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HR Zones and LTHR

Dear all, I have been doing endurance training for an Ironman (of course half) preparation and i am very close to this date. However, since i don't have proper coaching, I have not payed proper attention to my HR Zones or my LTHR threshold setting on my watch, so basically i was training blindly during last 6 month. I've just finished couple of Tri books and realized its importance. At the moment, I am a bit scared to do the guided LT test, not to exhaust my energy before the race.

I owe Garmin Forerunner 735XT watch and I saw it has an option of Auto Detection of Max HR as well as somehow it automatically sets LTHR (i think it takes from the past training).  Can you advise me if this auto detection functionality on the watch can be reliable at all?  or what is the best way forward to be clever before the race and have something at hand? Maybe I can use my HRs from the training history in my watch? 

I will be very grateful for your help.




  • Andrew4Andrew4 Posts: 190

    The auto detection is very much a guesstimate.  The conventional way to determine your lactate threshold is to do a conventional ramp test where the tester takes pin prick blood samples every time the intensity increases and your lactate threshold is the point at which lactate starts to build up very rapidly - if you look at a curve it goes bang off the charts.  You can then look at your heart rate and how fast you were running at that point and it gives you your thresholds.

    Clearly a Garmin isn't doing that - is it a perfect solution, no - my understanding is that you have to do a certain amount of proper hard running and intervals - if all you are doing is M-dot pace I don't think it will give you a helpful or accurate number.  If you are prepared to do a 30 minute test or so and bury yourself I would imagine it will give you a far more useful number (in principle).

    BUT - it sounds like you are now pretty close to race day (if you are worried about blowing yourself out) and therefore should by now know what you are going to do, how fast you can run, fuelling etc and therefore I'm not sure I'd want to mess about with all that - afterall you should by now know roughly how hard you can bike and how fast you can run.

    To give you an idea, I have one "threshold" that I use, and that's on the bike where I target a percentage of FTP - on the run, I know how I'm feeling, I know how fast I can run, I know how fast I am running at that moment and I know how much it hurts.  When a guy comes past you and you try and stick with him, look at your watch, realise you hurt like hell and its 15s per km faster than your OD run PB, you probably can't hold that for very long, similarly, if you're running your "usual pace" and feeling great in the second half, final 5k, whatever, its probably worth giving it a little extra squeeze and seeing if you've got anything left in the tank.

    One of the articles on the home page at the moment talks about how to use gadgets, might be worth a look for the balancing approach.

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