Greg and Lauren Glassman are the co-founders of CrossFit. In 1995, Greg Glassman was hired to train the Santa Cruz, CA police department. The first CrossFit gym opened in Santa Cruz in 1996. The CrossFit website, launched in 2001, now includes an extensive video library of exercise demonstrations and a very active discussion forum. The number of CrossFit-affiliated gyms has grown from 18 in 2005 to over 1,600 in 2010. According to Canada's Business News Network, CrossFit is "one of the fastest growing fitness movements on the planet."^[7]

Weightlifting coaches associated with CrossFit include Louie Simmons, Bill Starr, Mike Burgener and several national and Olympic level competitors. Former NFL player John Welbourn developed the CrossFit Football program. Other CrossFit subject matter experts include Dr. Nicholas Romanov, inventor of the Pose Method of running and Dr. Barry Sears, originator of the Zone diet. Weighlifting coach Dave Tate and Terry McLaughlin, inventor of the total immersion swimming technique, have been featured in the CrossFit Journal. Speciality certification seminars include CrossFit Football, powerlifting, Olympic weightlifting, gymnastics, rowing, mobility and recovery, kettlebells, running and endurance and CrossFit Kids.

CrossFit has been criticized for its perceived "cult-like" mentality.^[1][9] Some fitness professionals^[10] and a senior officer who commands the U.S. Navy’s Center for Personal and Professional Development^[11] believe CrossFit workouts are so intense that participants risk injury or even death from rhabdomyolysis. Mark Twight, Mark Rippetoe, Dan John, Greg Everett and Robb Wolf are trainers once very active in the CrossFit community who have parted company with CrossFit or reduced their association with it. Some of them question CrossFit's management practices and say it is not truly an open source movement open to change.^[12] CrossFit has also been criticized for lax certification standards and for failing to provide any oversight of affiliates. Everyone who pays $1,000 to attend a "Level 1" weekend seminar is certified as a CrossFit trainer; there are currently no pre-requisites or exams. Certification as a "Level 2" trainer requires extensive practical testing and the failure rate ranges from 50% and 80%. Certifications are not currently accredited by any outside body, but CrossFit has applied for accreditation from ANSI, the American National Standards Institute. CrossFit says ANSI accreditation would make its fitness certifications the world leader in terms of standards, credibility, scientific rigor and international recognition.

In October 2008, a Virginia jury awarded $300,000 in damages to a man disabled by a workout at a gym that had been CrossFit-affiliated, but was not affiliated at the time of the alleged injury. (The trainer was not certified by Crossfit and CrossFit was not named as a defendant.)^[11] CrossFit subsequently established the affiliate-owned CrossFit Risk Retention Group to provide a form of self-insurance and vigorously defend any future lawsuits. CrossFit says its rate of rhabdomyolysis is a small fraction of the rate for many other sports or conventional police and military training. It says that there are actuarial studies proving that claim forthcoming.