Fat burn, cardio and peak zone

[LynMM]

I having been working out fairly consistently lately.  I thought I was working out moderately however I think I am only in the Fat burn zone.  Some cardio zone but never Peak. Trying to understand the heart rate zones with Fitbit. So for me to get the recommended 150 minutes, is this in any zone or it had to be moderate (cardio)?  And if I use the 75 minutes that would be vigorous (peak zone)?  Fat burn zone can be something like a stroll around the neighbourhood right? (Just something more than sitting?).  I really need to up my game so I want to understand the zones. 

[JohnnyRow]

What zone you are in is based just on your heart rate.  On phone app, click the Zone Minutes circle.  That will tell you the heart rate limits of each zone.  No matter what activity you are doing or how hard you think you are working, it is just what is your heart rate compared to the zones.  A stroll around the neighborhood doesn't get you any points unless your heart rate reaches the lower limit of fat burn zone.  It might take some trial on your part to get a feel for how hard you have to be working to reach that.

  A minute in fat burn zone counts as 1 point; a minute in cardio counts as 2 points.  So to get to 150 points, it could be 150 minutes in fat burn zone, or 75 minutes in cardio zone, or any combination of them that reaches 150.  Peak zone is rarer but counts the same as cardio zone.

The daily goal of 22, is just arrived at by dividing 150 by 7, so that if you get that every day, you will reach 150.

[alexthecat]

Hi @LynMM and welcome! You can learn more about heart rate zones here 

One thing to keep in mind is that the zones are only as accurate as the calculations used to determine them. If you honestly feel that your definition of "moderate" isn't matching what Fitbit is calling moderate, your maximum heart rate could be different than what the app has calculated for you. You may want to set a custom max heart rate to get the app to give you more realistic zones. That's what I've had to do. 

[LynMM]

Thanks!  How do I set a custom max heart rate? I think this would make sense to do.  I have a fitbit charge4  (not sure if I can customize on it)

[alexthecat]

@LynMM In the app, tap on your photo in the upper left. Tap on "Activity and Wellness" about halfway down. Select "Heart Settings" and then "Heart Health". Tick the box next to "Custom Max Heart Rate" and enter your new heart rate. Click "Done" and then go back into the "Heart Health" screen. It will show you the new zones, so you can see if they makes sense. 

[t.parker]

@LynMMComparing to other models (this is based on my individual data, I use several models of HR zones which define 5-7 zones), Fat-burn is equivalent to a warm-up zone which may still take a little more effort than just "more than sitting", although it should be very easy to elevate the heart rate to that zone. The Cardio zone is a very wide one and it contains efforts between low-aerobic, tempo and sub-threshold. It means, it's light intensity, moderate and vigorous. Peak is a threshold (very hard) and anaerobic (all-out) intensity. In my case, walking does not take me to fat burn (warm-up) almost at all but a light run does it quite easily. I'm not sure whether it's clear. Basically, the model Fitbit uses for defining zones is one of many (and unique for Fitbit). See how it corresponds to other models (these are zones based on my HR):

 If you look at FirstBeat and TrainingPeaks models, they in fact want you to work harder than Fitbit. TrainingPeaks however has no "below zones" definition and a whole range from 0 serves as zone 1 (recovery and the higher HR goes, gets into the warm-up). When I'm in low fat-burn, I'm still below any zone in the FirstBeat model.

As you can see, the other models define more zones than Fitbit does. This is because there is a huge difference in effort between Aerobic, Tempo and Threshold. Fitbit throws everything into one zone - Cardio hence it's really hard to say how hard you should be working for this zone. Low cardio is just easy Aerobic (you can freely speak, light jog, you can go like this for a very long time) while high Cardio reaches Threshold (the name derives from Lactate Threshold, when lactic acid appears in your muscles, the major fatigue kicks in, you can't freely speak without catching breath). Reaching Fat-Burn then should be relatively easy but not "something more than sitting" 🙂 Low cardio shouldn't be hard either but Peak should force you into the almost all-out effort (although in my case, it's partially in threshold and threshold effort can be kept for longer).

Fitbit's HR zones model is very simplified (to the point of being useless for anything serious) and (in my opinion) it's quite hard to match effort with any zone. If you say that you feel like you work moderate you may be in low Cardio. Like @alexthecat , try to set up your max HR and make zones be what you feel they should be. The Fitbit zones don't really mean anything from the training point of view (even the names of zones are just silly, not to say misleading) so users can redefine what they mean to them.

[LZeeW]

@LynMM   You mention activity level in your first post.  About four years ago, the CDC and WHO changed their activity guidelines.  This is where the 150 min/wk of moderate activity or 75 min/wk of vigorous activity came from.  The CDC changed the heart rate zones.  They are very consistent with Fitbit's active zone minutes.

Please take a look at this link: How much physical activity do adults need?   You mention a stroll around the neighborhood.  With moderate activity, you should raise your heart rate and break a sweat.  As an example, you should be able to speak the words to a song, but not sing them.  With vigorous activity, you can't get more than a few words out before needing a breath.

Please take a good look at this information before you think about changing your max heart rate to change your zones.  You don't want to short change yourself.

I think Fitbit made things more confusing by naming these zones fat burn, cardio, and peak.  The equations are very different from the old (defunct) active minutes, yet they have the same name.  Think of them as moderate, vigorous, and peak activity.

[t.parker]

---

@LZeeW wrote:

Please take a good look at this information before you think about changing your max heart rate to change your zones.  You don't want to short change yourself.

This is a very good point. Changing max HR to redefine the zones model requires a) knowing your max HR, b) being able to verify that the model works. Otherwise, it's just a guessing game and since Fitbit doesn't allow changing ranges individually, while one zone may get corrected, others may go totally wrong.

Think of them as moderate, vigorous, and peak activity.

---

This is the problem because there is no way to match Fitbit zones like that (at least for me). If Fat Burn is moderate, I would need to start this zone at 152-165bpm, vigorous as cardio: something like 165-173bpm and Peak for anaerobic (everything above). Understanding zones like that makes sense to me but there is no way to define all three zones numerically to reflect that meaning 😕 Just with max HR, it's just not possible.

[LZeeW]

@t.parker   That's because you are in a league of your own.  😉

[t.parker]

@LZeeW I'm pretty sure there are more people like me. It's all about understanding the data. I have a theory that most users are collectors. They record the activity and never really use the data for anything else (probably a topic for a different thread). However, when you start using it you will find out that one source of data and one way of interpreting it isn't really enough because you'll find holes here and there. I realize that I may be going too much into details but who knows, to some users it may help to understand certain things. Fitbit is very secretive about the ways it interprets the data and software (and hardware) are only as good as our understanding of it 🙂 Believe me, there are a lot more users for whom the zone model won't correlate with the levels of effort. Even more complex models have their own issues (for example, FirstBeat has a problem with a very high lactate threshold so sometimes my "anaerobic" effort isn't really anaerobic, I can't fix it but at least I know why is that and how to compensate for it).

[MomNixon]

************

This is based on me doing research as someone trying to get in better health per doctors suggestion.

I am not certified and have not studied health or fitness classes in school.

************

I've been working on understanding the Heart Rate Zones in Fitbit last couple of months because doctor asked me to do daily cardio where I have a high enough heart rate to where I am sweating for 20min.

With the research I found with normal Heart Rate Zones (calculation is based on age) and Fitbit Zones (uses age and Resting Heart Rate) I found that I need to focus on (50%-85%)  HR zone in Fitbit. This is the middle of Fat Burn Zone and end of Cardio Zone, for me (with a resting HR of 66) it is HR (120-160).  I created a custom zone in Fitbit app, I write it down after my workouts because I don't get custom zone notifications on my watch.

To get into my custom zone, it requires more than just walking the neighborhood or other casual cardio (by that I mean, I can't reading or watching videos). It requires full concentration and focus. On the Elliptical I have to go +5MPH or using an audio run with intensity cues (I use these on the elliptical as well).  At home workouts have to be all cardio or a mix of strength training and cardio.  I have to track the workout and the HR numbers after each workout to know what got me there and which workouts I need to save fore exhausted days.

As for the 150min vs 75min I have not figured out yet. I have just been focusing on getting over 20min in the custom zone.

** Peak is the equivalent of Sprinting. You don't want to be there too long. Though, you can get a lot of Peak time with a really good playlist in a Spin class.

For me, not great shape, if I was to focus on it I would go for something like this.

Fat Burn (warm-up) Cardio (actual workout) Peak (sprinting)

150 minutes = combination of Fat Burn and Cardio Zones (for 30 min workout, 10-15min in Fat Burn; 15-20 in Cardio)

 75 minutes = combination of Cardio Zone and Peak Zone (for 5 min workout, 3-4min in Cardio; 1-2min in Peak)

Below Zone Zone 0	< 40%	heart beats at a slower pace. You’re at rest.
Fat Burn Zone Zone 0-1	40%-59%	light - moderate activity. hr and breathing might be elevated, can still carry on a conversation.
Cardio Zone Zone 2-4	60%-84%	doing a moderate - vigorous activity.
Peak Zone Zone 4-5	85%-100%	vigorous - maximum effort. doing a short, intense activity that improves performance and speed (sprinting or HITT)