Heart rate precision chest belt

Former Member over 5 years ago

I am using a Fenix 5X with a chest belt connected.

I did Intervalls running (10x 400m at 3:30 Pace with 400m rest).

If you look at the attached image you can see the Pace and overlayed with my heart rate (measured by the belt). Actually they do not at all match which is also contrary to my perception.

How can it be that the heart rate is not going up during each kf the more than 1 minute of high intensity 400m and goes down accordingly for the phase of slow pace? Actually it only seem to have worked during the 7th intervall.

Is there sth wrong with my physiology or is the chest belt not as good as I thought? On long runs and monotone runs i think the chest belt works well with realistic values.

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trux over 5 years ago +1 suggested

Looks credible and normal to me. The fast pace runs are more or less anaerobic, hence the need to circulate the blood is not as high as when in an aerobic mode. And when you then slow down, the body switches…

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0 trux over 5 years ago

Looks credible and normal to me. The fast pace runs are more or less anaerobic, hence the need to circulate the blood is not as high as when in an aerobic mode. And when you then slow down, the body switches back to the aerobic mode, tries to evacuate the anaerobic byproducts, and to bring fresh oxygen from the lungs, hence the HR may even increase in comparison to the previous fast interval.