Heart Rate Guidelines

Hi Austin and Jordan,

I’m a bit confused about what heart rate boundaries you would consider appropriate for moderate and vigorous intensity conditioning, as applied to the “150 to 300 minutes per week of moderate-intensity aerobic physical activity, or 75 to 150 minutes per week of vigorous-intensity aerobic physical activity​” recommendation. I had previously been using brisk walking (3.5-3.8mph) as moderate-intensity conditioning, based on the 4.3 MET value listed in the Compendium of Physical Activities for walking at 3.5 mph. However, my heart rate during these brisk walks is generally in the 50-60% range, aside from brief periods where I’m going up a significant incline. In your recent podcast series on cardio, I believe you were referring to moderate-intensity conditioning as being toward the high end of Zone 2 (using the five zone system), which would suggest a target heart rate significantly higher than what I reach in a 4-5 MET activity. My conditioning level is mediocre at best, so I’m surprised that I seem to need much more intense cardio than what the general recommendations indicate.

Am I misunderstanding your recommendations? I was having trouble keeping up with the relationships between heart rate, RPE, METs, zones, and light/moderate/vigorous conditioning that you drew in the podcast, so I’m hoping that you can clarify. I’m most interested in how to translate the physical activity guidelines use of moderate and vigorous intensity into heart rate ranges, since the 3-6 and 6+ MET ranges seem to be way off.

Thanks!

Shem,

I don’t think you’re misunderstanding the recommendations, but rather corroborating the issues we pointed out regarding using METs to determine intensity. For many, brisk walking at the pace you mentioned will be sufficient for moderate intensity conditioning. For others, it won’t. If your HR is < 60% Max during conditioning, I’d call that zone 1 in the 5 zone model.

To your question regarding HR, RPE, METs, and zones, I think the 5-zone model works best for this:

  1. Zone 1

  2. < 3 METs

  3. <RPE 5-6

  4. HR 60-75% max

  • Zone 2
  1. 3-6 METs
  2. RPE 5-6
  3. HR 75-83% max
  • Zone 3
  1. ~6-9 METs
  2. RPE 7-8
  3. HR 83-90% max
  • Zone 4
  1. ~9-12 METs
  2. RPE 8-9
  3. HR 90-94% max
  • Zone 5
  1. 12 METs

  2. RPE 9+
  3. HR 95-100% HR max

The MET and RPE data for z4 and 5 are fuzzy, admittedly.

Thank you for the clarification. Reviewing my recent training logs in light of your zone breakdowns, it seems like the conditioning recommendations are much more difficult than I thought. I just did 10 minutes of Zone 2 cardio on an air bike (along with about 5 minutes of time that my heart rate was too low to hit Zone 2), and that was pretty tiring. That’s a completely different universe than the activities that the Compendium of Physical Activities would classify as moderate intensity.

For many, brisk walking at the pace you mentioned will be sufficient for moderate intensity conditioning.

It’s hard for me to comprehend that this is true for a reasonably healthy adult. Even when I was obese and doing zero conditioning, brisk walking wouldn’t have gotten my heart rate above 75%. My conditioning isn’t great now, and it was certainly worse then, so I don’t think I’m an outlier who needs much more intense exercise than normal.

Are the physical activity guidelines actually trying to say that we need 2.5 - 5 hours of 75-83% Max HR activity to meet the minimum standard? From my perspective, this is essentially doubling the conditioning recommendations that I had previously understood, since I need to do activities that are more like 7-8 METs to hit the 75% HR threshold. Honestly, this is quite discouraging, since I thought I had worked up to about 70-80% of the conditioning recommendation, and it turns out that I’m basically at zero, since I’m mostly doing activities in the 3-6 MET range.

What would be your recommendation for conditioning that I can do at home without a bunch of equipment? Am I basically just limited to running, since even walking as fast as I can with with a weighted vest doesn’t qualify as moderate intensity? I’m not thrilled about the idea of running for hours every week, but maybe that’s what I need to do.

I think if you haven’t tested your max HR or functional threshold HR (via a field test discussed in our podcast), it’s difficult to use the HR zones without a lot of squish.

The physical activity guidelines do not reference any HR cut points for exercise, but rather recommend some combination of 150 to 300 min moderate intensity and/or 75 to 150 minutes of vigorous intensity conditioning to accumulate at least 500 to 1000 MET-minutes of exercise per week.

I do not think that RPE 7-8 is likely to generate the HR targets for a sustained piece of conditioning. From a coaching perspective, I would be looking at auditing what your max HR actually is (or testing it via a field test) and doing the same with RPE for a short and a long piece of conditioning.

I think brisk walking with or without a vest, particularly through undulating terrain, is likely to get you into z2 as described. I think faster walking or jogging is likely to get you into z3, whereas running is likely necessary for z4 and 5.

Interesting; I thought the estimated max heart rate would be close enough for my purposes. My predicted max heart rate is around 185, I’ve recorded a heart rate in the low 170s several times in training, so I don’t think the estimate would be too far off. I’ll try testing my actual max heart rate and see how close I get to the predicted value.

However, it doesn’t seem to change the picture all that much for practical purposes. Even if we take the most extreme position and assume my actual max HR is only 172 instead of 185, I still need to hit an HR of 129 to be in Z2. Looking back at a recent session where I walked with a 15lb vest for a half hour at an average of 3.8 mph, my heart rate was in Z2 for about 3-4 minutes (as opposed to one minute if we calculate Z2 based on a max HR of 185). My average HR was 117 bpm.The walk wasn’t over hard terrain, but there were a few hills. Do you think that represents ~30 minutes of moderate intensity cardio (based on the activity of brisk walking) or only 1-4 minutes (based on HR targets)?

The field test for a functional threshold HR is a bit different than a max heart rate. I would predict some differences to be sure, but perhaps no meaningful ones.

I’m not sure what else to say to you other than yes, your HR needs to be a bit higher for z2 if it was < 125 or so before. If you’re not getting close to that, the mode of training needs to be harder. That doesn’t mean z1 stuff isn’t helpful, but I wouldn’t do all of my conditioning there. It does probably count as moderate intensity cardio, though that’s a label that doesn’t really mean anything. What you’re looking for from your training is the biggest improvement in your cardiorespiratory fitness. I don’t think spending the majority of your time in z1 is likely to do that.

I’m mainly trying to reconcile your previous recommendation to follow the physical activity guidelines with the HR-based recommendations that you’re making now. I can think of three main possibilities: 1. You’re consciously changing your recommendation and raising your recommended intensity thresholds in light of new evidence or perspectives.
2. You were always intending your recommended conditioning intensity to be higher, and you’re clarifying because the physical activity guidelines didn’t adequately capture that.
3. You are not changing your recommendations at all, and your HR-based recommendations are intended to match up with the physical activity guidelines. If option 1 or 2 is correct, I don’t know how to reconcile this:

I think brisk walking with or without a vest, particularly through undulating terrain, is likely to get you into z2 as described. I think faster walking or jogging is likely to get you into z3

with this:

your HR needs to be a bit higher for z2 if it was < 125 or so before

I did a quick walk last night as a test. For 15 minutes, I walked at about 4.1 mph, which is as fast as my walking gets. It’s fast enough that I was getting some weird soreness due to alterations in my gait to keep up the pace. If that doesn’t qualify as fast walking, I don’t know what does. My average heart rate was 116, which is between 63% and 68% of my max HR (between 172 and 185). Even with the lowest possible max HR estimate, I spent a maximum of about 30 seconds in Z2. What’s the difference between the brisk/fast walking that you’re recommending as Z2/Z3 cardio and the Z0/Z1 walking that I’m doing?

If option 3 is correct, I don’t really know what to do. Either I have significant error in measuring my heart rate (unlikely, given that multiple measurement methods are putting me in the same ballpark HR) or I’m a fairly extreme outlier for some reason.

They are the same as they were, as the HR-based rec’s match up with the guidelines.

I do believe that for most people, walking briskly/quickly with load is likely to generate a heart rate consistent with z2. The MET compendium predicts the activity would cost about 6-8 mets unless the pace is quicker, load is heavier, or grade is steeper. If your HR as an individual does not respond in the predicted way and it is accurately being measured, the intensity of the exercise should be raised.

For reference, walking at the pace you mentioned (~3.5 MPH) on level ground with no pack clocks in with a predicted met cost of ~ 4.3. I would not predict that would get some people into z2. Adding pace, grade, and/or load…it’s probable. If not, you’ll have to do something else, assuming no error in measurement or reason that your HR does not respond predictably to exercise (e.g. medicine). I don’t know what ways you’re using to measure your heart rate, but this does present some concern. The other thing to note here is that I would predict your HR to go up with a longer effort than 15-minutes.

In any case, I would encourage you to look at this as an opportunity for additional gainzZz. IF you need to generate a higher heart rate, you’ll need to go faster, heavier, steeper, etc. to do so. Walking does limit how much we can do if it’s the sole modality available. It would be cool to have other options, for sure.

They are the same as they were, as the HR-based rec’s match up with the guidelines.

Would you be able to point me to evidence that the MET-based and HR-based recommendations line up? They don’t line up at all for me, and my cursory search found some research that suggests the same is true for others.

In a 2016 study by Sarah E Stahl, Hyun-Sung An, Danae M Dinkel, John M Noble, Jung-Min Lee, entitled “How accurate are the wrist-based heart rate monitors during walking and running activities? Are they accurate enough?​”, the researchers recorded the heart rates of recreational runners (3x/week training, aged 19-45) at various paces. At 3 mph, the average heart rate was 90-95 bpm (47-50% of max HR). At 4 mph, the average heart rate was 105-110 (55-58% of max HR). Even at 5 mph, the average heart rate was only 135-140 (71-74% of max HR).

Those walking paces (3, 4, and 5 mph) are listed at 3.5, 5, and 8.3 METs in the compendium. The 5 mph pace would be at the high end of Z3 based on METs, but still in Z1 based on heart rate. The paper also reports standard deviations for the heart rate measurements, so I can estimate that approximately one person out of the 50 participants had a heart rate high enough to hit Z2 at the 4 mph pace. I know that these participants are fitter than the average American, but they seem like they’re probably typical of the people who are actually trying to follow the physical activity guidelines.

I also found a study from 1983 (“Cardiovascular and metabolic responses of trained and untrained middle-aged men to a graded treadmill walking test​”) with untrained participants walking at 3.5 mph on a treadmill at 5% grade, with an average HR around 65-70% of max, while that activity would be at least 5.3 METs. The listing is for “walking, 2.9 to 3.5 mph, uphill, 1 to 5% grade”, so the 3.5 mph walk @ 5% grade is at the extreme end of that and presumably worth more than 5.3 METs. Again, based on heart rate we’re in the middle of Z1, but based on METs we’re at the high end of Z2.

I understand that there is individual variation in heart rate responses to exercise, as well as some possibility of measurement error, but this discrepancy seems to go way beyond that. I’m using a Polar watch, but I’ve also tested my heart rate with the monitors on various pieces of exercise equipment, as well as just by manually counting my pulse, and the measurements are usually pretty close. I’m open to correction if there’s better evidence out there, but so far I’m not finding anything that suggests that 3-6 METs and 75-83% of max HR are roughly equivalent targets.

The other thing to note here is that I would predict your HR to go up with a longer effort than 15-minutes.

This is a good point, but it creates some practical difficulties. If I need to do an hour of conditioning to accumulate 20 minutes of time in Z2, reaching the activity targets gets pretty difficult.

In any case, I would encourage you to look at this as an opportunity for additional gainzZz.

That’s true. From my point of view as a fitness enthusiast, I’m excited to see how I can fit higher intensity conditioning into my training and have another avenue to improve. However, from a health perspective, it’s discouraging to think that I’m so far away from the minimum activity targets. Even beyond my own situation, it presents a much bleaker picture for the general population. When I think about how much effort it’s taken me to accumulate about an hour of Z2 cardio in the last week, I can’t imagine any of my loved ones even getting close to the minimum activity targets. When you said that only 20% of adults met the physical activity guidelines, I was imagining a scenario where people are getting 60 minutes of 3-6 MET activity a week instead of 150. Based on the heart rate targets, I now think that the large majority of my friends and family get zero activity in Z2 or higher, and I sadly don’t see much prospect of that changing.

Yes- they are linked in the conditioning podcast show notes. To your point, METs aren’t terribly accurate way to prescribe the load of training. We discussed this in our conditioning podcast series, which is why we also provided HR targets. That said, the question was whether or not these HR recommendations are designed to consciously raise the intensity compared to the guidelines or if I was clarifying. As mentioned in the podcast and here, I have not changed the targets, but the HR rec’s match the guidelines with respect to the definitions of moderate and vigorous intensity conditioning. The citations again are provided in the show notes


They don’t line up at all for me, and my cursory search found some research that suggests the same is true for others.

METs aren’t great I agree, but that is not the extent of the current guidelines.

In a 2016 study by Sarah E Stahl, Hyun-Sung An, Danae M Dinkel, John M Noble, Jung-Min Lee, entitled “How accurate are the wrist-based heart rate monitors during walking and running activities? Are they accurate enough?​”, the researchers recorded the heart rates of recreational runners (3x/week training, aged 19-45) at various paces. At 3 mph, the average heart rate was 90-95 bpm (47-50% of max HR). At 4 mph, the average heart rate was 105-110 (55-58% of max HR). Even at 5 mph, the average heart rate was only 135-140 (71-74% of max HR).

5mph would be z2 in these individuals, which would correspond to moderate intensity conditioning. This study does not compare METs to HR, but rather compares the HR measured by wearable devices to telemetry. We would expect trained individuals to have lower HR’s at various workloads compared to untrained individuals. This also does not change what you need to do to self-manage your conditioning.

Those walking paces (3, 4, and 5 mph) are listed at 3.5, 5, and 8.3 METs in the compendium. The 5 mph pace would be at the high end of Z3 based on METs, but still in Z1 based on heart rate. The paper also reports standard deviations for the heart rate measurements, so I can estimate that approximately one person out of the 50 participants had a heart rate high enough to hit Z2 at the 4 mph pace. I know that these participants are fitter than the average American, but they seem like they’re probably typical of the people who are actually trying to follow the physical activity guidelines.

If you look at the range of HR’s recorded during each activity, you will see there are a wide variety of different responses to the activity. Again, none of this information changes what you should do. It does corroborate the claim that METs are not terribly useful for prescribing exercise intensity for an individual.

I also found a study from 1983 (“Cardiovascular and metabolic responses of trained and untrained middle-aged men to a graded treadmill walking test​”) with untrained participants walking at 3.5 mph on a treadmill at 5% grade, with an average HR around 65-70% of max, while that activity would be at least 5.3 METs. The listing is for “walking, 2.9 to 3.5 mph, uphill, 1 to 5% grade”, so the 3.5 mph walk @ 5% grade is at the extreme end of that and presumably worth more than 5.3 METs. Again, based on heart rate we’re in the middle of Z1, but based on METs we’re at the high end of Z2.

Based on the guidelines, the MET-predicted intensity of this activity is 5.3 METs or moderate intensity activity. The HR corroborates that target. As far as whether its z2 or z1, you’d really need blood lactate levels to KNOW, but the HR response here is close enough to be considered z2 for me.

I understand that there is individual variation in heart rate responses to exercise, as well as some possibility of measurement error, but this discrepancy seems to go way beyond that. I’m using a Polar watch, but I’ve also tested my heart rate with the monitors on various pieces of exercise equipment, as well as just by manually counting my pulse, and the measurements are usually pretty close. I’m open to correction if there’s better evidence out there, but so far I’m not finding anything that suggests that 3-6 METs and 75-83% of max HR are roughly equivalent targets.

The MET compendium is based off of 1 70kg dude, which invites a series of problems. That said, moderate- and vigorous-intensity activity has been characterized by more than MET targets in the research, which is what we discussed in the podcast series and what I have listed here.

This is a good point, but it creates some practical difficulties. If I need to do an hour of conditioning to accumulate 20 minutes of time in Z2, reaching the activity targets gets pretty difficult.

Sure, if you don’t go faster, harder, steeper, etc. Ultimately, you’re going to need to do more than 15 min/d of conditioning anyway to meet the guidelines- think more like ~25-30 on most days to get to 150 min/wk. If I got to pick, 80% of this should be z1/z2 (or thereabouts) and 20% should be higher to maximize cardiorespiratory fitness response. Of the 80% “moderate” intensity conditioning, I would prefer most of it be z2 or close to it rather than z1. It may require a faster pace than you’re currently employing to do that, but I would not expect that to be true for someone else necessarily.

The majority of people do not exercise at all and 60 min/wk of moderate intensity conditioning would be a big move in the right direction.

I think we have thoroughly exhausted this topic for now. I appreciate your time.