Here's what he said:
Instead of using a hammer grip we are told to extend the thumb and mostly hold the stick firmly with the top three fingers. We tense the rest when striking. People often ask me why. And the way I understand it is that the thumb allows you to get a little bit more snap, more control and also a little bit more extension when the fingers are tensing.There are a variety of advantages to this method of gripping and he wanted me articulate the biomechanics of why this is so.
The first, and most important, is the way in which this grip allows you to control the weapon better. This matters more with an edged weapon than the Irish stick, but this is a difference of degrees.
The tips of your fingers are exquisitely sensitive with some of the highest nerve ending density in the body. This provides highly detailed information for adjusting edge alignment and positioning the weapon.
Further, by holding the weapon at the end of your fingers you are able to move them to move the weapon, making small changes. This improves edge alignment, it's how you make a disengage with a foyning weapon and a variety of other actions.
Now we get to something that seems trickier and would generate more debate but really doesn't vary as much as people think.
Do you hold the weapon with the first two or three fingers or the last two or three? As long as all the fingers are on the hilt all the time then it doesn't actually matter. What I would not want to see is an open hand where only the first one or two fingers are on the hilt - this is good for twirling a stick but bad for fighting.
If I have my first couple of fingers gripping the weapon firmly and the bottom two just holding on then I can squeeze those fingers as my strike approaches it's target to improve the hit. Or I can hold primarily with the bottom two fingers and squeeze the grip into the top two. It ends up being nearly the same.
Both are described and/or depicted in the source material and the biomechanics are just about the same.
What's going on is that the forearm muscles involved in both grip and ulnar deviation/adduction are all activating at once. These are mostly the muscles on the inside of your forearm - the paler side - with some of the muscles on the other side activating as well. These are probably fairly big muscles if you train a lot. (Flexor carpi radialis and extensor carpi radialis are the most significant but the flexor digitorums are also involved).
What's termed ulnar deviation or adduction of the wrist I like to think of as wrist extension, because that's how it's used related to the movement of the rest of the arm - as I extend my arm towards the target I adduct the wrist to extend farther.
(Similarly, I think of plantarflexion of the ankle as extension - this also makes the names less stupid)
So as I extend the wrist I add rotational energy to the weapon and a small motion at the hand creates a large motion at the tip i.e. it increases the velocity significantly. Increased velocity is increased power.
This also firms up the grip at the moment of impact so that you: a) transfer power efficiently in to the target; b) don't lose the weapon just because you actually hit something; c) can cut with opposition or parry effectively.
It's important to avoid over-extending the wrist as this means you lose the advantages I just described from the stronger grip. If you let your hand hang by your side you should note that it is not quite in line with the forearm.And this is as far as you should extend the wrist. Any further and the bones don't line up right for good energy transfer.
Training - the easiest way to train this tensing component is to strike a pell. The brain will automatically tense the wrist/forearm muscles when you work the pell with power and this will make it the default when you strike. Pell work is also one of the only training methods described in historical sources.
The ThumbWith the thumb on the back of the grip you can also add it's opposability muscles to the action of generating power. This works well for lighter weapons like saber and stick, but you need the thumb wrapped around the grip for a heavier weapon like a broadsword, rapier or Medieval sword. However, this is as much providing a solid pivot point to lever the grip as actually move it. The motion is still mostly generated by the lower finger muscles.
Seizing the Weapon
Another point that Max brings up is the vulnerability of the thumb in weapon grabbing techniques. Interestingly, the Irish Stick tradition takes basically the opposite thought on this from the way I've seen it described before.
It is easiest to seize the weapon or disarm your opponent by twisting it into the thumb side, as opposed to twisting towards the palm. Putting your thumb along the back of the grip makes it even easier to be disarmed. So if I was worried about being disarmed I'd keep my thumb wrapped around the grip like I do in Broadsword and with Medieval swords.
But the Irish Stick tradition says that getting your thumb in the way of a disarm is just going to get it injured, so holding the thumb along the back is viewed as protective and advantageous. Max said, "it allows you to let go of the stick more easily if it gets grabbed and twisted." That's an interesting difference in perspective. I wonder if it has to do with the relative safety of grabbing a stick versus a blade leading to more techniques based around disarms after grabs.
Weak Grip?(Remember, any time you see a question mark in a headline the answer is almost always, "no" - Betteridge's Law.)
One other question that Max poses is whether or not baton instructors are right to criticize this as a weak grip. Near as I can tell the answer is no. However, it has to do with style preferences and method of use. The baton that I've seen includes a lot of stick twirling and for that action wrapping the thumb around the stick will be stronger than the back of the grip alternative.
But if you are hitting to injure then the grip used for Irish Stick is just fine.
So, if you aren't planning to twirl the stick like a baton then it shouldn't matter. Read that how you like.
After I posted this Max replied. And he let me know that the baton he was talking about was things like police baton not French La Canne. As to why they cling to the hammer grip he suggests the following:
I think its one of those things that got developed out of simplicity's sake (easier and quicker to teach a hammer grip to soldiers and policemen) and then repeated on an on without anyone really questioning it.I have no trouble believing this explanation. That being said, I'll note that each approach has it's advantages and it's more important to know how to use the system to train to it's fullest rather than to compare systems.