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Footbed-Boot Planing interplay?

post #1 of 10
Thread Starter 
Hello,

I have a question about the interplay between footbeds and sole planing. I have new boots and an existing conformable footbed with life left in it. The footbed fits the new boot and liner just fine. I'll have the boots planed soon. If I purchase new footbeds later, does that substantially affect the planing values? My budget is very pinched this year and I cannot afford to do both.

Have bootfitters compared planing measurements while having the customer stand in stock and custom insoles?

I have the same question about liners. If I replace the liner at a later date, does that substantially change other elements of the mechanical setup?

I'm NOT a racer looking to tweak things, but good enough to appreciate when things are setup right.

Thanks in advance.
post #2 of 10
Quote:
Originally Posted by Duane View Post
Hello,

I have a question about the interplay between footbeds and sole planing. I have new boots and an existing conformable footbed with life left in it. The footbed fits the new boot and liner just fine. I'll have the boots planed soon. If I purchase new footbeds later, does that substantially affect the planing values? My budget is very pinched this year and I cannot afford to do both.
Good question. If you budget is tight this year, at least make sure that your current footbed is posted accurately and interfaced properly with the zeppa (bootboard) before you plane the bootsole. Older posted footbeds tend to have lost their original posting angles from repeated pronation loading (edging) and therefore sit more valgus in position than intended. It is an easy thing to laminate new material on the bottom and regrind the angle(s).

Quote:
Originally Posted by Duane View Post
Have bootfitters compared planing measurements while having the customer stand in stock and custom insoles?
This is a tricky topic . The best answer is that it depends on the natural foot alignment of the given customer. In general, there is little static change in knee mass position with or without footbeds, but there are some people (based on foot mechanics, amount of static pronation, mean talar angle, etc.) that do show a measureable change. The real challenge is assessing the link between footbed and knee mass position in a dynamic situation, i.e. skiing. Subjectively, most people feel a difference but I'm not aware of any data to support this.

Also - keep in mind that sometimes more important than the footbed/no footbed issue is whether the boot is blocking foot position/foot movement to the inside. This will definitely have an effect on canting measurement. So - make sure the boot is appropriately punched for the inside ankle bone and navicular if these structures are touching (or near) the shell.


Quote:
Originally Posted by Duane View Post
I have the same question about liners. If I replace the liner at a later date, does that substantially change other elements of the mechanical setup?
Liners break in like anything else, and tend to become more compressed on the working surface, i.e. medial side. Also, some liners are asymmetrical in terms of thickness. Hence, cuff alignment may require a small adjustment when changing to a new/different liner.

Quote:
Originally Posted by Duane View Post
I'm NOT a racer looking to tweak things, but good enough to appreciate when things are setup right.

Thanks in advance.
Good - then the best test is to understand this stuff, adjust it, ski, and reflect . If in doubt, plane your boots to 1/2-2/3 the assessed amount, then go ski. Like a haircut, you can always plane/shim a little bit more, but it's hard to put it back on.
post #3 of 10
All points very well put by Matt.

jim
post #4 of 10
Thread Starter 
Thanks... I had to look up much of the terminology, so let me see if I understand correctly.

Posting is the material placed under the orthotic to create a desired angle of support for the foot. If the posting breaks down or compresses over time due to pressure on the inside (medial?) of the orthotic, the ankle position can become angled in the same direction (valgus = knock-knees). Did I get it right?

I'm pretty sure the orthotic is fine. I only get out maybe 20 days per year and they're 2 years old. Getting it checked would be a challenge. There are shops around Cleveland who will make you an orthotic, but I'm not confident in their underlying knowledge... just a feeling on my part.

I believe my boots fit very well, thanks in no small part to what I've learned by lurking here and the recommendations of Brent at Park City pedorthics. I wasn't able to get a full fitting (time constraints) but got pointed in the right direction last year while vacationing there.

For me, the orthotic affects my edging and balance. A few years back I experimented with two different off-the-shelf insoles. I reasoned that I shouldn't feel much change to my skiing since my legs are firmly clamped in the boots and that, not what my ankle is doing inside, dictates the external angles. Well, an insole with a low arch versus a pronounced arch produced a distinctly different skiing feel. Edging and balance were affected. (I added a shim under the zeppa and felt similar changes). The changes were most noticeable when skiing one-footed. Not what I expected at all. This experience is why I asked my original question about the interplay between orthotics and sole planing.

I like your idea of taking this in baby steps and planing small amounts from the sole. Not sure If I can afford this route, but I'll bring it up and see. Maybe an alternative is to take a pocket full of shims or duct tape with me and play around with these between the binding and boot sole on an easy slope. I think someone else on this forum uses that method.

Last thing... I looked up the navicular bone, but can't relate it to what I feel with my hand. Is that the bone on the top/inside of the foot and slightly in front of the arch? This doesn't seem like an area one would punch out, so I'm not sure if I have it right.
post #5 of 10
Quote:
Originally Posted by Duane View Post
Posting is the material placed under the orthotic to create a desired angle of support for the foot. If the posting breaks down or compresses over time due to pressure on the inside (medial?) of the orthotic, the ankle position can become angled in the same direction (valgus = knock-knees). Did I get it right?
Dude

Quote:
Originally Posted by Duane View Post
For me, the orthotic affects my edging and balance. A few years back I experimented with two different off-the-shelf insoles. I reasoned that I shouldn't feel much change to my skiing since my legs are firmly clamped in the boots and that, not what my ankle is doing inside, dictates the external angles. Well, an insole with a low arch versus a pronounced arch produced a distinctly different skiing feel. Edging and balance were affected. (I added a shim under the zeppa and felt similar changes). The changes were most noticeable when skiing one-footed. Not what I expected at all. This experience is why I asked my original question about the interplay between orthotics and sole planing.
Nice summary . For sure the design and posting angle (and a shim on the bootboard is simply a post) effect edging feel and effort. The foot is supported, so less pronation is required to transmit subtle edging movements from the foot to the ski. This has an impact up the chain, hence my comment that dynamic changes in knee canting/ROM/angulation are likely present with footbeds vs. no footbeds, but we know this by feel and video analysis - not by any objective data (that I'm aware of).

However, I think it's important to separate this from sole planing which has a measureable effect on static alignment and often pronounced effects on knee mass position and ski performance on-hill. Sole planing uses the leverage of the boot/cast to bottom-up 'drive' the knee mass into a new starting position for active movement.

Quote:
Originally Posted by Duane View Post
I like your idea of taking this in baby steps and planing small amounts from the sole. Not sure If I can afford this route, but I'll bring it up and see. Maybe an alternative is to take a pocket full of shims or duct tape with me and play around with these between the binding and boot sole on an easy slope. I think someone else on this forum uses that method.
Shimming under the boot or binding is a totally reasonable approach. Make sure to do it on hard snow and get some independent observation or video to confirm what you're feeling. Hotel key cards cut 1cm wide when taped to the underside of the boot (either medial to increase cant or lateral to decrease it) are about 0.5-0.75 degree shims. I usually suggest stacking 2 so you can feel the difference as a baseline. Do not cant more than 2 degrees 'inside' (thick side outside) - going past this can preload structures in/around the need and also limits effective ROM for knee angulation (i.e. you're using too much of it up with canting).

Quote:
Originally Posted by Duane View Post
Last thing... I looked up the navicular bone, but can't relate it to what I feel with my hand. Is that the bone on the top/inside of the foot and slightly in front of the arch? This doesn't seem like an area one would punch out, so I'm not sure if I have it right.
Some people have a prominent navicular tubercle where the posterior tibialis tendon (the muscle that controls the rate of pronation) attaches. Other people don't. If you feel @ 2cm down and @ 3cm ahead from the center of your inside ankle bone you'll be in the right place. If you 'roll on edge', i.e. flatten the arch, you'll feel the navicular become more prominent. This is when it can bump up against the shell of the boot. Not everyone needs this punch, but some people have such a prominent navicular that it rubs against the boot/liner before they even start moving.
post #6 of 10
Thread Starter 
Quote:
Originally Posted by jdistefa View Post
Some people have a prominent navicular tubercle where the posterior tibialis tendon (the muscle that controls the rate of pronation) attaches. Other people don't. If you feel @ 2cm down and @ 3cm ahead from the center of your inside ankle bone you'll be in the right place. If you 'roll on edge', i.e. flatten the arch, you'll feel the navicular become more prominent.
Bingo. Right where you said it would be. Not much of a bump so that's why I've never noticed it.

Quote:
Originally Posted by jdistefa View Post
The foot is supported, so less pronation is required to transmit subtle edging movements from the foot to the ski. This has an impact up the chain, hence my comment that dynamic changes in knee
That's the part that's so counterintuitive. The foot is clamped in this cast/boot, yet there's still a subtle movement/pronation going on that affects the whole chain. My own experience with insoles bore this out, but it still grates on my engineering sensibilities because I can't put a number on it or diagram it. Guess that's why you guys get the big bucks.

Thanks for the education. This whole biomechanic bit is interesting. Wish I lived in a more ski-friendly area.

By the way.. thought you guys might like the link below since weight bearing versus non-weight bearing gets brought up from time to time. Probably not applicable to your work, but who knows.

http://www.ncbi.nlm.nih.gov/pubmed/9...?dopt=Abstract
post #7 of 10
I'll add a thought to Matt's excellent answer.

Things that are done inside the boot tend to primarily impact foot and ankle function. Things done externally (sole planing/binding cants) will create rotation at the hip, with less effect at the foot/ankle.

This is why I believe attempting to create the entire stance purely with the footbed, compromises foot and ankle function through the use of excessive or improper posting.

Prudent use of all the tools will yield the best result. If all you have is a hammer, everything eventually becomes a nail.

jl
post #8 of 10
Quote:
Originally Posted by jdistefa View Post
Do not cant more than 2 degrees 'inside' (thick side outside) - going past this can preload structures in/around the need and also limits effective ROM for knee angulation (i.e. you're using too much of it up with canting).
Uh, obviously I meant 'knee' here. Oops.
post #9 of 10
Quote:
Originally Posted by BOOTech,Inc. View Post
Things that are done inside the boot tend to primarily impact foot and ankle function. Things done externally (sole planing/binding cants) will create rotation at the hip, with less effect at the foot/ankle.

This is why I believe attempting to create the entire stance purely with the footbed, compromises foot and ankle function through the use of excessive or improper posting.
+1 gabillion

A thoughtful 'cocktail' approach - a little bit of several tools/techniques - usually gives the best outcome re. maintaining joint function at multiple levels while giving a structural and proprioceptive nudge to the system. Then add in some motor learning and voila .
post #10 of 10
Quote:
Originally Posted by Duane View Post
By the way.. thought you guys might like the link below since weight bearing versus non-weight bearing gets brought up from time to time. Probably not applicable to your work, but who knows.

http://www.ncbi.nlm.nih.gov/pubmed/9...?dopt=Abstract
Very applicable BTW. Forefoot varus measurement techniques are a bone of contention among foot gurus. Although the true incidence of structural forefoot varus is low, some pedorthists/podiatrists try to dial out some degree of rearfoot pronation (rightly or wrongly) by forefoot posting. There is also the issue of acquired or positional forefoot varus as a result of a parallel foot position (rearfoot 'drives' the forefoot), but this too is an art to sort out, and certainly open to debate.

FWIW, many retail weight bearing or partial weight bearing systems tend to create a false forefoot varus which the unwary (undertrained... but well intentioned... but ignorant) bootfitter will incorrectly 'correct' by posting. Woe be the skier who gets one of these puppies.

Anyway - topics for another thread .

Thx for your good questions and comments.
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