30 min LTHR test which will provide data on your LTHR heart rate, as well as a pacing guide for future runs. The zones to work off, are listed below. Take the average heart rate in the LAST 20 minutes of the 30 minute test, and apply this to the below numbers:Zone 1 Less than 85% of LTHRZone 2 85% to 89% of LTHRZone 3 90% to 94% of LTHRZone 4 95% to 99% of LTHRZone 5a 100% to 102% of LTHRZone 5b 103% to 106% of LTHRZone 5c More than 106% of LTHR