These days, it seems as though we have to dedicate ourselves to one particular training dogma at the exclusion of all others. You’re either a long, slow distance runner (LSD), or you’re a high-intensity interval training (HIIT) supporter. You’re either a low-rep lifter, or a high-rep circuit trainer. Why do we do this? Only training one way while ignoring all others generally results in imbalance and less than optimal efficiency.

Fighters use a mix of interval training and distance training to maximize their fitness

For this post, I’m going to focus specifically on cardio. It used to be that if you weren’t doing a ton of steady-state, endurance running, you weren’t “doing cardio.” Today, it seems that it is the opposite. If you’re not doing HIIT, you’re just wasting your time.

Let me say this: For the amount of time invested, it’s hard to beat HIIT for burning fat and improving VO2max (how much oxygen your body can effectively utilize during exercise; I discuss it further in this post). In well-trained individuals, HIIT effectively improves performance.

So, for HIIT, we have: Better fat burning, quicker workouts, improved VO2max and overall improved performance, even if you’re already highly trained. How could anything possibly be missing?

More than just sprinting

Well, it’s missing some kind of distance component. I can hear you asking already. “What’s the point of that if we get all these great benefits from HIIT in a shorter amount of time?” The answer lies in the physiological response to both kinds of training.

There are a few factors that go into how far, fast and long you can go. HIIT generally focuses only on improving your VO2max. And that’s fine. In fact, it’s more than fine. It’s great. The higher your VO2max, the better conditioned you are. But again, it’s only one part of performing at a high level.

Bernard Lagat often mixes up his training style

Endurance training increases mitochondrial enzyme activity. Remember that mitochondria are like the power centers of your cells. This increased enzymatic activity increases fat oxidation (burning) and decreases lactic acid accumulation. That’s all just a fancy way of saying that endurance training gives you a higher work capacity.

You can think of it this way: Improving your sprinting though HIIT allows your body to produce more power. Improving your endurance through long, steady cardio training allows your body to sustain that power for a longer period of time. HIIT generally makes your heart pump more powerfully, but endurance training allows your heart to move a larger volume of blood. Both of these things are important when it comes to performance.

Lifelong improvements

A study from the University of Texas calls this relationship the “blood lactate threshold.” The lactate threshold is basically how far you can push yourself before muscular fatigue, burning of muscle glycogen for energy and fatigue reach a breaking point. This study showed that the first 2-3 years of training are associated mainly with an increase in VO2max. After this period, VO2max reaches something of a plateau, with only minor increases seen. However, the lactate threshold continues to increase, possibly for a good number of years, after the initial VO2max increase. And one of the best ways to increase your lactate threshold is to do some endurance cardio.

Sprinters often do lots of distance work in the offseason to increase their fitness base

Most studies have shown that it is the combination of endurance training and a higher VO2max that gives you increased recovery capacity between repeated bouts of intense intervals. Endurance training also has been shown to produce higher muscle mitochondria content and increased insulin sensitivity.

The bottom line is that you should mix up how you train. You shouldn’t do HIIT every single day for a prolonged period of time, anyway. Doing so can lead to over-training and increased susceptibility to injury. So, on some of those in-between days, set aside some time for some longer distance runs. Do so, and you’ll see your overall fitness increase in very significant ways.

-Drew

7 Responses to “#5 Mix Distance Running with Interval Training”