My LTHR heart rate is very low only 48bpm??

Do a LTHR test if you can

9885816 said:

my threshold HR is usually around 154+ so I would assume my LTHR should be around 174bpm

If the threshold HR is 154 bpm, then LTHR cannot be 174 bpm, since LTHR is the threshold HR (LTHR stands for Lactate Threshold Heart Rate). If 48 is shown, then there is something wrong either with your settings, or with your watch. To get it right, first of all measure and set up your Max HR as accurately as you can, and then, as Blindy wrote, conduce the LTHR Guided Test. You will need a HRM chest strap for that, though.

More info in the article How Is Lactate Threshold Measured by My Garmin Device? | Garmin Customer Support 

Thank you - I will do a test this week

Thanks for the response.  The garmin has set my max HR to 189, I have a chest strap and will perform a test this week!

Much appreciated