Take a Day Off Between CrossFit Workouts, Study Says

By Jennifer Ouellette on at

Yeah, we know, your CrossFit gym has completely changed your life, you’ve never looked/felt better, and all other exercise programs pale in comparison. But you may want to ease off the intensive workouts now and then. All that over-exertion can actually impair your immune system, according to a new study just published in Frontiers in Physiology.

CrossFit, for the uninitiated, is a gruelling exercise program combining high-intensity cardio workouts with strength training, organised into circuits. The idea is to complete as many reps as possible in the allotted time, with little to no recovery time, and to vary the workouts constantly so your muscles don’t become too accustomed to any particular exercise.

It’s attracted a reasonable, extremely vocal and enthusiastic — and sometimes annoying — fan base since its introduction in 2000. Even Game of Thrones’s Jon Snow (and world’s worst dinner guest) is a confessed fan: “The high intensity interval training keeps me in shape for fighting wildlings, while the increased muscle mass helps me defend the seven kingdoms against 55-foot giants.”

But there’s a dark side to CrossFit. Too much exercise can be just as harmful to your health as too little. That hardcore culture of “deplete-endure-repeat” can lead to a rare condition known as Rhabdomyolsis (“rhabdo” for short). Basically, extreme exertion can cause muscle cells to explode, leaching proteins into the bloodstream — a place they really shouldn’t be. The kidneys have to work overtime to remove those proteins, and can become badly damaged.

Even if your kidneys recover, your muscles might not ever be the same, because the damaged muscle tissue has been replaced by fatty scar tissue. Do all the military pushups you want, your triceps will still be flabby.

Take a Day Off Between CrossFit Workouts, Study Says

Lead author Ramires Tibana doing a CrossFit workout. (Image: Ramires Tibana)

The good news is that relatively few CrossFit enthusiasts train hard enough to develop rhabdo. But a team of Brazilian researchers has identified another health risk of over-training: a weakened immune system.

The scientists recruited a group of experienced CrossFit enthusiasts to perform two consecutive days of intense workouts, finishing in the fastest time possible. Afterward, they assessed the participants’ muscle power, and levels of metabolic markers and anti-inflammatory proteins produced by white blood cells.

They found that too many consecutive CrossFit workouts, with no rest periods, can significantly reduce the number of anti-inflammatory proteins, resulting in a suppressed immune system. On the plus side, the workouts didn’t appear to have much of an adverse effect on overall muscle power.

What do these findings mean for your CrossFit habit?

“For non-athlete subjects who want to improve their health and quality of life through CrossFit training, we recommend that they decrease their training volume after two consecutive days of high-intensity training to prevent possible immunosuppression,” lead author Ramires Tibana of the Catholic University of Brasilia said in a statement. “A rest day is important for recovery for subsequent training sessions.”

So put down that kettle bell and give yourself a break from your Crossfit regime this weekend. Your body will thank you. And you can hit the gym with renewed gusto the day after. [Frontiers in Physiology]