Hour and a half of weight lifting without anaerobic effect :) Really?! :)

Did your HR reach your set zone 4 while lifting?  Are you confusing anaerobic with aerobic? 

This is the right question to ask.

Weightlifting isn't cardio.

I'm not confusing anything. Weight lifting is well-known ANAEROBIC exercise. 

Are you using a chest strap or the OHR? OHR is not very good when doing weight training. Though the calculation of training effect is more or less the same.

The way the watch works is by taking your pulse. If you reach a certain high zone, it will count that as anaerobic exercise. I do not think this model is particularly suited for measuring the effects of weight training. Sure if you do cross-fit style workouts, you will be able to measure aerobic and maybe even some anaerobic effects due to the high pulse, but if you just do short sets of heavy weights your pulse wont be up there before you are done.

For weight training if you wish to quantify your load and training effect, please use a log-book where you track the exercises and weights, thinking the watch can somehow magically determine how hard this effort was for you is very optimistic ;).

I think we need HermanB to comment here, but my guess is we are talking about different things here. When Firstbeat are talking Anaerobic they mean your heart rate is above your lactate threshold which is something like 90% of your maximum heart rate. What did you heart rate get to on the activity?

really?

because i do strength training (Kieser Studio) and mostly my HR is under 100, is the weigth lifting here described totally different?

my aerobic training effect ist mostly under 1,0 and anerobic is 0,0 on my Fenix 5! 

The watch does NOT take your pulse. Taking your pulse is a physical reading of the heart rate from a major artery; like the wrist. It's also a bit behind the actual, but fine enough for an average. Optical heart rate is a guess at your heart rate based on light shining back at it via capillaries. At its best, it's a tertiary algorithm based on a localized area, in this case, far away from the source (the heart) and what is happening. There are so many issues here that strength training with a wrist-based OHRM is a bad idea.

Muscle flexion interrupts the blood flow, so it never gets a proper response, the delay from the source and the lengthy lock-in is another. Bicep OHRM like Polar's OH1 are better at this, but not entirely as accurate as a chest strap which is taking your BPM in real time via electric impulse over the heart.

Anaerobic never worked right. Not here and not on the 935. I did/do a workout program that focuses on lifting and working two muscle groups for the first half, and a HIIT second half daily where my HR goes north of 165+ for elongated periods. During the lifting, it creeps close to my z4, and I get Anaerobic returns (like to 1-1.4) and then do work (in the same activity being recorded) well into that range for 10-25 seconds and get NO Anaerobic (or aerobic for that matter). 

I always end with a 2.0-2.4 Anaerobic and a 3.0-3.4 Aerobic regardless to the activity, HR ranges, intensity, added weights (I've tested this, I doubled weight for workouts, got same returns). I've tested this in the strength training activity and get these same results, I've done these same workouts using the cardio activity and got the same results, for years. I always use a chest strap. 

It would sure be great to perhaps, have a graph chart option for Anaerobic/Aerobic recorded alongside the other metrics in activities and not just have a non-informative number that shows nothing but the result. Perhaps letting us overlay these metrics over HR data so we can physically see when and where aerobic/anaerobic data rose or spiked during a workout?

All we have now is guesswork.