Part II: Comparison of Crossfit-Related Injury Presenting to Sports Medicine Clinic by Sex and Age

Differences in Injury Profiles Between Female and Male Athletes Across the Participant Classification Framework: A Systematic Review and Meta-Analysis

BACKGROUND

Female sex is a significant determinant of anterior cruciate ligament (ACL) injury. It is not understood if sex is a key determinant of other sports-related injuries.

OBJECTIVE

The aim of this systematic review was to identify where differences in injury profiles are most apparent between the sexes in all sports across the six-tiered participant classification framework.

METHODS

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and the 'implementing PRISMA in Exercise, Rehabilitation, Sport medicine and SporTs science'(PERSiST) guidance. The databases PubMed, CINAHL, Web of Science, SPORTDiscus, Medline, Scopus, Cochrane Library and EBSCO were searched from database inception to 24 April 2023. Longitudinal, prospective and retrospective cohort studies and cross-sectional and descriptive epidemiology studies that used standard injury data collection were included. Studies were excluded if injuries were not medically diagnosed and if injuries were not reported and/or analysed by sex. Two reviewers independently extracted data and assessed study quality using the Downs and Black checklist.

RESULTS

Overall, 180 studies were included (8 tier-5, 40 tier-4, 98 tier-3, 30 tier-2, 5 tier-1 studies; one study included data in two tiers). Of those, 174 studies were of moderate quality and six studies were of limited quality. In sex-comparable sports, there was moderate evidence that female athletes had greater risk of knee injury (relative risk (RR) 2.7; 95% CI 1.4-5.5), foot/ankle injuries (RR 1.25; 95% CI 1.17-1.34), bone stress injury (RR 3.4; 95% CI 2.1-5.4) and concussion (RR 8.46; 95% CI 1.04-68.77) than male athletes. Male athletes were at increased risk of hip/groin injuries (RR 2.26; 95% CI 1.31-3.88) and hamstring injuries (RR 2.4; 95% CI 1.8-3.2) compared with females, particularly in dynamic sports. Male athletes were 1.8 (1.37-2.7) to 2.8 (2.45-3.24) times more likely to sustain acute fractures than female athletes, with the highest risk in competition.

DISCUSSION

Most studies in all cohorts were of moderate quality (mean/range of scores tier-5: 17 ± 2.2 [14-20], tier-4: 16.9 ± 1.9 [11-21], tier-3: 16.9 ± 1.5 [11-20], tier-2: 16.3 ± 2.2 [11-20], tier-1 studies: 15.6 ± 1.3 [14-17] out of 28 on the Downs and Black checklist), with only six studies of limited quality. Female athletes' propensity for bone stress injuries highlights opportunities to reinforce development of optimal bone health during adolescence and to outline the effects of energy availability. Earlier strength development and exposure to neuromuscular training programmes and modification of skill development in female athletes may be effective strategies for reducing lower limb injury risk. Key components of neuromuscular training programmes could be beneficial for reducing hip/groin and hamstring injury risk in male athletes. There may be a need for sex-specific prevention and return-to-sport protocols for sports-related concussion in female athletes.

CONCLUSIONS

Female sex was a key determinant of sports-related injuries beyond ACL injury including foot/ankle injury, bone stress injury and sports-related concussion. Male sex was a key determinant of hip/groin, hamstring injury and upper limb injury.

TRIAL REGISTRY

PROSPERO registration number: CRD42017058806 (last updated on 7th June 2023).

Common Orthopaedic Injuries in CrossFit Athletes

CrossFit is a high-intensity exercise program that has gained popularity over the past few decades. CrossFit combines movements from Olympic weight lifting, gymnastics, powerlifting, and high-intensity interval training. As CrossFit continues to expand, knowledge of the associated orthopaedic injuries to aid providers in diagnosis, treatment, and prevention will be increasingly important. The most common CrossFit injuries occur in the shoulder (25% of all injuries), spine (14%), and knee (13%). Male athletes are markedly more likely to experience injuries than female athletes, and injuries occur markedly less when there is supervised coaching of the athletes. The most common causes of injury in CrossFit include improper form and exacerbation of a prior injury. The purpose of this article was to review the literature to aid clinicians in identifying and treating common orthopaedic injuries in CrossFit athletes. Understanding the injury patterns, treatment, and prevention options is important for a successful recovery and return to sport.

Epidemiological Profile among Greek CrossFit Practitioners

CrossFit (CF) is a popular and rapidly expanding training program in Greece and worldwide. However, there is a lack of scientific evidence on the risk of musculoskeletal injuries related to CF in the Greek population. A self-administered survey of 1224 Greek CF practitioners aged 18 to 59 was conducted and analyzed using the Statistical Package for Social Sciences (SPSS) software. The highest percentage of the participants (34%) practiced 5 days per week for 60 min (42.2%) and had 2 days per week of rest (41.7%). A total of 273 individuals (23%) participated in CF competitions and 948 (77%) did not. The results showed that the most common injuries were muscle injuries (51.3%), followed by tendinopathies (49.6%) and joint injuries (26.6%). The shoulders (56.6%; n = 303), knees (31.8%; n = 170), and lumbar spine (33.1%; n = 177) were the most commonly injured locations. The logistic regression model showed that participation in competitions (p = 0.001), rest per week (p = 0.01), duration of training per session (p = 0.001), and frequency of training per week (p = 0.03) were statistically significant factors for injury. Training level was not a statistically significant factor for injury (p = 0.43). As CF continues to gain popularity on a global scale and the number of athletes gradually increases, it is important to monitor the safety of practitioners. Clinicians should consider participation in competitions, rest, training duration, and frequency in order to make CF safer.

Risk Factors for Injury in CrossFit®-A Retrospective Analysis

CrossFit^® is a physical activity program and sport which is based on functional movements performed at high intensity and with high variability of exercises. It develops all motor skills. The study included 424 athletes (266 men and 158 women) from twelve centers in Poland, actively practicing CrossFit^® between 18 and 60 years of age. A questionnaire consisting of 25 questions was used, which was divided into four subsections concerning the characteristics of the sample, training routine, injuries, and information about environment. In total, 48% of respondents participating in the study suffered at least one injury during their entire training history. The injuries suffered most often involved shoulder joint and lumbar spine. Men were found to face a higher risk of injury than women, at 32.78% vs. 15.33% (p = 0.027). The shorter the training period, the smaller the number of injuries observed among the trainees. It was also noted that the shorter the training period, the lower the number of injuries that occurred (p = 0.041). An increase in the number of training sessions per week did not increase the incidence of injuries (p > 0.05). Performing isometric exercises during warm-up reduced the likelihood of injury during CrossFit^® training itself (p = 0.012). Training despite of concomitant acute pain had a significant adverse effect on the incidence of injuries (p = 0.002). The most common risk factors for injury in the CrossFit^® training process include, in particular: gender, training experience, and length of training sessions. Proper warm-up including isometric exercises and training conducted without accompanying pain symptoms reduces the risk of injury.

Characteristics of Fitness-Related Injuries in The Netherlands: A Descriptive Epidemiological Study

Although general information is available, specifically detailed information on gym-based fitness-related injuries in the general recreational fitness population is lacking. The aim of our study was to obtain more insight into injuries occurring as a result of gym-based fitness activities. A descriptive online epidemiological study was conducted in November 2020. The survey was distributed by a market research agency to members of their research panel. A total of 494 Dutch fitness participants aged ≥ 18 years (mean 38.9; 59% male) who had sustained a fitness-related injury in the preceding 12 months were included in the study. Most injuries occurred during strength training, individual cardio exercise, yoga/Pilates, cardio exercise in group lessons, and CrossFit. The shoulder, leg, and knee were the most common injured body parts; 73.1% of the injuries occurred during unsupervised gym-based fitness activities, and 46.2% of the injuries occurred during one specific exercise or when using a specific fitness device: running (e.g., on the treadmill) (22.8%); bench press (11.8%); or squats (9.6%). Overuse or overload (n = 119), missteps and sprains (n = 48), or an incorrect posture or movement (n = 43) were most often mentioned as causes of injury. Conclusions: Most self-reported gym-based fitness-related injuries occur during strength training and individual cardio exercise. Special attention should be given to the shoulder during strength training and to the lower extremities during cardio exercise. Injury prevention interventions should be able to be carried out without supervision.

Predicting the Clean Movement Technique in Crossfit® Athletes Using an Optimal Upper-Limb Range of Motion: A Prospective Cohort Study

BACKGROUND

The aim of this study was to determine the optimal upper-limb range of motion (ROM) profile for the catch phase of the clean movement (CPCM) and to identify the key ROMs for performing the CPCM in CrossFit® athletes.

METHODS

A prospective cohort study of twenty CrossFit® athletes aged 20-36 years was conducted. Data were collected regarding age, anthropometrics, CrossFit® training experience and upper-limb ROM. The ROM was measured using the ROM-SPORT method. After 7 months, athletes performed a clean movement with a load of 80% one repetition maximum. A Bayesian Student's t-analysis, binary logistic regression analysis and Receiver Operating Characteristic analysis were performed.

RESULTS

The optimal upper-limb ROM profile that predicted correct CPCM performance was 78° in shoulder extension, 173° in shoulder flexion, 107° in shoulder external rotation, 89° in shoulder internal rotation, 153° in elbow flexion, 99° in elbow pronation and 92° in wrist extension (area under the curve ≥ 651; positive predictive value ≥ 80%). Shoulder external rotation, elbow pronation and wrist extension were found to be the most important ROMs for the efficient and safe performance of CPCM (area under the curve ≥ 854; positive predictive value ≥ 85.7%).

CONCLUSION

The upper-limb ROM profile is associated with proper clean performance. Further studies are warranted to determine whether improving flexibility on upper-limb ROM may improve proper clean movement performance.

Upper Extremity Injuries in CrossFit Athletes-a Review of the Current Literature

PURPOSE OF REVIEW

Cross-discipline fitness, or CrossFit, has exploded in popularity during the last two decades. During this time, there have been a high volume of patients presenting to clinicians with a wide range of associated injuries. Given the high intensity, high repetition, and competitive nature of CrossFit training and competition, athletes are vulnerable to injury, particularly upper extremity injury. The rate of injury to the shoulder, elbow, and wrist in CrossFit is higher when compared to traditional weight-training and more comparable to elite-level gymnastics and Olympic-style lifting. Due to the growing popularity of CrossFit-style exercise and the relatively high rate of injury among its participants, clinicians are likely to encounter these athletes. The purpose of this review is to familiarize clinicians with CrossFit and the associated injuries they will likely encounter.

RECENT FINDINGS

The medical literature focusing on CrossFit has demonstrated exponential growth, with the first article published in 2012 and 59 articles published in 2020. Although the body of literature is growing, there are no high-level studies focusing on CrossFit. The literature mainly consists of level IV and V studies, primarily consisting of case reports and case series. Recent studies have proven that CrossFit athletes are vulnerable to high rates of upper extremity injury and a few studies have identified risk factors for injury. Future high-level research is required to study modifiable risk factors, diagnostic criteria, and treatment options for these high-risk athletes in order to improve the safety of their sport. The CrossFit body of research is limited to level IV and V studies; however, the literature is clear, CrossFit athletes face a high rate of upper extremity injury. For this reason, clinicians must be familiar with CrossFit and its associated pathology. The goal of this review is to familiarize clinicians with CrossFit and the associated pathologies they will likely encounter.

Joint and muscle injuries in men and women CrossFit® training participants

OBJECTIVE

Verify the incidence and rate of joint and muscle injuries with the practice of CrossFit® and the potential risk factors for injuries in men and women.

METHODS

A total of 184 CrossFit® participants (97 men and 87 women). A questionnaire was conducted based on characterization, training routine, injuries, and additional information. The incidence refers to the number of new cases of injury in the sample during the CrossFit® training. The injury rate was calculated by estimating the number of weekly training hours and converted into the number of injuries per 1000 training hours.

RESULTS

Among the participants, 38.6% reported some type of injury, being joint injuries (83.1%) and/or muscle injuries (45.1%). The injury rate was 3.4/1000 h, with men having a higher rate. The location of the joint injuries was shoulders, wrists, and elbows, in addition to the lumbar spine in women. As for muscle injuries, the deltoid, upper back muscles, and quadriceps femoris were the most reported in men and deltoid, trapezius, upper back muscles, and gastrocnemius in women.

CONCLUSIONS

A better understanding of the anatomical distribution of the injuries may help coaches prescribe the most adequate workout that may reduce the likelihood of injuries occurring in CrossFit® training participants. It was demonstrated that gender, experience, weekly frequency, and previous injuries are important factors, and professionals must be concerned with the assessment of the participants and with an individualized progression in order to avoid risks.

Injury in CrossFit®: A Systematic Review of Epidemiology and Risk Factors

OBJECTIVE

To review the characteristics of the injuries among CrossFit® practitioners, including prevalence and incidence, nature, location, and risk factors.

METHODS

PubMed/MEDLINE, EMBASE, Web of Science, Scopus, and SPORTDiscus databases were searched from inception through August 2020, and English-language articles reporting on CrossFit®-related injuries were included. Data including sample (sex, age, and demographics) and injuries' characteristics (prevalence, incidence rate, nature, location, percentage of injuries requiring surgery and risk factors) were extracted.

RESULTS

Overall, twenty-five studies involving a total of 12,079 CrossFit® practitioners met the inclusion criteria. The mean prevalence of injuries among the included studies was 35.3%, with an incidence rate varying between 0.2 and 18.9 per 1000 hours of training. The most injured areas were shoulder (26%), spine (24%), and knee (18%). Among the studies that reported the injuries requiring surgery, the mean percentage was 8.7%. Regarding the risk factors associated with injuries, older age, male sex, a greater body mass index, the existence of previous injuries, the lack of coach supervision, the experience on CrossFit® and the participation in competitions were reported by the studies.

CONCLUSIONS

CrossFit® training has an injury incidence rate similar to weightlifting and powerlifting. Findings from the studies suggest that the most affected areas are shoulder, spine, and knee. The limited quality of the studies prevents us from drawing solid conclusions about injury risk factors.

Weighted vests in CrossFit increase physiological stress during walking and running without changes in spatiotemporal gait parameters

This study quantified the physiological and biomechanical effects of the 20 lb (9.07 kg, males) and 14 lb (6.35 kg, females) weighted vest used in CrossFit, and whether they were predisposed to injury. Twenty subjects (10 males, 10 females) undertook walking (0%, 5% and 10% gradient) and running trials in two randomised study visits (weighted vest/no weighted vest). Physiological demand during walking was increased with the vest at 10% but not 5% or 0% with no change in gait variables. In the running trial, the weighted vest increased oxygen uptake (males; females) (+0.22L/min, p < 0.01; +0.07 L/min, p < 0.05), heart rate (+11bpm, p < 0.01; +11bpm, p < 0.05), carbohydrate oxidation (+0.6 g/min, p < 0.001; +0.2 g/min, p < 0.01), and energy expenditure (+3.8 kJ/min, p < 0.001; +1.5 kJ/min, p < 0.05) whilst blood lactate was increased only in males (+0.6 mmol/L, p < 0.05). There was no change in stride length or frequency. Weighted vest training increases physiological stress and carbohydrate oxidation without affecting measured gait parameters. Practitioner summary: We examined the effect of weighted vest training prescribed in CrossFit (20 lb/9.07 kg, males and 14 lb/6.35 kg, females) in a randomised controlled trial. We found that physiological stress is increased in both sexes, although three-fold greater in males, but with no change in biomechanical gait that predisposes to lower-limb injury.

Effects of an Injury Prevention Program in CrossFit Athletes: A Pilot Randomized Controlled Trial

The present study aimed to assess the effects of an injury prevention program in CrossFit athletes. Thirty-two CrossFit athletes were randomized to either an intervention group (n=16), that performed mobility and stability exercises during the warm-up of all CrossFit sessions for a 10-week period or to a control group (n=16) that kept performing their usual warm-up. Incidence of injuries (primary outcome) as well as average training loads, fatigue and pain perception were registered during the study. The overall injury incidence rate was 0.04 per 1000 training hours, with no differences between groups (p>0.05). Similarly, no between-group differences were found for injury severity, nor for average training volume, intensity, training load, pain, or fatigue perception during the study (all p>0.05 with trivial-to-small effect sizes). In summary, a 10-week injury prevention program consisting of stability and mobility exercises provided no benefits on injury rates, fatigue and pain perception in recreational CrossFit athletes. Further research might corroborate the preliminary evidence reported here.

Correlation between previous sedentary lifestyle and CrossFit-related injuries

Objective:

To correlate CrossFit-related injuries with previous sedentary lifestyle, and to investigate other factors potentially associated with higher rates of injury among practitioners.

Methods:

A nationwide cross-sectional study involving CrossFit practitioners who received a digital questionnaire inquiring into CrossFit-related injuries, previous sedentary life, training intensity and experience, site of injury and general demographics.

Results:

This sample included 121 CrossFit practitioners, 34.7% of participants were sedentary prior to starting CrossFit practice, from these, 45.2% reported CrossFit-related injuries, compared to 30.4% from previously active practitioners (p=0.104). The shoulder/elbow (60.5%), lumbar spine (30.3%) and wrist/hand (16.3%) were the most common sites of injury among participants reporting CrossFit-related injuries (35.5%). Participants performing intense weight training were more prone to injuries than those practicing light or moderate weight training (p=0.043). On average, participants with a history of injury spent significantly more time training than those with no history of injury (68.4 and 61.7 minutes, respectively; p=0.044).

Conclusion:

The incidence of CrossFit-related injuries did not differ significantly between previously sedentary and physically active participants. Intense weight training was associated with a higher incidence of injuries. The overall injury rate was 35.5%, similar to that found in previous studies, and the most common site of injury was shoulder/elbow.

Injuries in functional fitness: an updated systematic review

INTRODUCTION

This study aimed to analyze injuries of functional fitness participants through a systematic review.

EVIDENCE ACQUISITION

A systematic search of the literature was conducted in CINAHL, EMBASE, PEDro, PubMed, SCOPUS, SPORTDiscus, and Web of Science, supplemented by searching in the grey literature, from 2017 to November 2020. This systematic review followed the PRISMA guidelines and was documented in the PROSPERO registry (CRD42020201259). Two reviewers independently extracted data including methodological (age, sex, time of practice, location, period, time frame, and completion rate) and injury (definition, diagnosis, prevalence, incidence, severity, mechanism, type, location, risk factors, and treatment) variables, as well as assessing study quality and risk of bias.

EVIDENCE SYNTHESIS

Twenty-six studies were included (10967, range 6-3049, participants). Injury was defined fairly differently across studies. The majority of studies used a retrospective study design and the main variables reported were prevalence, body location, and associated factors of injuries. The mean prevalence of musculoskeletal injuries was 32.8%, ranging from 2.4 to 60.6%, and the injury incidence per 1000 hours ranged from 0.21 to 67 36. The most affected body location in the studies was the shoulder, followed by lumbar spine, and knee. Muscle, joint, and ligament/tendon injuries were the most frequently reported. The majority of studies were of moderate methodological quality. All studies were considered as high risk of bias.

CONCLUSIONS

This review broadened the scope of 75 previous reviews on injuries in functional fitness. There have been few investigations regarding severity, mechanism, and treatment of injuries, so further research is warranted.