Lactate Threshold Heart Rate Question

After 3 weeks stuck inside on the trainer due to the weather in the UK and a bit of a cold I finally got out with my mates for a ride today. 5 hours 2700kJ (Difficult according to Xert). After about 2000kj’s we hit an incline which we use to test ourselves and I set a string of PB’s on Power.
Interestingly though has suggested an increase in my LTHR of 5 beats to 158 based on 98% of 20mins at 161bpm. Irrespective of whether that’s correct or not I was wondering whether such a bump was valid so late into a ride when there would have been a considerable amount of HR drift present. Anybody got any thoughts on this?

In general, numbers can only be compared if the conditions were the same. If the 20 mins that compares with was taken during the first 30 minutes of another ride, i would ignore it.
How would it influence your training if the comparison was valid?

I tend to ride to power but put a cap on the intensity using heart rate so it would influence me in that way. Also as my HR zones are calculated by LTHR, it would raise the ceiling on them perhaps allowing me to train harder (maybe too hard as a result)
I’ve just had a look and the previous one from Intervals had me at 164bpm from 98% 20m@167 during my one and only TT in March 2018. As my maxHR was about 175 I didn’t believe it and lowered it as i didn’t want to repeatedly kill myself as it seemed far too high. I figured the adrenaline and excitement of doing my 1st competitive cycling event at 62yo got the better of me.

Your HR for a given power output can be higher if you did some threshold training recently (versus base training) and visa versa.
Best to realise the context in which the numbers were recorded.

@carytb I would tend to agree with you and think that’s pretty perceptive. Cardiac drift on a long ride will drive lower intensity heart rates up. It does have less of an impact on threshold heart rate, but I’d still try to get your threshold heart rate from a test performed when you’re pretty fresh

Hope that helps!