Why Do CrossFit Athletes Have a LOW V̇O2 max? Challenging Conventional Fitness Metrics

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VO2max is traditionally used to define fitness in a wide range of sports. We did a study in elite crossfit athletes (like Games level elite) and found relatively low VO2maxes...
In this video I discuss 4 reasons why and what you can do as a coach with this information!
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LINK to our CrossFit study - www.biorxiv.org/content/10.11... (soon published in peer-reviewed journal)
TIMESTAMPS
00:00 - Intro
01:35 - What is VO2max
3:25 - VO2max across different sports
04:53 - VO2max in CrossFit athletes - Our study
08:20 - Why CrossFit athletes have a lower VO2max
08:30 - 1. CrossFit is strength biased
09:40 - 2. Interference effect
12:35 - 3. Oxygen diffusion
14:30 - 4. Specificity of testing - are we using the right tests?

[@MarlonHameem]

Weight is a factor in VO2 calculations. Strength based athlete are heavier than a endurance athlete. Hence

[@wod-science]

I agree, but as discussed in other comments. CF atheltes also have a substrantially lower VO2 than fi rowers and cross-country skiers who are in the same weight cat.

[@danbarry7300]

Great video. I think specificity of testing is a key factor. VO2 max is a per kilogram measurement. Upper body muscle mass that isn’t being used during cycling is basically dead weight. Same performance (power output) on the bike by an athlete with 10 kg less upper body muscle mass will yield a higher VO2 max just because of the lower body weight.

[@wod-science]

Yes. But only part of the explanation imo. We had some world-class athletes in our cohort who were very familiar to the road bike. Still a low-ish VO2.

[@SettleNow]

@@wod-science I think his point is that if you take identical twins and one trains in CF and the other in cycling, the CF athlete has a lot more upper body muscle mass, and then it would come as no surprise that the VO2max, since it takes bodyweight as the denominator, is going to be less. Typical high level cyclist has very little upper body mass. High level long distance runner same, perhaps even more so.

[@adamsloane1748]

@@SettleNow Exactly. Quickest way to improve VO2 max is to lose weight.

[@MrStripedsocks]

Id be fine with the physique of a CF athlete at 75% VO2 max of an elite cyclist. Great video.

[@wod-science]

Same :)

[@87togabito]

I’d rather have the vo2 max of a cyclist, with half the strength of a weight lifter who does traditional gym. Not gonna waste time doing CF stuff and be neither here nor there.

[@corbinc4344]

@@87togabitoI agree

[@mr_Thursday]

@@87togabito do not assume a decent crossfit practitioner is not as strong as decent gym goer. I practiced CF for 3 years, now in a regular gym since pandemic. I have seen much more people in CF squatting 3 plates or deadlifting 4 than in regular gyms, or doing more and better strict pull ups with more ROM. Really, CF is wildly underrated by gym goers, but actually a fantastic sport (if practiced with good programming and leaving the ego at the door) that puts you in really good overall shape and strength, and helps wildly with adherence for people demotivated with regular lifting. Not optimal for strength/hypertrophy, that's true, but choice should depend on goals/sport specific training.

[@gokuryu]

You are an intelligent man. What a well done study and video. Normally when I hear people discuss the pros and cons of crossfit they sound bias and obviously don't know a thing about CF. You really know your stuff and gave an honest review. You made a fan today.

[@wod-science]

Thank you! Means a lot. I’d argue it’s not intelligence though, it’s willing to learn and critical thinking.

[@sneaky_pete_]

This channel is right up my alley. Take my sub, sir.

[@wod-science]

Gladly taken ser!

[@gwunder2003]

great video again! Can you speak to how watches (iWatch) or other estimates vo2 max and how well it compares to actual testing.

[@wod-science]

Thanks for the suggestion. It’s much lower accuracy for sure estimated vs. tested. How much I don’t know. Will do research and make a video when the data is robust.

[@HashimAlmadaniauthor]

Fantastic analysis and very well explained. I wonder to which level " good technic " can play a role in determining the level of VO2 max. For example, a good rower can last longer on a rowing machine due to the efficiency of the movement while performing the test compared to the same athlete performing it on a stationary bike. Is the correct VO2 max on the rower or on the stationary machine? Same in the case of Crossfit, and due to the variety of movements, is it better to test it in a combination of 2 movements that you are good at? or two challenging movements? ( thinking about an average athlete and not an elite one )

[@wod-science]

Good point. Don't confuse movement efficiency with VO2max. Movement efficiency basically means how much oxygen a person is consuming at a given intensity (submaximal). What you refer to is more related to total muscle mass use. Usually, VO2max is higher on a rower because it's a whole body exercise compared to biking. That said, it can be that specialists have better technique and oxygen extraction capacity within certain muscles (fi legs cyclists) which will result in a higher VO2 on the machine the athletes is used to. To your last point, I'd use movements where you are good at. You want to efficiently use as much muscles as possible to accurately determine VO2 max.

[@HashimAlmadaniauthor]

@@wod-sciencethanks for the reply Very logical 👍

[@Fusspilzsammler1]

There's a CF gym around the corner and every sunday they do a warm up jog around the block. It always sounds like an asthmatics convention 😆

[@wod-science]

Had to laugh out loud with this one. Warmup up jogs are always a race 😂

[@samuele.marcora]

I just gave a lecture about concurrent training to my students. After reviewing the literature I think that true interference is not so important. The volume explanation is more convincing to me

[@wod-science]

It’s just impossible to train as much as a bodybuilder/cyclist when you’re a hybrid athlete.

[@samuele.marcora]

@@wod-science Exactly!!!

[@danbarry7300]

The upper body muscle mass is not being used (not consuming oxygen) while cycling so it’s not helping the numerator (oxygen consumed) while working against the athlete by making the denominator larger (total kg).

[@wod-science]

Not untrue. But as briefly discussed, also absolute VO2 max was not that high in this cohort of athletes.

[@wadyn95]

What about kettlebell sport? Do they have vo2max bigger than CrossFit athletes?

[@wod-science]

This study found similar VO2max in kettlebell athletes as presented here in this video (45-50). Cool study - check it out journals.lww.com/nsca-jscr/fulltext/2020/06000/cardiopulmonary_demand_of_16_kg_kettlebell.17.aspx

[@viktor34567]

PhD candidate in psychology here. Your variance restriction greatly decreases the R2 of VO2 max, by design. And even then, 17% of variance explained is huge! It equals a r=0.41 correlation.

[@wod-science]

Agreed. We discuss this in the paper after revisions. More physiological variables were correlated to Open Rank in women because the spread in performance was slightly higher in that cohort compared to men.

[@ForgedGrit]

I can only see the basics of the paper. Grateful to see the data showing VO2 is not very high in CrossFit. Did you show any comparisons on volume of endurance training? A marathoner putting in 100 mile run weeks will have a different V02 than someone doing similar amount of hours of training that is split training volume. That's not interference due to concurrent training. That's interference due to time management, recovery, and focus. Endurance training in CrossFit is not the same as Endurance training for most other sports that have a high level of VO2. Need to see the V02 of someone training to go sub 2:45 marathon and competitive at CrossFit but that may be an outlier.

[@wod-science]

Agreed 💯 %. It’s likely volume. CrossFit athletes just train literally everything all the time 😀

[@DarthBane-zf8wv]

As a CrossFit athlete 6'2'' 220 lbs. I have a VO2 max of 56 when tested. But I like being big and jacked so I'll take it. Can still complete a half marathon in under 1:50 consistently too so there's a lot of give and take.

[@wod-science]

That's an excellent fitness profile!

[@user-it9vs3vq2z]

I think the overhead lifting of heavy weights hurts VO2max. that requires a thick stomach and holding your breath and building up pressure in your abdomen to support your spine. for team sports premier league soccer players have the highest vo2max around 60 to 70, and most of their muscle is in their legs. Or like muhommed ali you know would have the best cardio for boxers, and he has a bird chest and big legs. People built like that have higher vo2max because legs have way more muscular endurance and efficiency than the upper body muscles and the upper body is where your hear and lungs are. Pressure in your lungs effects the gas exchange. It can even cause edema and stuff in your lungs. That's what I want to see. the muscle distribution of the highest VO2max people. Upper body strength vs lower body strength. or specific exercises like bench. I bet if you can bench a ton your VO2max drops.

[@wod-science]

There are ways nowadays to determine what 'limits' VO2max in athletes (heart, lungs, muscles?). Would be interesting to do such studies on football players vs. CrossFitters or other sports. Video on those methods coming up soon.

[@mr_Thursday]

@@wod-science the study mentions cycling athletes, but I would argue there should be a big difference between road cycling and track cycling athletes, the latter being much stronger and explosive due to the nature of their sport, different body composition. Same as distance runners and 400m (or 200/100 for instance) runners.

[@samuele.marcora]

I will contact you in due time to discuss submissions to ECSS 2025 in Rimini. It would be nice to have enough submissions to put together an entire session dedicated to CF. Are you going to Glasgow?

[@wod-science]

Yes please. [e-mail].

[@wod-science]

Likely not Glasgow. Still contemplating.

[@haymie94]

VO2MAX is the volume consumed per kilo of body mass. An elite maraphoner is 55kg, an elite crossfit athlete is 100 kg. In ml/min crossfitters may have even higher numbers than marathoners or skiers

[@wod-science]

Discussed this briefly in the video. Absolute VO2 in CrossFit athletes is also not great. Better than relative obv (high muscle mass), but for instance much lower than those of cross-country skiers which also carry a lot of weight.

[@lostalbums5444]

While just looking at the critical power of Crossfit athletes, would we expect an higher VO2max or are they coherent?

[@wod-science]

Coherent. Critical power also 20-25% lower as reported for elite endurance athletes.

[@MrJhockley]

VO2max is a measurement based on oxygen consumption by body weight per minute. Smaller athletes may have an advantage here if we just look at raw numbers. I think an crossfit athlete's absolute VO2ml/min would be higher because their work is higher. Oxygen plus fuel is proportional to power output. Bigger moving athlete + Bigger moving weights equals more power thus more oxygen. A pro cyclist (maybe 70+ vo2max) can put out 531 watts for 5 minutes, the equivalent power would be doing a bodyweight squat every second for 5 minutes or a 50kg deadlift every 2 seconds for 5 minutes. Possible?

[@wod-science]

Agreed. But only partially 😃. In our paper, also absolute VO2 max is shown, which was - just like relative VO2 max - pretty mediocre. What’s interesting is that big athletes can also have large vo2maxes, like crosscountry skiers. In CrossFit athletes this does not really seem to be the case.

[@adamsloane1748]

What about genetics and, relatedly, self-selection? I have read that VO2 max and the ability to improve it have large genetic components: VO2 max is trainable, but only to a point. If that is true, then it may be that those who gravitate to endurance activities, and those who can rise to elite level in those activities, may be the people who start off with higher VO2 maxes and who are able to achieve high VO2 max levels through training: their VO2 max "potential" is superior. Of course, this may be unconscious; I am not suggesting that people assess their VO2 max potential in choosing an activity. But the point is that the population that is able to achieve elite CrossFit performance may just not be a population that is genetically able to obtain really "elite" level VO2 maxes, and as you strongly imply, it just may not matter. There isn't necessarily a correlation between super high VO2 max and performance in many endurance events,, and there almost certainly isn't such a correlation for CrossFit performance. So the question you are looking at is interesting, but the takeaway may be that it just doesn't matter, and CrossFitters shouldn't worry about their VO2 max, as long as it's functionally adequate, and certainly shouldn't alter their training if their VO2 max is functionally adequate.

[@wod-science]

Yes, I would add to this that you now see CrossFit athletes who choose to be competitive from young age. It might well be that we see very high VO2maxes in those cohorts, but only if the sport gravitates to more 'endurance' (like this year) in stead of strength (previous years).

[@yosefco3]

It's a great video! I have a small request. I am a kettlebell sport trainee. In our competitions, we perform one movement (for example, the kettlebell snatch with 16,24,32 kg) for 10 minutes, where the goal is to achieve the maximum number of repetitions. Please include kettlebell sport in your research! I believe that in kettlebell sport, the results would be better than in CrossFit because endurance is the most critical aspect.

[@28mouse85]

Fuck Israel and the zionists. 🇵🇸 the world is against you.

[@wod-science]

That’s crazy. Can’t imagine doing that. Muscle endurance very important factor here too. Similar as i CrossFit. Would expect same-ish VO2 max in you sport than in CF.

[@yosefco3]

@@wod-science I believe it would be a very different VO2 max for both sports. I train inside a CrossFit box mainly for the atmosphere and the friends. They do CrossFit and I do kettlebell sport. I have great respect for CrossFit and the amazing things they do, but these are completely different types of training with completely different emphases. Kettlebell sport is very endurance-focused. It takes about six months to a year to learn the technique, and then the focus is on progressively increasing the weights and the number of repetitions. I can do about 160 continuous one hand snatch repetitions with a 16 kg kettlebell, one hand switch, and I'm considered a "beginner" (16 kg for men is beginner level). When I started this sport, I was obese, and it has really helped me. It also slowed down my pulse rate.

[@28mouse85]

@@yosefco3 fuck the isreali zionists. Free Palestine 🇵🇸

[@Zeoilvia]

Pretty sure Crossfitters stack up fine if you compare absolute maximal oxygen uptake instead of VO2 max (per kg). You wouldn't call Mr Olympia fat, just because he has a high BMI.

[@wod-science]

I see your point, but even when compared to athletes from the same weigth category (elite rowers, cross-country skiers), their VO2 came out lower than expected, at least to me (15 to 20% lower)

[@powerismax6216]

As always interesting. I Wonder what would happen for pure hyrox athlete comparison cause IMHO vo2max may be more beneficial for them.

[@wod-science]

Excellent question. I’ve just been looking up some studies and there are NONE in pure hyrox athletes. To your point, I think the same. Hyrox athletes are less muscular, taller and more aerobically built. So yes, HYROX selects for higher VO2max.

[@powerismax6216]

@@wod-science I also do some hirox sometimes and I think I can push more since i am increasing vo2 max. Its mostly because running part is less painfull and I fell like i have more in my tank for following runs.

[@Dylan-vh9zz]

@@wod-scienceI’d say most of us sit between 64-75 for our Vo2max scores. It’s been a minute since I’ve tested mine but I have spoken with a few guys in the top 15 and they all test in that range.

[@wod-science]

@@Dylan-vh9zz Makes complete sense, thanks for sharing.

[@drewarnold6741]

I would guess that most of the 60 were quarterfinals athletes. 12:35

[@wod-science]

Yes, but we made a distinction between elite and well-trained. Differences were not that big between those cohorts. Overall both elites and well-trained performed 20-25% worse on endurance parameters compared to specialists.

[@tommybruen4686]

Long time athlete and coach here…You have completely missed that elite cyclists have risen through ranks BECAUSE of their ability to adapt and improve their cardio zones. While at the same time Cross Fit athletes have risen through the ranks BECAUSE of their ability to adapt to and improve on strength. This type of selection will cause divergent groups that at the extremes will be far apart.

[@wod-science]

Thanks for your reply. I agree and have not missed this point. CrossFit is a strenght biased sport as explained from 08:30 onwards.

[@rb3883]

Haven't watched your full video, but... CF isn't a cardio sport! Bradley Wiggins - tour de france champ and multiple olympic gold medalist - tried to switch to rowing based on the comparative watt output used by cyclists vs rowers but didn't even achieve result of a decent club rower, let alone get near Olympic level.

[@wod-science]

It’s very much a cardio sport. Latest data have shown that Fran, arguably the most ‘anaerobic’ workout in CrossFit lasting 2-3 minutes, is 60+ % aerobic.

[@wod-science]

Your arguments goes to say that there are many factors, next to the pure physiological, that determine performance. Exactly as explained in this vid. 👍

[@samuele.marcora]

I think an air bike would be a better way to test CF athletes, especially if we want to compare them with other athletes. I can't see a cyclist doing Fran :-)

[@wod-science]

Yes. I agreed. Still, some super elite athletes in our cohort were very familiar to a road bike. These athletes also had a low-ish VO2.

[@chrisward2k]

What are you defining as super similar? @wod-science

[@DrSomhairle]

It’s about body mass surely, too cyclists and runners with the highest VO2 max would weigh 63 - 70 kgs, these cross fit athletes would weigh much more! Take 15 - 20 kgs off a cross fit athlete you’d have a higher VO2 max.

[@wod-science]

Absolute VO2 max also lower than I would have expected in CrossFit athletes. See other comments for detailed explanation 👍

[@gustas0]

Your interpretation of the numbers is so bizarre. Of course Crossfit athletes have modest VO2max if you look at it relative to body weight (they are heavy). In absolute terms, which is what is really relevant here, elite CF athletes have a very high VO2max. It is more relevant because CF is not an activity that depends highly on bodyweight, not as much as Tour de France cyclists! According to your own data on the paper (54.7 mL·kg-1·min-1 in male athletes, versus reported 76.8 mL·kg-1·min-1 in male elite cyclists): an elite CF at 90kg would have a 4.9L total VO2max and an elite cyclist at 65kg would have a 4.9L total VO2max, thus completely comparable to each other. ie: the ability to exchange O2 is very similar. (and also, cyclists test their VO2max on a bike... big advantage).

[@wod-science]

Thanks for the elaborate response. I’d argue that if you want to compare absolute VO2 max you should do it against same caliber athletes - crosscountry skiers or rowers, who have much higher reported relative (70+ ml) and absolute VO2 max (6+L) at 85kg bw. However I look at it, our cohort had a low VO2 max, making me think that other physiological and non-physiological parameters are more determining for performance.

[@wod-science]

and btw. With a VO2 of 76 ml / 4.9L you are not going to follow the best climbers in de tdf. That is for sure. Hence I’d say that those numbers are not elite, at least not as elite as our cohort in the sport of CrossFit.

[@gustas0]

@@wod-science they are in the ballpark. The best climbers may have some more but you could flip this whole thing upside down. Imagine Jonas Vingegard puts on 30kg. What do you think will happen to his VO2 max /kg? It would for sure come down to CF athlete levels. So, again, we have elite CF with absolute VO2max that are completely similar to elite cyclists (doing VO2 tests on a bike). How could you possibly say CFers have "average" VO2 max? Makes no sense.

[@gustas0]

@@wod-science as far as comparing to rowers and skiers, well, those have more of a bodyweight component to their sport than CF and also tend to be quite tall. Comparing a 175cm/90kg crossfitter to a 190cm+ 100kg rower is a bit bonkers. Plus, you are comparing to the VO2 kings. In anyway you look at it you cannot possibly claim crossfit athletes have low VO2 max, defined by low capacity to absorbe O2. Crossfiters have a very high capacity to absorb O2. Your claim is misleading. To be clear for anyone reading, in a cycling ramp test, an elite crossfiter will absorb as much total O2 as an elite cyclist. The cyclist is able to do that with a lower bodyweight.

[@wod-science]

Van aert likely has 85 ml somewhere at 80kg this would equate to 7L. I don’t really see your point.

[@MA-ik7ys]

crossfit hater here. I think crossfitters are not that fit they have just learned a collection of silly exercises and excel in them. More strength skill than anything else. They would not transfer to running, swimming, cycling, anything of note. Especially not rugby or mma. They just do silly little exercises that do not require fitness. A bit like arm wrestlers. Really good at one movement. Not fit.

[@wod-science]

They produce a tremendous amount of work within a given timeframe across basically all sport modalities. So even when their VO2max not that high, I’d argue they are very fit.

[@MA-ik7ys]

@@wod-science fit needs a purpose. Fit fir cross fit and game shows

[@SuperAmazingAnt]

They have more muscle, what a waste of time video, it is in the unit kg. That chart have also wrestlers and ordinary people on same line. From there you can think how usefull the whole v02 scale is.

[@noosphericaltarzan]

That doesn't really matter, dude. Cross fitters have crap V02Max because their methodology is based on silly notions from the "fitness" world instead of sport. If they maybe thought about training each energy system to some adequate degree, they'd realize they were almost never really training their aerobic system. If they run distance at all, they conceive of it as "work" and maybe a "calorie burn". I.e. fitness world bs that gets you nowhere. To get a high V02Max, you first need to build an aerobic base, which is to say you have vastly increased the numbers, size, and efficiency of mitochondria in skeletal muscle, as well as increased the density of capillaries to those fibers. This results in greater gas exchange in the muscles (more O2 goes in, more CO2 goes out). Gas exchange is the primary bottleneck to VO2Max. What I have seen crossfitters try to do is adapt "Vo2Max interval workouts" to use on machines like ergs and assault bikes without understanding those are the final refinements in periodized training. 90% of what goes into a high Vo2Max is low heart rate work. Crossfitters are exactly the kinds of guys running around the park on Sunday at threshold pace, passing the "slow people", never realizing some of those slow people are elite runners. That's why they have trash metrics in general. They just don't understand how adaptations actually work because crossfit is like the prodigal child of the American "fitness" industry. Look into sports.

[@SuperAmazingAnt]

@@noosphericaltarzan 90% just muscle mass from the upperbody, if you have 20kg of extra muscle you will have shitty v02. The end.

[@noosphericaltarzan]

@@SuperAmazingAnt That is completely untrue. It depends upon gas exchange in those muscles. I just explained the science to you. Go read a book if you don't believe it. lol

[@SuperAmazingAnt]

@@noosphericaltarzan E=mc^2 get lost.

[@noosphericaltarzan]

@@SuperAmazingAnt You have never even been to college cross fit clown. I just explained basic exercise science to you.

[@TrueFilter]

Because they’re not that fit.

[@wod-science]

Which type of athlete or which sport would you can ‘fitter’?