I found Brian's website here:
http://www.gojumphouse.com. Good stuff!

I also found a couple of his vids on youtube (they're also on his website). The two I reviewed tonight were:
A Pole Vault Technical Model - Clymer Version:
http://www.youtube.com/watch?v=rTci0CBznEU and
The Pole Vault - After the Toe Leaves the Ground:
http://www.youtube.com/watch?v=j9UuCpwEWLE.
In these vids, I saw several mentions of the term "Active-I".
From what I learned by viewing his vids, the Active-I is a synonym for the gymnastic "tap". He also referred to the "early swing", which I would say is a synonym for the "downswing".
I now understand what Brian means by the Active-I being active. It means active in the same sense that the gymnastic "tap" is active. This is not a point in time, but a duration of a split second in time, where the body switches from the "Inverted-C" to the "I", and then ends with the "C". Don't confuse this with the entire downswing - it's not. Its duration is the same as the duration of a gymnast's tap - it's just a split second when the body switches from a very shallow Inverted-C to a very shallow/hollow C. If you have ever FELT the gymnastic "tap", or perhaps even if you've ever SEEN it, you'll know what I mean. It's NOT the entire downswing - it's just the very last bit of it. And it's certainly not part of the upswing. It's just when the downswing transitions into the upswing.
So I think I now understand the part that PVDaddy was referring to - about using the abs, etc, to intitiate the upswing - and I replied that using the abs, etc wasn't necessary if you had a vigorous downswing like Bubka (or something like that). I'm not sure of the duration that PVDaddy was referring to, but Brian was only referring to the "tap" part of the upswing - just the very first little bit of it!
Now what I have to say about this may sound strange, but I can only say what I FELT during my vaulting days ...
I was a fairly good gymnast (compared to other elite vaulters), and I often 'tapped" when I did giants or a kip-to-a-handstand. So I KNEW (and still KNOW) what a "tap" felt like (feels like).
When I explained my downswing in my Bryde Bend thread 5 years ago, and when I continue to explain/clarify what I consider good Petrov technique today, I have never felt that the end of the downswing was a "tap". I do understand Brian's POV, but it's something that I've never personally felt.
I definitely felt a "pop" feeling - a feeling of popping out of the downswing and into the upswing (when I bent at the hips) without any (or hardly any) abs or arms effort at all.
Was this a "tap" that I was doing? I don't think so. It certainly didn't feel like the taps that I did on the highbar. But maybe I was tapping during my vaults but just didn't realize it? Or is this just all symantics?
I'm questioning this, but I think there's only a 10% chance that I was tapping, and an 90% chance that I wasn't. I think the end of my downswing was just that - the end of my downswing and the start of my upswing. I just didn't feel a "tap" at that point of my vault!
I would be very interested in hearing from other vaulters that have FELT what a "tap" on the highbar felt like, versus what their so-called "tap" on the pole (at the end of their downswing) felt like.
I think if we can reach a mutual understanding of what really SHOULD be DONE or FELT during this point of the vault, we can use it to (1) coach our vaulters better; and (2) at least understand what each other's talking about when we say "tap" or "Active-I" or downswing or upswing.
Brian Clymer and PVDaddy are free to use the terms "Active-I" and "tap" just as I'm free to use the terms "downswing" and "upswing". I just don't see the value of the term "Active-I" if it doesn't mean anything different than the term "tap". If it's a tap, then call it a tap!
Or is it the same as a "pop" - just like what I felt and described?

Kirk