The latest CrossFit research was conducted at the University of Wisconsin, LaCrosse. The American Council on Exercise (ACE), a non-profit organization, sponsored the study. Its findings were published in the November edition of ACE’s online monthly publication. The study looked at the metabolic effects of two official Crossfit workouts.
The study utilized 16 healthy male and female volunteers age 20-47. Subjects completed two official CrossFit workouts—Donkey Kong and Fran. Donkey Kong consists of 3 rounds of burpees, kettleball swings, and box jumps. For each exercise, there are 21, 15, then 9 reps per round. The second workout, Fran, consists of thrusters and assisted pullups. Thrusters are explosive barbell front squats flowing directly into overhead push presses. For Fran, there are again three rounds using the same rep scheme. For both workouts the goal is to complete all reps in the shortest amount of time.
Prior to the CrossFit workouts, investigators used treadmill testing to measure VO2 max, heart rates, and rating of perceived effort (RPE) for each subject. During the CrossFit workouts, the participants’ heart rates were recorded every minute and RPE was assessed after each round. VO2 max was estimated using statistical analysis based on the treadmill results because the testing gear was deemed too cumbersome to wear while doing CrossFit.
During the workouts, Vo2 averaged 80% of max, at the upper range of commonly accepted recommendations (40-85%) to improve cardiovascular fitness.
Heart rates averaged 90% of maximum, also at the upper end of the conventional training range (64-94%).
Male subjects burned 20.5 calories per minute and females burned 12.3 per minute.
Researchers concluded that “CrossFit works.”
Expected improvements in aerobic fitness from CrossFit are greater than those of traditional aerobic training. This is seen in other forms of high intensity exercise, likely owing to the effect of training well above anaerobic thresholds. Since the workouts were completed in less than 12 minutes, it is expected that comparable or superior results can be attained with less time spent compared to traditional steady-state cardio.
Using the data from this study, we can get a better sense of how intense CrossFit workouts are by comparing the caloric expenditure to other activities. If the subjects had maintained the same intensity for a full 30 minutes, theoretically males would have torched through 615 calories and females would have fried 369 calories. Using data from Harvard Medical School, these numbers exceed all other common gym activities including step aerobics, rowing machines, ellipticals, and vigorous weightlifting. They also exceed almost all competitive sports including football, basketball, and water polo. Only running and bicycling exceedingly fast burns more calories per 30 minutes. Of course, we don’t know if subjects would continue to burn through calories at the same rate if these CrossFit workouts were extended to a full 30 minutes.
The bottom line is that CrossFit workouts are brutally intense and very likely to improve cardiovascular fitness. One author noted, “you look at the intensity of CrossFit and it’s off the charts.” The researchers noted that the workouts “seemed very difficult” for all subjects regardless of how fit they were or how long they took.
Of note, this report is unique and valuable but it is not a clinical trial so much as a collection of data points gathered during isolated workouts. The long term efficacy of these workouts cannot be determined by this study alone. Further studies will be be needed to make direct comparisons to other techniques and to answer contentious questions about safety. In the least, however, this study shows that CrossFit is an extremely effective way to push people right up to the limits of recommended exercise demands.