Retrospective injury epidemiology and risk factors for injury in CrossFit.

Author:Montalvo, Alicia M.
Position:Research article - Report
 
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Introduction

CrossFit is a strength and conditioning program that emphasizes functional and constantly varied exercise performed at a relatively high intensity. A key characterizing feature of CrossFit exercise is scalability. Scalability refers not only to progressions in load, but to modifications to movements that involve greater skill and/or flexibility. Through the use of these modifications, individuals of varying fitness levels ranging from beginner to advanced can participate in a similar training regimen, or the "workout of the day" (WOD). The issue of scalability is particularly important in group settings because of the types of WODs that are typically programmed. WODs are usually completed for time, sometimes with a time cap, or as many rounds of the exercise are completed as possible within a given period of time. Scaling of high skill movements, such as muscle-ups and toes-to-bar, allows less skilled athletes to both participate in the WOD in a manner similar to how it was prescribed and to build towards achieving the strength and skill necessary to execute the prescribed movement. Scalability enables another feature of CrossFit: community. Athletes of varying skill levels can share the experience of a WOD together.

While some CrossFit athletes complete WODs individually or informally, many CrossFit athletes belong to CrossFit affiliates, or independently operated facilities, where they may participate in individual or group-based CrossFit. Many affiliates promote another key feature of CrossFit which is the purported reason for CrossFit's effectiveness--a sense of community. CrossFit affiliate members reported experiencing significantly greater bonding (friendship development) and community belongingness compared to traditional gym members (Whiteman-Sandland et al., 2016). Research indicates that cohesion contributes to exercise adherence, which may explain this belief related to CrossFit's effectiveness (Burke et al., 2008).

CrossFit's popularity has increased substantially since 2005. With the rapid increase in participation and limited associated literature on injury epidemiology, CrossFit has been questioned for its safety. CrossFit WODs combine traditional cardiovascular exercises, such as running, biking, and rowing, with elements from Olympic weightlifting, powerlifting, strongman, and gymnastics. The elements from other sports include, but are not limited to, the clean, jerk, and snatch from Olympic weightlifting, the squat and deadlift from powerlifting, the farmer walk, tire flip, and yoke from strongman, and the handstand walk and muscle-up from gymnastics. While it borrows elements from these sports, CrossFit is different from them in distinct ways. Olympic weightlifting and powerlifting have events that occur in a specific order. For example, in Olympic weightlifting the snatch always precedes the clean and jerk. The goals of these sports is to lift the greatest loads. CrossFit is more similar to strongman in the sense that events within a competition vary. Strongman, as the name implies, has a greater emphasis on feats of strength whereas CrossFit utilizes WODs that test cardiovascular and muscular power, strength, and endurance. WODs typically mix aerobic and anaerobic exercises with high skill movements, including jerks, snatches and muscle-ups, which are performed under cardiovascular and muscular fatigue conditions. This is in contrast to traditional training principles that promote the execution of multi-joint power movements first in order to maximize load and preserve technique (Baechle and Earle, 2008). Furthermore, traditional training principles emphasize technical competence, especially with multi-joint power movements. Fatigue associated with high intensity anaerobic exercise may result in the deterioration of concentration and skill. This fatigue is believed to put athletes at greater risk of injury. The unorthodox combination and order of exercises and decreased focus on technical competence compared to related sports have contributed to the concerns about CrossFit's safety. As a result, newspapers and media outlets have noted the potential danger of CrossFit participation (Cooperman, 2005; Diamond, 2015; Robertson, 2013).

Despite the safety concerns, little evidence exists to either support or refute safety-related claims for CrossFit athletes. Existing research on CrossFit injury epidemiology utilizes methods that may not result in representative findings as sampling techniques did not address participant self-selection. Hak et al. (2013) utilized online CrossFit forums to collect data on CrossFit injury epidemiology using a retrospective survey, but were unable to determine how many individuals viewed the survey and opted not to take it. Weisenthal et al. (2014) sent their retrospective injury epidemiology survey to specific affiliates and made it available on the main CrossFit website. They also were unable to determine how many individuals viewed the survey and opted not to take it. In addition, there is a dearth of research that uses advanced statistical techniques to identify risk factors that may lead to injury in CrossFit athletes. Therefore, the purpose of this research was to examine injury epidemiology and risk factors for injury in CrossFit. Results of this research may be used to determine relative safety of the sport and to identify potential factors that put athletes at greater risk of injury.

Methods

Subjects

Fourteen CrossFit affiliates in South Florida were asked to participate in the research. Only four affiliates agreed to participate. All participating affiliates were owner-operated facilities, or facilities owned and managed by the same individual. A total of 255 athletes from participating affiliates were asked to participate in the research. Of those athletes who were asked, 191 completed the survey. CrossFit athletes were eligible for participation if they were members at the facilities and were present the day of data collection. There were no exclusion criteria. The research was approved by the university's Institutional Review Board. Consent was implied upon submission of each survey.

Instrumentation

The purpose of this investigation was to examine the location, severity, and number of injuries, and potential risk factors for injury in the preceding six months. The survey was developed and used to collect data on these variables. In addition to original questions, the survey contained questions similar to those posed by Winwood et al. (2014) in a retrospective injury survey for strongman athletes. Content validity was established via review by a Level I certified CrossFit coach, two Division I collegiate athletic trainers, and an exercise science professional. The survey was modified based on suggestions to improve clarity. Next, the survey was piloted at one CrossFit affiliate and changes were made to questions based on feedback from pilot participants.

The survey was composed of three sections. Section one pertained to the athletes' participation. These questions were related to athletes' participation in CrossFit, including length of participation in CrossFit (years), frequency of participation in CrossFit (weekly athlete training days, weekly athlete training hours, and weekly athlete-exposures), and whether or not athletes incorporated warm-ups and cool-downs. Section two pertained to CrossFit injury history within the preceding six months. Injury was defined as any physical damage...

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