Following my article on why HIIT is not the body composition God send that we make it out to be (and that cardio is not the evil that some people think it is), I’ve had several people comment that “sprinters are lean and muscular while endurance athletes are small and skinny fat” to “prove” that HIIT is superior to steady state cardio to improve your physique.

There is no doubt that sprinters are more muscular and leaner than endurance athletes, but this has nothing to do with HIIT being superior to endurance for body composition. It’s like saying that basketball players are tall while gymnasts are short, therefore basketball is better at making you tall.

Sprinters don’t do HIIT. And the “cardio” that people do in the gym after a workout or in the morning has nothing in common with elite endurance training. Stop using the sprinter vs. marathon runner as an analogy, it is simply not applicable.

 Here’s the truth.

 1. Elite sprinters do not have the same genetic makeup as elite endurance runners. Sprinters are among the 10-15%-ish of the population with the ACTN3 RR variant. This gives them a much higher ratio of fast twitch fibers (which are not only stronger, but A LOT more prone to growth than other fibers). It also gives them a great mTOR response to training (meaning that they build muscle more easily).

Many of the best track coaches have mentioned that sprinters are born, not made, and science tends to prove that this is indeed true. These guys are programmed to be muscular, lean and explosive and they would likely be that way without any training.

A friend of mine was 180lbs on a 5’6” frame with minimal body fat, round muscle bellies and striations everywhere…and he never lifted a weight in his life and was in high school! Those who become world class sprinters have those kinds of genetics. You can’t look at what they are doing and assume that it will lead to the same results with you.


2. Elite endurance athletes, on the other hand, tend to have the ACTN3 XX variant, which gives them a much higher ratio of slow twitch fibers, lower mTOR activation, and slower muscle damage recovery. This makes it much harder for them to build muscle. That alone explains why they are less muscular.

Elite endurance athletes have a genetic makeup that is almost impossible to make muscular. As a coach, I’ve been faced with some of these people and no amount of knowledge or know-how can make them as muscular as sprinters. You could have them stop endurance training and train like a sprinter and they would not look anywhere close to being as lean and muscular. 

Just because a class of athletes looks a certain way doesn’t mean that this type of work will lead to the same results in everybody.


3. Sprinters put an emphasis on heavy lifting in their training. They pretty much all squat and bench heavy and a lot of them clean and deadlift heavy too. It is not unusual for a sprinter to squat 500lbs+ and bench 385-400lbs+.

Ben Johnson squatted 600lbs for reps and bench pressed 425lbs; Linford Christie squatted 660lbs, Maurice Greene 505, etc. You get the picture: you rarely become an elite sprinter without an emphasis on heavy training.

 And it might be shocking to read that heavy training will contribute to making you more muscular. Could it be that sprinters are muscular because of their heavy lifting and genetics, not their sprinting?

 I’ve worked with a few sprinters as well as “sprinter types”. By sprinter types, I’m referring to athletes who focus on speed and power development and have similar characteristics as sprinters. Bobsleigh athletes are a good example of that.

While they used to go for the big brutes, the football types, now they go for the sprinter body. I’ve worked with 3 guys on the national team and they could all squat over 500 and power clean over 335. Two of them benched over 400 and they all did a lot of heavy work in their training, 3 to 6 days a week depending on the athlete.


4. A lot of endurance athletes don’t even train with weights. And when they do, most of them do light work using isolation exercises (at least all those I’ve been around). Is it surprising that they have less muscle? They just don’t train to build muscle at all.

While I’ve seen exceptions, the above is 100% accurate. For every one endurance athlete I’ve seen squat anything above 135lbs, I’ve seen ten doing curls while lunging or doing BOSU ball split squats.

 They rarely use any amount of weights, don’t go anywhere close to failure and don’t try to progressively overload their body. This might have to do with their neurotype (endurance athletes tend to be Type 3, who are more cautious) or just that they don’t believe that strength is important.

But the fact remains, endurance athletes don’t do anything that will add a significant amount of muscle to their body. Is it that surprising that they don’t carry much muscle?

I know an exception. A Crossfit girl/ultra-endurance athlete I worked with. She does Ironman, Ultra-ironman and any other crazy type of event you can think of. But she also squats (has squatted over 265lbs), benches (has benched 165lbs for reps), cleans (has power cleaned 195lbs), etc. And surprise-surprise: she is muscular!

I’ve also trained a 52-year-old woman who did 2 hours of endurance work (in the form of cycling or cross-country skiing) 3-4 times a week and did 45 minutes of cardio per day in the gym. I trained her hard and heavy… in fact at 52 years of age and 123lbs, she deadlifted 315 and benched 175lbs. You know what, she was muscular enough to win a natural bodybuilding contest.

 While endurance athletes will never look super jacked as long as they are doing 4 hours of endurance work per day, they would look better if they did heavy lifting, like sprinters do.


5. You cannot use endurance athletes’ physiques to show that steady state cardio will lead to muscle loss. First, as I explained, endurance athletes are not built to be muscular and don’t do anything training-wise to build muscle. On top of that, they exercise 2, 3, 4 hours every day… sometimes more. That burns a lot of fuel… it is very hard for them to consume enough food to stimulate growth.

BUT anyway, there is a huge difference between running 3h per day at a competitive pace and doing 30-40 minutes of moderate, steady-state cardio.

By the way, most endurance athletes also do intervals/HIIT in their training.


6. You cannot use the physique of sprinters to prove how HIIT is great for body comp. Sprinters don’t do anything remotely close to HIIT in their training. They sprint for anywhere between 3 and 25 seconds (100m runners… those they use to show how HIIT will get you muscular), and then rest for as long as 6-10 minutes between sprints. In total, they will do 4-6 sprints, no more.

That is not even remotely close to being related to HIIT. And as I mentioned they do tons of heavy lifting and are genetically predisposed to building muscle.

Endurance athletes do more HIIT work than sprinters!

I’ve trained with a sprinter (I wanted to try-out for the bobsleigh team and needed to sprint fast) and I was never winded, sweating, out of breath or filled with lactic acid. The density of work is minimal and is not physically draining at all. That is literally the opposite of how HIIT makes you feel.



Using the “sprinter vs. endurance athlete” image is intellectually dishonest and takes way too many shortcuts. It’s a mistake that I made myself when I was starting out as a coach before I understood better. I know that the shortcut is tempting. And the human brain loves simple images and analogies.

But the reality is that sprint training has nothing to do with HIIT and competitive endurance training has nothing to do with the cardio done by average bros. Furthermore, between sprinters and endurance athletes, only the latter actually do HIIT in their training. 


Christian Thibaudeau

Written by Christian Thibaudeau

Christian Thibaudeau has been involved in the business of training for over the last 16 years. During this period, he worked with athletes from 28 different sports. He has been “Head Strength Coach” for the Central Institute for Human Performance (of…