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

Even though weightlifting is anaerobic for the most part, I can't imagine how any amount of weightlifting would improve your anaerobic threshold while running, so there must be a difference. 

In running, it seems to me that your body is switching from aerobic to anaerobic as the availability of oxygen becomes a limiting factor. 

Whereas, in weight training, you are using anaerobic energy production, presumably in spite of the availability of plenty of oxygen.

I don't really have a problem with the watch not showing an anaerobic benefit to lifting since I know lifting is doing nothing to improve my running anaerobic threshold. 

Just thought I'd add my $0.02 here, given that I've had the same experience.

I used to only use my HR watches, for cycling, way back when I was racing.  More recently, I picked up a FB Charge, and then a Charge2, neither of which would do any sort of halfway-decent job with my HR, lifting weights (if I got ANY anaerobic data, it was VERY minimal).

Anyway, fast-forward, and I'm using a Suunto Ambit3, my old "ski tracking watch" now, for tracking my rides, too (a VA3 tracks my everyday, and hopefully soon, a 945).

Anyway, when I went to my VA3, I would sometimes use it, for rides (forgot my Suunto at home, whatever), and other activities, and then lift weights when returning.  Using these for riding , I ended up with a Rhythm Optical strap (which, for me, is pretty much dead on my old EKG strap, I tested this a couple of times, before deciding the Rhythm was so close, for me, that it didn't matter).  
If I leave the Rhythm on, when lifting, I get a pretty good "picture" of my anaerobic efforts (perhaps not perfect, since it's still my arm being used for lifting/measuring), but if I just using just the wrist HRM, it's almost a joke, by comparison (I'm lucky if I get 1-2 anaerobic "bursts", out of say 75), wrist HRM is clearly NOT a good way to track weight-lifting, on the whole.  Which is what most of these answers suggest, just offering my way where it "works" with an OHRM, just one further up my arm...

tx911 said:

Even though weightlifting is anaerobic for the most part, I can't imagine how any amount of weightlifting would improve your anaerobic threshold while running, so there must be a difference. 

This is the key point.

Weightlifting is anaerobic, but unless it's intense HIIT type training, it won't cause improvements to your cardiovascular system, which is what the FirstBeat aerobic/anaerobic effects are measuring.

@chunkywizard, Not really. It's actually more about increases and decreases in your HR rather than a particular zone, although obviously, large increases in HR typically result in your being in an upper zone. BUT, as your maintain your effort in that upper HR zone, your aerobic energy system has a chance to catch up to the level of demand, and a massive amount of that energy demand is satisfied aerobically and minimizes the anaerobic contribution to the degree possible. 

My thinking is that with a HR strap you will get sufficiently accurate training effect data from the gym too - when talking about cardiovascular TE, which is what Firstbeat algorithms are aimed at. Most likely you will not be overloading the cardiovascular system with weight training.

On the other hand, to accurately assess if you are overtraining your neuromuscular system may be a bit too much to ask from HR based algorithms. For this you would need pay close attention to your personal observations - and the way your weights and running fitness are evolving over a period of time.

I think no matter what device you use, you'll be disappointed in the results if you're expecting to track anaerobic activity by HR.  As many others have said, you simply cannot get to the upper HR zones in the short sets that are done in typical weightlifting routines.  By definition they are anaerobic though, so if you want to track you'll need to find other means (spreadsheet, inputting into something like Training Peaks or SportTracks, etc).

i think there is a missing point in this discussion.

HR zones aren't equal between different types of activities.
for example:
My running HR zones are greater than cycling zones, witch are greater than my swimming zones.

That said, only from my own experience, my HR zones for weightlifit activities will be lower than all above. At least, lower than running and cycling HR zones.

So, I don't know if there is a protocol to measure it, but if you set your weightlifitting HR zones correctly, I belive that the firstbeat algorithm can track the anaerobic training effect.

You do have a point here: the HR zones for different sports differ, mainly due to different amount of muscles activated within the sport.

Now, the problem with applying this idea to weight training is that each exercise would require a specific set of HR zones. The zones for deadlift would differ from one-hand bicep curls - by a mile or maybe two.