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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.

This 2015 review hypothesizes how insulin resistance develops in the brain and cerebral insulin resistance contributes to neurological and metabolic disease. The authors argue brain insulin resistance is both a consequence and cause of metabolic distress, and impaired brain insulin signaling can account for both the difficulty of reversing obesity and some of its neurological and metabolic comorbidities.

Read MoreImpaired insulin action in the human brain: causes and metabolic consequences

“What scientists do and what journalists do are similar in that we’re both supposed to be establishing reliable knowledge about the universe,” Gary Taubes told the audience at the annual CrossFit Health Conference on July 31, 2019. Taubes, an award-winning investigative journalist, has spent the last several decades turning a critical eye toward places where received wisdom in the fields of science and medicine has diverged from reliable knowledge. In this presentation, he evaluates what the experts say about why we get fat and explains why has become a critic of the consensus.

Watch The Quality of Calories: Competing Paradigms of Obesity Pathogenesis, a Historical Perspective

Prof. Timothy Noakes explicates the most persuasive critiques of Ancel Keys’ claim that dietary fat causes coronary heart disease. First among these is one by two of Keys’ contemporaries, Jacob Yerushalmy and Herman Hilleboe, who warned, "No matter how plausible such an association may appear, it is not in itself proof of a cause-effect relationship. ... But quotation and repetition of the suggestive association soon creates the impression that the relationship is truly valid, and ultimately it acquires status as a supporting link in a chain of presumed proof." Noakes claims quotation and repetition became the hallmark of the method by which Keys convinced the world his hypothesis was the singular truth, thereby altering the trajectory of 70 years of medical practice and dietary guidelines and contributing to the global obesity epidemic.

Read MoreIt's the Insulin Resistance, Stupid: Part 7

There are three layers of posterior vertebral muscles overlaying the vertebral column, and each layer affects vertebral position in postural stability and movement. The anterior musculature is also organized in an approximation of a three-layer structure. When considering gross movement of the vertebral column, vis-à-vis arching and rounding, we often only think of the erector spinae as driving arching and the rectus abdominis as driving rounding. However, movement into those positions is complex and requires more than the action of the prime movers.

Read MoreVertebral arching and rounding

Individuals on low-carbohydrate diets have lower levels of ingested glucose and smaller liver and muscle glycogen stores. In this 2016 trial, endurance athletes following a low-carbohydrate diet were shown to maintain energy sufficiency during exercise through increased reliance on fat oxidation.

Read MoreGluconeogenesis during endurance exercise in cyclists habituated to a long‐term low carbohydrate high‐fat diet

Over the past 40 years, sugar intake (and thus fructose intake) has increased dramatically in Western diets, rising to 15-17% of total daily caloric consumption. This rise comes alongside increasing evidence linking fructose to diabetes, fatty liver disease, and cardiometabolic risk factors. This brief 2019 review summarizes the mechanisms by which fructose drives these metabolic diseases.

Read MoreDietary Fructose and the metabolic Syndrome

Type 2 diabetes is generally thought to be chronic and progressive, marked by an inevitable decline in beta cell function and increase in plasma glucose levels. Current pharmaceutical treatments are fundamentally unable to alter the course of the disease. Bariatric surgery has been shown to rapidly normalize glucose levels, even prior to weight loss. This study tested whether severe caloric restriction — similar to that seen alongside bariatric surgery — could lead to similar glycemic benefits. The study found that a very low-calorie diet rapidly improves liver insulin sensitivity and gradually improves pancreatic function in the process reversing Type 2 diabetes.

Read MoreReversal of type 2 diabetes: normalisation of beta cell function in association with decreased pancreas and liver triacylglycerol

In parts 1-4 of the “Power of Progression” series, we covered standard progressions used in CrossFit certificate courses to teach complex movements like the push press and push jerk, sumo deadlift high pull, med-ball clean, and snatch. These are a few examples of progressions, and while we have found these particular examples effective, they are not the only possible progressions for these movements. There are also many other movements for which a progression may be an appropriate teaching tool. Thinking about and attempting to create your own progressions is a great way to develop a better understanding of a given movement while also providing your athletes with new learning tools.

Read MoreThe Power Of Progression, Part 5: Building Progressions

Many muscles act upon the lumbar vertebrae during anterior flexion, rotation, and lateral flexion. What we commonly refer to as abdominal muscles carry a major role in lumbar movement. Some of these muscles attach to and act directly upon the lumbar vertebrae. Others that are not attached to the vertebrae act indirectly through moving bones that are.

Read MoreLumbar Muscles, Part 2

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