Page 130 - 2022 Spring JSOM

1.4 and 1.5 injuries/1000 h for men and women, respectively, CrossFit-affiliated gyms might have a lower injury preva-
although injury rates varied widely between 0.5 to 2.5 inju- lence and rate because of the closer supervision provided by
ries/1000 h. 57,58 In summary, the overall HIFT injury prevalence coaches; however, in CrossFit gyms, participants often train in
(36%) and variability found in the data are broadly similar to groups, which provides social facilitation and adds an element
those found in other studies involving similar activities. How- of competition. Competition and social facilitation induced by
ever, the overall injury rate effect size found in the current re- the presence of other can increase performance on maximal
view (4.29 injuries/100 h) was higher than that reported for lifting and endurance tasks. 63–65 However, the higher exercise
resistance training and gymnastics. intensity may increase the risk of injury. 66
The higher overall injury rates compared to resistance training
and gymnastics was largely accounted for by rates in prospec- Conclusions
tive cohort studies. Prospective cohort studies produced a much This systematic review and meta-analysis of injuries during
higher injury rate effect size (9.87 injuries/1000 h) than retro- HIFT found an overall injury prevalence of 36% (95% CI =
spective, cross-sectional studies (2.58 injuries/1000 h). Injury 32–41%) and injury rate of 4.29 injuries/1000 h (95% CI =
rates in three of the four prospective cohort studies were the 3.35–5.23 injuries/1000 h). The most commonly injured ana-
highest among studies in this review: 9.0, 9.5, and 18.9 tomical locations were the shoulder (26%), back/spine (26%),
48
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injuries/1000 h. The study with the highest injury rate asked knee (14%), wrist/hands/fingers (12%), arm/elbow (10%),
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participants to self-report every 2 weeks any musculoskeletal and ankle/foot (6%). While overall injury prevalence in HIFT
condition that preventing training for >1 day (12-week study, was similar to that of other studies involving similar activities
six reporting periods). The other two investigations 38,48 had (i.e., resistance training, gymnastics, running), overall injury
participants self-report injuries on a post-study questionnaire. rates were higher. Higher injury rates were found largely in
Their 38,48 reporting periods were relatively short: 2 months prospective cohort studies that tracked injuries over shorter
38
and 6 weeks. These shorter reporting periods may have min- periods of time and likely reduced recall bias compared to ret-
48
imized recall errors since recollection of injuries decays over rospective cross-sectional investigations. To more effectively
time. 59,60 The retrospective cross-sectional studies asked partic- define the injury rate during HIFT, there is a need for more
ipants to report over much longer periods increasing the risk prospective studies that have adequate sample sizes, account
of recall error. 59 for the volume of HIFT, assess confounders, and track of inju-
The shoulder, back/spine, and knees were the most often in- ries progressively (i.e., while the study is ongoing).
jured anatomic locations accounting for about 66% of all
injuries. Reviews of injuries experienced in resistance train- Disclaimer
ing 55,56,61 also indicate that these three sites are the most com- The views expressed in this presentation are those of the au-
monly injured; in running, the knee is the most common injury thor(s) and do not necessarily reflect the official policy of the
52
site. As noted above, weightlifting and gymnastic movements Department of Defense, Department of the Army, US Army
involving the upper body are often used in HIFT, especially Medical Department, or the US. The use of trademark names
in CrossFit training. Movements of these types place con- do not imply endorsement by the US Army but is intended
51
siderable stress on the shoulder and thoracic/lumbar spine. only to assist in the identification of a specific product.
In weightlifting the shoulder is often placing at its extreme
range of motion while under heavy loading, thus increasing References
1. Knapik JJ. Extreme conditioning programs: potential benefits and po-
the potential for both acute and chronic injury. 55,61,62 Also, the tential risks. J Spec Oper Med. 2015;15(3):54–59.
requirement for rapid movement in many types of HIFT may 2. Knapik JJ. Injuries during high intensity functional training. J Spec
Oper Med. 2021;21(4):111–114.
lead to loss of proper form, which can place stress on anatom- 3. Feito Y, Heinrich KM, Butcher SJ, Poston WSC. High-intensity func-
ical structures not accustom to these stresses. The wrist/hands/ tional training (HIFT): definitions and research implications. Sports.
fingers also had a high injury rate and many HIFT activities 2018;6:76.
like push-ups, handstands, power cleans, and squats also re- 4. Henrich KM, Spencer V, Fehl N, Poston WSC. Mission essential fitness:
comparison of functional circuit training to traditional Army physical
quire movements at the extremes of ranges of motion that training for active duty military. Mil Med. 2012;177:1125–1130.
can put excessive stress on the hands and wrist. Weisenthal 5. Knapik JJ, Rieger W, Palkoska F, VanCamp S, Darakjy S. United
et al. found that powerlifting, weightlifting, and gymnastic States Army Physical Readiness Training: rationale and evalua-
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tion of the physical training doctrine J Strength Condit Res. 2009;
activities accounted for 23%, 17%, and 20% of all injuries in 23:685–697.
their study of injuries in CrossFit training. The few studies that 6. Galic B. 81 CrossFit statistics you should know. Accessed: 27 October
2021, 2021
examined injuries associated with specific exercises in HIFT 7. Poston WSC, Haddock CK, Heinrich KM, Jahnke SA, Jitnarin
reported that resistance training exercises accounted for most N, Batchelor DB. Is high intensity functional training (HIFT)/
injuries. The exercises most often associated with injury were CrossFit safe for military fitness training? Mil Med. 2016;181(7):
627–637.
the squat, deadlift, snatch, and clean and jerk. 37,40,44 8. Tibana RA, Frade-deSousa NM. Are extreme conditioning pro-
grammes effective and safe? A narrative review of high intensity func-
Other factors examined here included injury case definitions tional training methods research paradigms and findings. BMJ Open.
and type of HIFT. When studies with similar injury case defi- 2018;4:e000435.
nitions were examined, the overall injury prevalence effect size 9. Meyer J, Morrison J, Zuniga J. The benefits and risks of CrossFit.
Workplace Health Saf. 2017;65(12):612–619.
was similar to that of the analysis with all studies included, but 10. Klimek C, Ashbeck C, Brook AJ, Durall C. Are injuries more common
the injury rate effect size was lower. It is not clear why this was with CrossFit training than other froms of exercise? J Sport Rehabil.
the case. When examining only CrossFit studies, injury rates 2018;27:295–299.
were somewhat lower than found for all studies combined, but 11. Claudino JG, Gabbett TJ, Bourgeois F et al. CrossFit overview: sys-
tematic review and meta-analysis. Sports Med Open. 2018;4:11.
participants training in CrossFit-affiliated gyms had a higher 12. Barranco-Ruiz Y, Villa-Gonzalez E, Martinez-Amat A, Silva-Grigo-
injury rate compared to the data with all studies included letto MED. Prevalence of injuries in exercise programs based on
(Figure 2). It was hypothesized that participants training in CrossFit cross-training and high-intensity functional training method-
ologies: a systematic review. J Hum Kinet. 2020;73:251–265.

128 | JSOM Volume 22, Edition 1 / Sping 2022