You’ve heard of metabolic conditioning. Many of your clients and prospects have as well. But chances are, what they’ve heard is exactly what metabolic conditioning isn’t.

Contrary to what many of us used to believe, it’s not a magical fat-melting system. It doesn’t “confuse” your muscles or induce an “afterburn” that makes you incinerate post-workout calories like an excitable lumberjack. And it won’t give you all the benefits of traditional cardio in a small fraction of the time.

So what is it? And more important, how do you employ it to help your clients get the results they want without injury, excessive soreness, or reinforcing all the reasons why they hate exercise in general and personal trainers specifically?

Let’s dig in.

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What is metabolic conditioning?

Simply put, metabolic conditioning is a type of training designed to consume maximum calories during your workout, and to create an oxygen deficit that forces your body to burn calories at an accelerated rate for hours afterwards.

But you probably knew that. And even if you didn’t, it kind of sounds like what you’re trying to do in any good workout. So let’s focus on the “metabolic” part.

As explained in this classic article from Vox, metabolism is a process that happens in every cell to keep you alive. The number of calories you burn at rest is largely governed by genetics and muscle mass.

Building more lean mass, and thus burning more calories throughout the day, is one obvious goal of exercise. Another is to burn more calories through physical activity. Yet another is to train hard enough to create a large oxygen deficit.

That oxygen debt is followed by EPOC (excess post-exercise oxygen consumption), a temporary increase in your metabolic rate to allow your body to recover from the workout.

This is the process you target with metabolic conditioning, aka metcon, and it’s the goal of everything from CrossFit WODs to Orangetheory to SoulCycle. All of them promise to create a level of EPOC that, over time, contributes to a significant improvement in body composition.

As you can see by those examples, there are many ways to approach metabolic conditioning, from souped-up strength training to circuit training to something that looks a lot like traditional cardio, only with louder music at a higher price.

I’ll cover three types of metcon here, but you can mix and match exercises and intensities any number of ways, depending on your client’s abilities and goals.

Common metabolic conditioning workouts

Before I get into the specifics, let’s consider the word “conditioning.” In the most general sense, it means “getting in shape.”

We know there are lots of ways to do it. For a severely deconditioned client, walking around the track a few times might improve their VO2 max, the standard measure of aerobic fitness. If the walking includes some stairs, they may also improve their leg strength and perhaps even gain a little muscle.

Give that same client virtually any amount of strength training, and they’ll increase their strength, power, lean mass, and muscular endurance, along with their mobility and movement skill. That client could also improve their VO2 max—either directly, by doing more exercise than before, or indirectly, if the additional strength and mobility motivates them to do other types of physical activity.

The more someone’s conditioning improves, the more specific their training needs to be if they want to keep improving. To increase strength and power, they need a program focused on strength and power. Same with aerobic fitness: Someone whose goal is to run farther and get there faster has to train specifically for endurance.

So when we talk about metabolic conditioning, we’re talking about achieving something beyond aerobic or muscular fitness. We do that by targeting anaerobic glycolysis, one of your body’s three energy systems.

As I explained in this article, glycolysis is the fantastically complex series of chemical interactions your body needs to produce energy when you’re working too hard to use the aerobic system. Your heart is beating so fast, and you’re breathing so hard, that you can’t continue for longer than about 60 seconds. You need to slow down at that point, catch your breath, and let your muscles clear lactic acid, a byproduct of glycolysis.

The more you train this pathway, using the workout techniques I’m about to describe, the better you get at using it. And the better you get at using it, the greater the oxygen deficit you can create with your training. Thus, improved metabolic conditioning means you can train harder, burning more calories both during and after your workout.

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High-intensity interval training (HIIT)

HIIT is the most popular method of interval training for good reasons. Not only is it a great way to generate significant oxygen debt, it’s simple and straightforward. You typically use just one piece of equipment, like a stationary bike or rowing machine, both of which are relatively easy on the joints.

For an inexperienced client, you’ll probably start with 30-second intervals and a work-rest ratio of two-to-one or even three-to-one.

The client can progress in multiple ways:

  • Add intervals.
  • Raise the intensity.
  • Do longer intervals at the same intensity.
  • Reduce the rest periods.

You can also vary the equipment, so a client uses the rower for shorter, higher-intensity intervals with longer rest periods, and a bike for longer bouts with less recovery.

But you don’t want to change things up so much that the workouts become random. The goal of any type of training is to create a training effect, which means repeating the same challenges often enough to see a measurable improvement in performance.

With more advanced clients, you can progress to a one-to-one work-rest ratio. Anything beyond that becomes counterproductive because your client simply doesn’t have enough time to recover from one interval before starting the next one. That lowers the intensity of the workout, which defeats the point.

One final note about interval training: The intervals don’t actually have to be high intensity.

A deconditioned client will still benefit from low-intensity intervals, aka LIIT. As long as the intervals are harder than the client’s typical pace, they’ll get the benefits of metabolic conditioning without pushing them too far, too soon.

There’s also a place for medium-intensity intervals (MIIT). It’s obviously a bridge between LIIT and HIIT for some clients, while for others it’s a nice break from high-intensity sessions.

Traditional circuit training

Circuit training—typically five to seven exercises done consecutively, with little to no rest in between—is a classic model of increased work capacity.

The idea is simple: Build muscle while also increasing metabolic demand. Does it actually work that way? Depends.

The more you emphasize building muscle, the more recovery you need between sets, and the less oxygen debt you accumulate. The more you emphasize metabolic conditioning, the less you can focus on hypertrophy. You have to use lighter weights and stop your sets before you fully fatigue muscles.

But it’s not like you’re wasting time if you get more of one benefit than the other, or if you find a sweet spot in between. You’re still training something. It’s just hard to train an intermediate to advanced client effectively for multiple goals at the same time.

As with interval training, you can use a variety of intensities. High-effort circuits can create a massive oxygen debt for more advanced clients. Medium-intensity circuits are a good way to deload after a period of heavy lifting. And low-intensity circuits are perfect for complete beginners who still want to feel as if they’ve gotten a good workout.

Combination training

This catch-all category targets everything in the same workout.

After a thorough warm-up, you start your client with the exercises that call for the highest effort and focus. It could be technically complex lifts with low reps for strength and power. Or you could use less technical lifts with medium reps for strength and hypertrophy.

From there you might go to supersets or mini-circuits with the goal of creating an oxygen debt. You’d finish with some steady-state cardio.

Thus, you’d train all three energy systems—ATP-CP, glycolytic, and aerobic—and achieve multiple benefits without compromising anything.

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Exercise selection for metabolic conditioning

The greater the metabolic challenge, the simpler the exercises need to be. You can’t ask clients to perform exercises at high intensity when they’re still learning to do them.

I had to learn that lesson the hard way.

Early in my career, I wanted to give participants in my metcon classes stuff they hadn’t seen before. The more novel it was, the better it must be. The logic seemed irrefutable: “Do cool s*** and become popular.”

In time, I moved closer to the combination training I just described. My warm-ups included corrective, mobility, and stability exercises. I followed those with the most challenging exercises and the heaviest loads. Then we’d get to the metcon portion, where I’d emphasize multiple rounds of simple loaded and unloaded exercises to fatigue muscles and create an oxygen deficit.

I’d finish the class with a low-intensity, low-complexity round, in which the participants used their aerobic systems.

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How to program metabolic conditioning

Let’s start with a stipulation: Almost all the clients you train, individually or in group classes, are in the general population category.

Even the strongest or most jacked clients, male or female, young or old, are gen pop unless they’re actually competing in something. The odds are pretty close to 100 percent that they’re missing something important. A strong and muscular guy may not have an aerobic base or movement skill. A lean endurance enthusiast may lack strength and mobility.

Even if someone has the whole package, there’s a very good chance they achieved it by pushing their bodies to the breaking point. You don’t want your metcon workouts to push them over the edge.

I think metabolic conditioning works best when it’s part of a well-balanced program, and worst when it’s the primary component.

Let’s say a client trains with you two or three times a week. Most of your program will focus on strength, hypertrophy, movement skill, and any rehab or corrective exercises the client needs. Ten to 15 minutes of metcon at the end of more traditional workouts should work well.

For an intermediate-level client who wants to add an extra workout beyond your program, metcon makes sense. It can include anything from group cycling to bootcamps—whatever they enjoy and feel they can recover from. Just make sure you adjust your own program to account for it.

And for the ambitious client who wants to train six days a week, two bouts of 30 to 40 minutes per week should be the optimal upper limit for metabolic conditioning. Any more than that puts too much stress on the joints and central nervous system. (Chris Beardsley has a terrific explanation of CNS fatigue in this article.)

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Final thoughts

I want to close with a cautionary note:

Metabolic conditioning is not a beginner’s program, especially for clients who’re significantly overweight, recovering from an injury or illness, or otherwise deconditioned. In fact, one could argue that it’s highly irresponsible to emphasize output in someone who’s new to the gym, doesn’t move well, or hasn’t yet built a base of strength and endurance.

That doesn’t mean you can’t challenge these clients. Just do it in short, low-intensity intervals or circuits, using exercises the client can do proficiently. And for the love of all that’s good in the world, don’t have someone who’s 100 pounds overweight do a burpee. That doesn’t make you a good trainer. It makes you a jerk.

Your job is to meet the needs of the client, regardless of what’s trending at the moment.