People around the world—nearly 10 million to be exact—can speak firsthand about the benefits of CrossFit, yet very little scientific research has been done on this high-intensity style workout program to see just how effective it truly is. To gauge both intensity and caloric expenditure of this ever popular workout format the American Council on Exercise® (ACE) enlisted the research team at the University of Wisconsin-LaCrosse to select and study two different CrossFit official workouts of the day (WODs) to see just how these short yet intense workouts really stack up.
The research team, led by John Porcari, Ph.D. and Paige Babiash, M.S., recruited 16 moderately to very fit men and women ages 20-47 to participate in the CrossFit study in which each subject completed two different WODs—Donkey Kong and Fran—in which the goal of each was to complete the workout in the shortest amount of time possible. Each workout included a five-minute dynamic warm-up, a skill phase, a WOD and a five-minute cool-down phase. Before completing each CrossFit workout the subjects were required to practice and demonstrate each of the movements to the researchers in order to ensure they were proficient in each one.
Donkey Kong consisted of three rounds of the following three exercises—burpees, kettlebell swings and box jumps. Subjects performed 21 repetitions of each exercise for the first round, 15 repetitions of each move during the second round, and nine repetitions of each exercise during the third round. Also between each exercise the subjects climbed a flight of stairs. On the other hand, Fran—one of the most popular WODs in the CrossFit community—consisted of just two exercises: thrusters and assisted pull-ups yet was performed in the same sequence as the first.
Measuring rating of perceived exertion (RPE) and heart rate and using a regression equation to calculate individual VO2 max since completing the WODs in bulky metabolic testing gear would be impossible, the researchers discovered that the caloric expenditure for both WODs averaged 20.5 kcal/minute for the male subjects and 12.3 kcal/min for females. It is important to note that the time it took each participate to complete the WODs varied greatly—ranging from less than five minutes to as long as 20 minutes—which affected the averages for the total number of calories burned during each workout. For the males, the Donkey Kong burned an average of 169.9 calories while taking an average of 8:23 to complete the workout, and Fran burned an average of 112.5 calories with an average time of 5:52. The women on the other hand completed Donkey Kong with an average time of 9:08 burning an average of 117.2 calories for the workout and finished Fran in the same average time as their male counterparts yet burned an average of 63.9 calories for the workout.
During the first round of both CrossFit workouts the subjects’ heart rates were elevated to 90 percent of maximum heart rate (HRmax) and that was maintained throughout both workouts which falls near the top of the fitness industry guidelines that suggest maintain a training range of 64 percent to 94 percent HRmax in order to improve cardio endurance. Researchers also found that subjects averaged 80 percent of VO2max, which also meets and exceeds industry guidelines—40 to 85 percent of VO2max—for improving cardio fitness and body composition.
The bottom line is like other high-intensity interval training (HIIT) workouts, CrossFit is effective in terms of helping individuals improve their aerobic fitness while also burning a good number of calories in the process—all within a relatively short amount of time. Yet while this time-efficient and effective approach to exercise does have its benefits just like any HIIT workout CrossFit does come with risks and this intense workout format may not be appropriate for everyone. Dr. Porcari cautions that the intensity of CrossFit may not be appropriate for everyone, especially considering that form is imperative when it comes to safety. “The thing we’ve seen with a lot of these workouts is you go flat-out as fast as you can, but then your form falls apart. You really need to be technically correct with a lot of these exercises or else you may get hurt,” says Porcari. Working with a certified personal trainer can not only help you to learn proper form, but he or she can also provide you with modifications to exercises that best suits your fitness capabilities, goals, and needs.
So if you’re planning to hit the box—CrossFit speak for their gyms—be sure to be mindful of form and focus first on mastering movements before performing workouts for time in order to ensure that your workout experience is both a safe and effective one—one which will help you to build and maintain a fit body.
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