Wednesday, August 12, 2009

Video Analysis of the Back Flip

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:
  1. 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.
  2. 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.
  3. 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.
  4. 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:
  1. 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.
  2. 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.
  3. 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.

If you are a gymnastics fan, look out for video from the 2009 US Gymnastics Championships starting today in Dallas, Texas. You can watch a live webcast at .

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