by skijim13 » Wed Dec 06, 2017 5:00 am
CoContraction of a muscle Cocontraction (the simultaneous activation of antagonist muscles around a joint) provides the nervous system with a way to adapt the mechanical properties of the limb to changing task requirements—both in statics and during movement.
This is from the forum: You may be reading here and think the phantom move is like a ghost - a figment of someone's marketing imagination. You may actually be justified in these conclusions after conducting their personal tests of this on the hill. So, how can these important authors all be wrong when many skiers still hold to active steering as the way to go and have never felt any effect of the phantom move.
I now understand the little piece that is missing. Someone that actively steers and is used to guiding and following the skis with active steering in their legs will almost by definition NOT be able to feel anything at all when they try Phantom Edging (lito's version) or Phantom Move (Eski, HH, Craig McNeil version).
Ok, read slow:
In people's nervous system there is the normal voluntary muscle system. You can illustrate this to yourself by simply bending your arm at the elbow. Your bicep pulls your arm up. Muscles cannot "push" but only contract, so to make your arm go the other way, your opposing muscle, your tricep contracts.
That's the voluntary system.
The voluntary system is weak. The voluntary system is slow. (this comes in later when you see that to create torque for rotation you can use the voluntary system (what HH calls bad rotation) or you can use a much stronger system that I'll introduce here in such a way so everyone reading this can actually experience the phantom move for themselves. (even if they never have before)
You'll need a friend for this one. To illustrate how the voluntary system is slow, hold your hand out with the finger and thumb ready to grasp a falling object. Have your friend hold a dollar bill with the very bottom of the bill just between your thumb and forefinger. Have your friend drop the dollar bill when you don't know they are going to do it and try to catch the dollar bill. You'll not be able to do it unless you read and anticipate something from your friend. There is just no way the slow voluntary system can do it. This is because the voluntary system relies on direct control from your brain and there is a time delay along your nerves.
Thankfully, the muscles have a 2nd way of being activated that is much faster and happens to be much stronger - measurably.
This also requires your friend, but you can also do it yourself. Lock your arm in a 90 degree bend. By locking I mean do whatever comes naturally when you want to make your arm be a certain angle and not allow it to be bent. Now have your friend hit your arm from top to bottom. Then do it from bottom to top. You will notice that your bicep and tricep will fire, without any conscious effort on your part to keep that joint at the same angle. It's almost as if you arm is "locked" by friction in the joint, but it's not. Your joint is just a free as ever. But our involuntary nervous system is smarter than we are and can maintain this active counter to force instantly. This proves your brain is not involved in directing this activity other than the initial command to hold your joint lock in place.
The other fascinating thing about this phenomenon whose technical name is co-contraction is that it's very strong. Lets say you can normally bicep curl 80 pounds with one arm. You can easily have a 140 pound person grab on your co-contracted elbow and hold them in place. You can't raise them, but you can keep your joint in that position. Negative reps in weight training is this same effect to some degree but not quite the same.
Ok, now that you've digested the above here is another weird phenomenon. When you did your first bicep curl above - the voluntary kind, medical science has discovered that your tricep - the nerves to it, will not react and pass on external electrical stimulation. This is called pre-synaptic inhibition. This is evolutions way of having us move efficiently. When you contract one muscle the pathways to the opposing muscle are mostly shut down. It's like the old radio buttons on a car. Only one button can be pressed at a time.
Now for the kicker. When a muscle is co-contracted as in locking a joint, until your brain calls this off, both muscles are inhibited from external stimulation. This is weird stuff and is late 90's research. You can easily feel this yourself. Just lock your elbow and while keeping it in a locked state, do a bicep curl. It's real hard. It's not hard because your actually doing any work, because you're not, you're just experiencing the lockout your own body does on co-contracted joints.
Ok, what does this mean for the phantom move and the people visiting this board trying to understand it.
In doing the phantom move, you start with your skis parallel. You tip the inside foot. If your hips are relaxed and not in a co-contracted state you will feel absolutely nothing happen on your other leg. However, if you apply a little, and just a little of that co-contracted feeling to your hip-rotators so that you have told your hips and rotators maintain position, when you tip that inside foot you'll almost feel strong pressure on the other foot to match the tipping angles of the inside foot.
My theory is that the people that don't know what the phantom move is all about, don't ski by co-contracting their hips rotators but leave them loose and actively direct their skis with these same hip rotator muscles. A skier that does this is creating their rotation with the weak voluntary system. A skier using the phantom move controls both rotational torque and tipping angles with that one simple movement. And the rotational control is finer yet stronger than the direct way. (try it in a doorway and see - but don't injure your outside foot)
Further - you'll note in your arm and it's also true in your leg - when you co-contract your elbow joint, you'll find rotation of your forearm becomes harder, yet even with the most co-contraction you can muster, you have complete freedom of movement of your hand. Medical science has discovered the same thing happens in the legs. When you are co-contracted in both your hip rotators and your weight bearing knee joints, you are limiting the upper thigh and lower leg steering ability as compared to a relaxed leg due to pre-synaptic inhibition. But, your foot is free to tip even in a co-contracted state.
This may be why the proponents of a wider stance and active steering and even weighting have adapted their skiing that way because it would be a natural result to a person that skis using only the voluntary system and who is not using co-contraction to their advantage.
Also, since the feet are not affected by co-contraction even the weighted release in PMTS where all the weight is left on the downhill about to be inside ski works. The active tipping of that foot initiates the turn no matter what the weight distribution is.
So, if you've never felt the effect of the phantom move have your friend hold your foot in place while you co-contract your hip rotators. Then have your friend (like the elbow exercise) distrupt your foot. (sit in a chair - raise a foot). Once you're sure what it feels like to apply co-contraction to your hip-rotators, stand in a doorway. Support yourself in a comfortable stance (legs dangling straight out of your hip sockets), then tip your right foot while leaving your hip rotators relaxed. (this will point the knee out but is totally different then pointing the knee out) Then do it again with your hip rotators co-contracted. You will feel a strong action on your outside foot.
Then go read Eskis, HH's, Lito's, Craig McNeil's books again and realize the only reason you thought the phantom move was bunk was because you never had anyone bother to tell you the hips need a tad of tension (co-contraction of the hip rotators) for any of this to work. Once you discover this, play with it on the slopes. Just stand on your outside ski, apply a little hip rotator lock, tip your inside ski.
Oh, back to knee pointing for one moment. I've heard people say that tipping the inside foot which results in the knee pointing is the same bio-mechanically as simply pointing the knee. This is not true. If you don't consciously tip the foot that then result in that legs knee pointing into the turn, then you may be actually pointing the knee into the new turn with your hip-rotators. If your doing that, you're not co-contracted in your hip-rotators and your skiing the hard way. There is a big difference.