CrossFit | Exercise Science


The CrossFit stimulus—constantly varied high-intensity functional movement coupled with meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar—prepares you for the demands of a healthy, functional, independent life and provides a hedge against chronic disease and incapacity. This stimulus is elegant in the mathematical sense of being marked by simplicity and efficacy. The proven elements of this broad, general, and inclusive fitness, in terms of both movement and nutrition, are what we term our CrossFit Essentials.

"Movement quality is critically important," says neurosurgeon Dr. David Johnson. Good movement leads to long-term mobility and functionality. Poor movement leads to increased “risk of developing musculoskeletal pain, and over time, an increased risk for the requirement of musculoskeletal surgery.” According to Johnson, functional movement is key. “Without ... physiological stimulus, you won't recover from your musculoskeletal pain.”

Watch Movement Matters

Training and nutrition are the two most powerful mechanisms for improving human health, but they exert their influence from opposite directions. Diet supplies energy and is the source of the body’s structural components. Exercise consumes energy and actually breaks down the body in various ways. Here, Tyler Hass explores how to optimize both mechanisms by dialing the body’s activity and nutrition patterns up or down.

Read MoreMake Every Calorie Count: Dialing in Nutrition and Exercise

Will focusing on running endurance interfere with your strength numbers? Will prioritizing your back squat slow down your mile time? Traditional exercise science has consistently reported differing training stimuli interfere with one another. Tyler Hass examines the research and explains what happens when we ask a different question: How can we maximize the total physical adaptation of the human body?

Read MoreMake Every Calorie Count: Optimizing Adaptation

Borrowed from physics, the idea that all calories are created equal is gravely wrong when applied to biology. Calories from protein, carbs, and fat have very different effects on our hormones and ultimately our body composition. A new paradigm asserts the quality of calories you consume is key, but less has been said about the quality of various calorie-burning methods. Here, Tyler Hass explains why exercising with intensity has a more profound effect on body comp and overall health than steady-state cardio.

Read MoreMake Every Calorie Count: Exercise Intensity

The GARD principle stands for “general adaptations to related demands.” Physical adaptations to exercise are not compartmentalized. Everything is connected. Improve at one thing and the resulting adaptations will improve everything related as well.

Read MoreThe GARD Principle

Periodization is overwhelmingly presented as best practice in all NSCA publications on programming — as superior to all other models of programming. ... [Yet] if we perform a quality and relevance check on the citations at the end of the periodization chapter in [the NSCA’s] “Essentials,” we find only three truly experimental papers cited in this “authoritative” chapter. Three experiments produced in more than three decades? Surely there has to be a larger evidence base for such a central tenet of a professional organization and world authority.

Read the articlePeriodization: Period or Question Mark?

In this 2012 review, Tim Noakes argues the traditional, purely biological understanding of fatigue (i.e., that exercise failure occurs when the heart or muscles reach a biochemical limitation) is inconsistent with observed data. Noakes proposes an alternative model — the “central governor” model as opposed to the “brainless” model — rooted in the observations of coaches, athletes, and neuroscientists.

Read MoreFatigue Is a Brain-Derived Emotion That Regulates the Exercise Behavior to Ensure the Protection of Whole Body Homeostasis

What is the mechanism behind muscle growth? The exercise-induced muscle damage (EIMD) hypothesis posits intense exercise causes damage to muscle fibers, which then repair and adapt to better tolerate future exposure to stress. Eccentric training is thought to be particularly effective in stimulating hypertrophy (muscle growth). Tyler Hass discusses related studies and evaluates popular theories about promoting muscle growth.

Read MoreMuscle Damage for Size and Strength?

Prof. Timothy Noakes provides evidence in support of Nina Teicholz’s argument that “the story of nutritional science is not, as we would expect, one of sober-minded researchers moving with measured judicious steps.” Teicholz claims it instead falls under “the ‘great man’ theory of history, whereby strong personalities steer events using their personal charisma, intelligence, wisdom, or wits.” According to Noakes, these qualities are precisely what allowed Ancel Keys to convince his colleagues to support his diet-heart and lipid hypotheses — even when the science did not.

Read MoreIt’s the Insulin Resistance, Stupid: Part 10

Applying resistance training to a CrossFit Kids program should be done with the same considerations as with adults: minimize risk and develop adaptations; however, considering the developmental process and length of the available timeframe to see results in this younger age group, perhaps the tension between technique and intensity (speed and load) should lean in favor of technique.

Read the article CrossFit Kids Research Brief: Kids and Resistance Training

In this 2019 trial, Tim Noakes et al. demonstrate that athletes can achieve similar performances on a 5K time trial while following a low-carb or high-carb diet, contrary to the widely assumed understanding that low-carb diets cannot support effective exercise at high intensities. At minimum, this research indicates a low-carbohydrate diet does not negatively affect performance beyond a small impairment seen during an initial two-week transition period.

Read MoreHigh Rates of Fat Oxidation Induced by a Low-Carbohydrate, High-Fat Diet Do Not Impair 5-km Running Performance in Competitive Recreational Athletes

Prof. Tim Noakes separates fact from fiction in his examination of the data from the Framingham Heart Study (FHS). Despite the efforts of some of the study's lead scientists to wrench the data into supporting the association of dietary fat and blood cholesterol concentration with coronary heart disease (CHD), the study instead demonstrated insulin resistance is a significant risk factor for CHD mortality whereas blood cholesterol concentration has little or no practical predictive value, especially after age 50. Noakes also highlights the insights shared by Dr. George Mann, “who was initially one of the scientific leaders of the FHS but later resigned to express his displeasure at the fake science he detected."

Read MoreIt’s the Insulin Resistance, Stupid: Part 9