Glassman began refining his approach. He favored gymnastic and powerlifting moves he knew from growing up, and functional calisthenics (squatting, pull-ups) that forced the body to use large muscle groups together, like in real life. He liked the idea of throwing exercises at clients seemingly randomly, believing it resembled the way early humans had to overcome daily physical obstacles. To goose participants' natural competitiveness, he mandated that the workouts be for time, or for as many rounds or reps as possible in a set time period, so that no one slacked off.
The rationale for the Paleolithic diet derives from proponents' claims relating to evolutionary medicine.:594 Advocates of the diet state that humans were genetically adapted to eating specifically those foods that were readily available to them in their local environments. These foods therefore shaped the nutritional needs of Paleolithic humans. They argue that the physiology and metabolism of modern humans have changed little since the Paleolithic era.:594–95 Natural selection is a long process, and the cultural and lifestyle changes introduced by western culture have occurred quickly. The argument is that modern humans have therefore not been able to adapt to the new circumstances. The agricultural revolution brought the addition of grains and dairy to the diet.
Greg Glassman and Lauren Jenai founded CrossFit, Inc. in 2000. The company was conceived a few years earlier, in 1996, as Cross-Fit. The original CrossFit gym is in Santa Cruz, California, and the first affiliated gym was CrossFit North in Seattle, Washington; there were 13 by 2005, and today there are more than 13,000. Coaches associated with CrossFit include Louie Simmons, John Welbourn, Bob Harper, and Mike Burgener.
Fruits are not only delicious, but they’re also great for you. That said, fruits (even paleo-approved ones) contain large amounts of fructose which, while much better than HFCS (high-fructose corn syrup), is still sugar. If you’re looking to lose weight on the paleo diet, you’ll want to cut back on your fruit intake and focus more on the vegetables allowed on the paleo diet. However, feel free to have one to three servings of fruit a day. Check out this list of paleo diet fruits and see if you’re not hungry by the end! (We’ll admit, we’re partial to blackberries!)
CrossFit is promoted as both a physical exercise philosophy and a competitive fitness sport, incorporating elements from high-intensity interval training, Olympic weightlifting, plyometrics, powerlifting, gymnastics, girevoy sport, calisthenics, strongman, and other exercises. It is practiced by members of over 13,000 affiliated gyms, roughly half of which are located in the United States, and by individuals who complete daily workouts (otherwise known as "WODs" or "workouts of the day"). CrossFit has been criticized for allegedly causing people to suffer from unnecessary injuries and exertional rhabdomyolysis.