HR way lower than usual

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thursdaystgiles
thursdaystgiles Posts: 98 Member
in Fitness and Exercise
I alternate between Spinning, Running, and Zumba for my cardio. My heart rate for Spinning and Running is usually between 168-175 when doing endurance and 145-190 when doing intervals. For Zumba it pretty much stays at 170-175 for the entirety of the class, though it might spike up to 180.
I know with conditioning your heart rate slows, but it changed dramatically from one day to the next. I ran yesterday (endurance) and my heart was hanging out right at 174, totally normal. Today I did Zumba and it barely got above 154. I was working just as hard as usual--in fact I pushed myself even harder than normal when I noticed my heart rate, but it didn't change much. Sometimes it was getting down in the 120s! My legs are definitely wobbly and I feel physically exhausted.
What other reason could there be for such a big difference from one day to the next, besides conditioning? And should I use my heart rate or perceived exertion for calorie burn? Perceived tells me 970 based on age/height/weight, which seems obscenely high. But the 480 from my HR feels somewhat low.

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  • arabianhorselover
    arabianhorselover Posts: 1,488 Member
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    Your feeling sounds like low blood sugar, but I don't know if that explains the heart rate thing.
  • MeanderingMammal
    MeanderingMammal Posts: 7,866 Member
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    Dodgy battery on your HRM?

    Other than that, what do you define as endurance running? That's quite high for easy paced running but you might be a bit overtrained at the moment
  • alekth
    alekth Posts: 33 Member
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    Probably battery, yeah.

    On the calories, can't really tell without knowing the duration at the very least. 970 kcal at 170ish bpm for me would be nearly 2 hours of cardio and we are pretty close in age/weight going by profile/pic, so if you did considerably less, it is likely a way too high estimate.

    Endurance runs usually go by close to 180-age HR, although it depends on the regimen/source you're following. This is just the most common one (seems based on Endurance Training and Racing by Dr. Philip Maffetone), but I'm getting into Daniel's Running Formula now, and it has the concept of easy running for conditioning and training the cardiovascular system/growing more resistant to injury, which doesn't aim quite as low for the HR.
  • scottb81
    scottb81 Posts: 2,538 Member
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    When running, calorie burn isn't drastically different as you speed up. At my weight, 177 lbs, 970 calories is between an 8 and 9 mile run. How far did you go?
  • madmickie
    madmickie Posts: 221 Member
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    try a new battery before worrying about anything else. Try a different hrm if you can and compare results. Cal burn estimates are notoriously inaccurate anyway and your HR feeds into the estimate so if it's off then the cal burn will be off too. You will burn around 100 kcal/mile running - a bit less if you are slow or small - bit more if you are big or fast - anything wildly away from that and it's probably wrong.
  • fbinsc
    fbinsc Posts: 735 Member
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    That is a symptom of overtraining, you need rest. Google "overtraining syndrome" for more info. Symptoms: fatigue, elevated heart rate at rest, diminished heart rate on exertion. It can take a while to recover but if you don't let your body recover properly you will have much longer downtime.

    I've noticed a big trigger of this for me is eating way too little food for the amount of calories burned in exercise. Too much too soon.

    Good luck, be sure to google this.

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