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Cannot get my heart rate above threshold
First a little background on myself, as I am a new user here 
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My activity level has gone up and down over the years. As a teenager a did a lot of biking on the road. During university years, it was more partying than sporting though. Then I started mountainbiking, did that a lot, participated in mountainbike marathons, up to 120km/5000hm on one day. Then family+kids came, and my activities dropped again. A couple of years ago I started running, mainly trailrunning. I think about 20-30km per week. Last year I almost did not run though, for various reasons, but mainly lack of motivation. A few months ago I got a new watch (Garmin Forerunner 245) and this watch gave me a motivation boost. In the past I had used heart rate watches, but always only very simple ones. But this Garmin watch has so many features, navigation, health statistics, etc. Somehow this watch gave me the motivation to start running again. Now I am 51 years old, and running about 30km/week.
One of the features that I like on my Garmin watch is the recommended workout. My runs are usually slow long runs, but my watch once in a while suggests to do a threshold run or a vo2max run. I actually enjoy these variations in training a lot, and I guess they are good for me, so I have started to follow the recommendations. But I have trouble with the vo2max runs.
Threshold runs, where I am supposed to run with heart rate just below threshold, are fine. The typical workout is 22 minutes @155bpm. Not easy, but I can do that and maintain that heart rate during the whole workout. I have to admit that I do not know my LT heart rate exactly. I had it measured 20 years ago, it was 164 at that time, but I suppose it has dropped over the years. Based on I how I feel during the the threshold runs, I guess it is now just below 160 or so.
But when I do a vo2max run, where my heart rate is supposed to go quite a bit above threshold, I just cannot do it. Just today I did a 8x2min interval @165 bpm, at least that is what Garmin suggested me to do. But my heart rate just does not go that high. Typically, during one section of 2 minutes, my heart rate steadily goes up to about 150, then starts flattening and usually never goes above 156-157. I am exhausted after two minutes. One week ago I had a 5x3min session, and I did not even manage to finish the 3minutes each time out of fatigue. Still my heart rate never went higher than about 157.
How is this possible? How can I run for 22 minutes with a 155 HR average, but if try to run faster, my HR just does not go higher than that, but I am exhausted after two minutes?
I guess it is all related to the fact that I have not done these kind of hard intervals for a long time, and my body is just not used to perform at this level. Has anybody else experienced this? And what would be your advice to me?
:My activity level has gone up and down over the years. As a teenager a did a lot of biking on the road. During university years, it was more partying than sporting though. Then I started mountainbiking, did that a lot, participated in mountainbike marathons, up to 120km/5000hm on one day. Then family+kids came, and my activities dropped again. A couple of years ago I started running, mainly trailrunning. I think about 20-30km per week. Last year I almost did not run though, for various reasons, but mainly lack of motivation. A few months ago I got a new watch (Garmin Forerunner 245) and this watch gave me a motivation boost. In the past I had used heart rate watches, but always only very simple ones. But this Garmin watch has so many features, navigation, health statistics, etc. Somehow this watch gave me the motivation to start running again. Now I am 51 years old, and running about 30km/week.
One of the features that I like on my Garmin watch is the recommended workout. My runs are usually slow long runs, but my watch once in a while suggests to do a threshold run or a vo2max run. I actually enjoy these variations in training a lot, and I guess they are good for me, so I have started to follow the recommendations. But I have trouble with the vo2max runs.
Threshold runs, where I am supposed to run with heart rate just below threshold, are fine. The typical workout is 22 minutes @155bpm. Not easy, but I can do that and maintain that heart rate during the whole workout. I have to admit that I do not know my LT heart rate exactly. I had it measured 20 years ago, it was 164 at that time, but I suppose it has dropped over the years. Based on I how I feel during the the threshold runs, I guess it is now just below 160 or so.
But when I do a vo2max run, where my heart rate is supposed to go quite a bit above threshold, I just cannot do it. Just today I did a 8x2min interval @165 bpm, at least that is what Garmin suggested me to do.
But my heart rate just does not go that high. Typically, during one section of 2 minutes, my heart rate steadily goes up to about 150, then starts flattening and usually never goes above 156-157. I am exhausted after two minutes. One week ago I had a 5x3min session, and I did not even manage to finish the 3minutes each time out of fatigue. Still my heart rate never went higher than about 157.How is this possible? How can I run for 22 minutes with a 155 HR average, but if try to run faster, my HR just does not go higher than that, but I am exhausted after two minutes?
I guess it is all related to the fact that I have not done these kind of hard intervals for a long time, and my body is just not used to perform at this level. Has anybody else experienced this? And what would be your advice to me?
https://www.strava.com/athletes/90620900
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Comments
this isn't for your model of Garmin but applies to all wrist based HRM's and will be in the manual somewhere
About wrist HR accuracy... (Garmin response) - fēnix 6 series - Wearables - Garmin Forums
My MHR is 160, I do all my base training at 70-75% MHR, not WHR. I'd run a marathon at roughly 85% MHR.
The readings are at least consistent over the couple of runs I did at higher rates, but I will see what happens if I disable the optical function.
First of all, I am pretty sure that the heart rate measurements are accurate. I have disabled the optical function and I do not get really different results.
During my vo2max runs, lately I seem to slowly increase my ability to push my heart rate a little bit higher. In my last interval training, my heart rate frequently went up to 160, with some peaks up to 164. Yet I did not feel the complete exhaustion that I had two months ago during such workouts. So my guess is that my body just was not used anymore to do exercises above LT. Now I am becoming fitter, and my body is getting used to being pushed to the limit.
My heart rate during my threshold runs is typically around 150. I have taken a look again at the runs from a few months, where it went up to 155. The typical run was 20 minutes, where I reached the 155 HR after about 5 minutes. So it increases rather slowly in the first 5 minutes before it stays steady. It seems if I let my heart rate slowly increase, I can indeed run for a longer time at rates close to 155. But if I get there too fast, I am actually performing at above-threshold level, while my HR is not keeping up somehow.
I guess it all makes sense in some way. I think my threshold is between 150-155, but I still plan to do an appropriate LT test to check this. On good days, I can indeed run with 155 for a somewhat longer time, but only if I do not get there too quickly, if that makes sense. And my body is getting used now to do workouts above threshold, so now I am able to run intervals of 2-3 minutes at rates above the threshold.
A short summary of last year. I kept following the recommended Garmin workouts, as I really enjoyed them. This meant effectively running five times a week on average, with quite strictly 80% base runs, and 20% high intensity runs like tempo runs and V02max runs. Base runs around 125 HR, ranging from 40min to 60min, sometimes up to 80min, tempo runs at 145-150 HR, intervals at or above 155. This was all satisfying, but I kept struggling with the intervals a bit.
I did the lactate test one week ago at a medical center, where I also got a cardiac ultrasound, blood tests, etc. After the test I had a very interesting discussion with the lead medical scientist.
Some conclusions:
My anaerobic threshold is 153, which was exactly in the range that I estimated myself. Also my max HR (168) is very close to my own estimate of 170.
My aerobic threshold is 127. We discussed this quite a bit. I typically do my base runs with an average HR of around 125. This is 75% of my MHR, and it is also what the watch recommends for my base runs. But according to the medical scientist this is actually a little bit too low as it is in my recovery zone, i.e. not really effective. So, whereas most hobby runners are running too fast, according to him, I actually am running a bit too slow, LOL.
This was quite an eye-opener. So, even if you know your anaerobic threshold and max HR exactly, the estimates for your training heart rate zones based on percentages of those can be off. What counts is the aerobic threshold. The aerobic threshold is actually harder to estimate yourself than the anaerobic threshold, so you really would need a test like this.
We also discussed the 80-20 rule and the threshold/VO2max trainings quite a bit. The medical scientist was quite skeptical about this 20% high intensity runs, especially about the intervals above threshold. He claimed that even the very best runners do less than 20%.
I told him that what you typically hear/read is that this high intensity training is very effective for improving V02max. He explained that that is right, but it is only a short term effect. So, it makes good sense to do that in preparation of an upcoming race, but in order to increase V02max with a long term effect, you better do more base runs. So basically he recommended to do maybe a tempo run once week, but to avoid higher intensity trainings, unless in the weeks before a race, and again claimed that that is also what the best runners do. This was the second eye-opener.
The third learning was about the length of the base runs. I have been getting used to doing many relatively short runs. I am running almost every day, but my runs are seldom longer than one hour. The medical scientist explained that base runs should be a bit longer, i.e. 60-90 minutes. This in order to train the metabolism to really become more efficient, as with runs under an hour the body does not experience glycogen depletion, etc.
So, that was a really helpful test and advice! Now, I am going to run a little bit faster, targeting average HR of 130 in my base runs, I will not do intervals anymore for a while, and I am going to slowly increase my training load!
Good luck with your training.