What going on here....training? nutrition? dehydration?

Can someone give me some pointers about what's going on in this graph. It's a trend that I've seen a lot over the year but I've never really tried to work out what's going on until now. The reason I ask is because I've always ran up to half marathons without any water or gels etc and I've been fine, so when I'm running and my heart rate is constantly increasing throughout the run and never plateauing It hasn't been a problem. Now I want to push the distances more and the increase in heart rate is now leading me to get incredibly close to my max heart rate (2-3bpm lower than MHR by the end), whilst at the same time my pace is either pretty constant, or even dropping. Clearly this indicates that I'm very unlikely to go much further than the 27km you can see in this graph. Indeed at the end of this run (my longest ever) I was having to repeatedly stop in the last ~4km as I just couldn't keep going. I was completely spent by the time I finished.

What causes this endless increase in HR? Is it that I'm getting dehydrated and my heart is having to work harder to push, I assume, slightly more viscous blood around to meet the same demand for fuel/oxygen? is it my body burning through my reserves of glycogen? something else?

Any ideas on how to get on top of this and stop the HR constantly rising like this? I guess I'd expected one's HR to flatten out and remain more or less at a constant level but that's not what I see. I should add that this graph is just one run and a longer one that normal for me, but I see the same pattern in most runs.

For info, I'm 44, 95kg with a max heart rate of probably about 185 and I'm running something like 50 miles per week and I do at least one half marathon every month, and I've been running for about 20 years, so this isn't a new sport for me.



  • rich164hrich164h ✭✭
    oh and by "push the distances", I mean that one day it would be nice to do a full marathon or maybe even and ultra of some sort, but really, I've recently moved to Sweden and I'm keen to take advantage of the amazing trails that they have over here. For that, I'd like to not be limited to only 22km or so. I'm not so bothered about speed, but I do want to increase the distances I can cover.
  • chamolkchamolk ✭✭✭
    Hi Rich

    Looks like cardiac drift to me - plenty of sources online can give a better explanation of this than I could try to do here, just search for the term on Google or similar. Basically your HR needs to increase over time to maintain the same output

    Regarding being near max hr/spent at the end - that sounds to me like you're simply going too hard/fast for a long run. If you're looking to go longer, you'll probably need to slow down. Either look at the McMillan calculator for suggested training paces, or various coaches suggest different heart rate ranges (as far as I can recall 75% of max HR was a general ball park for long runs, but acknowledging that this rises through a long run due to cardiac drift)

    Good luck with the training
    Rich - I agree with chamolk, looks like you're running too fast.   

    I would suggest you do a MHR test if you don't know what it is, pointless using HR stats if you don't know what your MHR is.    Then do roughly 80% of your weekly training at no more than 70-75% of MHR ( lower %'s if using WHR).
  • rich164hrich164h ✭✭
    Thanks both. Cardiac Drift does fit the problem perfectly, which does appear to be linked to one's hydration levels (from a very rapid read on the subject - I'll read more about it).

    My MHR used to be around 192bpm but that was about 5 or so years ago. I've seen it go up to 185 more recently so I'm assuming that this it's probably something like my current MHR - maybe 186/187.

    Regardless, your comment about running to fast and that I should probably slow down it a good one and I'll definitely try to do that. It's hard though as I usually run at a pace that feel comfortable and running slower I find causes my technique to breakdown. I guess it's just a case of practice and more of a conscious focus on running form. Looking back at past runs (fast and slow) I normally go over 80% in the first few hundred metres, so I have no idea how I can keep it below that level. I guess I'll just have to try, but my feeling is that instead of my usual 4:45-5:20 min/km pace I'll be down more like 6:30-7:00 min/km which is a totally different running experience and style. Hopefully it won't cause other injuries in the process, but I'll give it a go.
  • elspeth fayelspeth fay ✭✭✭
    To go longer you should initially slow your pace and you will find it easier to keep running for longer, short walk breaks can be useful anyhow when increasing your distances. Just returned from trip visiting our son in Sweden, enjoy the trails! (I managed to get lost when running there!).
    rich - you won't see your MHR unless you are close to throwing up or need oxygen.   Do a MHR test and if you don't throw up etc then add on a couple of beats to get your MHR stats.   It's very hard to reach MHR especially if you are already a regular runner.

    I would suggest you do some research on base training, McMillan has a good piece on that.   Also Hadd and Maffetone if you want to do HR training.   Base training won't cause you injuries, it will make you stronger but you do have to go through the initial slow phase until the aerobic training starts to kick in.   

    Cardiac drift is not just caused by dehydration.
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