Are you asking a method to differentiate aerobic capacity from anaerobic capacity?
That is, rule out any aerobic input.....
Or anaerobic threshold, as has been discussed?
Your anaerobic capacity will improve due to an enhanced aerobic system, as discussed...so are you seeking to improve anaerobic function separate from aerobic? And if by measuring 'something' how will you know those markers are only anaerobic? Because by working the anaerobic system, you improve the aerobic system.....
Chicken and egg, really isn't it?
Thing is to get better and more efficient and skilled in your pursuit....making you better at the thing.
Faster. Faster for longer. More work, less effort. More power for less energy. More reps in less time. Less fatigue. What was once hard now isn't as hard, or even easy.
All those things are trackable, measurable however you choose to do it.
And then there's specificity....and efficient biomechanics....
Better snatch technique improves anaerobic capacity as you require less energy to do the thing than you did with crappy technique....so you can do more ie improve capacity.
Or slog it out huffing and a puffing...if you see what I mean. Likewise, being stronger makes stuff easier....improving capacity.
It's difficult to parse out as everything is connected, one way or another.
Competition. Testing sporadically using hr/reps/set/time....strength to weight ratio if bodyweight is a thing....in turn, fat loss as that too will improve capacity.
It all bounces off each other....
Or go to a lab. Have bloods, muscle biopsies and breath analysed.
For anaerobic capacity. Run a 400 all out. Clock time. Train for a bit...do it again to beat your time.
Or a 200. At max. Must be all out
A 400 will involve some aerobic input, a 200 less so. You may or may not use full anaerobic capacity in the 100, depending on condition/age/training history.
Sprinting and into mid distances are pretty good markers for where anaerobic capacity is the limiting factor for the event. So how deep is your pain cave?
A thought experiment that could have been a real time study in physiology.....a 400m race between sprinter Bolt and 800m champ Rushida.
One anaerobic power and capacity v aerobic power. The world's best clashing and testing at the threshold of cellular function, in a sense.
So that's why a 400 is a good measure of anaerobic function.
Some would argue anyway....