A new study on CrossFit recently published by the American Council on Exercise concludes what many devotees have known for years.
ACE enlisted researchers from the University of Wisconsin, LaCrosse, to gauge the energy expenditure and relative intensity of a pair of popular CrossFit workouts.
The results: "CrossFit works," concluded the researchers.
The scientists tested 15 fit men and women ages 20 to 47 on two of the more popular WODs: The "Donkey Kong," a blaster of burpees, box jumps and kettlebell swings, and "Fran," which focuses on thrusters – a hybrid front squat with a barbell that transitions into a push press – along with assisted pullups.
Part 2 of CrossFit week:
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"You look at the intensity of CrossFit and it's off the charts," says lead researcher John P. Porcari, head of the university's Clinical Exercise Physiology program. While workouts were completed in less than 12 minutes, subjects still burned an average of 115.8 calories while nearly maxing out VO2 measurements and spiking blood lactate to more than three times the average.
"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," Porcari says. "And it's nice to be competitive with other CrossFitters, but at what point are you pushing yourself outside the realm of safety?"
The findings are certainly no surprise to Dave Werner.
"For those two WODs, 80 percent of VO2 Max sounds about right," Werner says. "That means those guys are pushing nearly as a hard as they can."
Profiled in the Military Times issues on newwstands the week of Dec. 9, the former Navy SEAL opened the very first CrossFit affiliate on the planet more than a decade ago. These days, with a stable of nine full-time coaches and more than 500 regular CrossFitters calling it their workout home, Level 4 CrossFit Seattle is one of the largest "boxes" in the country.
The huge jump in blood lactate researchers observed jibes with what Werner has seen in coaching over the years.
"Blood lactate is a byproduct of anaerobic metabolism, where you don't have enough oxygen in your system to keep up and so it' s another way of quantifying how hard are they pushing themselves."
Lactate is reabsorbed by the body and actually used as fuel, Werner says.
"How quickly depends on training. Our bodies adapt to this, when trained to do it. That training is painful. It hurts. Because you're in the anaerobic limits and pushing up these metabolic byproducts. The more you do that to yourself, the better your body gets at dealing with it.," he says.
"This is getting into the physiology of why this CrossFit stuff works. Basically, we get better at recovering on the fly, which is an extremely good skill for operators. You sprint for cover and your body very quickly recovers from that challenge and you're ready to do it again. You jump up – throw, push, pull, carry, fight – and then you get a quick breather and then you're ready to go. In terms of combat-type challenges, this is good stuff."
While Werner says he isn't surprised at the calorie burn rates recorded, he's not much of fan of that particular measure.
"I've learned to not look at calorie rates at all. The normal reaction in general when it comes to calories burned is to say, 'Wow, that's surprisingly low.'"
When he's measured calorie burn rates on rowing machines, "you see someone bust their ass for five minutes and then fall off the machine and just kind of twitch, and they've burned 300 calories. Less than a Cinnabon. That's pretty discouraging," he says.
But what isn't measured – or captured in this study – is how much is burned in the following hours and even days after the workout ends. It's what some call the "metabolic afterburn."
"There's a lot of argument among experts and non-experts over the mechanism of how this works," Werner says. He just knows that it does.
"My sense is that we're putting our body under stress and kicking some adaptive mechanisms into gear. Maybe it's testosterone levels, growth hormone levels, but what I know is that people get leaner and more muscular when they do this stuff."
Jon R. Anderson is a staff writer for OFFduty. Contact him at jona@militarytimes.com.
