High intensity, short duration exercise programs are growing in popularity. Evidence shows that such exercise programs lead to significant improvements in cardiorespiratory fitness (aka aerobic fitness), body composition, muscular strength, and of course, health. Crossfit is a company that believes in this fitness principle and emphasizes programming focused on functional fitness. It has had much success and is continuing to grow in popularity. Unfortunately, there is no peer-reviewed research available on the effectiveness of Crossfit training. I am certain that anyone involved with Crossfit would happily provide anecdotal evidence that it has led to significant improvements in their fitness, health and quality of life. But for a program to be endorsed by professionals in the field, evidence is required.
As such, I was delighted to see a paper recently published in the Journal of Strength and Conditioning Research entitled “Crossfit-based high intensity power training improves maximal aerobic fitness and body composition” (doi: 10.1519/JSC.0b013e318289e59f); In Press). I was particularly delighted to see that they used cardiorespiratory fitness as an outcome since the program consists primarily of strength and power based exercises. The study was a 10 week intervention with a total of 23 males and 20 females. The average age of this sample was approximately 32 years. Participants completed a maximal treadmill exercise test to determine VO2max; a measure of cardiorespiratory fitness that is considered to be the gold standard. The second main outcome assessed in the study was body composition as measured by the Bod Pod (air-displacement plethysmography). Unfortunately, this is not considered to be a highly reliable or valid method for assessing changes in body composition. The researchers would have been better off taking measures such as waist circumference, flexed bicep circumference or skinfolds at specific sites. These would have been more accurate in describing changes over the 10 week training period. Nonetheless, significant improvements in VO2max, body fat% and lean mass (i.e. muscle mass) were found. Another significant shortcoming of the present study is the lack of a control or comparison group. We know that exercise leads to improvements in fitness and body composition, but does Crossfit training provide additional benefit over other forms of exercise? We can’t answer that question with this data. More importantly, given the unreliable measure of body composition, the only take away from this study is that Crossfit training may lead to significant improvements in VO2max. Just in case I’m starting to sound cynical, I would like to emphasize that cardiorespiratory fitness or VO2max is the strongest predictor of health and mortality, so this is a very important finding.
TAKE HOME MESSAGE: There is no doubt that exercise is good for you and that high intensity exercise is better. For those of you interested in improving your health and cardiorespiratory fitness, Crossfit may be a great option. It provides a social support system, motivating coaches and a positive environment for exercise; all things that will really help you adhere to a Healthy, Active Lifestyle Forever!
NOTE: High intensity requires that you have a certain baseline level of fitness, so be sure to ease yourself into such a program; this will minimize your risk for injury and make for a much more enjoyable experience.