Biomechanics and the Olympics: Part III

 In my opinion, some of the best athletes in the world are gymnasts.  The combination of strength, power, flexibility, balance, and stamina are a rare combination.  All of the events are extremely difficult, but the one I find the most fascinating is the balance beam.  The balance beam has a width of 10 cm (3.9 inches).  There are many factors when it comes to maintaining balance, but two of the most critical are the base of support and the center of gravity.  The majority of the time during human locomotion, our base of support is our feet.  In the second picture below, the gymnast's base of support is her hands and chin.  We can change our base of support in order to be in a more stable position or a less stable position.  A wider base of support is better for stability and balance, but does not allow for a great deal of mobility (try walking with your feet spread far apart, you can't move very quickly, but you are less likely to fall over), while a narrower base of support is better for mobility but does place us in a less stable position.  The second factor is the center of gravity.  This is the balance point for the body, or the point where the weight of the body acts.  The center of gravity is slightly lower in females versus males in a standing position.  When we move, the location of the center of gravity will change.  In order to remain in a stable position, the line from the center of gravity (directed towards the ground) must remain within the base of support.  Consider what happens when you are standing in an upright position and start to lean forward.  As you lean forward, your center of gravity moves forward.  If you lean forward far enough, your center of gravity will move outside of your base of support, and if you don't take a step forward to change your base of support, you will fall.  Now, consider how a gymnast moves when she is performing a routine on the balance beam.  The shape of the balance beam automatically reduces the size of the base of support, making it difficult not to fall.  Many people, including myself, would have difficulty just walking across the beam.  When you factor in all the different moves, jumps, and landings the gymnasts have during their routine, which constantly changes the location of their center of gravity, it is truly remarkable what they are able to do on the balance beam.  Many of the gymnasts use their hands as their base of support during the routine, which increases the difficulty.