Proof that those short yet intense WODs are totally worth sweating through

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With nearly 10 million CrossFitters worldwide-60 percent of whom are women-

many people can attest firsthand to the benefits of this high-intensity style workout program, yet little scientific research has looked at how effective it is. So the American Council on Exercise® (ACE) enlisted the research team at the University of Wisconsin-LaCrosse to examine two workouts of the day (WODs) to see just how these short yet challenging sessions really stack up.

Sixteen men and women completed two different WODs-Donkey Kong and Fran-each preceded by a warm-up and followed by a cool-down. Donkey Kong consists of three rounds of burpees, kettlebell swings, and box jumps, with stair-climbing between exercises. Repetitions decrease each round, starting with 21 reps the first round, 15 the second, and nine the third. Fran-one of the most popular WODs in the CrossFit community-consists of just two exercises, thrusters and assisted pull-ups, and is performed in the same sequence as Donkey Kong. The goal of both is to complete the workout in the shortest amount of time possible.

Researchers of the CrossFit study discovered that the caloric expenditure for both WODs averaged 12.3 calories per minute for females. [Click to tweet this stat!] 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-which affected the averages for the total number of calories burned during each workout. The women completed Donkey Kong in an average time of 9:08, burning an average of 117.2 calories for the workout, and worked off 63.9 calories in 5:52 minutes for Fran.

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. This falls near the top of the fitness industry guidelines that suggest maintaining a training range of 64 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 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.

While this time-efficient and effective approach to exercise has its benefits, lead researcher John Pocari, Ph.D., cautions that the intensity of CrossFit may not be appropriate for everyone, especially considering that form is key 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're going to get hurt," he says.

So if you're planning to hit the box, stay mindful of form and focus first on mastering movements before performing workouts for time in order to ensure that your workout experience is both safe and effective-one that will help you build and maintain a fit body.