Archive for the ‘triple lutz’ Category

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Figure Skating Jumps – A Review of Minimum Air Times (Trevor Laak)

July 2, 2014

With the prevalence of low cost video analysis apps on mobile phones and tablet computers, video analysis of figure skating jumps is within reach of EVERY coach and skater. Past research into minimum air times for each jump can now be used by all figure skating participants to help assess skater progress and minimize injuries.

To my knowledge, no formal publication of jump minimum air times has yet been made. However, a large number of researchers including this author have compiled statistics on minimum air times that should provide helpful guidelines for those interested.

I have received a huge number of requests for this information so I hope this post addresses the interest in this topic.

 

Why Minimum Air Times Are Important

Knowledge of minimum air times is important to coaches because it provides a relatively clear way of assessing a skater’s athletic progress and technical progress with any given jump. If a skater is matching or exceeding the minimum air time for the jump and has solid technique and an appropriate body type, they should be able to get close to full rotation of the jump under ideal conditions.

Air time information serves two important and related purposes in the development of figure skating jumps.

1. It reduces the pressure on skaters to complete elements that they physically have no chance of completing, and

2. It dramatically minimizes injuries from attempting jumps a skater is not yet ready to attempt.

Skaters have historically been under extreme pressure to land more advanced jumps at younger and younger ages. As the sport progresses technically, this pressure is only continuing to grow.

How many skaters feel guilty about not landing their double axel (or any jump) after working on it for months or years? Skaters often feel that they are letting their parents and coaches down and they often experience extreme frustration at themselves for not learning a new jump sooner.

But minimum air time measurements can help to reduce this guilt and frustration. If a skater knows she or he is not jumping high enough to land a jump cleanly, the focus turns to solving that problem rather than remaining fixated on just landing the jump.

Similarly, coaches can help their skaters dramatically reduce injuries by knowing their skaters’ air times and not expecting or demanding that the skater stand up and land the jump when they are simply not ready. It then becomes the coach’s job to help the skater optimize jump technique and develop the necessary jump height through off-ice training.

The days of repeated futile jump attempts are over, or at least they should be. In this day and age, no coach should continue to apply the just-stand-up-and-land-it mentality without knowing air times.

How These Numbers Were Generated

The minimum air time numbers for each of the major figure skating jumps provided below were compiled from measurements of many jumps over a long period of time. By measuring air time on as many jumps as possible over a period of many years, certain air times stand out for each jump.

Some of the measurements were made on practice jumps videoed directly by a coach or skating parent while others are a result of digitizing televised broadcasts of competitions or other events of elite skaters. Historically, a televised skating competition or event could be recorded and then digitized to provide model jumps for analysis.

 

Caution With The Numbers

It should be noted that attaining minimum air time does not automatically mean a skater should be able to land a given jump. Minimum air times are typically only possible by skaters with extremely efficient technique and an optimal body type.

Skater body type plays a big role as smaller and thinner skaters typically have an advantage for faster rotation. Even this is an over-generalization because some tall skaters can rotate very fast, but as a general rule, it is small and thin skaters that these minimum air time numbers were generated from.

Thus, larger skaters or those that have a more substantial frame will almost always need more than the minimum air times listed below.

Rotation rates are obviously also affected by take-off mechanics. This means that a skater may jump higher than the minimum air time but lack the ability to create enough rotational energy on the take-off to spin fast enough in the air, even with a perfect air position and body type.

Coaches should strive to help their skaters optimize jump take-off technique and air position. Jump height is a result of jump technique as well, but overall skater athleticism appears to have a very strong influence on the ability to jump high. The development of athleticism is probably best attained through significant focus on off-ice training methods.

For more information about jump technique or off-ice training methods, please visit iCoachSkating.com. That website is committed to providing the best educational information on the nuts and bolts of how to figure skate.  It has literally hundreds of videos on jump technique from some of the world’s best coaches.

 

How to Measure Air Time

For accuracy, it’s important to maintain correct measurement methods. When analyzing jump air time, the measurement should be made from the first video frame a skater’s blade is in the air to the first frame the skater’s blade touches the ice.

It is NOT accurate to measure from the last frame on the ice to the first frame back on the ice. This measurement method will result in air time measurement that are too large. The details of this are beyond the scope of this article and will be provided elsewhere.

Simply use first-frame-off-the-ice to first-frame-on-the-ice and you’ll be fine. Most apps don’t have a way to reset the clock to zero on the first frame in the air, so record the time at the first frame in the air and the first frame back on the ice and subtract to get air time.

 

Shout Out to Christy Krall

At the 2011 PSA World Conference in Dallas, TX, World and Olympic figure skating coach and video analysis expert Christy Krall gave a presentation in which she provided insights about minimum air times for all the main jumps from double loop through triple lutz. To my knowledge, Christy has not published these findings elsewhere, partly since she uses these only as guidelines and there may be some skaters with successful jumps at lower air times.

I am publishing both Christy’s numbers and my own observations here for your reference. But remember, these numbers only represent our experience and are not absolute. Christy provided numbers for both male and female skaters (female/male). Air times are provided in seconds.

Jump                     Trevor                   Christy
Abbrev.               Air Time                Air Time

1A                           0.30

2S                           0.30

2T                           0.30

2Lo                         0.33                        0.35

2F                           0.35                        0.35

2Lz                          0.35                        0.35+/0.36

2A                           0.45                        0.45/0.47-0.51

3S                           0.47                        0.47/0.48-0.51

3T                           0.48                        0.47+/0.48-0.51

3Lo                         0.50                        0.51/0.52-0.53

3F                           0.53                        0.53+/0.56-0.58

3Lz                          0.53                        0.53+/0.56-0.58

3A                           0.60-0.62

4S                           0.63

4T                           0.63

 

These Minimums Are Not Absolute

Again, these numbers are not absolute. For example, I’ve seen 2 double axels with an air time of only 0.43 seconds. One was during practice sessions with a young skater in Korea with extremely efficient technique and a very thin body type and the other was off video taken by another coach of a similar Japanese skater who eventually became a World Champion. I do not consider 0.43 seconds to be a reasonable minimum air time for double axel because my experience shows that only an extremely rare and talented skater can pull it off.

Similarly, Sasha Cohen was capable of landing a quad salchow with just 0.60 seconds of air time. This astonishing feat of optimization may represent the absolute lowest possible air time for quad salchow, but most quad salchows are being landed with air times of 0.65 and higher. A significant number of skaters have landed the quad salchow at 0.63 seconds which is why it’s listed on the chart as the “reasonable” minimum.

When we use minimum air times with our skaters, we want them to target a reasonable number for their body type. So based on the skater’s body type and my experience, I may shift the numbers slightly so they have a more appropriate air time goal. We want skaters focused on meeting and exceeding air times that should provide success.

I hope this article is helpful. I did not ask Christy for permission to publish her air time numbers here but felt that her work deserves your awareness. Her groundbreaking research was a starting point for my own observations and this article would not be possible without her contributions.

 

Final Note

To get an idea of what these air times mean in regards to actual jump height, please see my previous post comparing air times with projectile height (Are Figure Skaters Projectiles?).  Sometimes it’s helpful for skaters to understand how much more jump height they need. Knowing that your double axel air time is 0.40 seconds and you need 0.45 seconds is somewhat abstract. But knowing you need to generate an additional 2 inches of jump height is very tangible to most skaters.

Please leave a comment and let me know if this article was beneficial.

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Are Figure Skaters Projectiles?

August 28, 2007

The title above is eye-catching on a number of levels.  Have you ever been on those high sessions with 25 skaters?

Actually, this post is a follow-up to my discussion of slo-motion versus computer analysis.  In that post I made the bold claim that the minimum height for a double axel is 60% higher than the minimum height for a double lutz.  In this post, I’ll show how I got those numbers.

Warning:  This post is extremely technical so if you just want the final answer, see the height and flight time tables below.

The work of figure skating video analysis experts has demonstrated that there is a minimum flight time requirement for each of the jumps.  For example, a double lutz needs to be in the air for 0.367 seconds or longer while a double axel needs to be in the air for 0.467 seconds or longer.  These values have been determined by analyzing hundreds of jumps with various video analysis programs such as Dartfish or Pro-Trainer.

Using the video analysis software, a coach can count the number of frames a skater is in the air.  You do this by advancing the jump entry and take-off frame-by-frame until the skate blade just leaves the ice.  You mark that as your starting point and advance the jump frame-by-frame through the flight until the skate blade just touches the ice.  The number of frames from the start to the end point give the flight time, as video cameras shoot frames at fixed time intervals.

In North America, the video standard is 29.97 frames per second but the magic of modern video analysis software such as Dartfish and Pro-Trainer allows those programs to double the number of pictures for certain consumer video cameras.  (In a future post I’ll discuss the technical details of interlace vs. progressive scan.)  That means we can resolve the jump flight time to 1/60th of a second (actually 1/59.94 of a second).

So here’s an example.  I’ve never analyzed a double axel with less than 28 frames of flight time at 60 frames per second.

28/60 = 0.467 seconds.  Dartfish and Pro-Trainer have timers so you don’t actually have to count the frames.

Now to calculate an estimate of how high the jump was, I apply the laws of physics.  In basic physics courses, there is almost always a part of the course devoted to “projectile motion” and the associated equations.  We’re going to consider our in-flight skaters as projectiles!  For our situation, the equation of interest is the simplified time-acceleration-distance equation. 

This equation states that the distance an object travels under constant acceleration from rest is one half the acceleration rate times the square of the time.  The equation looks like:  Distance = 1/2 x Acceleration x Time x Time.  For our skating jump analysis, we need to use half the total flight time as the Time in the equation as the skater at the peak of the jump has no vertical speed (“from rest” at the top of the jump to full speed at landing… to use the simplified equation).

The acceleration of a projectile is simply the pull of gravity.  And gravity has a constant acceleration of 386.088 inches/sec2.  Using the double axel minimum flight time of 0.467,  the decent-only time is 0.467/2 = .2335 seconds.  Plugging all of this into the equation yields:

Distance = 0.5 x 386.088 x .2335 x .2335 = 10.53 inches

Just for theoretical completeness, the actual jump height is slightly lower.  The reason is that a skater always points his or her toe at take-off but usually flexes the toe in the air and upon landing.  This makes the number of frames method a tiny bit inaccurate.  But the result is close to the theoretical.  A double axel must be 10.5 inches high or you can forget it.

(Some skaters land with their landing leg slightly bent.  Their jumps are actually slightly smaller than that indicated by the table below.)

Here’s the whole table:

Frames in Air

Flight Time in Seconds

Height in Inches

10

0.1667

1.3

11

0.1833

1.6

12

0.2000

1.9

13

0.2167

2.3

14

0.2333

2.6

15

0.2500

3.0

16

0.2667

3.4

17

0.2833

3.9

18

0.3000

4.3

19

0.3167

4.8

20

0.3333

5.4

21

0.3500

5.9

22

0.3667

6.5

23

0.3833

7.1

24

0.4000

7.7

25

0.4167

8.4

26

0.4333

9.1

27

0.4500

9.8

28

0.4667

10.5

29

0.4833

11.3

30

0.5000

12.1

31

0.5167

12.9

32

0.5333

13.7

33

0.5500

14.6

34

0.5667

15.5

35

0.5833

16.4

36

0.6000

17.4

37

0.6167

18.4

38

0.6333

19.4

39

0.6500

20.4

40

0.6667

21.4

It’s pretty fascinating to understand the ramifications of this table.  For example

  • A double lutz needs to be have a miminum flight time of about 0.36 seconds, so it will be 6.5 inches high. 
  • If a triple lutz needs to have a minimum flight time of 0.58 seconds (estimated), it will be 16.4 inches high.

OK…has that sunk in yet???  The triple lutz needs to be 250% higher than the double!!  WOW!  Do you see why so few skaters actually get all those triples?

I hope this was interesting and useful.  If you are enjoying this blog, please pass the URL along to your friends that may be interested.  Also, please leave a comment as I would love to hear from you.

Trevor