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The Stretch Reflex

post #1 of 21
Thread Starter 
To gain the best response from a muscle or muscle group, the muscle should be put on stretch. For example, throwing a ball at high velocity requires the pitcher to reach back with the throwing arm while stepping forward with his leading leg to put the muscles into full stretch. The elasticity of the muscle when positioned near full stretch helps initiate movement. This is known as the "stretch reflex."
This is from the PGA Teaching Manual, p. 26. (Thank you, mikewil.)

I bring it to our attention to add to the discussion on Inside Leg Extension, Independent Leg Steering, and so on. The passage goes on to say,
Muscles can develop more force in a concentric motion (forward) if they are first worked eccentrically (away). For example, a person is given two trials to make a maximum jump vertically. In the first trial, the person squats 90 degrees at the knee joint and leaps into the air. On trial two, the same person stands vertically, then drops to the same 90 degree knee position, then rebounds vertically to jump even higher. The eccentric stretch caused by trying to halt the downward movement makes the upward movement even stronger. This is another example of the stretch reflex..."
It seems to me that recruiting the stretch reflex is a key element of ski technique, yet other than Fastman's Inside Leg Extension paper, I have never seen anything in the technical literature about it.

Any thoughts on this?
post #2 of 21

Glad you got the manual-I think you'll really enjoy it.

And now, unfortunately, back to standardized recipes, portion control and other F&B niceities for my exams. God, I can't wait for December 2nd and 3rd to come and go!!
post #3 of 21
Hi Nolo. I've forwarded this to a teacher of mine (a physical therapist who skis!) She offered to forward it to another faculty member who is doing a project on exercise physiology in various sports. Who know, maybe they can get a student (!) to do some research on this, with University funding paying travel expenses of course!
post #4 of 21

In skiing, there certainly are a lot of body parts that do concentric motion (forward) and eccentric (backward) motions. So I'd have to agree that the stretch reflex is an element of ski technique. But there are two aspects of this that might be contributing to the lack of discussion on this in skiing.

In golf, power can provide a big advantage. Although it is not a required ingredient for a good game, it is one that is often sought. For recreational skiing, the search for efficiency is much more productive than applying more power against inefficient technique. For racers, increased power can provide a competitive advantage. So, for racing, maybe this is a worthwhile discussion.

But in skiing, the stretch reflex is almost automatic due to the nature of the sport. Just by making smooth continuous turns, the stretch reflex is invoked for every body part. But we do see situations where the lack of a stretch reflex may be contributing to problems. In powder skiing, for example, we often see people getting "stuck" at the end of one turn and unable to get the next turn initiated. Is this caused (or partially caused) by a lack of power? Does the "bounce in powder" tip help the turns because it induces the stretch reflex or because it gets the skier closer to the surface with less resistance and less power required? But because racers typically don't have fundamental problems with continuous turning, it would seem a discussion of stretch reflex would not help them much.
post #5 of 21
Thread Starter 

Plyometrics & SR

Thanks DM. I hope you get that grant.

Rusty, in researching the topic, I came across an interesting article on plyometrics, which arguably is the best dryland training a person can do to improve their skiing.

Physiologically, plyometrics work by harnessing both the stretch reflex and the elasticity of the connective tissue in and around the muscles during this "stretch". The stretch reflex is the reflex contraction of a muscle in response to an applied stretch.
post #6 of 21
nolo, i'm having a hard time incorporating the movements of the body in baseball or golf to skiing. i can relate the feelings of loading the muscles to throw,jump or swing, but not in ski technique. seems to me that skiing is more akin to surfing(i'm not a surfer). more of a flow and building and use of natural forces instead of internal generation. perhaps you can trigger my thought in another direction.
post #7 of 21
Thread Starter 
post #8 of 21

regarding the last two links you posted - I don't see how the "dynamic edge" is a plyometrics aid as your feet remain stationary. Plus pylos reply on "explosion and absorbtion".

anyway - I searched and found some other artcles for folks who want to read more/incorporate plyo exercises into their practice.

I work out with a trainer and my ski prep workouts combine strength training and plyos to achieve endurance.
- one-legged leg press superset with 5-dot jumps
- reverse lunges with weight, rear foot on reebok step superset with box jumps on reebok step
- squats with weight superset with toe-taps (on a reebok step or stairs)

post #9 of 21

For some reason the web picture with the baseball bat just cracks me up. I do wish my gym would get one of these skiers edge devices. I'm just not ready to drop a grand (roughly- ebay has an old used one with a $350 bid on it) for one of these things sight unseen. Meanwhile I enter the drawings every year for a free one and they send me expensive brochures and sale mailings by the ton.

One of the reasons I like racquetball is the plyometric nature of the sport (once you get past "B" level of play - there's a lot of high intensity reversing of direction). All the other pure plyometric exercises I've seen/done are just sooooo boring, except for the slide thing and maybe jumping rope. I don't know why. Lifting weights should be just as boring.
post #10 of 21
When I think of the stretch reflex in skiing I think of the external forces overpowering our muscles, such as in flexing and the end of a turn, or as in skiing in the bumps, and as someone mentioned, skiing powder. Those times when we "allow" the external forces to overpower our muscles. The yin and yang of skiing, letting our softness mask and release our power.

Our connective tissue does give our body much of it's stretch, or range of motion, which is why it so important to maintain this aspect of our body. Use it or lose it.

I would say that this phenomenon isn't talked about because it isn't widely understood or recognized. Later, RicB.
post #11 of 21
I would suggest that in executing dynamically linked, highly carved turns that create a lateral falline-to-falline trampoline effect from the deep flexing and releasing of the skis that one would most definitely be engaging (and enjoying) the streatch reflex and/or plyometric principle.
post #12 of 21
Rebounding muscle + rebounding ski =

I just read yesterday that some individual muscle cells are up to 75cm long?

Like, wow.
post #13 of 21
Originally Posted by Downwardly Mobile
Rebounding muscle + rebounding ski =

I just read yesterday that some individual muscle cells are up to 75cm long?

Like, wow.
Don't you mean muscle fibre and not cell?
post #14 of 21
I was thinking that a muscle fiber(re) IS a muscle cell. That's where the "wow factor" comes in for me. Here's one citation (cyt/ation, ha ha) in support of this statement.

"A single muscle fiber is a cyclindrical, elongated cell. Muscle cells can be extremely short, or long. The sartorious muscle contains single fibers that are at least 30 cm long." -

Thanks for testing me here. I have a basic A&P exam in 3 hours, on classification of tissues. Am I right?
post #15 of 21
Shameless plug! A plyometric routine will be included in this year's emailed fitness program for ESA participants! Stay tuned! Also, do a search in the Health and Fitness section for plyometrics. Tons of topics!
post #16 of 21
Originally Posted by Downwardly Mobile
I was thinking that a muscle fiber(re) IS a muscle cell. That's where the "wow factor" comes in for me. Here's one citation (cyt/ation, ha ha) in support of this statement.

"A single muscle fiber is a cyclindrical, elongated cell. Muscle cells can be extremely short, or long. The sartorious muscle contains single fibers that are at least 30 cm long." -

Thanks for testing me here. I have a basic A&P exam in 3 hours, on classification of tissues. Am I right?
Well, looking it up to refresh, they are used interchagably, but most references are to muscle fibres. Muscle cell seems confusing to me, because this doesn't acknowledge all the various components making up each muscle, like the repeating units, sarcomeres, and inside of the sarcomeres are the myofibrils which carry the proteins actin and myosin that cause contraction, not to mention the neuron cells that carry the impulse from the brain, along with some others. Hope you did well on your test. Later, RicB.
post #17 of 21
Well, thanks for wishing me luck, RicB. I think I should have spent more time studying and less on epic.

Also, didn't intend to muddy the waters here by getting down to the cellular level. Did want to share my sense of wonder at learning that one cell can be really, really long. I'm a returning student and am just blown away by the opportunity to learn about this kind of stuff. (Being back in school really makes me appreciate the saying "youth is wasted on the young".)

And kinda wanted to share this example of how I thought I knew something (in this case, "cells are always tiny and round"), when the actuality of things is something quite different.

Uh, oh, I feel a bratty new thread idea about "what we know" vs. "what we think we know" welling up. No, no, no...must study! Maybe I should have Dchan exile me from epic, for my own good?

post #18 of 21
Thread Starter 
Thinking about this further, especially in the light of Arc's comments about SR being a feature of the dynamic, shorter radius, fall-line to fall-line turn, it occurs to me that the reason we don't read about SR is because the ink devoted to "beyond parallel skiing" in professional skiing journals is sparse. Why? Perhaps because as a practical matter, very few professional ski instructors need that level of knowledge to perform their jobs.

I wonder if it's a self-fulfilling prophesy that our effectiveness diminishes as the student's ability begins approaching our own, if we only dip from a shallow well?
post #19 of 21
Well. If we don't think we need it, how in the world will we ever know if our students need it or benifit from it? Last thing I want to do is accept a ceiling to my learning, or my student progress. It's accepted that plyometrics training benefit all athletes if properly done, and they are included in many ski workouts. So isn't it resonable to discuss and understand how they benefit our skiing, and the role the strecth reflex plays in our skiing? Later, RicB
post #20 of 21
I'm trying to deepen my own well, but the sides keep caving in on me. :

Seriously, though, I know what you mean about the "self-fulfilling prophesy" question.

It would be nice to have that deeper well, but how: Do you believe that the required resources (economic and other) available to ski instruction are available to undertake this particular construction project? I'm guessing that you do or maybe you wouldn't have asked the question.

Is it more a matter of an attitude issue: An "If it ain't broke don't fix it" kind of thing?

What are you getting at, Nolo?
post #21 of 21
Thread Starter 
I think it's the 80/20 Rule. A member will spend 80% of their total contribution to PSIA in the process of getting Level I, II, III certified, and only 20% the remainder of their years in the organization. The average PSIA member spends 5 years or less as a member (this is an extrapolation of the length of the average instructor's "career" as a ski instructor).

In addition, probably 80% of ski school customers are just beginning in the sport. PSIA's partner, NSAA, has been quite effective at getting PSIA to commit most of its resources to serving the lower level student.

Both the PSIA and the member school economies predicate a situation where advancement leads people to the exit.
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