Delays in speed and pace makes it impossible to follow suggested sprint workout with Fenix 6X Pro Solar version 12.10 RC

I see, its two different suggestions then. They are probably personalized based on activity history.

I did a deep dive in the .FIT file data for record.distance[m], record.enhanced_speed[m/s] and gps_metadata.enhanced_speed[m/s] from my 19.52km run last week. I have compared the data in the file vs own calculations and also vs odometer. And there are big differences in the numbers for both distance, speed and pace. 

I had similar issues with low anaerobic score with this workout, my sprints were suggested as 10s. I struggled too see how 10s could get my HR high enough. So on next occasion instead of 10s I did the sprint for 1min and the anaerobic score came out on target. I don't know if it's a glitch in the system where 10 sec should be 1 minute or if that just works for me.

I wear a hr belt.

Today I did a new try on this workout but with a twist this time.

I jumpstarted the intervals with 7-10 seconds and ended the intervals 7-10 seconds earlier than the workout suggested. A workaround to solve the delay issues. Now the speed/pace data are in line and and the anaerobic points and training load increased compared to last time.

The conditions was not exactly the same. I was a little bit tired today and the weather was colder today (around 0 degrees Celsius). Winter is coming here in Sweden. Due to the conditions my heart rate was higher today compared to the last time.

The anaerobic points was received on interval 1, 2, 4 and 6.

Got Training Effect "Sprint" this time and 131 points in Load. Last time I got Training Effect "Base" and 82 points in Load.

I think that you only need to be on the move when the timer starts. not necessarily end earlier.

Suppose you did this without any laps, just sprinted for 15 secs, stopped for 15secs and so on.

Would not this produce the exact same result?

To make my point more clear, I think the issue is that the HR does not correspond to the pace for short sprints.

When someones starts sprinting, pace goes up (more or less immediately) but the HR is lagging behind.

As soon as the HR climbs, then the 15 sec sprint is over and the watch observes zero speed (pace) and high HR.

Last time I ran I noticed a 7-9 seconds delay in picking up speed/pace so that's why I did the jumpstarts today.

Yes, that will probably work. To run intervals like in your example. But that is not the case here, because I sometimes want to follow the suggested workouts. If Garmin suggests workouts it must work to follow them. Why suggest workouts if its impossible to follow them?

I'll be curious to see if the speed/pace issue is resolved, but it seems most people here are misunderstanding the heart rate. Heart rate in nature is a slightly delayed response to effort so it is a poor proxy for intensity, especially with short, high intensity intervals. You heart rate on a 15 second sprint will never truly reflect the effort that was given. The effort will be over before the heart rate truly reflects the effort. This is why in cycling for example, power from a power meter is a much better reflection of the effort you are giving at any given moment because that's exactly what it's measuring. The reason you saw a higher peak heart rate on the 10,63 km jog was because your heart rate was at a higher rate at the beginning of the sprints and had less to climb in response to the effort. The efforts weren't necessarily harder. I suspect that if you used something like Stryd you would get more accurate reflections of aerobic and anaerobic work load. I know with my cycling that is the case when I use the power meter. Relying on heart rate along to gauge intensity of sprints instead of power is like using heart rate while lifting heavy weights to measure intensity instead of weight on the bar. You can, but it's a poor approximation. Not getting your heart rate into the anaerobic zone does not mean that you had a "bad workout." It's the limitations of what heart rate can tell you. Ignoring the delay for a moment, it looks like you hit the correct pace targets so that is what you should be looking at as to whether you achieved what you were supposed to for the work out. This is also why Garmin suggested a pace target instead of a HR target for the intervals.

For more on this read the section: Anaerobic training and HR in this article. blog.nasm.org/.../heart-rate-zone-methodology-know

Which on another note, is why I don't put a huge amount of stock in the aerobic/anaerobic loads that Garmin shows. My Garmin routinely gives me a small amount of aerobic benefit from my strength work outs. This is simply not the case. My work sets currently at most nine reps, so the work outs are completely anaerobic in nature. Yet because occasionally my heart rate gets fairly elevated, my lifting sessions are actually adding to my total intensity minutes for the week which is simply wrong. I've asked and wish that you could manually remove certain activities from being counted towards intensity minutes because my weekly total is skewed as a result.

The bottom line, the speed/pace thing needs to be fixed for running it seems. Also, if you care about the training load score more accurately reflecting the work you do, probably invest in a Stryd for running. If all you really care about are the results from the training, stick to the pace targets, or just use RPE and you'll be fine.

LJSkywalker74

Thank you for your post! 

Did you see my earlier post from today? Three posts above yours. I did the same workout today but jumpstarted the intervals which gave almost the same points that the suggested workout estimated. So, the delays are clearly affecting the result of these kind of workouts with short sprints.

I did see that. Yes, it looks like that resolved the pace delay issue, which hopefully can be resolved without having to do that. However, while it looks better with regards to the aerobic and anaerobic training loads, a couple of things there. One, this is partially due to you getting your heart rate up earlier so that by the time your watch started tracking the interval you were already at an elevated heart rate instead of resting like you would be normally. This effect is for the same reasons as the 10,63 km run you did. Starting from a higher heart rate. However, if Garmin fixes the pace delay, your anaerobic training loads will again show low if you go back to starting your sprints when prompted instead of early. Are you following me there? If the pace delay is eliminated, while the pace overlay will actually line up with the target when you start on time, the heart rate will still have a delayed reaction as per physiology. So once again, don't rely on that to gauge how good your work out is when doing short sprints like that.