Metcon is Mandatory: Cardio for Physical Dominance

Metabolic Conditioning Workouts

Metcon is the missing ingredient. Here’s how metabolic conditioning workouts will improve everything, from fat loss to muscle growth.

Most strength athletes and bodybuilders hate cardio. They even dislike its cousin, metabolic conditioning or metcon. Sure, being muscular and strong will help you look like a badass, but if you fizzle out after only a minute or so, can you really say you’re a badass?

Even if a mixed martial artist is jacked and strong, if he gasses out by the middle of the first round, he’ll get his butt kicked. Strength, power, and speed are all important for being physically dominant. A physique that’s a byproduct of those qualities is intimidating. But if you lack conditioning and physical resilience, you’ll get pummeled.

Metcon Is Hardcore

In sports, you can find examples of athletes being physically overmatched but winning anyway by tiring out their opponents. If you tire more slowly and maintain 80% of your capacities while your opponent is at 40%, the odds easily shift in your favor.

Ask any hockey or basketball coach about the common element between the best defensive players. Those relentless athletes who always stick to their guy have the best conditioning. The moment you get tired, you get sloppy and slow. That means your opponents can fake you out, overpower you, or beat you with speed.

The point is, you can’t be a true badass if your conditioning sucks. And better conditioning will help you build more muscle too. Let’s look at the benefits of great conditioning and how to build warrior-like resilience.

Conditioning and Longevity

Improving your conditioning improves “quality aging” – maintaining better functionality as you grow older. This probably increases longevity as well.

With aging comes a decrease in both mitochondrial density and function (1). This leads to a decrease in energy production to feed the various cells in your body, which negatively affects them. It leads to a decline in cognition, muscle performance, and glucose disposal (which can cause insulin resistance and high blood sugar, making it harder to lose fat).

The capacity of the mitochondria to produce energy decreases by 5-8% with each decade after age 30 (2). Conditioning work, especially in fairly intense zones, can increase mitochondrial density and function. As such, it could be useful to slow down cellular dysfunction and aging.

Even in older individuals, conditioning work can improve mitochondrial function significantly and could essentially keep that function equivalent to that of younger individuals (3).

The bottom line: Conditioning will prevent the age-related decline in cellular energy production capacity, making sure your body’s cells keep functioning properly. In short, conditioning work is anti-aging work.

Conditioning and Fat Loss

Conditioning work can help you lose fat via direct caloric expenditure but also through improvements in the machinery responsible for mobilizing and using fat for fuel.

Some people only look at the direct impact of physical activity (calories/fatty acids burned through exercise) and conclude that the impact of cardio or conditioning on fat loss is much less important than dieting. After all, we don’t “burn” as many calories as we think during exercise. Also, the body becomes more efficient over time and burns less energy for the same workload.

However, these arguments disregard the impact of improving your capacity to mobilize and burn fat for fuel, mostly through an increase in fat-mobilizing enzymes and transport systems. Conditioning also improves glucose metabolism, which tends to favor positive nutrient repartitioning – more of the carbs you eat get shuttled to muscles instead of fat cells.

Basically, as you become better conditioned, you make your body better at utilizing fat for fuel.

Hard conditioning work that causes an increase in lactate could help with fat loss by increasing growth hormone, which can improve fat mobilization. I don’t put a lot of emphasis on the effect of short-term hormonal changes, but even if it’s small, the effect could still be positive when it comes to getting leaner while preserving muscle.

Conditioning and Muscle Gain

A lot of people fear that metcon will “eat away their gainz, bro.” Where does that belief come from? Here are a few things that might be giving you that impression:

1. Endurance athletes normally have a low level of muscle mass.

However, this is mostly because they don’t perform any training that triggers muscle growth.

Also, remember, elite endurance athletes have a genetic predisposition for their sport. The best endurance athletes have the ACTN3 XX genotype, which makes their muscles primarily slow-twitch dominant and gives them a much lower mTOR response. Both make them less genetically suited to build muscle but naturally gives them a higher VO2 max.

Also, endurance athletes normally have more muscle mass than sedentary folks, so the endurance work didn’t eat away their muscles, “bro.”

When you look at people combining conditioning work and hard lifting (CrossFit athletes, rugby and hockey players, etc.), they normally don’t have a problem with losing their gains. Most exhibit muscular and lean bodies.

2. The “interference effect.”

Too much cardio can interfere with size and strength adaptations if it’s performed in the same workout as your lifting. This is likely due to a decrease in the mTOR response to the muscles trained. However, it’s worth mentioning…

  • This is “muscle-specific.” Doing cardio involving the lower body will not negatively impact upper-body growth.
  • It refers to a session where the endurance work is done immediately after lifting. If the cardio is done separately, it won’t affect the adaptations from the session.
  • The amount of cardio you do must be fairly high to interfere with size and strength adaptations. Adding 20-30 minutes of steady-state work or 6-10 minutes of interval work isn’t likely to cause slower size and strength gains.
  • Modalities that include resistance during the conditioning part of the workout (loaded carries, sled pushes, air bike, rowing ergometer, kettlebell swings, barbell complexes, etc.) won’t have a negative impact because of the amount of force produced by the muscles due to the external resistance.

There will be no interference if you do steady-state cardio on upper-body days or on your days off, and you use high-resistance conditioning work on lower-body days.

3. The “feeling” effect.

When you do conditioning, you feel like you have flatter and smaller muscles after the workout. If you combine conditioning with lifting, you also get less of a pump. Because of that, it’s easy to think you’re losing muscle.

In reality, it’s more likely due to losing lots of water and electrolytes through increased sweating, as well as the increased blood flow to the muscles which “take out” the metabolites that cause the pump like lactate and hydrogen ions (as well as intramuscular water). You might also be using a lot of muscle glycogen, which will also leave the muscles feeling flat.

That doesn’t mean you’re losing muscle. It does mean you need to rehydrate and replenish electrolytes and glycogen. If you leave your muscles flat, it can lead to an increase in protein breakdown and a reduction in protein synthesis, so you don’t want to stay that way for long.

Conditioning and Muscle Growth

When done in modest amounts, conditioning won’t lead to muscle loss, nor will it slow muscle gain. However, you must make sure to stay hydrated and replenish electrolytes. It’s the dehydration and electrolyte loss that’ll make you weaker, flatter, and maybe even lose muscle, not the cardio itself.

In fact, an argument could be made for intense conditioning potentially increasing muscle growth.

Lactate itself can be anabolic. For example, it can lead to an increase in follistatin. This is a binding protein that inhibits myostatin. Myostatin is a myokine (a protein released by the muscles) that limits muscle growth. The more myostatin you produce, the less muscle you can build.

Lactate can thus indirectly lower myostatin which can increase your body’s capacity to build muscle. Hard conditioning that leads to an increase in lactate might actually help you build more muscle.

I also have this theory that because the muscles require a lot of support from the cardiovascular system, a natural lifter’s conditioning level can be a limiting factor for muscle growth. The body won’t allow you to build muscle tissue that your heart can’t fully support. It’d be hazardous for your health, and the body wants to avoid doing something that’ll put it in harm’s way.

Conditioning, Work Capacity, and Recovery

Louie Simmons said that the biggest problem of North American lifters is poor conditioning or work capacity. Both are tightly connected: the better your conditioning, the greater your work capacity.

If your conditioning is bad and you’re out of shape, not only does it take you longer to recover from your work sets, but the training session will represent a larger stress. The better conditioned you are, the more work you can do in the gym without the body being in the red. If you can do more work and recover faster, you can stimulate more gains.

That’s why the Westside guys use so much long sled pulling and Prowler pushing. Most of the time, it’s not hard and short. It’s long duration.

They also include a form of conditioning from what they call lactate training: using minimal rest periods between sets of speed work. If you do 10-12 sets of two-rep squats, but with only 30-45 seconds of rest, lactate will build up and actually become a form of anaerobic power conditioning work.

I’ve also worked with a lot of CrossFit athletes. I trained a few that competed in the CrossFit Games and at regionals. Most of them can do a ridiculous amount of volume – an amount that “shouldn’t” work and would be considered overtraining. Yet, they can not only handle it but progress from it. Genetics can play a role, but so does being extremely well-conditioned.

Conditioning and Performance While Fatigued

When I was training CrossFit athletes, the thing that always baffled me was when they were capable of lifting loads close to their maximum even while fatigued.

For example, I had a regional-level female athlete hit a snatch PR during a workout where she had to gradually ramp the weight up while running 400 meters between every attempt. She hit her PR after running 5 x 400.

Now, can you imagine the benefit of that if you’re an athlete? You can keep performing at near maximal levels in strength and speed even when fatigued.

Deep Dive: The Energy Systems and How to Train Them

Conditioning, in the context of physical preparation, refers to being able to perform at a high level while challenging one of the energy systems.

There are various classifications of the energy systems or capacities involved in conditioning. Regardless of the classification, the effort (either a percentage of your max heart rate or your VO2 max) and duration are the two key components.

So let’s look at the training zones. The exercise you’re doing at any given time will fit into one of these categories.

The Training Zones

Neuromuscular Capacity

Also called anaerobic power, it’s when you produce the most intense effort tolerable for 20 seconds or less. It leads to the highest power output of all the zones. We practice this when we lift. Short Prowler sprints, Assault Bike sprints, and all-out rowing for 10-20 seconds are also very effective.

The sprints can actually be as long as 30-40 seconds since it takes a few seconds to ramp up the intensity. This is normally trained with ample rest between sets because the goal is to reach the highest power output possible.

Best modalities: Sprints, hill sprints, sled work, air bike, rowing ergometer, ski erg, barbell complexes, and kettlebell swings done for bouts of 20-40 seconds as hard as possible and with 2-3 minutes of rest between sets.

Anaerobic Capacity

This is where you go as hard as you can tolerate for 1 to 3 minutes. While the duration is important, it’s the intensity that’s key. The intensity should be high enough that it’s not sustainable for more than 1-3 minutes. But just because you’re doing bouts of 1-3 minutes, it doesn’t mean you’re working in that zone.

This can be trained either with longer “sets” (1-3 minutes) with fairly long rest intervals or through high-intensity intervals. But remember, when doing true HIIT, to improve anaerobic capacity, the “hard” part of the intervals must be all-out. It needs to be I’m-getting-chased-by-a-tiger hard or I’m-running-away-from-a-vegan fast.

Best modalities: Whole-body lifting circuits, medium-distance loaded carries (150-300 meters), 400-800 meter sprints; air bike, rowing ergometer or ski erg (1-3 minutes hard); stationary bike, treadmill, elliptical, or running (HIIT with 15-30 seconds hard and 30-45 seconds easy).

VO2 Max

To improve VO2 max, you want bouts of 3-8 minutes at a heart rate level of 90-100%. Again, going for 3-8 minutes isn’t enough. It needs to be done at the proper intensity. Doing 5-8 minutes at a heart rate of 75% will not train VO2 max. This can also be done through a constant bout of exercise in the target zone or via intervals. Proper HIIT trains both anaerobic capacity and VO2 max.

Best modalities: Running, stationary bike, treadmill, air bike, rowing ergometer, or ski erg for bouts of 3-8 minutes at 90-100% of max heart rate.

Anaerobic Threshold

This zone is a bit more complex. The goal is to spend an extensive amount of time (several minutes, up to 15) with some lactate in your muscles. This zone causes the greatest increase in mitochondria, which means it positively impacts performance in many zones.

Normally, once lactate builds up, you don’t have much longer to go in a set. The best way to train in this zone? Use a “fartlek” approach. Go hard enough so that you start to feel a small amount of lactate built up (the burn, even though the burn comes from hydrogen ions and not lactate). When it starts to be less tolerable, decrease the intensity enough for the lactate to decrease (less burning). Then you go back up until there’s once again a small burning sensation. Wave this way, up and down, until you hit your desired duration.

Typically, the heart rate will wave between 80 and 90% of max. But going by the burning feeling is a better way of knowing if you’re in the proper zone.

Note that circuit training with an active rest period also trains this capacity. For example, 3-5 lifting exercises without rest, covering the whole body, then doing a 2-minute active rest between sets.

Best modalities: Whole-body circuit training with active rest or fartlek intervals.


This is what we traditionally see as steady-state cardio or low-intensity steady-state cardio (LISS). However, this second term is often misleading because, if the intensity is indeed lower than all the preceding zones, if you go too low, you won’t get the adequate training effect.

Typically, we’re targeting a heart rate of 60-70% of your maximum heart rate for longer durations. This zone will improve the body’s capacity to mobilize and utilize fat for fuel, and it can also develop the mitochondria.

More importantly, it lays the foundation to be able to train in the more demanding zones. A big mistake is jumping right into the more demanding intervals, circuits, or sprints because you think it’ll provide faster results. But if you’re not prepared for them and have a decent endurance capacity, the higher intensity energy system work will be too much of a stress and will be hard to perform and recover from.

To be “highly conditioned,” you need to be efficient in all of those zones. The good news? There’s a carryover between zones. For example, training for VO2 max will improve most other capacities.

The Bottom Line

Regardless of your goal – being a better athlete, increasing longevity, being leaner, or building muscle – improving your conditioning is a huge part of the equation.

The key? Start conservatively and gradually increase the difficulty to avoid overstressing your body. You didn’t build all of your muscle in a short period of time. The same thing is true for conditioning, although improvements will come faster than building muscle.

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  1. Conley KE et al. Oxidative capacity and aging in human muscle. J Physiol. 2000;526:203–210. PubMed.
  2. Short KR et al. Decline in skeletal muscle mitochondrial function with aging in humans. Proc Natl Acad Sci U S A. 2005;102:5618–5623. PubMed.
  3. Coggan AR et al. Skeletal muscle adaptations to endurance training in 60- to 70-yr-old men and women. J Appl Physiol. 1992;72:1780–1786. PubMed.

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