This topic makes my blood boil! I’ll try and keep my ranting to a minimum and focus on the facts.
– In 1985 the American Congress of Obstetricians and Gynecologists (ACOG) indicated that maximum heart rate during pregnancy should not exceed 140 bpm.
– In 1994 ACOG removed the heart rate guideline…”there are
no data in humans to indicate that pregnant women should limit exercise intensity and lower target heart rate because of adverse effects.’’
– In 2002 (and reaffirmed again in 2009) ACOG stated “in the absence of either medical or obstetric complications, 30 minutes or more of moderate exercise a day on most, if not all, days of the week is recommended for pregnant women.”
Heart rate hasn’t been part of the recommendations for quite some time now and yet most doctors still throw out the old keep your HR under 140 bpm nonsense. And it makes me want to scream.
In a nutshell, ACOG states that because of the variability in a woman’s heart rate during exercise throughout pregnancy, target heart rates are an unreliable measure of intensity (source – this is a great book, by the way).
So why do doctors still give outdated advice? To cover their asses, in my opinion. Can’t say I blame them either (in a small way). Patients lie. How many times have you lied to your dentist about flossing every day? I’m sure newly pregnant women often inflate the truth about their current exercise level (or lack of) to their doctors.
I think pregnancy is a wake-up call for some women to start exercising. In this population, heart rate guidelines may be the way to go (as opposed to The Borg Scale of Perceived Exertion) and maybe that is why doctors are still using this guidance. It took me a few years after I started running to really understand what my body could handle in terms of pace and exertion.
But to tell a runner (or any other avid exerciser) to keep their heart rate under 140 bpm is ridiculous. The first time I encountered such nonsense was my reproductive endocrinologist. Although his guidelines were far more strict – 120 bpm. I told him that was a brisk walk and those guidelines were outdated. He told me those were “his guidelines”. I left the office frustrated and that prompted me to do my own research (note: I never followed any heart rate guideline, just the Borg scale).
Luckily I was released to my OB at 8 weeks and she supports my running as long as I listen to my body. I have no issues with that recommendation – I’ve been doing that for many years and it has served me well so far.
Matt repeatedly urged me to do a run with a HR monitor just to see. At the end of May I set out for an 8-miler, HR monitor strapped to my chest, and didn’t look at pace on my Garmin. The result? An average pace of 9:15 and my heart rate never went above 144 bpm.
I was astonished! I never train with a HR monitor and I thought for sure my heart rate would be sky high. After doing all that research the common theme was frustration at how slow your pace had to be in order to stay within 140 bpm.
*I have to add that this was a one-time experiment (on a cool day) and I need to do it again (ideally monthly) in order to accurately see what my range is. I would imagine my heart rate to be higher now at the same pace with (sadly) some loss of fitness.
I would love to hear your thoughts and experiences!