Dr. Lon Kilgore on Exercise Science’s Defining Failure

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Fitness: the ability to inflate a balloon while pedaling a pretend bike?

While we are often critical of the work of exercise scientists, these critiques are aimed not at the pursuit of scientific knowledge, but the failure of the academic leadership in this field to meet the basic requirements of the scientific method.

But there are exceptions. Consider Dr. Lon Kilgore. Kilgore has authored and co-authored many works that integrated science and practice. If that feat sounds easy, it’s not. Take a look at his Amazon.com author page, for example:

Image On June 20 Kilgore published a new article in “Research in Sports Medicine: An International Journal.” Entitled, A Consideration of the Paradigm of Exercise Physiology,” the article criticizes modern science for lacking a scientific foundation and commonly-agreed upon definitions of key terms. Kilgore asks, “How can one perform research into exercise and fitness if there is no measurable and agreeable definition of what fitness is?”

According to Kilgore, both the National Strength and Conditioning Association (NSCA), “has never included a definition of fitness in its flagship textbook.” And the American College of Sports Medicine (ACSM), “did not produce any substantive definition in its publications until issuing, in 2006, a quite verbose definition consisting of an extensive list of scientific and clinical, but ultimately arbitrary, ‘attributes’ of fitness.”

The NSCA and ACSM’s failure to define fitness created an opportunity for those outside the American exercise science establishment. In 2007, Kilgore and his co-author Mark Rippetoe defined fitness as,

Possession of adequate levels of strength, endurance and mobility to provide for successful participation in occupational effort, recreational pursuits and familial obligations, and that is consistent with a functional phenotypic expression of the human genotype.

In 2002, Greg Glassman published his third CrossFit Journal article, “What is Fitness,” introducing three overlapping definitions of fitness: development of the 10 general physical skills, the hopper model, and capacity across all the metabolic pathways. Four years later, Greg first introduced a fourth definition of fitness, work capacity measured across broad time and modal domains. What do these competing definitions of fitness mean for academic exercise science, headed by the ACSM and NSCA? Kilgore concludes that

“the CrossFit-based definition, with over 100,000,000 people having read it, has supplanted that of the ACSM and any other organizations’ definition of fitness in acceptance in the public, industry, and in many instances, academia. This further signals an academic paradigm problem.”

For example, ACSM fellows evaluated CrossFit’s efficacy not by measuring what CrossFit claims to deliver: “increased work capacity measured across broad time and modal domains,” but rather by testing the ACSM’s own idea of fitness: performance on a treadmill Vo2Max test. So academic exercise scientists don’t pay attention to dramatic documented increases in work capacity, unless they are verified by VO2Max results published in their peer-reviewed journals. Isn’t this exactly backwards? Isn’t oxygen intake capacity irrelevant to fitness unless it is manifested in the ability to do various types of physical work? And in that case, is VO2Max not a correlate of fitness, not fitness itself?

1:30 Grace, 7:39 Helen, 2:08 Fran. But how good is she at the pedal and blow up a balloon test?

1:30 Grace, 7:39 Helen, 2:08 Fran.
But how good is she at the pedal and blow up a balloon test?

If Kilgore is correct, then CrossFit’s definition of fitness has overcome the ACSM’s. CrossFit is threatening the American exercise science establishment in the marketplace of ideas, not just in the market for seminars and certificates. For more on how Kilgore thinks exercise science’s paradigm should change, read the full version of his article here. If you don’t have access to the academic journals, Kilgore covered a similar topic in this free CrossFit Journal article, Paradigm Lost. Also, check out Tony Leyland’s article, VO2 Max: Not the Gold Standard?


  1. Climbing is almost purely anaerobic and eccentric..

    But then most Sports Scientists still don’t know we are primates. So these functions importance is often over-looked.

    “Fit” for what is the question.

  2. Pingback: CrossFit SAC | Thursday 7/3

  3. The wise-fool

    Albert Einstein said “If you can’t explain it simply you understand it well enough.” What is fitness? Three words… ADAPTATION TO CHANGE !!! 😉

  4. Russ Greene


    So if I change my training from 6 days a week, to 0, and my muscles adapt by growing smaller and weaker, this is fitness?

    Lloyd Shaw,

    What word would you use to describe the capacity to do a large variety of physical tasks well? I’d call it fitness. And I’d call the people who are most capable across a large variety of tasks and durations the fittest.

  5. You are correct in your definition of “fitness” . The same definition I believe that should be taught at school.

    But the word “fitness” has been highjacked by marketers. As you are well aware. Now the average person thinks fitness is cardio.

    The definition for “fitness” in my area of expertise is ” fit to be independent”… ” not voluntarily disabled due to obesity “

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