Intensity is relative.

I’m a moderately fast runner. For me, I’ll never do a 10K slower than an hour unless I’m trudging through snow. For others, running a 10K under 60 minutes is a goal they’re chasing. For others still, anything longer than 45 minutes is plodding. So, we won’t be talking in terms of speed, but intensity. And this information doesn’t just apply to running, but any type of aerobic activity (in vernacular people call it “cardio.”)

So, is your cardio hit or miss?

Wait, I meant those as acronyms. Is your cardio HIIT or MISS? What about LISS or HISS?

I guess I should spell those out.

  • HIIT = High intensity interval training
  • LISS = Low intensity steady state (steady state means maintaining the same pace throughout)
  • MISS = Moderate intensity steady state
  • HISS = You guessed it, high intensity steady state

This isn’t really about race training, although people wanting to get faster for race day use these various training modalities. But implementing a variety of intensities for running goes way beyond performance. It also affects appetite, total daily caloric burn, fat loss, muscle retention / gain, and how you perform in non-aerobic activities.

If you’re someone who likes to lift for strength and physique goals, this is your aerobic cheat sheet for how to use things like running wisely. Let’s start off easy with …

Low Intensity Steady State
In race training the acronym is LSD: long, slow distance. It’s about racking up the miles to build a solid base for getting faster, not about mind-altering chemicals, although it can be so boring you begin to hallucinate. This is the typical type of cardio that a lot of people do for fat loss, but it’s actually one of the less useful ones for that.

LISS is what the gym bros tend to criticize, and that criticism is not without merit. The problem is that when some factually challenged article is written about running they often presume that all runners are doing nothing but LISS. I think if you’re looking for a well-rounded aerobic routine where you’re running four times a week, LISS should only be one of them.


  • It is good for base building and preventing injury by not going hard all the time but still logging the miles.
  • On days you’re tired or don’t feel like it, it can be easier to get out the door when you know you don’t have to push it today.


  • LISS can be boring. You’re going slow and it’s time consuming and I just really hate it.
  • It’s time consuming. It takes longer to cover the same distance as going fast would. Duh.
  • Because of its lower intensity, it doesn’t have much of an appetite suppressing effect.
  • If all you ever do is LISS, you won’t get better.

Moderate Intensity Steady State
As I mentioned, for me a LISS 10K is going to take, at most, 60 minutes. For a MISS 10K it’s going to take closer to 55 minutes. That may not seem like much difference, but trust me that shaving 5 minutes off a 10K suddenly starts to feel like work.


  • Feels more like you had a good workout without wiping you out.
  • Reasonable appetite suppression effect.
  • Saves some time.
  • Decent caloric burn rate.


  • Training effect is only moderate. This kind of pace doesn’t do much to make you faster.

High Intensity Stead State
I don’t see many people doing this unless they’re actually training for a race. If you’re just looking to do cardio for fitness and fat loss, there is a good chance you skip this one. Well, you shouldn’t, because it just might be the best of the lot. However, you’ll likely want take a pass on listening to music during this type of intensity because it can hold you back from a maximum effort. For me, this is running a 10K in 50 minutes or less. Each minute I shave off creates exponential pain and exhaustion. For me, a 47-minute 10K is hard; a 45-minute 10K is brutal and will require at least two days of rest afterwards. Again, intensity is relative. For some, these times are easy, whereas for others they’re unachievable.


  • Excellent training effect. These runs are great for boosting your performance as a runner and even for other sports; it toughens you up.
  • High metabolic rate for increased caloric burn.
  • Usually results in strong appetite suppression and reduced cravings for treat food for those looking to lose weight.


  • Increased potential for injury.
  • Can be very exhausting and decrease total daily caloric burn due to turning you into a couch zombie for the rest of the day. Your non-exercise activity takes a big hit.

High Intensity Interval Training
This is when you go all out for somewhere in the one to three-minute range, followed by a slow pace recovery period. Interval training has often been sold as the holy grail of fat loss, but that’s largely bullshit. At least, it is in terms of the way it’s been explained, which is due to some alleged caloric after burn effect. As I showed here and here, the caloric burn rate doesn’t change based on whether or not you did intervals, but is based on total work done in a specific time period.

Nevertheless, it does have an important place in your rotation, but like with HISS, I again suggest ditching the tunes to focus on an intense effort.


  • Out of the four, it’s the only one with an anaerobic component, training a different energy system. (Learn more about bodily energy systems in my Cardio vs. Weights Cheat Sheet.)
  • It can significantly improve your ability in other sports that require shorter burst output like basketball, hockey and downhill skiing.
  • It activates more muscle fibers and can actually increase muscle mass (although not the same way intense resistance training does).
  • Can have a significant appetite suppressing effect for those interested in fat loss.
  • Tremendous training effect for those looking to get faster.
  • Makes you badass. These are friggin’ hard and doing them on a regular basis increases mental toughness for other activities.


  • Highest rate of injury for all four types. Should not be done more than twice per week.
  • Even for good runners, they are hard to implement. It takes a while to build up tolerance. This is because it kind of feels like you’re dying. It’s the longest two minutes of your life, followed by the shortest two minutes, following by the longest two minutes …
  • They demand a lot of you and are not doable on an “off day.” And they can turn you into a bag of ass for the rest of the day, lowering NEAT, so don’t plan too much that’s strenuous for afterwards.

If you’re not much for racing but more interested in general fitness and enhanced performance in other sports as well as improved body composition, running can still be a valuable tool. If you did each of these once per week, coupled with an intense lifting regimen, you’d be rock solid and ready for almost anything.


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James S. Fell, MBA, writes for the Los Angeles Times, Chicago Tribune, Women’s Health, Men’s Health, AskMen, the Guardian, TIME Magazine and many other fine publications. His first book was published by Random House Canada in 2014. He is currently working on his next book, which is about life-changing moments.