Winter is definitely here and many of us will be heading to the slopes this season for some skiing or snowboarding. When heading out, it is a great idea to have a trick or skill in mind that you plan on learning. Anything from slaloming on skis to riding your first rail on a snowboard will help to motivate your sessions on the slopes and ensure you do not get too frustrated with crowds.
Whatever trick it is that you plan on learning, see if you can find some video of it being done. Study the video carefully and keep it in your mind as you try the skill once you get out on the snow
We will keep it basic this time and take a look at the snowboard ollie. We have discussed the ollie in skateboarding in a previous post. On snow and a snowboard the trick is performed similarly. As in skateboarding, the ollie is the basis for most aerial tricks on a snowboard and therefore it is important to learn how to do a great one.
Try the ollie from a standing position first. Get used to the mechanics of the movement before you try the jump while moving.
Start with your knees bent and body upright. You do not want to bend at the hips and lean forward or backward. If you do you will have difficulty landing your ollie as you will have started the trick off balance. Bend at your knees a little though to give you some spring.
To start the trick, push down on your back foot moving your center of mass backward over your back foot. This will allow you to pull the front of your snowboard up and prepare you to jump off your back foot. Remember that a snowboard is also pretty flexible so pushing down on your tail will bend the board giving you some spring into the air.
As the nose of your board begins to pull up into the air, jump off your back foot so that your back foot comes as high as your front foot. To get higher into the air, pull your front leg higher up and jump higher off your back foot to allow your back leg to catch up in the air.
Once your back foot and front foot are at the same height position yourself over the center of the board and stabilize yourself for landing. Your center of mass should now be in between your feet.
Land on both feet evenly, so that you do not slide out once you hit the ground. Once again do not bend at the hips. Bend your knees slightly to absorb the landing.
Take a look at this video of a small ollie on a snowboard.
Watch lots of videos of the pros and film yourself to see if you can improve your style or get higher in your ollie or any other trick you try this winter.
Skateboarding has taken off as a sport over the last decade and the tricks being performed are often incredible. To perfect these tricks skateboarders spend hours practicing and falling over and over again.
Video analysis is the perfect tool to learn how to do skateboard tricks. If you are learning a trick that someone else has already perfected you have the advantage of watching them do the trick and learning from them. You can also get video of yourself performing the trick and compare your technique to theirs.
Another benefit is that it is easy to setup a camera to get the best view for analyzing the video. Because most tricks are done over a defined area and in a specific direction, you can easily setup a camera to get the best field of view and angle to analyze the trick.
One of the more basic skateboarding tricks is the "Ollie" (jump). The Ollie is the basis for most aerial tricks in skateboarding and therefore it is important to learn how to do a great one.
Here is a really good video with a lesson on how to do an ollie. The video of the ollie itself is excellent because the camera is setup well and looking directly at the skateboard and movement and not at an angle.
The video gives a comprehensive description of how its done. We can get some other tips from analyzing the video more closely.
At the beginning of the ollie, the rider applies pressure to the tail of board. He does this to force the front of the board up into the air to start the movement. However if he only applied pressure to the tail he would simply fall off the back of the board. Watch how he also maintains his weight over his front foot so that the front of the board will only move up as he lifts and shifts his front foot.
Coming to the take off, the rider jumps up into the air but notice that he does not use his arms to jump. The idea with an ollie is to stay connected or at least close to your skateboard throughout the trick. If you use your arms to jump, you may jump too high above your board and end up having a long way to fall back onto your skateboard.
The rider in the video also lets us know that to make your ollie higher you "suck your knees up to your chest after you have jumped". This helps you to raise your center of mass and of course the height of your feet and therefore allows the board to lift higher into the air. Your center of mass is the center of all the limbs of your body, and is usually somewhere around your navel. You can move your center of mass by moving limbs. Therefore if you raise your arms you raise your center of mass. If you jump and lift your knees up higher you will also raise your center of mass.
Your center of mass is also important for maintaining your balance when landing the ollie. In the video note how the skaters right arm ends up behind him on the landing while his left arm is in front. He is balancing his center of mass over the center of the skateboard by opposite and equal balance of his arms. This does not mean that you need to have your right arm back and left arm forward when landing your ollie, but you should be aware that you need to balance your weight over the center of the skateboard (both forward and back as well as left and right) so that you do not fall off on landing.
Good luck with learning to do an ollie. You can try practicing your ollie first on grass or softer ground before moving to the cement. Remember to also wear a helmet, all the pros do.
When most people think of the Olympic Games, the first sport that comes to mind is Gymnastics. Supremely strong and fit athletes flying through the air, somersaulting and twisting. The sport defies gravity and leaves us all in awe.
The sport of Artistic Gymnastics is performed by moving the body, often through the air, and there are no rackets, bats or balls involved. Because of this, video analysis of different gymnastics movements can provide excellent coaching and feedback for the athlete. Gymnastics is all about the technique. By applying the correct technique and timing, the athlete will achieve the desired results. In most cases, there are no outside influences and therefore good biomechanics will result in good performance.
As a young gymnast myself, I watched and analyzed countless hours of my own technique on video. It really is very easy to set up. Most gymnastics moves take place in a small area, so you only need to ensure that the camera is set up so you can see the complete movement in the field of view and also that the camera is set up at the correct angle to analyze the movement you want to assess.
In college, I continued to analyze my own and my teammates gymnastics technique using video. One very common analysis we did was of the standing back flip. Many gymnastics elements have the back flip as a core component. A double back flip is simply 2 back flips in a row without touching the ground in between, a full in - full out is a double back flip with a twist in each of the flips. The list goes on, but what is important is that the technique used to start a back flip is the same technique that is used to begin many of these other flipping and twisting maneuvers.
Capture video to analyze your back flip requires some easy setup:
Set up your video camera, so that the gymnast is standing sideways to the camera. Most of the analysis of a back flip is done in this side on (sagittal) view, such as jump height, lean and rotation.
Remember to fill the field of view. You do not want your camera to be too far away so you have a lot of empty space around your subject. You also do not want it too close, so that the gymnast jumps out of the camera view. A little trick to know, is that most cameras have a rectangular field of view (they are wider than they are high). So flip the camera on its side to get closer to the gymnast but still be able to capture the height of his flip. If you do decide to flip your camera on its side, make sure you have some video editing software that will allow you to view the video right way up, otherwise it may be difficult to view properly.
Set your gymnast up with a plane background (such as a white wall) behind them in the image. This will allow you to mark a specific height on the wall and thereby measure their height.
If you really want to measure angles of the joints, such as the knee or hip, it is best to mark these points with a bold marker pen so that you can see them in the video.
Lets take a look at some video I found on YouTube. The video also give you some instructions on how to do a good back flip. The video camera itself is not setup in the optimal position to make good measurements of the gymnasts jump height, rotation or proper take off technique, but it is still easy to see that he has good technique.
This gymnast really does a very good standing back flip. The most important part being the take off which will allow the gymnast to perform any variation on his back flip from there.
There are 3 phases to the back flip take off:
The loading phase: In this phase the gymnast bends his knees and swings his arms backward in preparation. The idea is to create the energy needed to jump up into the air and rotate over in the flip. By swinging his arms backward and bending his knees, the gymnast is loading up with potential energy. As the video points out , you do not want to bend your knees too much or you will need to use the energy to get yourself back into a good load position for the take off.
The take off phase: Now the gymnast drives his arms upward and straightens his knees quickly as he jumps off the ground. The head is very important in this phase of the take off. If you throw your head backward , you may create a lot of rotation but you will not be able to jump as high. Therefore it is important to keep the head looking forward and still. Coaches suggest that the optimum angle of lean for the take off is between 75 and 80 degrees from the floor. The gymnast in this video looks to have this angle perfected.
The tuck: For the last part of the flip, the gymnast needs to rotate over so that he can land back on his feet. If the take off is good, then this part should be easy. By taking off leaning slightly backward (angle of 75 to 80 degrees), you have already created the rotation you require and all you need to do is bring your knees up to your chest. By bringing your knees up you will increase this rotational speed and easily complete the flip.
OK, before you try a back flip on your hardwood floors, remember that it takes practice and numerous drills before most gymnasts are doing good back flips. If you are intent on learning one, then get into a gym with mats or a foam pit and a coach. Then get out your video camera and film yourself to see what you are doing and correct your biomechanics from there.
From personal experience, I will say it is well worth the effort to learn how to do a good back flip.
Playing volleyball on the beach is a fun (albeit tiring) way to spend a day in the sun. For those of us who haven't played in a while, it's always a bit of a shock to realize just how difficult it is to jump on the sand. At first glance, the nets don't look all that high and you think to yourself, "Is this regulation? This looks too easy." But when you make that first attempt at a spike, it's immediately apparent the game isn't as easy as the pros on TV make it out to be.
One study suggests that if you can jump and reach 10 feet in a gym, you can expect to only reach 9 feet on the sand. So why is it so much more difficult to jump in the sand, compared to jumping in a gym? The answer is quite obvious: when jumping on the sand, your feet sink into the ground so there's less of a reaction pushing back on your feet, reducing how high you can elevate. In the gym, the floor does sink in a bit when you push off, but the floorboards spring back to their original position, pushing you off the ground for a nice jump. But sand doesn't have this springlike property; for the most part, it just gives way to the downward force you apply with your feet.
Understanding why it's more difficult to jump in the sand allows us to make some educated changes to our technique that may give us better results (i.e., higher elevation).
Take a little hop into a flat-footed position before jumping. The landing from the hop will compact the sand beneath your feet, giving you a stable platform from which to jump. The compacted sand will also increase the sand's reaction force to your push off, and will act a little more like the gym's surface (not a lot, but every bit helps). Landing flat-footed (as opposed to the front parts of your feet) increases the surface area in contact between your feet and the sand, minimizing how far you'll sink into the sand.
Get your back and arms into it. Bend at the waist a little, and swing your arms back during the loading phase of the jump. Building up this potential energy is a recommended technique when jumping on any surface, but it's especially important when you can't just rely on getting good push off the ground. Swinging your arms upward during the jump not only helps elevate you off the ground, it also gets your arms into position for a block or spike.
Jump upward, not outward. Your body can only produce so much force to propel itself; so if you use some of that force to jump forward, not as much of the force will be used to elevate yourself and you won't be able to reach as high a point during the jump. Again, this is true regardless of what surface you're playing on; but on the sand, where the ability to jump high is really valued, it's that much more important to get as much as you can out of each attempt.
While there's no guarantee you'll be able to elevate as high as the professional beach volleyball players, employing some of these techniques may help you get a little more out of your time on the beach. If you're interested in using video to calculate how high you can jump in the sand, please read our recent posting on that topic: http://videosportsanalysis.blogspot.com/2009/06/measuring-your-vertical-leap-using.html
Below is a highlight video from a beach volleyball tournament in southern California. It's not an ideal video clip, in that the camera doesn't seem to be mounted on tripod, but you can clearly view the concepts described above. Enjoy!
Before Kobe Bryant or Dwight Howard was considered for a contract in the NBA, they likely had to undergo a series of physical tests and exercises. In fact, most if not all professional and college sports programs require prospective players to complete these "combines", so that they can have a quantifiable way to compare the athletes. Some of the commonly used tests include the 40 yard dash, bench press, and vertical leap. For players in the NBA, the vertical leap test is the most crucial.
The vertical leap test demonstrates how high a player can jump and reach. Ideally, the test shows how high the athlete's center of mass (COM) moves. But since a person's COM is often difficult to determine, the test usually estimates the results by measuring the difference between how high a subject can reach from a standing position, and how high the subject can reach when they jump (either from a stationary or running start). One variation of this test is to simply see how high the athlete can jump and reach. While this latter method measures the maximum height the athlete can touch, it doesn't provide us with how high he/she actually jumped. In simple terms a player with an 9' reach, jumping 1' will reach 10'. A player with a 7' reach, jumping 3' will also reach 10', although it is obvious that the 7' player jumped higher. Simply measuring how high the subject can reach from a standing position before they jump, gives us the additional information needed to calculate how high the athlete jumped.
Professional and college organizations often conduct this test by having the athlete stand next to a tall pole that has little plastic flags extending from it, as shown below. The athlete then jumps and swipes the highest flags he can, and the result is recorded.
If you want to measure your own vertical leap but don't have access to one of these testing devices, you can simply film yourself jumping from a standing position. Besides the basic principles of video analysis (see http://videosportsanalysis.blogspot.com/2009/03/video-analysis-of-sports-101.html), there are two important concepts to keep in mind:
In your video clip, you must be able to see an object of known height. This object should also be in the same vertical plane the subject is jumping in. If you're jumping next to a wall, marking a known height on the wall should be good enough. The reason you need to have this information is so the analysis software can scale the distance measurement appropriately (this concept will be shown on the video below).
The video analysis software you're using must be able to calculate the distance between two points and be able to use the known height of the object to calibrate the measured distance accordingly; otherwise, the distance between the two points will simply be in units of pixels, which isn't very useful. We need to be able to convert the distance to something like inches or centimeters. If you're interested in finding out more about software packages that offer this type of feature, just let us know and we'll be happy to point you in the right direction.
Below we have a video clip of a subject performing the vertical leap test:
As you can see, we have one point identifying the highest point the subject reached while standing, and one point identifying the highest point the subject reached during the jump. As mentioned in the two concepts above, we have also shown the known height of another object (in this case, the distance from the ground to a point marked on the wall is 37"); and the software automatically uses this information to display the distance between the two points the subject reached in units of inches (23.7").
Compare this subject's results with the likes of NBA superstars Kobe Bryant (38") and Dwight Howard (40"), set to meet in the 2009 NBA Finals. Bryant has been vitually unguardable, draining shots while having defenders' hands in his face, and zipping around opponents with his lightning-quick first step. Howard is a physical force to be reckoned with; players move out of his way when he elevates, to avoid getting "posterized" when he throws down one of his thunderous dunks. It's amazing what these athletes are capable of; and using tests such as the vertical leap allows us to have a more complete understanding of how incredible they really are.
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