Listen up bootcampers: Intense exercise can cause low blood counts. Yes, yes, it’s true–you can overdo it. Do not take this news lightly, especially you youngsters; you are not as invincible as you think.

A recent study looked at incoming recruits for an elite combat unit in the Israeli Defense Forces and found that many (18%) came in anemic–an unusual occurrence for healthy young men. But more alarming was that the numbers tripled to over 50% following six weeks of intense military training. Whoa! The anemia was the iron deficiency-type and is known as sports anemia. Very strange, indeed.

Scientists are unsure of the exact physiological cause of the anemia, but believe that intense exercise is at fault, particularly since 18% came into the training with the condition. Because young men hoping to join the elite forces prepare themselves through intense workouts to begin with, it’s not a total surprise that so many came in iron deficient. But to what degree the recruits developed anemia is startling, and goes to show that too much of a good thing does exist.

I talk about overtraining syndrome in my book, The Six Keys to Optimal Health. It is a real phenomenon, and I see the effects on clients in my West Hollywood/Beverly Hills sports chiropractic practice. No matter how much I preach moderation, there always will be people who deny the data and overdo it anyway. It’s really a shame, because if these same people would just understand that they are actually hampering their growth and progress, they might cool it. I have one client, a female in her forties, who works out every day! That’s too much. And guess what? She’s always injured, hurting and/or tired. She looks, forgive me for saying so, like she’s been run over by a truck most of the time I see her. I tell her to slow down, but she tells me it makes her feel good. Yeah, right.

So here’s the deal: If you are not training for a marathon, triathlon, UFC title bout or any other athletic event, three to four days of moderate to intense exercise is sufficient (and efficient, by the way). Anything more than that and you are risking burnout.

If you are training for an event or special forces–military training units and personnel pay close attention here–too much intensity will put the troops at risk. This is a true military public health issue and needs to be monitored and addressed.