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Post by wez on Jul 13, 2009 8:26:03 GMT 1
Welcome Les, Cheers for the thumbs up, i'm always happy to help, or atleast provoke discussion. What route did you eventually take with the elbow thing? Since my surgery mine has been basically fine except that i have lost about 10 degrees of mobility and some feeling there. Otherwise its pretty stable and trustworthy for training. I just don't seem to have much time for the later, so sadly my comeback is still a work in progress, although i have started to have a few good throws appear in training lately. I did have a play with the model by the way and it does quite practically underline the important variables in distance terms but not being able to see the stuff going on behind the scenes left me a bit in the dark about the results. The important part to us throwers however of course is not whats going on in terms of physics but how we might be able to influence our distance by adjusting to the conditions of the competition on the day. So things we can certainly be capable of doing are: to throw left-center or right down the sector to take best advantage of wind direction, adjust the height of our throw, and angle of the javelin at release. It would be really helpful to have a simple guide, eg what to do when we have a tail wind, headwind and cross wind etc. I say 'simple guide' because as i'm sure you are aware we throwers have enough going through our heads trying to deal with the pressure of competition, staying relaxed, and reproducing our regular techniques, so we can probably only add one or two basic technical adjustments ontop of that. The only things i have ever know to do is to drill it low in blustery or head winds and to throw it higher in a tail wind. In addition to this i always try to release the jav with a tilt angle as close to 180 degrees as possible but i do that in all conditions and always choose a blunt pointed jav. One technical thing though (for me) ;)if you have time to do it, do you happen to have a diagram or some kind of more clear explanation about how a javelin creates lift please. As far as i can see as the jav is basically symetrical about its axis, the bit you say about attack angle and center of gravity are the main influences but it would be nice to hear it from someone whos studied it in detail. Cheers, Wez Just an after thought, its interesting what you mentioned about wobble, we are generally led to believe that it is bad for our throwing and certainly manufacturers do their best to reduce it, like with the high carbon models and even the composite Fx by OTE that actually dampens the wobble mid flight. In practical terms though Zelezny threw very far with alot of wobble and i know from my experience also that many of my best throws were like that too. Out of interest did they hypothesise that oscillation over a short path but at higher frequency was better than a lower frequency but longer oscillation path wobble That would backup the use of stiffer javs atleast but maybe not the OTE unless wobble is more critical in the earlier part of the throw only....
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Post by slinger on Jul 13, 2009 16:42:06 GMT 1
The subject of "wobble" is interesting, Les - which of Zelezny's throws do you have on film that show large amounts of "wobble" This is quite a good one from Stuttgart WC's in '93 www.youtube.com/watch?v=MagV32U4yN8
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Post by leshatto on Jul 14, 2009 17:42:54 GMT 1
Wes said: --------------------------------------------------- Cheers for the thumbs up, i'm always happy to help, or atleast provoke discussion. What route did you eventually take with the elbow thing? Since my surgery mine has been basically fine except that i have lost about 10 degrees of mobility and some feeling there. Otherwise its pretty stable and trustworthy for training. I just don't seem to have much time for the later, so sadly my comeback is still a work in progress, although i have started to have a few good throws appear in training lately. --------------------------------------------------- Very glad to hear you are coming along OK Wez and the good ones are coming back. I would imagine the slight loss of feeling is some small damage to the ulnar nerve when the break occurred which I am told can happen. Felix first of all had to have his olecranon re-built with a bone graft from the hip to clear out the stress fracture. This of itself was an extraordinary piece of surgery which we were told could only be done in the USA. It took over 3 hours. He managed to clear 70m in April with this done and a couple of cancellous screws in. Second, there was some residual damage to the UCL which he has just had sorted out and he has also had his screws out. After more rehab, he should be fine. We are producing a medical publication on this with his surgeons so that any other thrower who suffers this will have a defined recovery path rather than groping around in the dark as we did and I think you had to as well. We will also produce a more digestible version. A long saga - I hope we can meet up and I will tell you all about it. Bring sandwiches. BW, Les.
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Post by leshatto on Jul 14, 2009 18:33:00 GMT 1
More on altitude and lift ...........................
1) For Wez. A javelin behaves like a thin aerofoil. The lift on a thin aerofoil is 2.pi.density.Relative_velocity.circulation. Because the javelin is symmetric, the circulation is zero when the wind is parallel to the javelin and there is no lift as you say. However, it rarely is so you get lift. In classic aerofoil theory, a symmetric thin aerofoil has no drag. However, a blunt javelin nose generates turbulent boundary layers which lead to drag (but also crucially move the centre of pressure forward a bit to give less pitching moment which is why tailwind javelins always fly further - the headwind stuff is a myth as Dick Held knew when he invented them. That should get somebody started :-) ). Approximately, the drag is 0.5.pi.density.Relative_velocity_squared.radius_of_nosecone. So there is always drag and there is lift when the airflow is at an angle to the javelin, (the attack angle).
2) For everybody. The effect of altitude. I have now modelled this. The two extremes are a baseball (which has little lift relative to its drag) and an aeroplane (which has a lot more lift relative to its drag). At altitude, it is known that baseballs fly further, (which is why people like hitting home runs in Denver, the mile-high city). However, for objects requiring lots more lift relative to drag, like aeroplanes, runways have to be longer at altitude so they can get off the ground. The javelin falls nicely in the middle. It is more like a baseball than an aeroplane and in all my simulations, it flies a little further, (up to 3%) at 1500m altitude. Interestingly, you have to throw it lower which wasn't obvious to me and this also helps the biomechanics contribute more. Whether this would be observed in practice I have no idea. I am not aware of any calibration data at altitude.
Note that its useless comparing the altitude throws with sea-level throws for any thrower as there are never enough to give a statistically significant result given the natural variation in most throwers, (10-15% in 6 throws is fairly common). You would need 20-30 complete series before any reliable pattern emerged and there are lots of other confounding variables. (There are lots of statistics on baseball hits though which is why it is known they fly further at altitude).
3) For Phil and Wez. Wobble. You have no control over the wobble frequency. This is basically a function of the stiffness of the javelin, its length and to a much lesser extent, how dirty the thrower hits it. Its been known for quite a long time (Mont Hubbard's work I think) that a wobbly javelin tends to generate more lift. However it also soaks up energy to wobble a javelin so there is a trade-off. My own simulations suggest that the cleaner a particular thrower hits it, the further it goes. This is where it gets very complicated though. The highly exaggerated wrap of throwers like JZ mean that his kinetic chain is not very linear and although perfectly possible to model, would require the construction of an avatar with the required constraints from motion capture. (My colleagues do lots of this stuff but not with javelin throwers as they tend to rip all the damn sensors off and at a few hundred quid a time, its easy to get unpopular). In contrast SB's linear style would make this much easier to model.
(Thanks for the link Phil. That was a good clip. The one I was thinking about was I think one of the Olympic finals where JZ hit one so badly, I thought it would break up. It went about 40m. His next throw was around 88m I think.)
4) (Finally) I am not a fan of stiff javelins I'm afraid. If you miss the centre of gravity, the effect is exactly like missing the centre of mass of a cricket bat with the ball. Cricket bats have built in rubber shock absorbers specifically to take up some of the reflected force os a mis-hit but even so I can remember deadening my whole arm with a mis-timed attempt to hit a bowler into orbit in my distant youth. Stiff javelins have no shock absorbing properties and simply reflect it back into the arm which can be very bad news for the thrower who is already under considerable stress from the throw itself. An engineer might call this impedance contrast. These days, when I do a bit of coaching, I worry far more about injury prevention (because mis-hit throws are more common than good ones), than I do about exotica like a javelin that might go a bit further if you just happen to hit it right. Doesn't sound like a promising trade-off to me although I expect everybody will have their own views on this.
BW, Les.
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Post by slinger on Jul 14, 2009 23:10:54 GMT 1
Thanks for the reply Les. Indeed it is concerning the number of younger throwers who still physically maturing are throwing stiffer carbon material Javelins - mostly down to it's the "in thing" and what the pro's use. Zelezny did describe them as "the javelin for 100m" and they do potentially go further, but like you say at the possible detriment for one's health if they are thrown badly for long enough. It was also interesting to note even Zelezny soley threw steel champs in training, when throwing in any great volume. That throw from Stuttgart was with one of the original orbits and I'd imagine like the champ they are very forgiving and it was actually a fairly clean hit! In the Gothenburg '95 WC's on analysis his yaw angles at release were not very much more than anyone else's really, so perhaps like you say it's also down to implement and not thrower - I'll always remember getting him to sign one of my OTE tailwinds, the WR model and he said it was a "very stable javelin" in his broken English and by this I think he was suggesting it was a minimum wobble steel javelin. www.youtube.com/watch?v=xUv4pF9OdAIThis clip is maybe the 88m throw you are thinking of....and have I seen this throw a few times over the years - I had this on VHS as a kid and watched in over and over again. I'm not sure if you remember the Atlanta OG's but Makarov had a 87/88m foul [was well over the line btw] and they also showed the aerial shot like on that Zelezny throw and he never got out of his wrap at all and hit across the spear massively, it's a wonder how they throw so far with all that wasted energy - or rather how far would they throw if it was clean. Pitkamaki is another - wraps, lines it up right and then throws it down the left hand sector.
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Post by wez on Jul 15, 2009 8:13:31 GMT 1
Wow Les, That was probably our most informative and to the point post ever made! About elbows, it seems you all went through alot more than i did to get your solution. In my case the fracture eventually became a complete break so corrective surgery was the only option as the Olecranon was completely split and my tricep pulled the end off into my upper arm. The surgery to screw it back tightly together coupled with all the bleeding makes for pretty efficient healing and i am lucky that my bone density is naturally very high good so that the break has become reliably strong. I think its great that you are going to publish the results, because there is not really much out there that i found useful except these: This one about throwers elbow www.jbjs.org.uk/cgi/reprint/42-B/4/788This is quite a good one about damage to the Olecranon www.ncbi.nlm.nih.gov/pubmed/3759300(1)Thanks for the lift explanation that makes sense to me, so when we throw with a tilt angle of 0 there is no lift atall assuming no wind. In what conditions do we then get lift, eg what should be the attack angle of the javelin and wind direction? (2) I imagined altitude would in theory help a bit, i wonder if IAAF know this? (3-4) So stiff jav are in theory better but vibration can help also, that leads me to think that given the velocity of the javelin is greatest at release the advantage from vibration is mostly likely going to help in the early phases of the throw. In that case there is a strong argument for the OTE composite FX, in that it will bend and vibrate on release being more forgiving to the thrower and it gradually dampens that vibration through the flight. Does this get you the best of both worlds perhaps? One more thing though, you can control your wobble frequency by choosing a different javelin, thats what i was getting at. eg carbon more high frequency wobble than steel and OTE composite FX a mixture of the two. IMO carbon javs are scary and i personally don't trust my technique enough to use one so i'm totally with you on that but maybe for top level internationals its a worthwhile risk.
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Post by leshatto on Jul 16, 2009 8:33:57 GMT 1
Wez/Phil:
Thanks for feedback - very welcome as always.
Phil: Wobble. Thanks also for this clip. I remember that Makarov throw. Makes you think doesn't it ! If I had a bit of time, I would like to study the biomechanical trade-offs of pulling across a javelin. The javelin always wobbles a bit simply because the arm is attached to the shoulder, (relatively weakly in my case these days), so the hand moves in an arc pulling along a linear object. Linear throwers like SB and Lusis would punch up through the javelin wobbling it in a vertical plane whereas JZ tended to pull across it sideways, yawing it.
Aerodynamically these are quite different but it seems to me that it would be perfectly possible to match a throwing style with an athlete's body far more efficiently for distance and injury prevention than we do. That would be a nice project but would take a lot of measurement and modelling but there is nothing intrinsically difficult about it. This is the sort of thing I think we should be doing for our throwers but its hard enough getting any exposure at all. One day maybe ...
Wez: Olecranons. The only alternative for Felix was to break the elbow. Although this sets up the healing nicely as you say, it can cause bony extrusions along the fracture line which in his case would have prejudiced mobility as the initial crack was unusually on the inside of the Olecranon and there is also a possibility of dinging the ulnar nerve. In the end, the surgeon hollowed it out from the inside without breaking the surface and packed it with bone graft from his hip, completing the job with a couple of 5 cm cancellous screws, which we now have as a rather macabre souvenir. The skill necessary to do this is very rare. It must be javelin throwers but the surgeon told me that Felix' bone density was so high that it took him over three hours to do this, (he had expected half that). It takes about 9 months to reform with the right rehab. The result from the scans though show that it is completely orthopaedically sound now.
Very interestingly, the surgeon also told me that for sports related injuries, he felt that the rehab was at least as important as the surgery, strongly supporting what you put yourself through Wez. For example, the rehab for damaged UCLs (ulnar collateral nerve) and commonly though somewhat inaccurately known as javelin elbow, is vitally important with a daily regime spread over several months. We discovered that 11% of major league baseball pitchers in the USA have had a reconstruction procedure on the UCL and reconstructions are now stronger than the original ligament leading to pressure for young pitchers to have the operation before they damage their own UCL. Its a mad world.
(1) The lift you get is related to the attack angle which is the angle between the long axis of the javelin and the wind direction, ** relative to the javelin itself **. You have to compute this using the triangle of vectors. The distance it travels is very sensitive to attack and the ideal attack angle can be negative. There is no simply relationship for optimal choice of attack angle and delivery angle as the thrower's biomechanics also intrudes. You just have to model it but the javelin flight analyser downloadable from my website can do that.
(2) I presume the IAAF know this. It is good that they flag altitude performance whether its beneficial or detrimental because at least you can always go back and analyse them later.
(3-4) Maybe. I like the composite but that's probably because I have a soft spot for OTE javelins generally as I did my own PB with one 40 years ago when they were still Held. Of course, we cannot quantify the comfy feeling we get throwing a favourite javelin which may overcome any aerodynamic efficiencies.
A final word on wobble. Its not at all clear to me that a stiff javelin should fly farther for a particular athlete. A stiff javelin resists the athlete's movement. The argument is (I think) that this allows more of the energy to be transferred to moving the javelin than bending it. However this may prejudice the athlete's movement itself and we already know that a wobbly javelin does generate more lift, so I think you would have to say that the jury is still out on this one.
BW, Les.
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Post by leshatto on Jul 16, 2009 8:37:50 GMT 1
Sorry, a correction. The UCL is the Ulnar Collateral Ligament of course.
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Post by wez on Jul 16, 2009 11:39:34 GMT 1
Funny that Felixes surgeon also had difficulties, mine told me that she had to change the drill bits half way through because they wore out! I think that either Javelin throwing induces high bone density or then the sort of people who throw javelins are naturally biased towards it...or then a combination of the two When you think about it though, if we both have such high bone density why have we both ended up with fractured elbows? Maybe they become too brittle when too much mineral is added to the bone and thereby lose some of the natural flexibility that would be normal for a lower density bone.... Afterall bone is a mixture of protein (flexible) and minerals (hard/brittle) and density is increased by adding extra mineral to the structure. I'm just thinking, could there be a way of avoiding such injury by injecting a bone softening agent to the joint like acetic acid to avoid surgery....any experimental physicians out there
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Post by slinger on Jul 16, 2009 13:23:49 GMT 1
"I'm just thinking, could there be a way of avoiding such injury by injecting a bone softening agent to the joint like acetic acid to avoid surgery....any experimental physicians out there"
Now that really is commitment Wez!
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Post by pembrokian on Jul 21, 2009 13:31:09 GMT 1
Apologies, Prof hatton did give me a lot of info about his sons injuries and the saga around getting them sorted but I've been away a lot this last week and didn't get a chance to post them. It looks like Prof Hatton has already shared most of those insights here but let me know if you want a "cut-and-paste" of the emails we exchanged.
See (most of) you at Birmingham this weekend.
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Post by sam on Jul 21, 2009 13:56:56 GMT 1
see you there dave, i'll be throwing :-)
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Post by pembrokian on Jul 21, 2009 14:56:29 GMT 1
Good luck Sam; not sure if I've got in but, failing that I'm be winging a discus instead. Bringing young javelin and discus throwers with me.
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