Principles Of The Inline Speed Skating Stroke

Principles of the Inline Speedskating Stroke Practical inline speedskating tips anchored in an overall framework of how skating works Blake Dempster August 2009 www.pdfcoke.com/doc/17708830/Principles-of-the-InlineSpeed-Skating-Stroke

Contents

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Introduction ........................................................................................................................... 3 The Skate as a Machine ....................................................................................................... 4 Lateral Force (LF) ................................................................................................................. 5 Centre of Gravity (CoG) / Set-Down ...................................................................................... 6 Outward Push (OP): Push Leg / Sweet Spot ........................................................................ 7 Outward Push: Recovery Leg .............................................................................................. 9 Lowness ............................................................................................................................. 10 Arms and Upper Body......................................................................................................... 11 Set-down / Inward Push ...................................................................................................... 12 Crossovers ......................................................................................................................... 13 Cadence ............................................................................................................................. 14 Skate Stroke’s Moment of Truth: Criticalities ...................................................................... 15 Some Practicalities ............................................................................................................. 16 Acknowledgements ............................................................................................................. 17

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INTRODUCTION This outline is put together by a London Speedskaters club skater of modest capabilities. It has been written because there doesn’t appear to be an easily available systematic theoretical and practical guide to the inline speedskating stroke. The intent is that any practical skating tips need to be anchored in an overall framework of how skating works. Without being so anchored, many tips are without foundation and often actively counterproductive. It’s not enough to know what or how if you don’t know why. Many good skaters apply all the principles, but do so in such an intuitive way that they’re not always aware of or interested in what they’re doing. That’s fine whilst everything is working smoothly, but eventually problems arise and it helps to have a diagnostic framework. This outline won’t help absolute beginners. It will only be useful once you can imaginatively feel the skate stroke whilst reading. The outline doesn’t try to use diagrams. In the author’s experience, these are difficult to get clear for such a dynamic process as skating. A narrative approach allows easy switching between freeze-frame and continuous motion.

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THE SKATE AS A MACHINE Inline speedskating centres on the biomechanical challenge of achieving forward motion via the weird device of wheels strapped to your feet. Start with the mechanical bit: the skate. The skate is a machine which in principle has 100% lateral resistance and 0% forward/backward (f/b) resistance. That means that when you push, you need to push laterally. If the direction of push is f/b, the skate moves but you stay still. If your push has any f/b component, to that extent it is wasted. Lateral pushing is hard but useful, f/b pushing is easy but useless. So because of the characteristics of the skate as a machine, skating largely resolves into a question of maximizing lateral force, and translating that into forward motion. A priori it isn’t a given that such an enterprise is possible at all, or feasible without unacceptable bodily strain. But luckily it turns out that not only is it possible, it can in fact be achieved with no biomechanical damage, and is actually an unbeatable way of conditioning the human body. Plus, it can generate amazing speed. Plus, it’s fun. All those good things are true – if your technique’s good. Conversely, without good technique, the body gets damaged rather than conditioned, and you go slow not fast. Plus, it doesn’t stay fun for long.

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LATERAL FORCE (LF) Okay, you want to maximize lateral force. What is force? A cornerstone of Newtonian physics is that force equals mass times acceleration. In skating, mass corresponds to your bodyweight. The acceleration in skating is provided by your mulekick push. This outline adopts the term “mulekick” because “push” by itself is altogether too tame to do justice to the explosiveness involved. Mulekick acceleration is largely a question of strength and fitness. Control of mass/weight is largely technical, though significant bodily strength is required to implement the technique. In short you maximize force if all your bodyweight is applied in the direction of your mulekick. If your weight is only partially applied in the direction of your mulekick, force is correspondingly reduced. This happens if your non-pushing skate has been set down too soon. It also happens if your body or any of its parts is misaligned or moving in a contrary way. Mass and mulekick produce force, but for it to be useful it needs to be lateral, ie as close to horizontal as you can make it given the limitations of body geometry and muscular strength. Making the force lateral is the reason for skating low. Minimizing wind resistance is very secondary.

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CENTRE OF GRAVITY (COG) / SET-DOWN It is often useful in biomechanical analysis to adopt a simplification in which you think of your body mass as being concentrated on a single point, the CoG. It is located around the centre of your pelvis. The CoG is important because it is the key to the technique of supporting your weight. This is crucial and demanding in skating, unlike eg in cycling where the saddle can do this job for you, When you set down your skate, your wheels need to be right underneath your CoG. If they aren’t, you are necessarily off-balance, so the next thing you have to do is mess about regaining your balance, the resulting waste of time and effort having the effect of compromising your whole skate stroke whilst straining joints, ligaments, muscles and back. Viewing this same thing from underneath, the key is to set down the skate neutrally in relation to the forces it is supporting. You’ll know when you’re neutral on set-down because your foot. especially the outside half of it, will have complete freedom from stresses. Avoiding the trap of setting the skate down outside the CoG, ie on the wheels’ inside edges, is an ongoing challenge. But don’t make a fetish out of getting onto the wheels’ outside edges. Think about being neutral, not about edges. Being laterally neutral in relation to the forces means that the frame position on the skate needs to be in line with the forces, ie right beneath the load bearing part of your heel, running centrally down your foot to a point just adjacent to ball of the big toe. Adopting any other position, eg further inwards with the intent of setting down on the outside edges, reduces the effectiveness of your skate stroke and invites injury. Being f/b neutral in relation to the forces is achieved if your CoG is above your heels. If you set down with the CoG above your toes rather than heels, you’ll be leaning forward, with the result that you’ll push backwards rather than laterally. Also you’ll be prone to falling. For engineering analysis, the CoG is also technically relevant in relation to LF. The line from your CoG to your skate can be viewed as the axis along which total force is generated, ie the hypotenuse of a force triangle, LF being the horizontal side, the height of your CoG off the surface being the vertical side. This is an analytical representation of the need to be low – the smaller the vertical side, the more total force corresponds to useful LF.

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OUTWARD PUSH (OP): PUSH LEG / SWEET SPOT The nature of the mulekick OP is that your leg extends from a bent-knee to a straight-knee position. This uses your main muscles, not abductors which have insufficient strength. Okay, you’ve set down your right-leg, say, in a bent-knee position. Your CoG is above your right wheels and 100% of your weight is on your right skate. If you push immediately, you’ll go up. Fine if you’re entering a bobbing competition, not fine if you want speed. Half way to the outer extremity of the OP, you still don’t want to push because force will still be too vertical. You want to wait until the outer extremity in order to maximize LF. So most of the way through the OP, the skate is pointing outwards at an angle (quite a small angle if you’re going fast), getting as cleanly as possible, ie with minimal resistance, to the outer extremity. This is called the “glide” phase. Then, at the outer extremity of the OP, the skate squares off and you unleash your mulekick. The action of squaring off is called the “carve”. Reductio ad absurdum, you’d want to have zero push until your crotch touched the surface, your push leg was in the sideways splits position, and all your mass was somehow still in the push leg. Then you’d unload instantaneously, and the traction between the wheels and surface would somehow magically hold. And you’d do all this extreme stuff without compromising the next stroke on the other leg. Biologically and mechanically impossible, but the aim is to get close. In the real world, you carve out and unload in the last few inches of the OP, directing all your weight through the heel to the back wheels whilst straightening the skate so that the wheels are square to the direction of push , with the ankle curling inwards to angle the wheels towards vertical in order to maximize lateral traction. The mulekick originates in the haunch, ie the hip plus top six inches of the thigh, ie close to your CoG where the massive muscles are. Human bodies are constructed to work in this way – that’s why the massive muscles are located around the CoG. Learners generally get this wrong. They obsess about the path traced by their skate wheels on the surface, and try to work backwards to the push. But the skate wheels’ path is effect, not cause. Don’t let this tail wag the dog. Get it clear in your head: the skate wheels’ path is determined by a mulekick originating in the haunch and directed to the heel. Also get it clear, the thing that makes the OP go out is the glide, not any abductor muscles. If any of your weight is travelling through your front wheels, you’ll be pushing backwards, so you’re injecting useless f/b force and squandering useful LF. Plus, you’ll be straining your foot. ©B Dempster

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There’s real timing in the OP. Think of a tennis player getting the most powerful shot when the body’s mass is sweetly applied at the exact moment of contact with the ball, with the whole stroke constructed to that end. Ditto golf, baseball, cricket., javelin, etc. Similarly, our skate stroke needs to be constructed around our own sweet spot, the outer extremity of the OP.

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OUTWARD PUSH: RECOVERY LEG Essentially, the recovery leg forms the transmission mechanism by which LF, produced at the outer extremity of the OP, converts into forward motion. At that moment, the non-OP leg, known as the recovery leg – it is recovering from its own previous OP, needs to be driving straight forward immediately prior to set-down. To drive forward, the recovery leg has to come from behind, NOT direct from the side. So it has to loop backward during the glide phase of the other leg’s OP, getting in position to be driven forward. Make sure the looping backward isn’t so backward that it tips your upper body forward, thereby forcing your OP to go backwards, thereby squandering LF. At the end of the backward loop, the recovery thigh needs to point vertically down to the ground (as does the skate), moving inwards like a pendulum. In getting from the outer extremity to the thigh-vertical position you can use adductor muscles, This is the only place in the skate stroke where either adductor or abductor muscles are used in an important way. They’re not strong enough for main motor work. The only reason the adductors can be used here is that the recovery leg is not load-bearing. The other attraction of this recovery leg movement is that it consumes time, thus allowing the OP leg to finish. Hurrying the recovery leg cuts short the OP and squanders LF. The sweet spot of OP is the outer extremity. That’s also the moment of truth for the recovery leg. The idea is to drive the recovery leg from its thigh-vertical position forwards to a thighhorizontal position, or as close to horizontal as you can get, setting down the skate on the surface just as the OP leg finishes, thereby keeping weight on the OP leg until the end, and setting down with your body low. The simultaneity of the recovery leg’s forward drive with the OP mulekick is the key to transmission of LF into forward motion. The recovery leg’s forward drive also has the effect of tilting your pelvis backward. This stops you from leaning forward, and thus prevents the OP from going backwards instead of laterally. The pelvis’s backward tilt also allows your lower back to be convex, thus protecting you from back strain. Think of your recovery leg as being like a track sprinter’s, in particular, think of the way they pump their non-pushing knee high to the chest. That’s what you need to do on your skates too. Having a low knee lift means setting down too soon, thus making your CoG too high, thus compromising LF generation. Because of the way our bodies are constructed, the forward driving movement of the recovery skate accompanied by the OP dynamics have the effect that your recovery hip protrudes outward, and your recovery thigh rubs against your OP thigh. The result is a low and ultra-stable basic skate posture. ©B Dempster

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LOWNESS Vertical movement is the most ruinous in terms of energy expenditure, varying with the cube of mass. (That’s why elephants can’t leap, a cat can leap upwards about five times its body length, and fleas do it easily. On the elephant-flea scale, humans are much closer to elephants. Upward movement is very difficult for us.) If you bob up and down, you tire quickly and other skaters whisk past you. In short you need to keep your CoG at a steady height. The “fall”, often referred to by skaters, is a misnomer. No loss of height occurs. “Fall” refers to the glide phase, when your OP leg is straightening but you’re not gaining height – this has a floating feel as if you’re falling. The glide phase is also associated with a “pause”, as not much appears to be happening. To maximize LF, your CoG has to be low at the magic moment at the end of the OP. So the CoG needs to be at a steady height, and the steady height needs to be low. It follows that the challenge isn’t really to get low, it’s to stay low. Don’t think in terms of setting down your skate and then getting low, think in terms of being low at the point of setting down your skate. The best way of being low at the point of setting down your skate is to aim at having your recovery thigh horizontal at set-down. That’s why you need to have a track sprinter’s knee lift built into your skate stroke. Here’s an acid test of lowness. If you’re taking the strain on your glutes, you’re in the right zone. If you’re taking the strain on the front of your thighs and shins, you’re too high. Apart from reducing LF, you’ll strain your shins, knees, hips, back and neck. .

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ARMS AND UPPER BODY Your arms and upper body have the job of positive support for the big main-motor work of your lower body. If your arms and upper body aren’t providing positive support, they’re probably being negative. Your body will naturally try to gain relief from fatigue and strain, and one way of doing this is by subtly twisting out of the direction of the push. This makes everything feel easier, but it deprives the push of properly aligned mass, thereby losing LF. Analytically, think of this as being a question of controlling your CoG. Your body is capable of behaving in such a way that the CoG point in the force triangle is not where it is supposed to be. The point in skating’s arm and upper body movements is to position the CoG where it is most effective. The key to positive support is to recruit your biggest centres of mass, ie, your pelvis/bum and your shoulders. Both of these have the job of being exactly aligned in the direction of the push, and braced against the push, at the exact magic moment of the outer extremity of the push. In practice, aligning and bracing the shoulders and pelvis/hips involve a counter-rotational core muscle action timed to harmonise with the push. All this movement is complex but our bodies manage complexity all the time. In doing so, matching arm movement and leg movement is a major and natural help. Swinging your arms forward and backward helps to coordinate everything. By moving forwards and backwards, your arms also help transmit LF into forward motion, thus supporting the thigh-horizontal drive of the recovery leg. The upward movement of your front arm also helps you achieve high knee-lift, as with a track sprinter. The more smoothly this can all be done, the greater overall efficiency. Jerky action is a sign of the body fighting itself, expending energy doing that rather than producing forward motion. Think of this like a car engine – it feels smooth but underneath the pistons are pumping, just like the pushes in your skate stroke.

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SET-DOWN / INWARD PUSH Focus on the moment of set-down. Your OP leg has just finished its push, your recovery leg is driving forward. Your CoG is directly above your wheels, sure. That’s the freeze-frame. But the video is that as a result of the mulekick potency of the OP, and even in the face of your recovery leg and upper body and arms’ efforts to transmit LF into a forward direction, your CoG is still moving slightly across the set down wheels. Well, go with the flow. Use the momentum to initiate the OP with a prior inward push and carve. That way you get a little extra LF, plus, you bounce the skate back via the inward carve into the glide phase of the OP, thus making the glide phase a lot easier. Do this and you can inform your adoring fans that you’re doing a Double Push. In doing so, do yourself and them a favour by viewing it as a variation rather than a Copernican revolution. Don’t oversell it. Some people like it, some don’t. Some very good skaters don’t even notice that they’re doing it. It’s open to debate how much extra LF you get from the inward push. Probably, not much, but still, not nothing. The important thing is not to compromise your big mulekick OP by messing about with the inward push. You will however indeed compromise your OP if you set down your skate outside your CoG, give it a cutesy little inward pull, and wiggle it vaguely inwards for a bit. Ask yourself, where is the force coming from? It’s not from main mass, in fact, it’s against main mass, since your skate is misaligned against your CoG, so you’re fighting yourself. Essentially you’re using trivial leg mass and puny adductor muscles, and wasting time, and making things complex. Forget the puny stuff, get on with applying the heft of your main mass in the direction of whatever push you’re doing. So whether you’re doing an inward push or not, make sure that at the moment of set-down, your wheels are neutrally placed in relation to the forces they’re supporting.

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CROSSOVERS The same principles apply to crossovers. Say you’re turning left. Your right OP is as before. Your left leg sets down. Because of leaning left into the curve, your CoG will be left of your skates, balanced by the centrifugal force of the turn. Your CoG is moving left on account of your OP mulekick. Your left leg, instead of moving outwards, keeps moving under your body, straightening and carving and squaring up in an “underpush” which is a mirror image of the OP. Your right leg, instead of looping behind, loops in front, again transmitting LF into forward (and in this case, left, around the curve) motion, and again setting down low. Note that the underpush is similar to the inward push of the Double Push, though more fullon in the Crossover. The outside leg(the right one when you’re turning left) can be harder to set down in a low position, on account of the body leaning away from it, leftwards into the corner. There can be a loss of effectiveness on this right leg, offset however by extra LF arising from pushing against centrifugal force. The inside leg set-down again needs to be neutrally placed in relation to the forces your skate is supporting. Because of leaning into the corner, this means your wheels will set down on their outer edges. But don’t think of outer edges, think of being neutral.

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CADENCE Over a distance, LF can be increased in total by increasing stroke frequency, called “cadence” in skating, even if doing so results in less LF per stroke. High cadence is associated with aerobic work, high per-stroke LF with anaerobic. The tradeoffs between the two depend on skater preference and conditions. The body is not designed to stand too much concentrated anaerobic work. In distance skating, it favours aerobic. One effect is that the recovery thigh doesn’t achieve a nearhorizontal position at set down – more like 45°. Another is that with less acceleration in the push, arm movement is less important and arms can be rested behind the back.

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SKATE STROKE’S MOMENT OF TRUTH: CRITICALITIES In summary, the outer extremity of the OP, or sweet-spot, is the skate stroke’s moment of truth. Here are the criticalities (for the right-leg OP): 1.

Your bum is low

2.

Your shoulders and pelvis are in line with the direction of OP, having just counterrotated into that position, and are braced against the OP

3.

Your right leg is straight, having been straightened by a mulekick originating in your right haunch

4.

Your right skate is square to the direction of push, having just squared off in a carve from the angled glide

5.

Your right skate’s front wheel is as far forward as your nose

6.

Your weight is 100% on your right heel

7.

Your left thigh is near horizontal, having just been driven straight forward from vertical, rubbing against your right thigh

8.

Your pelvis is tilted backward

9.

Your left hip is protruding leftwards

10.

Your left skate is on the point of being set down, straight below your CoG, all wheels touching the surface at the same time, pointing straight ahead

11.

Your left ankle and foot feel neutral and passive, not tense, and your weight is about to be directed on to your left heel

12.

Your left glutes, not your left quads, are about to feel the strain

13.

Your right forearm is high, helping lift your left thigh like the track sprinter, and in front of your nose

14.

Your left arm is high and straight-ish behind you, helping balance the right leg OP carve

15.

Your movements are smooth

16.

Your rhythm, timing and coordination are centered on this moment of truth

17.

Nothing is tightening

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SOME PRACTICALITIES Don’t try to concentrate on every criticality at once. Pick on one, run with that for five minutes, move on. They’re all interdependent, so you find your concentration moving around them anyway. This interdependence of criticalities means that skating, like many sports, is a game of opposites. If you have a right-leg problem, check what your left leg is doing at the relevant time. If you have lower leg problems, check what your shoulders are doing. And so forth. While you’re skating, if you’re bored with thinking about the criticalities, try a different view. Think of the mulekick push as having the job of throwing your CoG to the position you want to get it into, ie just above the skate you’re about to set down. This can feel like a sideways skipping shuttle motion, though in fact, because of the angled glide, your CoG travels in a continuous line, not a zigzag. Do crossover drills, both directions, they make a lot of other things come right, especially the set-down. Many skaters’ technique carries a residue from the fear they had as a beginner of falling outwards, and they retain the habit of setting down with the CoG slightly to the inside. Crossovers root out this deficiency. In the aerobic/anaerobic spectrum, don’t get stuck in one place: vary the mix. Partly this is a question of making use of all of your body’s resources, spreading the burden and giving different systems a chance to rest. Partly it’s because the aerobic high cadence work is greatly improved if you have invested time in building high per-stroke LF anaerobic strength and technique, and the best way of doing this is by skating. Partly it’s because you need to be prepared to alter your cadence if you want to skate in a paceline. Vary your pace, don’t get stuck in a groove. Train with others, or, if that’s difficult, construct some sessions with intervals and sprints. Sprints put pressure on all the criticalities, and cause your technique to break down, but simultaneously turbocharge the process of building up the strength necessary to carry out your technique. Your body won’t let you do everything straight away after taking up the sport. You need to build main muscle strength, support muscle strength, and core strength. Oh, and you need cardiovascular fitness too. Unlike many other sports where you need to be strong and fit but which don’t themselves make you that way, skating is excellent for building all the necessary strength and fitness, but you don’t normally have enough when you start. A feature of skating is that each time you go out you have a lot of goes at getting the stroke right, unlike eg golf where you normally only have around seventy or a hundred shots or so in a four hour round. This is good if you are using the repetition to entrench good rather than bad habits. As the saying goes, practice doesn’t make perfect, it makes permanent.

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ACKNOWLEDGEMENTS Mike Ryan, for his analyses in FaSST. London Skaters for being fun to skate with, and especially Adrian, Gavin, Fred for regular technical help to me and others.

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