Interpreting Lactate Threshold values

The 945 will help you. One month is not much data, especially for LT and VO2.

One tip: If you use planed trainings, it is important to know that Garmin uses step pace and not actual pace for alarms/gauges.
An example: If you want to do an 20km run: 1km Warmup, 16km pace between 5 and 5:30/km, 2km cool down, there are two was to program it.

1.: Step 1 warmup target: Distance 1km
     Step 2 target: Distance 16km Pace 5:00-5:30
     Step 3 cool down target: 2 km

Effect: easy to programm, but when you do step 2, the average pace will be used. If you fatigue at km 11 and cross 5:30, it will not alert you to push harder because your average of the first 10km is faster than the 300m you are running to slow.

2.: Step 1 warmup target: Distance 1km
     Step 2 Intervall target: Distance 1km Pace 5:00-5:30 repeat 16 times
     Step 3 cool down target: 2 km

Effect: If you fatigue at km 11 and cross 5:30, it will alert you because it will only average the current lap. 

BeneGi that’s a good trick! I’ve never thought about it. Thanks for sharing!

Your pace should remain constant over the weeks and the effort should get easier ie lower HR. If you race every 4 weeks or so then use new 5k/10k time to reset tempo pace which should be around 88-90% or mhr. Use Daniels VDOT tables to set training paces 

Your pace should remain constant over the weeks and the effort should get easier ie lower HR. If you race every 4 weeks or so then use new 5k/10k time to reset tempo pace which should be around 88-90% or mhr. Use Daniels VDOT tables to set training paces 

Half marathon plans tend to include less work around LT than 5K and 10K plans, and full marathons even less again. So it is not surprising that you may have dropped a couple of BPM off your LTHR, as you have probably been doing less training in these zones. At the same time, the increased aerobic base from these longer distance plans is increasing your fitness and allowing you to run faster before you even start to hit the LT region.

If you want to get an updated idea of your LT, you need to do a run that includes data below and above your LT. Identify a speedwork day in your marathon training plan, and substitute in either a guided LTHR test from the watch, or an interval training run that triggered an LT update in some of your earlier training. This should give you an updated view of your LT, without disrupting your marathon training too much.

Thank you mcalista,

You are right and it might be because I'm switching to longer workouts.

Yesterday though I did a 4 x 5min Intervals workout at threshold pace and at the end of it my watch did ask me if I wanted to update my LT but it was way lower (5:38 min/km - 168 bpm). Looks like I'm getting slower... Lol

I think I will trust more my body and how I feel and less what this watch says.

Cheers

your bpm went lower because your body is getting accustomed to the workouts- that means you're getting fitter ;-). once you're going to include higher efforts - like 4:45 min / km runs for extended periods, your bpm is going to rise again together with the pace - or - if you're going to neglect training a few days (> 7 for example) and try to run at your threshold pace ~5:20 - your hr treshhold is going to rise again with a few beats. eventually at some point in time, you're going to reach a certain plateau (depending on your genetics, metabolism, eating / sleeping / drinking habits, etc); either way - looks like there is room to grow ;-)

Thank you tsofron, it’s a long way to 4:45 min/km... But there is definitely room for improvement! I’m working on it. 

Interestingly enough, in 1 month of Marathon Training (a lot of Intervals and Long Runs) my LT heartbeat went down to 163 (from 170) and same pace 5:25 min/km.

Because I have my HR zones based on LT though, I now have smaller HR zones, in particular Z2 and Z3. That makes it a bit more difficult to run in Z2 on my easy runs. Is this normal?

The LT HR dropped to 163, was this auto-calculated or did you perform a 30 mins LTHR test? If it was auto-calculated, why not perform the test to confirm the same. 

I usually use Custom HR Zones instead of auto zones based on LTHR. And I only rarely change the zones around - manually, when I truly believe there has been a shift in key parameters. I think constantly changing zones within the same season doesnt make sense. Run training is a long game and things dont move too fast, even if the watch would like us to believe it :-)