Category Archives: CrossFit

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Taking Care of the CrossFit Athlete

#Statins and Primary Prevention – USPSTF Weighs In.

‘Too busy’ to workout? Enter: HIIT

Coming out of the Crossfit Closet* -A CrossFit experience by a Physician, for Physicians

*Originally published in the “Uniformed Family Physician”-Journal of the Uniformed Services Academy of Family Physicians.  Reprinted with permission.  

Oh RC.  Coming out of the CrossFit Closet. Uniformed Family Physician Fall 2013. Vol 7(1). Edition 25.  Pages 31-33.

I have a confession to make. I am a CrossFitter. I am currently a fellow in the Sports Medicine Fellowship, and coming out is scary.   What will my fellowship director, my fellow fellows and the academic gurus at Uniformed Services think of me? I’ve heard it all. It’s insane. It’s dangerous. It causes rhabdomyolysis. Many have incredulous looks as they ponder why someone would do 100 pull-ups, 100 pushups, 100 sit-ups and 100 air squats, as fast as you can. I admit it; I thought it was crazy too. It was a fateful day in Iraq, where my first CrossFit workout kicked my little toosh in 2006. It was “Helen.” Three rounds for time of 400 meter run, 21 kettlebell swings and 12 pullups. I was hooked. 7 years later, I stand faster, stronger and fitter and continue to drink the kool-aid.


Love it, hate it or neutral, you probably have heard of CrossFit. You may have even done a CrossFit workout. From its grass roots beginning in the year 2000, to over 7000 worldwide affiliates, 10 million CrossFitters, 35,000 trainers, Reebok swag and the “Games” televised on ESPN, CrossFit is taking the fitness industry by storm.   CrossFit is especially popular among military servicemembers with CrossFit gyms popping up downrange and on military bases. As military family physicians, I am confident that you will run people who CrossFit. In this article, I hope I can give you a basic understanding of what CrossFit is about and take a closer look at the general underpinnings of CrossFit as an exercise program.


What is CrossFit?

“100 words” of CrossFit is a foundational statement by the CEO, Greg Glassman. This is probably the best definition to describe what this movement is about.

“Eat meat and vegetables, nuts and seeds, some fruit, little starch and no sugar. Keep intake to levels that will support exercise but not body fat. Practice and train major lifts: Deadlift, clean, squat, presses, clean&jerk and snatch. Similarly, master the basics of gymnastics: pull-ups, dips, rope climb, push-ups, sit-ups, presses to handstand, pirouettes, flips, splits, and holds. Bike, run, swim, row, etc, hard and fast. Five or six days per week mix these elements in as many combinations and patterns as creativity will allow. Routine is the enemy. Keep workouts short and intense. Regularly learn and play new sports.” Greg Glassman

The pyramid is another way to view CrossFit. See Figure 1. If you notice, CrossFit emphasizes nutrition as the base. That is a topic for another day. Then, metabolic conditioning (or aerobic exercise), gymnastics, weightlifting and finally, sport.


Figure 1.  The CrossFit Pyramid

Next, is to understand the basic programming of the workouts and the type of movements.   Generally, CrossFit workouts are boiled down into this statement: “Constantly varied, functional movements performed at high intensity.” Let’s break this down.


Constantly Varied

Routine is the enemy. Working on bench press and legs alternating with “cardio” can become stale. Performance also peaks and levels at 6 weeks if you don’t vary the routine. The theory is that by constantly varying different types of movements and exercise, the recreational athlete or Warrior will be able to face anything that comes at them. Tony Horton, who popularized P90x, stated it well with his concept of “muscle confusion.” CrossFit attempts to train for the untrainable, with constantly varied exercise.

Functional Movements

CrossFit promotes functional, two-joint movements—movements that you will do during life normal activities. For example, when have you done a biceps curl in life’s activities? Most biceps movements involve supination and arm flexion, generally involved in lifting and reaching for things. How about overhead lifts? Do you routinely isolate your deltoids and keep your back inclined to put a heavy box on top of a shelf? Top functional exercises includes the squat (body-weight) and the deadlift. For example, a squat is simply the ability to sit and get up from a chair. Or, better yet, getting up from the ground (try doing a Turkish Get-up—great for the core!). A deadlift is simply picking something off the ground. Whether it is a 20-lb box, a fallen Soldier on the battlefield, or a pencil dropped on the ground, we all have to do this basic functional movement.

Performed at High Intensity

High intensity training is a huge part of CrossFit. There are scores of published articles looking at high intensity exercise. High intensity training can improve cardiovascular fitness, body composition and modify cardiovascular risk factors (improved lipid profiles, insulin sensitivity, blood glucose), often in a fraction of the time. An easy to read review article published in the Australian Family Physician journal on HIT can be found at this link.1 For example, one cycling study found high intensity interval sprints, as compared to traditional endurance training, to exert similar benefits of performance on 2 different time trials. The HIT group, however, exercised 20% less than the traditional group.2


Another recent study looked at HIT on half marathon performance and body composition. The study randomized 34 recreational runners to two groups. An “After Work” group that did 30 minutes of intense training 4 days a week and one 30 min endurance run once a week after work (total 2.5 hours) versus a “Weekend” group that ran for 2 sessions totaling 2.5 hours on the weekend only.   After 12 weeks, both groups ran a half marathon as part of their final test. At the end of the study, there was no significant difference in half-marathon time. However, the “After Work” group had significantly improved oxygen uptake (VO2 max), velocity at peak lactate threshold, and had lower visceral fat compared to the “Weekend” group.3   This study was nice since it tried to replicate “real-world” scenarios.


Is CrossFit Effective?

The American College of Sports Medicine guidelines for exercise was revised in 2011 and is consistent with the American Heart Association guidelines for exercise. Basically, both societies recommend:

  1. At least 150 minutes a week of moderate aerobic activity at least 5 days a week OR
  2. At least 75 minutes a week of vigorous aerobic activity at least 3 days a week AND
  3. Resistance exercise: 2-3 days a week

CrossFit exercises are different in that resistance exercises are often combined with their workouts. Adding the intensity, gives the workout both an aerobic and anaerobic component. Bottom line, a short intense workout that simultaneously improves both aerobic and anaerobic capacity. Let’s take at this in more detail.

A recent study sponsored and published by the American Council of Exercise4 described physiologic response and caloric burn for two CrossFit workouts. One called “Fran” and one called “Donkey Kong.” “Fran” consists of 21 repetitions of thrusters (squat to overhead press using a weighted barbell) and 21 pull-ups, then 15 thrusters and 15 pull-ups, and finally 9 thrusters and 9 pull-ups.   “Donkey Kong” consists of 21 repetitions of burpees, kettlebells and box jumps, then 15 burpees, kettlebells and box jumps and finally 9 burpees, kettlebells and box jumps. On average, both workouts were completed in less than 12 minutes (although there was a great range) and burned an average of 20 calories/minute in males and 12 calories/minute in females. Interestingly, both workouts kept the participants heart rate at 90% of maximal heart rate and at 80% of VO2 max throughout the workout—levels that supports improvement of cardiovascular endurance; i.e. improvement of aerobic capacity. Also, blood lactate levels were high after workout (average 15.9 mmol/L for men and 12.4 mmol/L for women. Theoretically, increasing your lactate threshold can improve exercise endurance, since you can continue to process lactate without having to rest. I know this was a lot of numbers. Bottom line, this study demonstrates that an average 12-minute CrossFit exercise (incorporating both resistance and body weight exercises) can burn an average of 240 calories in males, 144 in females, and can potentially deliver both an aerobic and anaerobic training benefit.

Unfortunately, there are very few published studies in the medical literature focused on CrossFit. The only study published in the PubMed database showed improved VO2 max and decreased body fat in 43 subjects after 10 weeks of CrossFit. There were no control group for comparison.5


Is CrossFit safe?

No fitness activity is devoid of injury. From walking, running, football, to military physical training, the risk of injury always exist. Quantifying the injury risk of CrossFit, however is currently unavailable in the literature. Overall though, considering the type of movements of CrossFit, one can predict a constellation of injuries consistent with the different movements. Physicians should ask for and look for injury patterns consistent with patterns involving Olympic lifting, gymnastics, calisthenics, and plyometrics. One study just published attempted to quantify the injury rates from CrossFit and other HIT. This research found no difference in injury rates from those participating in HIT type exercises compared to normal Army Physical Training (PT).6 More studies looking at the benefits and risk of CrossFit are greatly needed.


My patients are interested in trying, what do I tell them?

There are two basic ways to begin CrossFit. Everything to get started is published and free to use on If they want to start on their own, a good rule of thumb is to learn the movements and exercises for about 1-2 months, and don’t worry about time or intensity. Trust me on this. You’ll realize you have muscles that have been lying dormant for years. Then as you begin to familiarize yourself with the movements and are able to perform them with good form, then you can increase the intensity. I started to read and watch the videos and work on learning with movements before I dialed in the intensity.

The other way is to join a CrossFit gym affiliate, affectionately known as a “box.”   Make sure you find a gym with a good “On-Ramp” program to teach the fundamentals and have good coaches. Most CrossFit gyms will give you a free introduction workout to get a feel of both the workout and the coaching team.


Bottom Line

Clearly, more research needs to be done on CrossFit. Exercise is medicine, and this movement, if nothing else, has gotten people excited about fitness. While caution should not be thrown to the wind, we should also not throw the baby out with the bathwater.   I hope this article gives you a basic understanding of CrossFit and the theories behind the movement. I also hope it stirs a response among our readers. What have been your experiences? Good or bad? Finally, to the other closet CrossFitters out there, what’s your “Fran” time? My PR is 5:52, Rx’d.



1. Shiraev T, Barclay G. Evidence based exercise – clinical benefits of high intensity interval training. Australian family physician. Dec 2012;41(12):960-962.

2. Gibala MJ, Little JP, van Essen M, et al. Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. The Journal of physiology. Sep 15 2006;575(Pt 3):901-911.

3. Hottenrott K, Ludyga S, Schulze S. Effects of high intensity training and continuous endurance training on aerobic capacity and body composition in recreationally active runners. Journal of sports science & medicine. 2012;11(3):483-488.

4. Babiash P, Porcari J, Steffen J, Doberstein S, Foster C. CrossFit: New research puts popular workout to the test. 2013. Accessed October 31, 2013.

5. Smith MM, Sommer AJ, Starkoff BE, Devor ST. Crossfit-based high intensity power training improves maximal aerobic fitness and body composition. Journal of strength and conditioning research 2013;27(11):3159-72.

6. Grier T, Canham-Chervak M, McNulty V, Jones BH. Extreme Conditioning Programs and Injury Risk in a US Army Brigade Combat Team. U.S. Army Medical Department journal. Oct-Dec 2013(4-13):36-47.