Remember that all of these factors interact. The answer is almost always, “it depends.”
Seiler says that to Extend, one must train for two hours just as a prelude to improving AeT fitness.
This totally depends on training history. A sedentary person likely won’t be able to go for two continuous hours. But for theme even 30 minutes, applied consistently, will improve their aerobic fitness (if it’s easy enough and they don’t get sucked into a HIIT intensity.)
So once a week, my goal is to train 4 hours nonstop.
That may be appropriate, but 50% of your weekly volume in one day sounds like a lot. I would start with one day at twice your average daily volume and see how you handle it (during and afterward.)
Trying to add impactful AeT volume, would adding a 15 minutes training session, although the body is probably just warming up, add to my AeT volume for the training week?
Do you mean 15 minutes totally on its own? If your average is eight hours per week, then I suspect not. Thirty minutes is probably a good minimum.
Or would 30 minutes training here and there as time permits going to have a significant value to my weekly volume or should it be a 40/45/50 or 60 minute minimum training duration???
Don’t drown yourself in details. If there were an official list of rules, coaches wouldn’t be required. It all depends on the state of fitness in the individual. For example, a program that would make me super fit will detrain Kilian Jornet.
What is the shortest that an AeT training be to be effective?
This is totally individual. The bigger the base, the bigger the minimum duration required to contribute.
