I recently got a heart rate monitor and have been trying to beat my time each week on the exercise bike. I'd say I'm in pretty good shape. During the 30 mins workout I am in zone 5, with an average rate of 171 and a max of 187. I feel fine during and feel worn out after as I've pushed it hard. I feel fine afterwards too as I just go back to work.

Is it bad for me to train like this? I enjoy it and feel great but not sure if being in the zone 5 of the heart rate zones is bad. I'm 33 and train about 5/6 times a week so I'm in good shape.

For the heart rate zones see this: enter image description here

  • Nice question, something I've been wondering as well. I'm curious to find out if common workout symptoms & feelings are a trustworthy metric for HR max training, or if damage can unexpectedly crop up. Great graph too!
    – andrewb
    Commented Dec 1, 2015 at 23:21
  • 2
    220 -age is outdated and shouldnt be used. I suspect you have a much higher potential MHR.
    – JohnP
    Commented Sep 23, 2016 at 19:12
  • 1
    Your zones are setup wrong. Zone 5 is intense and will make you puke. The definition of Zone 5 is an exertion you can only handle for 3-5 minutes without puking or passing out. Commented Feb 16, 2017 at 14:51
  • Average of 171 at your age might not even really be Zone 5. The first thing you need to do is work out your true maximum heart rate. Go find a decent hill and keep running up it for 2 minutes and back down and again while increasing the speed each time until you feel like you are as close to being ill as possible. That will be your maximum heart rate. I'm 52 and my maximum heart rate is still ~190 so yours is likely somewhat above 200 still easily. Zone 5 training for you will be closer to 200 bpm average. Commented Jan 4 at 2:45

4 Answers 4


First every HR monitor will read your HR differently. To get an actual reading you will need to do a Vo2Max test at a Doctor.

2nd You are listing quite a large range for 30 minutes. There is a difference between 30 minutes at 171 and 30 minutes solid at 190. What is your average?

Finally, the VO2Max is only attainable in the lab and a formula is only a formula.

You can see here http://www.runningforfitness.org/calc/heart-rate-calculators/hrmax?age=33&gender=M&Submit=Calculate that your Max HR can range almost 10bpm.

If you HR monitor is wrong, and you are not at 189 the entire time it is possible that your graph is completely wrong. If you can sustain the rate you are training at then perhaps there are some variables that are not correct. Your body will tell you that you are maxing out and if you can sustain 100% Max HR for 30 minutes then perhaps you are in better shape than you thought... or maybe your HR Monitor is wrong


If you enjoy it and feel great (and still do, after a week) then you aren't doing damage. But you may not be optimising your results either...

Perception of effort is a better guide to exercise intensity than HRM and "rules of thumb" about training zones. If you can train for 30 minutes at steady output (as measured by the exercise bike) then you are probably close to your anaerobic threshold, and not significantly over it. An HRM really becomes useful when you have calibrated the values against some reference points - either using fancy physiological testing gear or making inferences from your HR profile during ramp or flat-out tests.

I don't think you will harm yourself by training like this, if you are able to recover each day and tackle the next session without feeling worn out. But depending on your training goals, doing this kind of session 5 times per week is likely not the most effective programme.

For example, if you want to continue to see improvements in the distance covered (or time taken) during this type of session, I would mix in some steadier work (eg. an hour at a lower intensity) and some harder intervals (eg. 4 repetitions of 5 minutes each 10% faster than the speed you can maintain in this 30m session, with 4 minutes easy spinning in between) as well as at least 1 rest day per week.


There is a simple answer that lies in both your question and in the chart you provide.

Your question says, “…is it bad to train...”. Training implies you are trying to improve. Zone 5, is not improving and therefore not training. The chart says zone 5 is “Recommended for: Very fit persons with athletic training background.” Have you already been training (in the improvement zones) for several years? If the answer is not yes, you are not ready for zone 5.

I understand you are new, so you are smart for asking. Doing a google for “exercise target heart rate” returns 1,700,00 results. Taking just the first one says “It is recommended that you exercise within 55 to 85 percent of your maximum heart rate for at least 20 to 30 minutes to get the best results from aerobic exercise. The MHR (roughly calculated as 220 minus your age) is the upper limit of what your cardiovascular system can handle during physical activity.”

The key to understanding why is understanding aerobic exercise. To oversimplify for this context, aerobic exercise is the process in which the body has time to use oxygen and nutrients from the body to generate energy. Anaerobic exercise is when the body has been forced in to emergency or survival mode, thus it must find a faster way to generate energy. Essentially the faster method consumes resources the body has already stored and may need, such as energy used by the brain to function. The anaerobic method is more destructive to the body.

Yes, some athletes (sprinters, football players, etc.) need burst energy. So, yes, some athletes need training that includes anaerobic exercise. Those same athletes will do large levels of doing cardio vascular training first or at least at the time same time.

  • Zone 5, is not improving and therefore not training - can you have a source to back this up? I would say that zone 5 will give the maximum improvement in strength and capacity, if combined with enough rest time.
    – vgru
    Commented Apr 27, 2017 at 11:17
  • The OP provided the source. Simply read what was provided here.
    – Brian
    Commented Apr 16, 2019 at 14:12

I'm basing a lot of this on my own personal experience so, by all means, take it as anecdotal if you'd like.

I started exercising the week of my 34th birthday (about 8 months ago) after having smoked for 15-16 years and living a sedentary lifestyle. I discovered the heart rate zones early on, just like you, and I got my heart rate monitor (FitBit Charge HR) as well.

Some people will say that if you want an accurate heart rate, VO2 measurement, etc., you'll need to go see a medical professional, have a bunch of gear hooked up, and so on and so forth. They're right.

That being said, I have measured my FitBit heart rate against probably 20-30 different types of cardio machines (treadmills, bikes, stair stepper, etc...) from different manufacturers, and my heart rate on the Fitbit almost always matches the heart rate on the machine within 1-2 beats.

Considering that the FitBit uses a different methodology than ordinary cardio equipment, I feel like it's a decent enough approximation. Might I see a difference between my FitBit and a professional medical device? Sure. Is it going to be significant enough to where one day you find out you've never even hit zone 5? I highly doubt it.

Furthermore, the FitBit uses my heart rate to determine total caloric burn. Again... not a medical device, but considering that I've lost 35 pounds by studiously trying to keep to a -500 calorie daily deficit, and been successful with it, my guess is the FitBit is accurate enough to be useful.

So, that being said, the question is whether or not exercising at that heart rate is dangerous. Obviously, each individual is different, so it's not a one-size-fits-all answer. That being said, I imagine if you told your doctor you were doing this, they'd probably jump for joy. The first few weeks/months of exercise for me, as soon as I took a step, I was virtually in zone 5. Now... I have to push it very hard to get there. So, I somewhat suspect that the reason you're always in this zone is because you're once again challenging your body.

So, my guess is that, over time, and especially if you don't vary your routine, your heart and the rest of your cardiovascular system will learn to very quickly adapt to this exercise routine. As a result, you'll probably struggle to get into that range as time goes on.

For normal people, I haven't read that this is overly problematic. That being said, if you have an underlying or undiagnosed condition, I suppose it could be dangerous. One thing I noticed early on was that if I overtrained, the next day I might have a very mild heart flutter. It may have only happened for 2-3 seconds out of the entire day. It didn't happen all the time, and it was usually when I was at rest, but I knew that it was time for me to take an extra day off, and then I'd be fine.

Obviously, you know how you feel more than any of us do. I'd say that if you're feeling great, then you're doing fine. The more you do it, the better you'll feel. I'm at a point now where missing my gym days puts me in a bad mood. I look forward to it. I love it.

I like the heart rate monitor. I have learned its intricacies, it allows me to gauge my current performance against past performance, and although I can say that I am responsible for my weight loss and lifestyle change, the FitBit was an excellent enabler.

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