An Analysis of the Hormonal Response to CrossFit
I love a good study that takes a shot at CrossFit without ever mentioning its name. So is the case with today’s study from the Journal of Strength and Conditioning Research. Researchers wanted to measure the hormonal response of the human body to “extreme” conditioning programs. So they took the CrossFit workout “Linda,” swapped cleans for back squats, and put nine trained men and nine trained women to the task.
Researchers were interested in cortisol and lactate response. Cortisol is a stress hormone. Exercise always increases cortisol levels, but you want to keep cortisol levels as low as possible during daily life for optimal recovery. Lactate response is the production of lactic acid by the muscles. This phenomenon has been studied ad nauseam over the past twenty years, and unfortunately, we still don’t know very much about it. We once thought lactic acid was a waste product of exercise. Then we discovered that you can actually make energy from lactic acid. Oops. We also once thought it caused muscle soreness. Now we’re unsure if it has anything to do with soreness.
The eighteen participants completed a modified “Linda” workout, and then their hormone levels were compared to baseline. Their post-exercise lactate levels were in line with other studies on “high intensity, short-rest” protocols. These lactate levels are somewhat higher than traditional strength training that uses longer rest intervals of 2-3 minutes - with one notable exception: a 10RM back squat. Apparently no length of rest interval can save you from the burn of a 10RM squat. I agree.
Cortisol levels rose after the workout was completed, as they would with any type of strenuous workout. And even an hour after the workout was over, cortisol levels were still higher than baseline. But after 24 hours cortisol levels had not just returned to normal - they actually dropped just a tiny bit. The researchers pointed out that this means the workout “does not pose an immediate recovery problem in terms of circulating hormone concentrations.”
What do we learn from this study? Eighteen people performed a CrossFit workout. They didn’t die, get injured, or require immediate hospitalization. They produced a lot of lactic acid, but no more than if they had worked up to a heavy 10RM squat. The rise in cortisol after the workout was in line with other exercise programs, and participants actually enjoyed a small decline in cortisol the next day. Many people claim CrossFit results in chronic overtraining. This study shows that if someone does suffer those ailments under CrossFit training, the cause is likely bad coaching or too much training frequency, and not likely the inherent nature of the program itself.
1. Tunde Szivak, et. al. Adrenal Cortical Responses to High-Intensity, Short Rest Resistance Exercise in Men and Women. Journal of Strength & Conditioning Research: March 2013. Vol 27. Issue 3. p748–760. doi: 10.1519/JSC.0b013e318259e009
Photo courtesy of Miguel Tapia Images.