Too much intensity and too many intervals will turn you to mush.
According to most physicians, the ideal amount of exercise you want to get in over the course of a week is around 150 minutes if you’re keeping it moderate, or 75 minutes if you’re getting really intense with it. If you can push yourself to the limit, 90 minutes of intense exercise can do you a lot of good. However, it’s when you start going past that point that you’re officially overdoing it.
As a reminder, high-intensity interval training, or “HIIT,” is a methodology of exercise wherein one tries to condense a powerful burst of physical activity into a short span instead of spreading it out over time. Studies show that this kind of exercise increases the number of mitochondria present in your muscular cells. Now, as any former middle schooler can tell you, mitochondria is the powerhouse of the cell, so more of it means more powerful cells, which in turn means better cellular health and cleaner metabolic processes.
However, according to some studies, if you overindulge in HIIT exercise, while your mitochondria will improve at first, eventually they’ll begin to weaken and fail. Participants in these studies who worked out HIIT-style for multiple weeks on end began to lose control of their bodies’ ability to manage blood sugar as their mitochondria began to sputter out. This is just some speculation on my part, but if HIIT exercise raises the number of mitochondria in your cells, that means more organisms relying on your blood sugar for energy. With so many mitochondria trying to gobble up sugar to keep up with the increased need for energy, it’s no wonder those participants’ cells went out of whack. Your body’s over-capacity!
So if you like HIIT exercise, that’s perfectly fine, but remember to keep it at a reasonable pace. The whole point of HIIT is to condense more exercise into less time, but if you do as much as you would moderate exercise, that kind of defeats the purpose.