Baller Luzz Posted July 16, 2019 Baller Share Posted July 16, 2019 Ballers, I just wanted to share one rare instance of recent research in water skiing. In her masters thesis, Chiara Ferrari (@Kchiara) and colleagues looked at some kinematics with high-level jumpers. I’m sure she’ll be willing to answer any questions, in the meantime, here’s the abstract of the study: The aim of this study was to perform a kinematic analysis of the in-run, take-off and early flight phases in water ski jumping and to analyse the differences in linear/angular parameters between males and females. Forty-two elite skiers participated in this study (27 males; 15 females); their jumps were video recorded during competitions: the time course of absolute (trunk, thigh, ski) and relative (hip, knee, ankle) angles was calculated, as well as the (trochanter) resultant speed. Males were able to reach faster in-run speeds than females (25.4 ± 1.9 and 21.8 ± 1.2 m/s, respectively) and jumped further (56.2 ± 8.6 and 40.4 ± 6.3 m). Longer jumps were correlated with faster speeds in all phases (r range: 0.87–0.91, p < 0.001, n = 42). From take-off to early flight skiers extend their hip (86–109°) and knee (136–171°) angles, lean their trunk forward (49–41°) and raise their skis (20–51°); no major sex differences were observed in the body position (or ski incline) in these phases and none of the angular parameters was correlated with jump distance. Our results suggest that skiers should focus on achieving a larger in-run speed to maximise performance in this discipline. Ski coach at Jolly Ski, Organizer of the San Gervasio Pro Am (2023 Promo and others), Co-Organizer of the Jolly Clinics. Link to comment Share on other sites More sharing options...
Baller MillerTime38 Posted July 16, 2019 Baller Share Posted July 16, 2019 As a math nerd I would have assumed the key to jumping distance would be based on momentum (=mass*velocity) which would explain why men jump farther than women considering men are on average heavier and stronger (so able to achieve higher velocity). I think the ski angle is gonna be based off ramp angle? Curious did they jump off different height ramps? Link to comment Share on other sites More sharing options...
Baller andjules Posted July 16, 2019 Baller Share Posted July 16, 2019 @MillerTime38 in alpine ski jumping, it seems to be surface area to weight ratio, rather than momentum that helps (at least once in-flight); in other words (and given equal takeoff velocity), less weight is an advantage when using your body and skis for lift/float. I don't know for sure if that translates to waterski jumping, and it's interesting (to me, at least) that the abstract above only mentions "early flight" (not the whole flight). Link to comment Share on other sites More sharing options...
Baller Andre Posted July 16, 2019 Baller Share Posted July 16, 2019 @Luzz Got pics from Chiara ? ;) (Just kidding! She's Luca Spinelli girlfriend and a gymnast i think.Saw a pix of her last week on FB...WOW! ) You math nerds can get back to your numbers now... My ski finish in 16.95 but my ass is out of tolerance! Link to comment Share on other sites More sharing options...
Baller_ Bruce_Butterfield Posted July 16, 2019 Baller_ Share Posted July 16, 2019 Cool analysis, but how do you measure the testicular fortitude needed to cut REALLY late and generate all that speed? And yes many of the female jumpers have significant amounts of the aforementioned stuff. If it was easy, they would call it Wakeboarding Link to comment Share on other sites More sharing options...
Baller BraceMaker Posted July 16, 2019 Baller Share Posted July 16, 2019 Some of those ranges are crazy, 20-51 degrees of ski tip altitude. Would be interesting to see raw data on which angle generated the highest and the delta per skier, do some skiers for instance have jumps at 20 and jumps at 51 or are most skiers within a few degrees every jump? Link to comment Share on other sites More sharing options...
Baller MillerTime38 Posted July 16, 2019 Baller Share Posted July 16, 2019 @andjules I think the difference is alpine jumping you are not leveraging yourself against a boat to generate the velocity you are just trying to be aerodynamic as you let gravity take you down hill and alpine skiing you are jumping down hill, basically a controlled fall. Completely different than waterski jumping Link to comment Share on other sites More sharing options...
Supporting Member Than_Bogan Posted July 16, 2019 Supporting Member Share Posted July 16, 2019 "none of the angular parameters was correlated with jump distance" This statement seems shocking. Was it also shocking to the researchers? Were any hypotheses developed as to why the flight angle of the skis could be so unimportant when it seems visually obvious that lift is occurring during flight? Is that completely an illusion and the skier's path is almost entire dictated by gravity and air resistance? The nature of research is to make guesses, try to measure them, and then question both your guesses and your measurements! Here it seems so crazy that none of these angles are correlated that my first instinct would be to question the measurements. Fascinating in any case. Important note: I have landed zero jumps in my life. Less important note: I have learned to REALLY not trust my eyes to guess at physics during my ongoing journey to learn the pole vault. So I am quite aware that when I say "visually obvious," I may actually be referring to something that isn't happening at all! Link to comment Share on other sites More sharing options...
Baller klindy Posted July 16, 2019 Baller Share Posted July 16, 2019 @Kchiara any chance you would share your master's thesis? Interesting project for sure and the abstract has some intriguing information. Assuming you've already presented this, and it was well received, Congratulations would be in order for achieving a milestone relatively few in this world achieve! How fun to do your research on something that also has been part of your life for a long time! Link to comment Share on other sites More sharing options...
Baller jimbrake Posted July 16, 2019 Baller Share Posted July 16, 2019 @Than_Bogan - as a side note, if you're a pole vaulter, then you should also be a water ski jumper. Boom. Link to comment Share on other sites More sharing options...
Supporting Member Than_Bogan Posted July 16, 2019 Supporting Member Share Posted July 16, 2019 Pole vaulting looks far more dangerous that it really is. Water ski jumping actually is that dangerous... Link to comment Share on other sites More sharing options...
Baller klindy Posted July 16, 2019 Baller Share Posted July 16, 2019 @Than_Bogan Walking across the street is dangerous if you don't do it right.... Link to comment Share on other sites More sharing options...
Baller Luzz Posted July 22, 2019 Author Baller Share Posted July 22, 2019 For those who are interested in the full pub, there are some free eprints here Ski coach at Jolly Ski, Organizer of the San Gervasio Pro Am (2023 Promo and others), Co-Organizer of the Jolly Clinics. Link to comment Share on other sites More sharing options...
Baller disland Posted July 22, 2019 Baller Share Posted July 22, 2019 How were the results between Men and Women correlated for the fact that the boat goes faster in the Mens event? Link to comment Share on other sites More sharing options...
Baller disland Posted July 22, 2019 Baller Share Posted July 22, 2019 read the report, answered my own question Link to comment Share on other sites More sharing options...
Kchiara Posted July 28, 2019 Share Posted July 28, 2019 @MillerTime38 from the in run phase to take off phase the ski angle is based on the ramp angle. During the early flight phase is based on horizontal angle. The height of the ramp is different between males and females: f=1,65 (5.5feet) m: 1,80 (6 feet) Link to comment Share on other sites More sharing options...
Kchiara Posted July 28, 2019 Share Posted July 28, 2019 @andjules unfortunately I could not analyzed all jump distance because I had one camera only. Link to comment Share on other sites More sharing options...
Kchiara Posted July 28, 2019 Share Posted July 28, 2019 @BraceMaker you need to consider that some of the jumps were not well executed so the range is bigger. If you what all datas you have got to read all the article. Link to comment Share on other sites More sharing options...
Kchiara Posted July 28, 2019 Share Posted July 28, 2019 @Than_Bogan if you read carrefully the whole thesis you will find that some angles are correlated to the jump distance, but not enough significant for many reasons ( not so many athletes, not all jumps were well performed...) The most significant angles are trunk and ski angle after the take off. For sure It would be nice make other research about it Link to comment Share on other sites More sharing options...
Baller ral Posted July 28, 2019 Baller Share Posted July 28, 2019 Sorry, OCD kicking in... Nordic ski jump, not alpine... Link to comment Share on other sites More sharing options...
Baller ral Posted July 29, 2019 Baller Share Posted July 29, 2019 @Luzz , I was not able to find how to download it at the link... Link to comment Share on other sites More sharing options...
Baller Luzz Posted July 29, 2019 Author Baller Share Posted July 29, 2019 @ral I think the free downloads for the article ran out. Maybe @Kchiara can help out with that? Ski coach at Jolly Ski, Organizer of the San Gervasio Pro Am (2023 Promo and others), Co-Organizer of the Jolly Clinics. Link to comment Share on other sites More sharing options...
Kchiara Posted July 29, 2019 Share Posted July 29, 2019 @ral send me an email and I will give you the PDF. Link to comment Share on other sites More sharing options...
Baller ral Posted August 1, 2019 Baller Share Posted August 1, 2019 @Kchiara , did you get my email? Thanks ! Link to comment Share on other sites More sharing options...
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