Women, You've Been Exercising Too Hard, Says Study

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By: , SparkPeople Blogger
7/7/2010 7:00 AM   :  75 comments   :  51,129 Views

When someone asks me whether X, Y or Z counts as "exercise" or "cardio," my first response is always, "Well, what does your heart rate tell you?"

Measuring your heart rate is an important action for every exerciser. It lets you know how hard you're working during cardio, as different heart-rate levels have different training and fitness benefits. It tells you whether your activity session really "counts" (too low of a heart rate doesn't provide the benefits of aerobic fitness, and heart rates that are too high can be problematic). It can even provide clues that you're overtraining or coming down with an illness (high heart rates at lower exertion levels can are a sign that something's not right).

There is a variety of ways to calculate your individual target heart rate for exercise. Getting tested at a university lab or medical center by way of a graded maximal exercise test is the gold standard, but since that's not accessible, safe or feasible for everyone, some standard formulas were created based on the available research at the time. However, a new study from Northwestern Medicine in Chicago says that the formulas experts have used for years to help people calculate their heart rates for exercise aren't accurate at all for women.

Researchers collected maximum heart rate date from approximately 5,500 healthy women between the ages of 35 and 93 during maximal graded exercise treadmill tests (the gold standard), and then followed the women for 16 years. While they were initially searching for a link between abnormal heart responses and heart attack risk, the researchers were able to use the data collected to generate a new formula for maximum heart rate in women.

It's no secret that a lot of the health, fitness and wellness information we have is based on research and that for a very long time, women were not even studied at all. We didn't know back then that you couldn't just apply the same results found in men to women, just as we didn't realize that different ages and racial and ethnic backgrounds could also alter the outcomes of research studies. The standard max heart rate formula (220 minus age) was based on generalizations from 10 studies done several years ago on men alone, but it's been applied to men and women of all ages for decades now.

I've always been somewhat skeptical of that generalized formula, since it assumes one's maximal heart rate declines with age and that one should work out less intensely with each year they celebrate another birthday. That doesn't make a lot of sense if you think about, and surely can't be the case for everyone. SparkPeople has always advocated the use of another formula that is touted among fitness professionals as being more accurate (although slightly more complex): the Karvonen heart rate formula. It's more accurate because it considers a person's resting heart rate (a good indicator of fitness level) when coming up with heart rate guidelines for exercise. The new formula developed by the Chicago researchers who conducted this study says that a women's max heart rate should be calculated as 206 minus 88% of a woman's age. That's not as easy to remember, but its results are said to be more accurate for women, according to these researchers. It also results in lower heart rate ranges for aerobic fitness benefits.

I wanted to conduct my own little experiment to see how the outcomes of all three of these heart rate formulas pan out, using myself (an almost 28-year-old) as the example.

  • Standard formula: MHR = 220-age = 220-28 = 192
    55%-85% target heart rate range = 106 – 163 beats per minute (bpm)
  • Karvonen formula: uses standard MHR formula (above), but also factors in resting heart rate
    55%-85% target heart rate range = 133 – 172 bpm
  • New women's formula: MHR = 206- (age *.88) = 206-25 = 181
    55%-85% target heart rate range = 100 – 154 bpm

While these ranges don't seem strikingly different at a glance, there is a large range between the lowest (100 bpm) and highest (175 bpm) numbers. Just a few beats per minute can feel like a major difference when you're exercising. You can see a large difference between my Karvonen results and the new formula, but keep in mind that the former also factors in my own resting heart rate level (about 60 bmp), so not every 28-year-old would have the same results.

Dr. Martha Gulati who led the study told the New York Times that, "There’s nothing wrong with achieving a higher heart rate with exercise, and if you can maintain that, it’s fine." She also said that some women might have had a hard time reaching the heart rates recommended by the standard formula—but perhaps they didn't need to! In my opinion, that makes exercise and achieving its benefits a little less daunting for beginners or people with physical challenges—no more frustration at working hard but not seeing your heart rate reach the recommended levels you were seeking based on a misapplied formula.

What this Means for You
Keep in mind that this is a single study, and while some are hailing it as the most accurate study to date of women's heart rates during exercise, I have not yet seen any official changes in recommendations from exercise organizations such as The American College of Sports Medicine. This study may change what fitness professionals recommend, but it's too early to jump to that conclusion yet. We'll wait and see if other exercise organizations change their recommendations before we alter our own.

What is interesting is that lower heart rates do seem to contribute to aerobic fitness benefits in women, if this study is any indication. That coincides with a growing body of research that says even low-intensity activity provides a multitude of health and fitness benefits, even if it doesn't push your heart rate sky high.

Just as the findings of one study on men can't always apply to women, the findings of this study may or may not apply to you. Put simply, these are averages based on the women in this study and they may not work for everyone. Heart rate formulas, calorie calculations, BMI—whatever the recommended levels are, they are still generalizations for the average population. We are all individuals and some of us may not fit into the standard. We are all an experiment of one, as Coach Nancy often says.

I've had many students in my classes ask me about their target heart rate ranges, some saying that they use these formulas but the results seem either too high or too low for them. My answer: You're probably right! I like to use a combo of formulas and RPE (Rate of Perceived Exertion) to help people achieve the proper exercise intensity, and that is exactly what the American Council on Exercise recommends as well. If your heart rate says you're working at 90% of your max (super intense!) but it feels like a walk in the park to you, then the formula probably isn't accurate—for you. Some people may have to tweak things here or there to find the right ranges for them. For women who have been trying your darndest to reach a specific heart rate level, but find it too tiring or impossible to get there, this newer formula, which results in lower heart rate ranges, might be a good one to try.

Personally, I'll stick with the Karvonen formula for now, but I won't discount low-intensity activity in my day as being useless. According to this formula at least, I'm working harder than I realized!

Do you measure your heart rate during exercise? What do you think about the results of this new study? Will it change how you exercise or how you calculate your own target heart rate?

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Comments

  • 25
    Really good article. The other day I was actually wondering how to calculate my target heart rate. Thanks for the info! - 7/7/2010   12:47:52 PM
  • 24
    I only track my heart rate when I have sensors on equipment I may be using. But I noticed the other day on the treadmill, that my heart rate was at 128, when my target HR was 145. I thought I was working hard, but I guess it's time to bump up my workout. anyway, this study is interesting and encouraging. - 7/7/2010   12:08:48 PM
  • 23
    This was an informative article, but I'm with DEBBEM AND 4URYOU... my body tells me when it is "really working." - 7/7/2010   11:58:55 AM
  • 22
    Interesting article. Then again, I don't track my HR during exercise any more. I've taken morning readings of BP, HR and FBS (fasting blood sugar) for decades because of lousy family history. When I weighed less and was more active, those numbers were lower. The opposite was also true. I don't need a specific number to tell me if I'm working out hard enough: hot + sweaty + breathing hard = work out. Plus I don't want to wear another gadget. Especially after having a cardiac ablation in May for sudden onset Paroxymal Atrial Fibrillation (no family history), I'll keep tracking my morning numbers and use those to track life-long progress. - 7/7/2010   10:54:29 AM
  • 21
    I monitor my heart rate with a chest monitor and I am SO relieved with the results of the new study. I am morbidly obese and I suffer from anxiety, so pushing my heart rate even to 130 makes me VERY uncomfortable. I always felt guilty that I was only getting up to 115, but now I am empowered! Thanks, Northwestern! - 7/7/2010   10:52:22 AM
  • STATS2332
    20
    I really enjoyed the article. I am one of those people who has always had difficulty hitting the appropriate heart rate to believe I am actually doing something. I am lucky that no matter how unfit I have let myself get I always have a low resting heart rate and my recovery after exercise is always faster than most people. These other formulas do seem quite a bit lower. My body has always been more athletic than my brain ever wanted to be. - 7/7/2010   10:46:09 AM
  • 19
    I can tell by the way my body feels ( sweaty, that exercise high and so on ) if I am doing Cardio. Why make it so difficult for everybody with a formula ? - 7/7/2010   10:31:52 AM
  • 18
    I use my HRM when exercising, I do not pay too much attention to the low/max, even turned the bleeper off was so annoying, I just set myself a target number of calories to burn and go that way.

    I would also have to say that although this is a new study that has been published, they actually followed the women for 16 years so I would say that is pretty comprehensive.
    So NO jibbie, I would not say it was a joke.
    Others may have followed something for 30 years, does not always may it right, as was said that was always based on MEN and their heart rate etc. - 7/7/2010   10:26:30 AM
  • 17
    I still have problems with this formula, as it fails to adjust for those of us who are aging but in good shape. My sister is about to turn 61 and I'm 49. We both exercise regularly and the target heart rate that results from using any of these formulas is a joke - I end up with an upper limit of about 120 BPM and I exceed that walking up a moderate hill! I'm going to keep right on ignoring these calculations and doing what works for me. - 7/7/2010   10:24:30 AM
  • TRAILMTNGRANNY
    16
    Boy, this article and all the comments opened my eyes to the heart rate issue and working out to hard. I am 64 year old female that stresses over every little detail of BP and heart rate numbers. I have arterial fribulation and also need a knee replacement so no gym for me for awhile. I am watching (and cutting back)the calories and not going to worry about what and where the charts say you should be. Listen to your body! - 7/7/2010   10:19:02 AM
  • 15
    Jibbie49 - it's not "one study" changing everything. This is probably one of the first big studies looking at women and heart rate during exercise. From the blog:

    "The standard max heart rate formula (220 minus age) was based on generalizations from 10 studies done several years ago on men alone, but it's been applied to men and women of all ages for decades now."

    That says to me that the previous research was flawed because it was an all-male sample. Men and women are equals, but we're pretty different in a lot of ways!

    I never measure my heart rate during exercise. I guess I should, but I usually just go by the "talk test" and how hard the workout feels. I find the monitor on my stationary bike is very inaccurate, with my heart rate supposedly jumping from 60 to 175 in a few seconds. - 7/7/2010   10:13:05 AM
  • 14
    I tried all the different formulas and the Karvonen is the closest to what I've been using. My Polor HRM is set at (low) 125 - (high) 165.... The Karvonen sets my limits at (low 50%) 124 - (high 85%) 165.
    When I'm power walking my heart rate stays between 145 - 160...
    When I jog for only a Half mile my HR gets up to 165-173 most of the time...
    I too have to keep my HR up or I just don't feel like I've had a good workout... 145-155 is my comfort zone. - 7/7/2010   10:12:35 AM
  • 13
    I measure my heart rate when exercising, as well as RPE. I do 60 minutes straight of hard cardio, and my heart rate tends to end up higher than my target maximum for a good portion of it, but I sustain my pace and it doesn't feel like I'm working out too hard.
    This study is certainly interesting in that it actually takes women into account, but it only says "healthy women," and doesn't necessarily include women with really good cardiovascular health and/or endurance. I'm glad a study has been done specifically for women, but I think this should only be the beginning- we need more data than just one study. - 7/7/2010   10:11:12 AM
  • 12
    Interesting.
    I've found quite the opposite as I'm getting fit... my resting heart rate is quite low (61bpm), but it races when I run. However, my RPE has improved greatly over the last 6 months of running. My heartrate still goes higher than the recommended range, but I feel fine.
    I've also come to feel like I haven't had a good workout unless I have had that rate up high. Hmmm... - 7/7/2010   10:06:09 AM
  • 11
    I have to be honesty I really don't keep track of my HR. I do some RPE but usually just pay attn to how I'm feeling. If on a treadmill I will check in with the machine to keep an eye on things but I also know that these aren't always accurate. I've toyed with the idea of getting a HR Monitor for some time and part of me thinks it would be great to know what's going on but I've always defaulted that I just enjoy my workout and working as hard as I feel like. - 7/7/2010   10:05:18 AM
  • 10
    Are you joking? ONE study to change what others have been studying for the past 30 years? WOW, what about all the other things that are "wrong" then, if ONE study can change everything. - 7/7/2010   9:23:56 AM
  • RANGERRUNNER
    9
    I use RPE when I exercise. I think it gives me a better idea of how i'm doing. - 7/7/2010   9:04:03 AM
  • 8
    This was helpful. I do track my heart rate when I do cardo, either through the machines at the gym or my garmin watch. I found them to be consistent with each other. According to this new formula for women, my heart rate does get a little faster then it should. I noticed ever since I got my fancy new watch, I think I hold back if I watch my heart rate and it goes to high. Not sure if this is a good thing or not. - 7/7/2010   8:50:54 AM
  • 7
    Keeping a record of RPE, total target range time, average heart rate, maximum heart rate, distance run, and other factors (e.g. food and drink, if any, taken prior to run) helps me set goals and avoid trouble. For example: as we entered into summer, my statistics warned me that I was overheating. Now I run in the morning on the treadmill with the fan on high.

    As a 25 year old female with a resting heart rate between 58-60 bpm, my average cardio heart rate is usually about 161-165 bpm and my peak heart rate is about 171-175 bpm. So according to the new formula, I'm almost always out of my target heart range. Uh, yeah... not sure I buy that. I'm going to continue working out to a level I'm comfortable with rather than worrying about the recommendations of another newfangled study. - 7/7/2010   8:32:49 AM
  • NICOLEMC2
    6
    Last summer my hubby bought me a Mio motiva petit for my birthday. I love it. it tracks my heart rate and calories burned; specific to me. I was doing Weight Watchers and found it hard to believe the 'blanket' activity points. So, I track with my Mio, and low and behold I wasn't eating enough. Now that I track with SP I realized I should have been eating a whole lot more for the calories I burn.
    It also caluclates my resting heart rate: which is right now 72 (a little high I believe, but I'm working on it)
    I would be lost without my Mio!!! - 7/7/2010   8:28:13 AM
  • 5
    Interesting! I sort of like the lower heart rate. I've never had access to a heart rate monitor, but have tried checking my heart a time or two and after 30 minutes of a brisk walk or working on the treadmill my heart rate was below 70 - depressing, if one has to be well over 100 to be getting 'exercise.' My resting heart rate is around 60 - it was actually 37 in a doctor's office once. - 7/7/2010   8:16:46 AM
  • 4
    FINALLY! Something sensible.. I have been on beta blocker for years and when I joined a gym and hired a 'professional trainer' and began exercising my goal was to get my heart rate up.... Well, guess what.. on beta blockers you can't.. but NO ONE ever made t hat connection... However, my bp did go down, so I was able to cut my dose in half..
    After that,we moved to a new state, new gym, and new professional trainer who also happened to have his Bachelor's in Physical Fitness or whatever it is to become a 'coach/ gym teacher'... he trained me like I was a football player...
    And, again, the heart rate was an issue... keep going, pushing, harder faster... heart rate wouldn't go up...

    The outcome of 5 / 6 years of training 5 days a week under the 'supervision' of 'professional trainers'...
    I now have an enlarged heart and congestive heart failure...

    I literally trained my heart out..

    I found out from my cardiologist that I worked out too hard trying t o push past the effects of the medicine...

    So... Ladies, watch out.. IF you are on any kind of blood pressure medicine that regulates your heart in anyway.. be sure to not let this happen to you.

    I'm still angry about it and the fact that now I am very limited in what I can do.. certainly no more gym time for me.

    - 7/7/2010   8:13:01 AM
  • 3
    That was a very helpful blog!! We all need to be monitorin our hearts. At my age, I DO. When at the gym, using a machine that does not have the built in monitor, I check my heart rate till I am where I want to be, then do not adjust the machine futher. Still check in 10 minutes to be sure I am within correct limits. - 7/7/2010   8:06:31 AM
  • 2
    I only use my HRM for calorie burn. RPE all the way, baby! - 7/7/2010   7:48:14 AM

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