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Crossfit Cardio: The Myth Debunked


One of the common misconceptions with individuals outside of the Crossfit community is that Crossfit “de-emphasizes” cardiovascular workout. Basically: “Where’s the Crossfit Cardio? or Where’s the Cardio in Crossfit?”

Admittedly our boxes don’t contain any elliptical machines, treadmills, or spin bikes. There’s always the Airdyne bike..but do 45 minutes on that thing and see if you can still walk…that’s not cardio, that’s torture.

In order to understand why we don’t spend hours on a treadmill or focus alot on long runs outside of the occasional sprint, mile run or 5k run, you have to understand the science behind your bodies response to that type of work.

Metabolic Pathways

FileMetabolism 790px partly labeled 300x217 Crossfit Cardio: The Myth Debunked

Fig A – Just some of the metabolic pathways in your body. – Img Source: Wikipedia

You need to start by understanding that one of the ways that your body transfers and consumes energy is through metabolic pathways. Now, while there are many pathways in your body (see fig A) we are concerned with the ones that transfer energy to your cells released by the breakdown of fuel molecules into ATP for energy transport. Specifically the Aerobic and Anaerobic respiration pathways.

Aerobic vs. Anaerobic

Volumes could be written on the differences between these two modalities, but here’s what we need to focus on. Aerobic workout stimulates fat loss & cardiovascular endurance, but not muscle growth. Anerobic on the other hand stimulates fat loss & muscle growth as well as cardiovascular endurance (but not as much as aerobic). Think about it, look at a marathon runner (aerobic)…they are typically very lean and “weak” muscle wise.

The Holy Crossfit Metabolic Trinity

metabolic pathway chart Crossfit Cardio: The Myth Debunked

Chart showing power over time and metabolic stimulation as a result

In Crossfit we focus mainly on these three metabolic pathways: Phospagen, Glycotic, and Oxidative. Each one serves it’s purpose and a workout regiment that contains a good balance of the three can help lead to overall fitness and muscle development. Correct training of all three of these metabolic pathways is a crucial element of what Crossfit defines as “fitness”. Let’s talk about each of these three pathways further…


The Phospagen pathway is stimulated with hard heavy work over short durations. Typically the duration is 1-10 seconds. The phosphagen pathway is Anaerobic, so in this modality you’ll be stimulating muscle growth and fat loss with a side effect of cardiovascular endurance. Workouts in this range would typically be along the lines of 1 rep maxes in exercises. WoDs with rep schemes like 1-1-1-1-1, etc….


The Glycotic pathway is stimulated with hard heavy work over medium durations. Usually you are spending roughly several minutes of hard work to stimulate this response. The Glycotic pathway is also Anaerobic like the phospagen pathway. Workouts here would include Fran, Grace, etc… The vast majority of Crossfit WoDs 15 minutes or less fit into this realm.


The Phospagen pathway is stimulated with low power work over long durations. These are workouts like Murph that have you sustain your heart and respiratory rate for a longer period while doing work. The primary benefit here is fat loss and cardiovascular endurance…with little to no muscle growth stimulation.

Crossfit Cardio: Bottom Line

Crossfit doesn’t focus heavily on cardio simply because we do it with each of our workouts. It’s not as straight forward as “go run 4 miles” all the time, but it’s built into each and every WoD based upon stimulation of the appropriate metabolic pathways. Crossfit calls in metabolic conditioning and with the right stack / arrangement of workouts pushing the right metabolic pathways you’ll reap the same (and more) benefits than the Elliptical queens at your local globo-gym.

So what should you say to someone when they ask you why Crossfit doesn’t emphasize cardio? Tell them to do Fran and see how they feel.