ATHLETE x SCIENCE
ATHLETE x SCIENCE
The benefits of CrossFit are under-researched in a long-term capacity, however, a number of studies have determined the potential benefits of this type of high-intensity functional power training on aerobic capacity and body composition. High-intensity interval training is desirable to many individuals looking to improve fitness levels with minimal time commitment to training. Typically, these types of workouts take a very short amount of time, averaging between 5 and 20 minutes, and reap maximal caloric burn due to the continuous nature of the workload, relative intensity, and minimal rest periods. In some workouts, participants target achieving as many rounds or reps as possible before the allotted time is up, whereas other workouts request the best time to completion of a given set of exercise rounds. A combination of power and Olympic lifts, cardio activity, gymnastics and other body weight movements, is used to stimulate positive adaptation of maximum aerobic capacity and body composition.
Smith, Sommer, Starkoff, & Devor (2013) prove such an example in their study on the effects of crossfit-based high-intensity power training (HIPT) on body composition and aerobic fitness. The 10-week HIPT program consisted of both traditional power and Olympic lifts including: squat, deadlift, clean, snatch, and overhead press, however performed in a non-traditional fashion of completing the designated number of repetitions as quickly as possible (Smith et al., 2013). After HIPT training, body fat reduced by 3.7% across all individuals, in both male and female categories (Smith et al., 2013). Oxygen consumption relative to body weight increased in all participants, resulting in a 13.6% and 11.8% improvement in VO2 max for men and women, respectively (Smith et al., 2013). This was independent of the changes in body mass, which is often attributed to the improvements of oxygen capacity (Smith et al., 2013).
CROSSFIT vs. NSCA
In this study, 16% of participants did not complete the program or return for follow-up testing (Smith et al., 2013). Although this limitation was expressed in a paragraph noting the potential for injury risk when partaking in this type of exercise, it was never claimed that the reason for the 16% failure was injury or overuse. This makes the claims staked by the defendant (CrossFit, Inc.) in the case of CrossFit vs. the National Strength and Conditioning Association (NSCA) completely invalid. This study, which is published in favor of CrossFit-style HIPT in the NSCA’s primary educational resource, the Journal of Strength and Conditioning Research, states as follows (Smith et al., 2013):
With more than 13,000 CrossFit gyms (or “boxes”) established throughout the country, intense scrutiny should be placed on this company’s mission and training principles in order to decipher whether or not this is a efficacious and safe form of athletic conditioning. Any emerging form of exercise or dieting should be challenged on the basis of evidence-based practice in order to properly validate and promote programs which are both safe and effective for the long-term health and well-being of all participants, with long-term being the key word here.
In a review of the pros and cons of extreme conditioning programs such as CrossFit, a 2013 survey was referenced in which CrossFit participants were asked to disclose any injuries that had prevented them from working, training, or competing over the past 19 months (Knapik, 2015). The survey 132 respondents averaged 5.3 hours/week during this time, and 74% claimed to have sustained an injury during that time, 7% having an injury which required surgery (Knapik, 2015). The most common injuries were distributed to the shoulder (32%), spine (28%), and arm (20%) (Knapik, 2015).
Other cases have been reported for exertional rhabdoymyolysis and carotid artery dissection (CAD) in association with CrossFit activity (Knapik, 2015). The four cases of CAD were attributed to lifting significantly more weight than previously done (20% more) and/or to performing exercise which involved rapid, twisting movements (Knapik, 2015). CAD can result in a partial blockage of the carotid artery, a partial tear in the vessel wall resulting in a hematoma, or a total rupture and subsequent aneurysm, with the goal of treatment being the reduction of neurologic deficits and the stability of blood flow (Knapik, 2015). Repetitive eccentric contractions produce the muscle damage that leads to exertional rhabdomyolysis (Su, 2008). Extreme muscle breakdown results in leakage of muscle enzymes, including creatine kinase, lactate dehydrogenase, and myoglobin, and electrolytes such as potassium. When the level of myoglobin in the blood exceeds 3mg/L, it spills into the urine (termed myoglobinuria) and produces a tea/cola coloration (Su, 2008). Myoglobin damages renal tubules, which can lead to tubular necrosis, and if renal blood flow is further limited by a high exertion level and dehydration, the kidneys are less capable of clearing the muscle breakdown products which can lead to fatal complications (Su, 2008). The very nature of CrossFit workouts brings an increased likelihood for these injuries of ‘overexertion’ to occur.
Weisenthal et al. (2014), conducted a similar survey via the main CrossFit website reaching 386 participants meeting the inclusion criteria for CrossFit participation. Data from the study concluded that injury rate over the prior 6 months was determined to be 19.4% having had at least one injury across all individuals, with males being injured more frequently than females. The shoulder was the most commonly injured body part during gymnastic movements, while the lower back was most often from power lifting movements, without have had prior discomfort in that area (Weisenthal et al., 2014).
High-risk should not be confused with “ineffective,” since most all exercises provide benefit in some manner; though, the aim of exercise should always be to maximize benefits and minimize risks (Mullins, 2015). Two very high risk exercises commonly performed in a CrossFit setting are unassisted pistol squats and kipping pullups, both of which are rarely able to be performed with proper execution (Mullins, 2015). In the pistol squat, the lordodic curve of the lumbar spine should be maintained, the knee should track over the toes with virtually no mediolateral shift, and the heel should remain in contact with the ground (Mullins, 2015). Rounding of the back is a compensatory mechanism used to achieve depth in the pistol squat and places unnecessary strain on the lower back (Mullins, 2015). Kipping pullups result in lumbar hyperextension, unlike traditional pullups which allow the spine to stay in neutral (Mullins, 2015). Hyperextension of the spine has long been contraindicated by medical professionals due to the high potential for injuring the spinal discs, nerves and joints (Mullins, 2015).
The incidence of injury was reported to be much less when an individual was working with a trainer, and the lower female incidence rate can be attributed to their likelihood of seeking a coach prior to training (Weisenthal et al., 2014). With nearly a 20% injury rate, however, the jury is still out on whether or the risk-benefit ratio is in an athlete’s favor. Similar rates of injury are seen in the sport of gymnastics and on the Power/Olympic lifting scenes.
Assigning high volume repetitions and speed to technically-demanding exercises opposes USA Weightlifting’s recommendation to keep “repetitions to three or less on technical exercises [Olympic movements] and five or less for strength exercises (e.g. squats), and never continue repetitions if form is breaking down” (Mullins, 2015). The entire foundation of CrossFit is based around a total-body fatigue, forced-adaptation model, risking form break-down and injury with every repetition that passes. The NSCA aligns with the USAW philosophy, and stressed the importance of exercise order for maximal adaptation gains and the insurance of safety (Mullins, 2015):
Some CrossFit facilities are run by well-educated, exercise science professionals who make an effort to ensure all participants are practicing safe technique and sound progressions with individualized program design. One such individual is Dr. Mike Young, Director of Performance and Research with Athletic Lab in Cary, NC. When incorporating CrossFit programming into his Sports Performance and Athletic Development facility, he takes the following approach:
CrossFit v. National Strength and Conditioning Association, No. 3:14-cv-01191-JLS-KSC (S.D. Cal. May 12, 2014).
Knapik, J. J. (2015). Extreme Conditioning Programs: Potential Benefits and Potential Risks. Journal Of Special Operations Medicine: A Peer Reviewed Journal For SOF Medical Professionals, 15(3), 108-113.
Mullins, N. (2015). CrossFit: Remember What You Have Learned; Apply What You Know. Journal Of Exercise Physiology Online, 18(6), 32-44.
National Strength and Conditioning Association. (n.d.). NSCA update to CrossFit Inc claims and allegations.
Smith, M. M., Sommer, A. J., Starkoff, B. E., & Devor, S. T. (2013). Crossfit-based high-intensity power training improves maximal aerobic fitness and body composition. Journal of Strength and Conditioning Research, 27(11), 3159- 3172.
Su, J. (2008). Exertional rhabdomyolysis. Athletic Therapy Today, 13(5), 20-22.
Weisenthal, B. M., Beck, C. A., Maloney, M. D., DeHaven, K. E., & Giordano, B. D. (2014). Injury Rate and Patterns Among CrossFit Athletes. Orthopaedic Journal Of Sports Medicine, 2(4), 2325967114531177.