tracking your CoM and your BoS

[LiquidFeet]

It sounds like most people posting in this thread never feel nor pay attention to the two points
identified in this diagram below (the CoM and the feet), as their spatial relationship changes
during turns. (Thanks to Bob Barnes and @graham418.) Have I got that right?
Hope not.

Help me out here. I don't like being perceived as an overthinker who surely is suffering from
paralysis by analysis.

I find all the nopes hard to believe, given that some here have raced. For instance, flush gates
require a seriously different spatial relationship between the CoM and the BoS than do GS gates.
Knee wag and hip-to-snow require very different lateral spacing between the two points, and surely
the skier maintains awareness of that spacing when navigating gates.

Surviving hard snow luge lines in New England trees requires that the spatial relationship between
CoM and BoS be different than when making long radius carved turns on a traffic-free blue/green
groomer. I think of those as "reaching short radius turns." They certainly require a different
relationship than those delightful long speeding turns on the way back to the lodge.

Attempting to get "upside down" on the hill in order to get high edge angles before the skis
point down the fall line requires some serious manipulation of where the CoM is relative to
the feet at the top of the turn. That may even require pulling the feet back, then moving them
out, relative to ... well, relative to the CoM. When one topples fast at the top of the turn, surely
that creates a sensation of CoM doing something dramatic relative to the feet. (Wheee!!!)

 

[rustypouch]

Yep. One of the things I was working on last season was how my CoM moved between turns, getting it more to the inside of the new turn to increase angulation and edge angle.

 

[mdf]

It sounds like most people posting in this thread never feel nor pay attention to the two points
identified in this diagram (the CoM and the feet), as their spatial relationship changes during turns.

I think maybe the "nopes" come from asking about tracking them as two separate things. You feel their relationship.

 

[LiquidFeet]

I think maybe the "nopes" come from asking about tracking them as two separate things. You feel their relationship.

How can one feel the spatial relationship between two things without sensing each of those things?
One is here. The other is there.
So the relationship is here-to-there.
And in skiing, the relationship changes. Here and there keep moving.
So if you pay attention to the changes between where the here and the there go,
then you are tracking the changes in the relationship, and each point, right?

 

[James]

I’d say yes to tracking com a fair amount. At transition, I know it’s in the wrong spot if I have to do something like stem to start the turn. It might be almost unnoticeable, but you can feel it.
Tracking skis? Well line yes. If skis get way out from the body I guess it’s tracked buy more unconscious. You need to know where to be when the moment is critical. That’s probably more unconscious.

In very steep terrain I pretty much have one focus and thtay’s commiting downhill with the body/com. So that would be com tracking. It goes with bos in that you can’t be too aft when pressure comes if the goal is a low energy turn to stop for example. That’s more unconscious and adjusted by feel.

There’s not a lot of feedback to where the com is until it’s too late. You can still sense it in the ai/unweighted state. That’s why I say it’s tracked. I think it’s more conscious than the feet because you have more feedback from the feet and it’s more unconscious.

But, I might have to reevaluate this when I’m on snow.

 

[cantunamunch]

How can one feel the relationship between two things without sensing each of those things? One is here. The other is there. So the relationship is here-to-there. I don't get it.

You are only tracking -one- quantity -> the offset between the two.


Look at the picture you posted about the Infinity Move: the CoM is the origin point of the coordinate system. There is absolutely *no* information in that graphic with regard to how the CoM is moving.

If you want to say "yes we need to track CoM" the question becomes "Relative to what?". Relative to external objects/obstacles? Mostly done by default because your eyeballs and ears, your sense of "I", is almost coincident with the CoM.

I can think of several situations in which sense of self is not necessarily coincident with where the CoM actually is - but they're all pretty durn nasty. Like avalanche burial. Hence my post earlier in the thread where I propose that actively sensing CoM is actually sensing error.

 

[LiquidFeet]

Look at the picture you posted about the Infinity Move: the CoM is the origin point of the coordinate system. There is absolutely *no* information in that graphic with regard to how the CoM is moving.

Correct. The video describes a relationship between the CoM and the BoS, just two things. Where on the hill either is located is irrelevant to my thread topic. Indicating how the CoM is moving left-right on the hill, and how it is moving downwards towards the lift, would require including a third factor in the graphic. But that is not an issue in the questions I've posed.

However, one could redo Bob's video by making the feet the "origin point" of the coordinate system, instead of the CoM. The feet would appear as a stable point in the middle of the graphic, and the CoM would move in the reverse direction along that sideways figure eight. Is that what you are suggesting?

Anyone want to talk about why Bob didn't choose to illustrate his infinity move the way he did, with CoM the "origin point" aka frame of reference point?

 

[Ski&ride]

Am I aware my com is in a different relationship with bos in angulation vs inclination? Sure.

But I don’t need to think about it. It just happens. Sometimes on purpose, other times as a result of my legs/skis went to a different spot than I intended. I either react or intend.

But I’m not “tracking” them. Ok, my body does, as trained/practiced. My brain however, is NOT involved. It’s too slow to “think” while the ski is flying down the slope at 30mph!

Analogy to mtn biking: I pay attention to where my bike goes. My body (com) does the right thing to effect the trajectory of my bike. I’m not “tracking” the two separately!

 

[Scruffy]

Does a professional ballet dancer/skater think about his/her CoM/BOS as they spin or pirouette fast and over and over? I don't think so.

Does a long bow archer that shoots instinctively without sights or a release, and can hit a target at any range ( within the bow's range ) and with any windage, and even if the target is moving, think about what they are doing within the milliseconds they have to gauge all of that and make the shot? The answer is no here, from experience.

As an ex-ski racer ( amateur ), I personally, whenever I was in the course ever thought about where my CoM/BOS was or wasn't. All that stuff has to be ingrained, instinctive, and unconscious. In the course you are thinking about your line and making it. Maybe if I thought about my CoM/BOS while racing I'd be a on top of the podium That's prolly where I went wrong

 

[Crank]

Think only of balancing over BoS. Where the CoM goes is merely a byproduct of staying in balance.

@LiquidFeet , when you ride a bicycle do you track both CoM and BoS (the tyres) or just think about maintaining grip and incline as needed to get around a corner?

I once had Gary Fisher tape some mountain biking tips for some TV segments. Yeah pre hi-def when we recorded on tape...16mm film for theses if I remember correctly. Anyway - gary said that what we call the crankset, (the middle of the chain ring) the Italians call the central movement. And he then went on to describe how your balance needs to be over that central movement depending on the steepness, variations in terrain etc. etc.

Kind of feel like that equates to the COM in skiing.

We have spoken here about unconscious competence. Paying attention to where you COM is in relation to your skis and your upper body, for an accomplished skier, is possibly something an instructor might want to leave the realm of unconscious action to dissect. However, would you, could you teach dynamic balance using that?

 

[François Pugh]

Never say "never".

At one time or another I have tracked everything about my skiing. Doing endless repeated laps of my tiny hill, making turn after turn, my mind sometimes wanders. I do remember keeping track of both while carving tighter and tighter turns. I do remember keeping track of both while playing a little game I'll call "Don't get tripped", where I try to see how far uphill I can keep turning (by tipping) my skis after releasing my com, and making sure I turn (again by tipping) them back downhill in time to prevent disaster. This game is fun to play with SL skis at relatively slow speeds, and exciting (higher consequences for failure) with GS skis at high speeds.

 

[markojp]

Yep. One of the things I was working on last season was how my CoM moved between turns, getting it more to the inside of the new turn to increase angulation and edge angle.

Not saying this is the case for you, but if I had a dollar for every hip dump I've seen/tried to correct when coaching/teaching for people trying to get their CoM inside, I could open the bar up for a couple of hours for everyone here.

I like to think of it as getting my Mass ahead of my feet DOWN the hill AND over the outside ski at apex.

 

[S.H.]

It sounds like most people posting in this thread never feel nor pay attention to the two points
identified in this diagram below (the CoM and the feet), as their spatial relationship changes
during turns. (Thanks to Bob Barnes and @graham418.) Have I got that right?
Hope not.

Help me out here. I don't like being perceived as an overthinker who surely is suffering from
paralysis by analysis.
View attachment 81163

I find all the nopes hard to believe, given that some here have raced. For instance, flush gates
require a seriously different spatial relationship between the CoM and the BoS than do GS gates.
Knee wag and hip-to-snow require very different lateral spacing between the two points, and surely
the skier maintains awareness of that spacing when navigating gates.

Surviving hard snow luge lines in New England trees requires that the spatial relationship between
CoM and BoS be different than when making long radius carved turns on a traffic-free blue/green
groomer. I think of those as "reaching short radius turns." They certainly require a different
relationship than those delightful long speeding turns on the way back to the lodge.

Attempting to get "upside down" on the hill in order to get high edge angles before the skis
point down the fall line requires some serious manipulation of where the CoM is relative to
the feet at the top of the turn. That may even require pulling the feet back, then moving them
out, relative to ... well, relative to the CoM. When one topples fast at the top of the turn, surely
that creates a sensation of CoM doing something dramatic relative to the feet. (Wheee!!!)

Generally speaking:

• I care about where my feet are in SL more than in GS or speed.
• I care about where my pelvis/hips/torso/shoulders are more in GS/speed than in SL; and I care about where my feet are relative to the groove/microterrain.
  
• I'm not consciously tracking anything, but the focus of my awareness is different.

I think in reality, though - I *can* frame my awareness in a BoS/CoM framework, but I don't. The focus, if there is one, is on line, tactics, and maybe one overarching technique thought/trigger. The BoS/CoM is unconscious (nearly instinctive), to be (maybe) thought about/focused on during drills, skill acquisition/refinement, when trying to make changes in base technique, etc. *if necessary*. It's not the framework in which many people/athletes think, and focusing on it directly may or may not lead to performance gains. Depends on the learner.

 

[razie]

Nope.

I mean I am aware of where my feet are, but most of the time they don't support much, as we glide between apexes. I also am aware of what my upper body is doing, but I do not track their relationship specifically. The body needs to be relaxed so the feet and ankles can move. Not much support implied there.

Neither consciously or subconsciously (I think).

Not tracking any trajectory of body parts either. I generally would be aware of where I'd like my feet to be at the apex of each turn, i.e. "turn there, there and there", especially in gates, and the ski, speed and desired radius dictates where my upper body should be to support that. That's how that equation goes, for me.

I think I would find it weird to plan a line for my body and have feet be pushed around and hit random patches of snow to support that, that's backwards.

A flush is a wiggle, so it dictates that (less turning, more upright). Big offset is hip to snow, so that's that but it's not a function of me deciding hip here and feet there, it's the turn that needs made that dictates where the hip must be to get the radius from the ski...

I don't think focusing on the com and bos relationship is that useful, that's more like something I would diagram out for someone, while explaining something, but it's what the body parts do that deserves the focus of the skier. Relax, close, tip, extend, counter etc

Cheers

 

[Chris V.]

Paragraph by paragraph:

1. Tracking two points. To the extent I'm thinking about where my BOS is located, I expect the word that's in my brain is not BOS, but simply "skis." Or inside edge of the outside ski, mostly, though during the transition that's not quite accurate. Yes, I continuously sense where my skis are, because they're firmly attached to, and very close to my feet. And what is one of the parts of the body where our sense of touch is most acute, and the part where we use the most? The soles of our feet. I sense a great deal in the soles of my feet while skiing--movements of forces coming up from the snow fore and aft, and from side to side, and changes in the overall magnitudes of those forces. The information received from the sense of touch in the soles of my feet feeds into my brain continuously, but most of it is processed only by the subconscious brain. My conscious brain gives attention to it selectively. Further to what Scruffy and S.H. were saying, the goal of training and practice is to make movements, and responses to outside stimuli, mostly products of the subconscious brain. The conscious brain isn't capable of handling the huge number of tasks that the nervous system has to handle in rapid succession. We have to be selective as to what to give the conscious brain's attention. When learning and practicing, we generally pick out a few things to think about consciously, and build the motor patterns for which the subconscious brain can then take over responsibility.

I don't ever think about the exact location of my COM, not in those terms. It would be too difficult to constantly calculate the changing exact location of my COM as my body went through contortions. We all sense instinctively that our COM is somewhere in our belly while standing straight, but I wouldn't have known more precisely than that if experts hadn't told me. In less precise terms, I will from time to time think about where my body is located, relative to the snow and relative to my skis, and where it's going. Not continuously. See more under paragraph 2 below. But again, proprioception continuously and primarily feeds into the subconscious brain.

The relationship between the COM and the BOS in one or more of the planes--fore-aft, lateral, and up and down--is fundamental to most of the movements that we want to develop and refine. So I will be giving conscious attention to that relationship in one or more planes when working on changes to my skiing, but I wouldn't say that I'm giving conscious attention to all those aspects of that relationship CONTINUOUSLY.

2. Tracking two lines. I wouldn't say that I track these two lines CONTINUOUSLY, but I do devote a good deal of the limited attention capacity of my conscious brain to recognizing the different paths taken by my body and my skis. This really is the basis of a huge part of what we do while skiing. Most of the fine tuning of movements that we make, consciously or subconsciously, have to be built on this foundation--if they're going to be in the direction of making improvements and increasing versatility. I don't so much visualize lines drawn on the snow, as FEEL my body moving down the mountain in the direction I want to go, achieving the appropriate amount of movement from side to side as I turn back and forth, and FEEL my feet and skis moving away from my body and then coming back under my body, in smooth and progressive movements.

3. Conscious or unconscious tracking. As I've gone into above, I think that the vast majority of what I'm doing while skiing comes out of the subconscious brain. It just has to work that way. Whether I'm doing a physical activity well, or doing it badly, what I'm doing is mostly the result of nerve impulses arising in the subconscious. When I'm trying to change or improve my skiing, that's when I focus my conscious mind on some particular aspect of the movements involved. From time to time, that could well involve a direct focus on the relationship between the location and path of my body, and the location and path of my skis. Most of the time, my conscious mind is largely occupied with adapting to the terrain and snow conditions, and making little adjustments to aspects of my movements to suit those conditions.

4. Learning to do this tracking. The idea and FEELING of the body and skis taking separate paths took time for me to grasp. As a beginner, and I expect like most beginners, I tended to think of myself as being locked onto the skis, and fated to go just where the skis went. Improvement came in part from instruction--but I think that I finally came to a breakthrough in my thinking and sensations on my own. I remember a time when I started thinking more about where my body was headed, and making that happen smoothly, and worrying less about what my skis were doing. I know, that sounds contrary to the advice to ski from the feet up. But I think this allowed me to improve separation of the upper body from what the feet were doing, and to realize that yes, the skis were going to come around and catch up to my body. I now think that getting students to this realization and feeling as early as possible will speed their progress tremendously. This isn't about teaching a particular, discrete movement. It's more about just letting go.

One more point. There's no need to teach inclination. It happens instinctively. We know about it from running, from leaning into a strong wind, and from all kinds of other common physical activities. If you don't incline in just the amount needed to counteract the forces created by the radius of your turn, and the speed you're traveling, you'll be on your face in the snow very quickly. So people tend to learn inclination fast. What's more difficult is teaching smooth transitions from turn to turn, staying away from sudden increases or decreases in forces--which leads to the rounded turns we tell students we'd like to see. Beginners and novices tend to lurch from one static position to another. A skier can have perfect inclination--and angulation!--in a static position, but that in itself won't lead to an elegant and pretty relationship between the lines taken by the COM and the BOS.

5. Why do it. Right now, I don't have anything to add to what I've written above.

 

[Dakine]

Boot tongue pressure.
If I have it, things are good.
If I don't I have to figure out why and fix it.

 

[LiquidFeet]

.... @LiquidFeet , when you ride a bicycle do you track both CoM and BoS (the tyres) or just think about maintaining grip and incline as needed to get around a corner?

Interlude.

@geepers, I've stopped riding a mountain bike on our narrow hilly New England singletrack trails. They are filled with rocks and roots. I run those trails instead. The downhills are the big challenge. Let me know if the following answers your question.

I have taught myself, especially on the downhills, to plant my feet beneath/behind my CoM (should I call it the body/hips/core/torso?) rather than out in front of it, and to extend the support leg waaay baaack afterwards. Doing this on the downhills while dodging granite boulders and rocks requires me to consciously monitor (rather intensely) that spatial relationship between my support foot and my CoM. If I don't monitor it, I can't control it, I revert to autopilot and plant the foot out in front. When I do monitor it continuously, I plant the foot back up under me (my CoM). As a result of my conscious tracking, my downhill running is smooth and flowing and I've deleted most of the impact on my knees.

The alternative (my autopilot gremlin) is overstriding: planting the foot out in front of the CoM, thus creating a small braking impact at the start of each stride. On the downhills this is an especially strong temptation.

Perhaps with another few seasons of trail running I will have this monitoring focus so deeply embedded that I won't have to do it consciously. It's hard to embed new motor patterns at my age (probably easier for young folks). Working with conscious competence hopefully will eventually translate to unconscious competence. I'm not there yet, but moving in the right direction.

Now back to the skiing discussion.

 

[graham418]

I don't think focusing on the com and bos relationship is that useful, that's more like something I would diagram out for someone, while explaining something, but it's what the body parts do that deserves the focus of the skier. Relax, close, tip, extend, counter etc

I think @razie has it. Its not something that you need to pay active attention too, or track, but its a useful piece of knowledge to have. Like everything else in life, in order to do well in the practical, you have to know the theory behind it.

 

[Chris V.]

I think my main mental focus when working to achieve the high C, well rounded carvy turns, the infinity move, is this. Eliminate excess, counterproductive movements. DON'T pivot the feet into the new turn. DON'T muscle the skis. DON'T put direct effort into creating the turn. Tip and balance. So I'm not focusing DIRECTLY on the lateral relationship of the COM and BOS. It's more of a result of focus on other things, and a good feeling I get if things are going well.

 

[JESinstr]

I think my main mental focus when working to achieve the high C, well rounded carvy turns, the infinity move, is this. Eliminate excess, counterproductive movements. DON'T pivot the feet into the new turn. DON'T muscle the skis. DON'T put direct effort into creating the turn. Tip and balance. So I'm not focusing DIRECTLY on the lateral relationship of the COM and BOS. It's more of a result of focus on other things, and a good feeling I get if things are going well.

I submit a video that puts what you said into action. To me this is the fundamental carved turn. From here you can add rotary, increase edge angles more rapidly, use retraction transitions etc. But the fundamental way we get a ski to carve a turn, with all your stated conditions above including that GREAT FEELING, is shown here.