If you’ve ever spent any time around CrossFitters, you’ve probably realized two things pretty quickly: They love talking about CrossFit, and they love talking about how hard their CrossFit workouts are.
But as any dedicated gym rat knows (and this isn’t exclusive to CrossFit, of course), too many tough workouts in a row can leave your body feeling worn out—so much so, in fact, that you might even get the achy feeling you get before you’re about to get sick.
And as a new study shows, as few as two consecutive CrossFit-style workouts can actually suppress your immune system.
In the study, which was published in the journal Frontiers in Physiology, Brazilian researchers put nine participants through two workouts exactly 24 hours apart. Each workout had three components: strength training, gymnastics, and metabolic conditioning. (Important to note: CrossFit, Inc., did not sponsor the study; the study was not conducted in a licensed CrossFit gym; the study was not conducted by a CrossFit coach; nor was the programming designed by CrossFit.)
The participants averaged about 28 years old and 173 lbs with around 13.5% body fat. All of them had participated in CrossFit for at least six months, and had done strength and cardio training prior to the experiment. They skipped caffeine and booze during the experiment, too.
To test power output before and after the workouts, the participants also did a set of standard barbell back squats (5×5 at 50% of 1RM)—before, immediately after, and 24 hours after each workout—while they were hooked up to a device that measured the athletes’ power output during each lift.
The workouts look pretty tough—WOD 1 was apparently a little worse than WOD 2. Although each one is fairly typical of a CrossFit-style workout, CrossFit gyms typically do not program workouts so similar to each other back-to-back.
An in-depth look:
5 reps x 1 snatch at 80% of one-rep max (1RM) from knee-height blocks; rest 2–5 mins
3 sets x 5 touch-and-go snatches at 75% of five-rep max (5RM); rest 90 seconds between sets.
3 sets of 60-second weighted plank hold at maximum weight; rest 90 seconds between sets.
As many rounds as possible (AMRAP) for 10 minutes of:
15 snatches (34kg / 75 lbs)
5 sets x 1 clean and jerk at 80% of 1RM from blocks; rest 2-5 mins
3 sets x 5 touch-and-go cleans at 70% of 5 RM; rest 2-5 mins between sets
3 sets x 10 strict handstand pushup as fast as possible; rest 2 mins between sets
12-minute AMRAP of:
250m row on a rowing machine
25 “target” burpees (jumping to a target 6” above an athlete’s reach)
So What’s the Conclusion?
When the chalk dust finally settled, the researchers found that the participants’ immune systems had been suppressed after the second consecutive workout, even though they were lifting with the same amount of power. In other words, even though the participants’ performance didn’t decline, their immune systems did, according to key markers of immunosuppression in blood samples taken before and after the workouts.
“While we observed no negative effect on muscular power, it is still recommended that caution be exercised due to the suppressive effect two consecutive days of [CrossFit-based training] had on the immune system,” the researchers wrote.
Bottom line: Even though they were probably feeling fine and had experience navigating tough WODs, the athletes’ bodies were sending signals that they needed a rest.
The study was quite small, so it is difficult to draw too many broad conclusions from it, and (as always) plenty of questions still remain: Can athletes ever adjust to consecutive workouts of this difficulty—and if so, how long does it take? Will such workouts always impact an athlete’s immune system? And is this kind of immune suppression typical of CrossFit training, or does it also happen with endurance-specific or sport-specific work? The researchers admit that more research is needed.
Until then? “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,” wrote lead study author Ramires Tibana, a CrossFitter and Ph.D. student in biology at the Catholic University of Brazil.