Improving your Basketball Free Throw with Video

The NBA playoffs are now in full swing. King Lebron James is showing us all why he deserves the MVP and why the Cleveland Cavaliers must be considered the favorites for the title. Free throw shooting in the playoffs is even more critical than during the regular season and therefore we bring you a second installment of our video analysis of the basketball free throw.

In March we introduced the Video Analysis of the Basketball Freethrow and compared two different subjects and their respective shooting techniques. We focused on the angle of release in particular. This week, we captured video of our Subject 1 from March, to see if he was able to use the video analysis to make improvements. Once again we will use video analysis software to determine and quantify whether any significant improvements have been made with his technique.

As you may recall from our first analysis, it was noted that this subject could improve his chances of making a successful free throw by increasing the angle of release of the ball, so it falls on more of a downward arc as it gets closer to the hoop. Let's take a look at some stillshots that were created with some analysis software.





This week we filmed our video at a different court and set up our camera on the right side of the subject so we could see his right arm more clearly. Unfortunately in the earlier video (top photo), we needed to set up on the left side of the subject for lighting reasons. In order to compare the subjects free throw technique, we used our analysis software to create a mirror image of the subject from the March video (top photo). This allows us to watch the video and study the still shots with more clarity. When we mirror the image, it looks as if the subject in the mirror image is left handed, but of course this is not the case. The mirror image function of video analysis software is very useful for comparing left and right handed players or comparing video of movement in different directions, as we do here.

Ok, let's get onto the analysis. For the "before" shot (subject with blue shirt, top photo), we see the angle of release is 48 degrees from horizontal. For the "after" shot (subject with red shirt, bottom photo), the angle of release is 61 degrees from horizontal. This is approximately a 27% increase in the angle of release from the first to second shot. As we mentioned in the March post the higher the angle the higher the arc of the free throw. Therefore, we can safely say the ball will be coming down in more of a downward arc as it approaches the rim. If the subject continues to shoot with the technique seen in the more recent shot; this will likely result in more free throws made.

The video below shows a side by side view of the subject's free throw attempts in full motion.




Besides the improvement in release angle we can also note how the subject follows through on each shot. Although it would be easier to see from a behind or front-on view, we can still see that the "before" subject follows through across his body, whereas the "after" subject follows through more towards the hoop. Following through towards the hoop is going to help the subject's chances of shooting the ball towards the middle of the hoop, rather than to one side or another. For obvious reasons a ball moving straight toward the hoop is more likely to go in to the basket.

Following through towards the hoop on a free throw (or jump shot) helps ensure the player moves the ball towards the target throughout the shot, rather than having to rely on perfect timing to get the ball going towards the hoop. Minimizing this error of the shot going left or right makes it easier for the subject to now focus most of his attention on the angle of release relative to horizontal.

Remember to use your video camera, so that you can see and analyze your own free throws. Once you see your shot you will have a better understanding of how to improve it. We hope this posting helps you get the most out of your free throw practice sessions. Whether you need to make free throws to get into a pickup game at a park, or your team's relying on you to hit the game winning foul shot, the ability to make free throws consistently is an important skill for every basketball player to have.

Cricket Bowling: Video Analysis of a Throwing Action

On the Video Analysis of Sports we are excited to show how video can be used to improve your performance in almost any sport. We are also interested when video or motion capture is used to study the intricacies of laws in sports.

This week Dudley came across an article about the use of a motion capture system to study the bowling action of a cricketer, http://www.gulfnews.com/sport/Cricket/10308342.html . For many years there has been controversy over legal bowling actions and numerous players have been called for suspect bowling. In fact the leading wicket taker in world cricket, Muttiah Muralitharan, was regularly called for a suspect action, early in his career. With the performance of 3D motion capture studies at the University of Western Australia, his action was finally ratified and was no longer called into question.

For those of you who know very little about cricket, here is a link with a brief explanation http://uk.cricinfo.com/link_to_database/ABOUT_CRICKET/EXPLANATION/ .
Bowling is the action of pitching the ball at the wicket (see link above) in an attempt to beat the batter.

There is a law in international cricket that the angle of the bowling arm (arm with the ball) cannot straighten more than 15 degrees during the final part of the bowling motion before releasing the ball. If it does then this motion can be considered illegal and in the end can result in a player being suspended from International cricket until he corrects his action.

It therefore makes perfect sense that video analysis is used to evaluate a cricket bowler's action before they are suspended. In fact the maximum change in angle was increased to 15 degrees based on a study using 3D motion capture analysis. Motion capture and biomechanical tests proved that it is almost impossible to bowl the ball without some flex or bending at the elbow and in 2004, it was discovered that many bowlers in International cricket flex their elbow more than the previously set limit during their bowling motion.

With video analysis we can:

1. Capture the motion with high speed cameras, so we can assess the motion frame-by-frame and concentrate on the part of the bowling action that is relevant.
2. Set up our cameras appropriately so we get a good view of the arm and how and where it bends.
3. Measure the change in angle of the arm using mathematical concepts rather than "eyeballing" it.
4. Capture the bowling action using multiple cameras to obtain a 3D view of the action and find the physical change in elbow angle rather than a 2D simple angle assessment.
   

The International Cricket Council (ICC) actually appoints a panel of human movement specialists to assess any possibly illegal bowling actions. This panel is instructed to use video and motion capture to analyze a suspect player's bowling and present their findings to a review board.

Here is a video of Muttiah Muralitharan bowling and taking the last few wickets on his way to the world record. His once suspect bowling delivery called the "doosra" is the first delivery you will see. In full speed and with the naked eye, it certainly looks like he is throwing the ball (straightening his arm by more than 10 degrees), but further investigation using 3D motion capture proved that this was not the case.

It is commendable that the ICC uses motion capture and technology to evaluate a rule that could cost a player his career. There are not many sports in which the player's action can be called into question; but all sports can benefit from some form of video analysis to improve players' performances.

If you have some sports video or are interested in analysis of a particular sport, let us know with a comment or send us an email.

Video Analysis of Sports 101

Welcome to the Video Analysis of Sports blog. As this is our first article, we will take this opportunity to introduce ourselves.

We (Dennis and Dudley) have a combined 20 years experience in motion capture and biomechanics with a special interest in sports performance and injury prevention. Through our consulting company Sadaka, LLC http://www.sadakallc.com ,we offer services to sports professionals, sports equipment manufacturers, hospitals and motion analysis software and hardware companies. Some of our past clients include Titleist, FootJoy, Warrior Hockey, National Pitching Association, NASA, Shriners Childrens Hospital and Vicon Motion Systems.

Video analysis of sports performance is often the domain of professional athletes and large companies or research institutions. This analysis is done with expensive 3D video camera equipment and complicated software to ensure high speeds and accuracy. However there are some basic techniques that can be used by any individual to evaluate their own performance and get great results using a simple digital video camera and a little understanding of biomechanics. The video camera will require a small cost (we will discuss what makes a good camera in a future posting), but we will supply you with much of the biomechanics understanding for free on this blog.

Reviewing video clips can be a great way to provide coaching feedback to players, as well as a means to emulate one's favorite athletes. Whether you're a professional all-star, high school athlete, or weekend warrior, seeing yourself from a different perspective can help improve your performance and/or minimize your chances of injury.

So in this first posting, we'll start right at the beginning and describe what features make a sports clip suitable for video analysis of an individual, and what you can do to ensure the clips you film will meet those requirements. Future postings will demonstrate the various levels of analysis that can be performed on suitable videos, using a range of available software, from basic free software to detailed 3D analysis.

What makes a good sports clip?
A good sports clip of an individual shows the athlete's full range of motion (ROM) during an action, with the camera positioned such that angles can be accurately calculated (this will be discussed in more detail later). Filming the athlete's ROM can be accomplished by simply zooming out or moving the camera backwards until all the desired features are in the viewer. In general, it's recommended to have the camera as close to the athlete as possible and still capture the entire ROM, as this will make the most use of the camera sensor's resolution. For example, if we were to capture a basketball player dunking the ball we would want to ensure that our camera can see the complete action from take off until the player puts the ball in the net. Our camera would therefore need to see the ground at the take off point as well as some space above the rim of the the net.

Another important factor in obtaining a great sports clip is to make sure that your camera is stationary. There are some motion capture software available that can handle a moving camera, but for now we suggest that the camera is mounted on a tripod and is not moved while the video clip is being filmed. This means that you should ensure the full ROM (described above) can be captured in this one shot.

How you can film useful footage:
Camera placement
In general, most sports clips we watch on tv are best suited for analyzing strategy and teamwork because they provide an overall picture of many or all of the competitors and the playing field. However, when it comes to analyzing an individual's performance or technique, it's not only important to focus the camera on the single athlete, but the angle we film from must also be taken into account. It's best to use "orthogonal angles", meaning the camera is directly in front of, behind, or to the side of the athlete. Golf coverage usually does a nice job of this, providing shots of the golfer either "face-on" or "down-the-line". Here's a great face-on view of Tiger Woods' swing:



And here is a down-the-line shot of his swing:



Notice these cameras are level with the golfer; they're not filmed at an upward or downward angle, meaning it's possible to accurately calculate some angles, if that's what is desired from the analysis.

Background/contrast
Although the above clip is a beautiful view of Tiger's swing, the footage could have been improved by having him wear clothes that were a different color from the background. Black clothing with a black background can make it difficult to accurately evaluate the amount of hip and shoulder rotation - two commonly analyzed characteristics of a golf swing. Not that having a solid black background is a bad thing though; on the contrary, if you can manage to film your athlete with a solid-colored background, you are well on your way to filming some nice footage for analysis.

Lighting
As is true with taking most photos, it's ideal to position the camera and athlete such that the light source (e.g., the sun) is behind the camera and illuminates the athlete. This will provide a crisp view of the athlete, and will allow you to use a more open setting on the camera's aperture.

Now that you're up to speed on the basics of filming great video for analysis, grab your video camera and start practicing! Follow our regular blog postings, and see how you can create your own analyses of your videos, using a variety of software packages.

-Dennis Ho