabata.

Link to article: http://fitness.mercola.com/sites/fi...ta-workout.aspx

In this link, there is a recommendation to do only 30 seconds of HIIT followed by 90 seconds of a slower pace. The goal is a total of 8 of these HIIT segments. He suggests 3 times a week. There's also a demo video of what the HIIT part should be like on an elliptical. I was happy to find these because this is what I've been doing, more or less, although my level of intensity isn't as much as in the video. Today I did 12 HIIT segments, so maybe I'll scale back a bit to 8. But I'm doing 3x per week, never two days i a row.

From the linked page: "High-intensity interval training (HIIT) gives a natural boost to human growth hormone (HGH) production, which is essential for optimal health, strength and vigor. HIIT has also been shown to significantly improve insulin sensitivity, boost fat loss, and increase muscle growth
According to Japanese research, a mere four minutes of exercise performed at extreme intensity, four times a week, can improve your anaerobic capacity by 28 percent, and your VO2 max and maximal aerobic power by 15 percent in as little as six weeks
Study participants who performed an hour of steady cardiovascular exercise on a stationary bike five times a week only improved VO2 max by 10 percent, and their regimen had no effect on their anaerobic capacity after six weeks
Previous research showed that just three minutes of HIIT per week for four weeks improved participants’ insulin sensitivity by an average of 24 percent"

I also thought this was an amazing statement, within same link above:

Other research has also demonstrated that 20 minutes of high intensity training, two to three times a week, can yield greater results than slow and steady conventional aerobics done five times a week. But the fact that you can improve your insulin sensitivity by nearly 25 percent with a time investment of less than ONE HOUR A MONTH really shows that you can significantly improve your health without having to eliminate hours of other commitments from your calendar.