LTHR and zone discrepancy?

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    I am new to 80/20 and just started the maintenance running plan using training peaks. I did a 20 minute time trial test to establish my LTHR using the average HR of the last 15 minutes.

    The 80/20 zone calculator puts the top end of Zone 3 at 100% of the LTHR.

    I’m scheduled to do a fast finish run tomorrow. The note in the workout says “Note that CV = Critical Velocity, which is the fastest pace you could sustain for 30 minutes and falls toward the low end of Zone 4.”

    Zone 4 starts at 102% of my LTHR. If I can only manage 100% for 20 minutes, how am I to reach 102% for 30 minutes?

    Maybe I’m missing something? Thanks

    Leyla Porteous

    Hi Bryanhood,

    The LTHR test and calculation actually estimates the HR you could hold for an hour. It’s just not a tonne of fun and rather stressful to do this in a test, hence you do it as a 20 or 30min test taking the last 20-15mins when the HR has plateaued to determine an estimate for what you could theoretically hold for an hour.
    You may also find that HR is not as reliable as Pace/Power for these faster intervals as there can be many factors that impact your HR, and it will lag a bit behind the effort. A way around this is to use pace for intervals, or RPE, ie: use the “could I hold this effort for 30minutes” suggestion while doing your fast finish.


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