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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.

The wrist includes a complex aggregation of muscles that drive movement about its joints. The posterior muscles of the wrist are generally used for extension but in a few exceptions carry out an additional action. The wrist extensors are found on the posterior arm, opposite the flexors on the anterior side. These muscles can be attached proximally to the humerus, radius, or ulna and distally to the carpals, metacarpals, or phalanges.

Read MoreWrist Musculature, Part 2: Posterior Muscles

Dominic D’Agostino’s entry into the field of cancer biology involved two separate unexpected observations that were compelling enough to change the trajectory of his research: 1. Under high levels of pressurized oxygen, glioblastoma astrocytes die at a greater rate than normal cells. 2. In low-glucose, high-ketone environments, healthy neurons thrive but glioblastoma astrocytes die. In this article, D’Agostino and co-author Kristi Storoschuk explain what, based on our knowledge of cancer cell biology, was behind these observations. They also discuss the outcomes of their later research, which found nutritional ketosis, ketone supplementation, and hyperbaric oxygen therapy effectively slow the progression of cancer without the toxicity to patients that is so common in most other cancer therapies.

Read MoreCancer Cell Biology and Non-Toxic Treatment Options: Ketosis and Hyperbaric Oxygen Therapy

In the first article in his new series on diabetes, Dr. Malcolm Kendrick, MD, discusses the long history of diabetes research and introduces several models for understanding the causes of the disease, as well as its progression. While the mechanism underlying Type 1 diabetes is generally agreed upon, debate continues over whether Type 2 is related to fat consumption or raised insulin levels resulting from carbohydrate intake. Kendrick explains and evaluates the arguments for each model.

Read MoreDiabetes, Part 1: Disease Models

The burpee is a versatile movement. In its simplest form, it requires little skill, space, or equipment. However, the framework of the basic movement lends itself to many creative variations, such as burpee box jump-overs, which have the potential for greater intensity and challenge coordination, agility, and balance. 

WatchThe Burpee Box Jump-Over

Several studies support the hypothesis that diet, particularly carbohydrate consumption, affects vision. One study compares the eyesight of hunter-gatherer and industrialized groups and finds myopia skyrockets when indigenous populations adopt a Western diet involving more refined carbohydrates. Another study explores the mechanism behind dietary contribution to myopia and finds increases in insulin promote eyeball elongation in animal models. A third study explores dietary sugar’s links to glaucoma, cataracts, diabetic retinopathy, and macular degeneration. Its authors ultimately recommend avoiding high glycemic index foods.

Read MoreSugar and Sight

Brain insulin resistance is associated with Alzheimer’s disease and cognitive impairment, and the regions of the brain most closely associated with Alzheimer’s pathology are also the regions richest in insulin receptors. The authors of this 2019 review argue these associations may be causal and explore ways hyperglycemia and impaired brain insulin signaling may directly contribute to cognitive decline and Alzheimer’s disease.

Read MoreAlzheimer’s Disease and Diabetes: Insulin Signaling as the Bridge Linking Two Pathologies

"Trainers … apply exercises to their clients in order to induce adaptations in structure and function that lead to improved fitness. In order to do this effectively, reliably and safely, the working trainer must understand the structures they are stressing with exercise to produce the functional change that is fitness. This is the primary reason we learn anatomy and physiology."

Read the article Anatomy and Physiology Primer for CrossFit Trainers

The muscle-up is a movement that begins from the hang, passes through portions of a pull-up and a dip, then finishes in a supported position with arms extended. Many athletes experience the strict bar muscle up as more challenging than its counterpart on the rings. This is because the pull-up bar creates a fixed object the athlete must navigate around. Pulling the torso high enough and having the patience to delay the transition to the dip is critical to the success of the movement.

Watch The Strict Bar Muscle-Up

In the final installment of his landmark series on the history of heart disease research, Prof. Timothy Noakes summarizes the scientific malfeasance perpetrated by Ancel Keys, the famous progenitor of the diet-heart and lipid hypotheses. Taking on the voice of the prosecution in a hypothetical criminal trial, Noakes levels a series of charges against Keys. These range from scaremongering and manipulating data to withholding important trial results that could have saved millions of lives. Most important, Noakes charges Keys with defying the first rule of medicine — do no harm — and concludes with an indictment of Keys' character: "Keys and his acolytes must be held accountable for the wretchedness their over-promotion of his wrong ideas has wrought on the health of so many people."

Read MoreIt's the Insulin Resistance, Stupid: Part 11

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