Why is it that some athletes are so much better than others at stopping the soccer ball before it hits the net, hitting a baseball traveling at high speeds or backhanding a tennis ball they can’t see? Why is it that one individual is far more impaired by darkness when walking or running or biking at night? How is it that some carpenters go a lifetime without ever hitting their hand with the hammer, yet others do it two, three or even four times a year? In fact, occasional reports of a carpenter cutting off a finger with his/her own skill saw are not uncommon! How can two elderly people of relatively the same age or upbringing have tremendous variance in their ability to navigate across slick sidewalks, steps and floors, one having fallen on multiple occasions and the other free from such trauma?
The answer to these questions, to say the least, is very complex. The ability to determine exactly where to place your hand or foot in space to meet an incoming object, locate the ground or perceive the exact location of an extremity relative to a hammer or saw requires contribution from many special sense organs of the body. Some are extroceptive (receiving information from outside the body), and others are proprioceptive (receiving information from within the body). An athlete’s performance is often heavily reliant upon a synchronous effort from all relevant sensory organs.
To better understand how we can improve performance in our clients and athletes, we must know which extroceptors and proprioceptors factor into the training equation. We must also determine which methods to use in order to enhance their contribution to improved performance.
Part 1 of this article series will cover extroceptors and Part 2 will cover proprioceptors.
The eyes are the chief extroceptive organs. Your eyes function with two main systems for movement control:
- The focal system, specialized for object identification. It is mainly concerned with objects in the central field of vision and serves to answer the question, "What is it?" For example, the focal system is used in a football game to determine if the person running at you is an opponent or a teammate, a decision critical to organizing your response! Focal vision is significantly influenced by illumination. Considering the above example, if you are playing football at night and the lighting is poor, you may end up tackling your teammate.
- The ambient system, specialized for movement control involves the entire visual field, central and peripheral. The ambient system functions to detect motion and position of elements in the environment and provides information about your own movements in relation to them. Thus, the ambient system provides answers to the questions, "Where is it?" and "Where am I relative to it?"
- Optical flow is the term given to describe the light reflections passing through the eye from your environment. Optical flow provides numerous kinds of information about an individual’s movement in that environment, such as the following:
- Stability and balance
- Velocity of movement through the environment
- Direction of movement relative to objects in the environment
- Movement of environmental objects relative to the performer
- Time before contact between the performer and an object
Using the example given to describe "focal vision" above, ambient vision and optical flow will help you determine not only how fast the person is coming at you and from what angle but will tell you who the person is.
When working with a client, if there is a chronic tendency toward forward head carriage (see Figure 1), there may be problems with their focal vision. Poor eyesight can be a cause of forward head posture. I have had many orthopedic clients who responded poorly to a postural correction program due to near sightedness. In such cases, all attempts to correct posture through stretching, exercise and even instruction have limited results because the client subconsciously adopts a forward head carriage to bring the eyes into focal distance. When your client is repeatedly exposed to such postural programming, you will have a hard time reprogramming them through exercise.
|A - normal head and neck alignment
||B - forward head posture
In some cases, the motor commands associated with a given task (motor engram) will override those associated with focal problems. A quick way to determine the focal influence on your client’s training posture is simply to ask him to close his eyes while performing an exercise. For example, when performing a triceps press down, if your client’s posture improves when he closes his eyes, chances are he needs to see an ophthalmologist. If his posture becomes worse with his eyes closed, it is likely he has been using visual input to compensate for an orthopedic malalignment.
Ambient vision can be enhanced by practice. For example, try holding your head and eyes still with a forward gaze and reach your arm out so that you are looking at the tip of your index finger. Now, without letting your eyes follow your finger, begin taking your finger laterally as you horizontally abduct your arm, paying close attention to how far back you can still see your finger. The same exercise can be performed by moving the finger or a visual target in any direction. Although this may not actually improve your peripheral vision, it will enhance your awareness of movement in the peripheral field.
The Ear (Audition)
The auditory portion of your ear consists of the outer auricle and the tympanic membrane (ear drum), which serves as the barrier between your outer and middle ear. The ear detects extroceptive sound that is often useful to function and performance.
Examples of how sound can be used to enhance performance are:
- Taking note of exactly how you moved your body when you heard the sound of the ball on the bat during a home run hit or the sound of the golf ball on the clubhead when hitting an exceptionally good drive.
- The sound of your feet as you approach the high jump bar can be used to indicate optimal or suboptimal rhythm and timing.
- The sound, or lack of sound, when a diver enters the water are indicators of performance.
- The sound of a boxer’s punch landing on the heavy bag tells the boxer and coach about his speed, power, joint alignment and delivery angle, as well as fatigue level. When using the speed bag, information regarding timing, location of impact, as well as amplitude and velocity of impact can be noted. Many of the same sounds assist the boxer in the ring as well.
- When a client is performing the lunge, squat or step up exercise, a sharp ear will often hear the grating sound of the patella tracking laterally on the femur. Frequently, by activating the hip abductor muscles through the application of a belt around the thighs during the squat or modifying the length of the step and/or the position of the foot, optimal tracking can be restored and the retropatellar grating noise reduced or eliminated.
The skin is loaded with receptors. In fact, your skin has approximately 640,000 sensory receptors that are connected to the spinal cord by over half a million nerve fibers; tactile points vary from seven to 135 per square centimeter of skin. The skin receptors provide very useful and important information about movement and performance to the brain. Here are a few examples:
- The vibration, or lack of vibration, when hitting a ball with a bat of golf club provides an indication about performance that can be calculated in absence of other extroceptors once a sensory engram has been developed over time from practice.
- When lying on an object such as a Swiss ball, the skin will inform you as to slippage of the ball and even about slippage on the floor, often felt as a low frequency vibration.
- When swimming, the skin will tell you about the temperature as well as the direction and velocity of flow, which is particularly important in an ocean swim or when surfing.
When practicing outside sports such as volleyball or baseball on a windy day, experiment with exposing as much of your upper body as possible. This will allow you to begin programming your brain with information regarding wind and ball flight characteristics. Although you can often feel the wind on your face, the more skin you have, the more information you have and the better your ability to make decisions regarding how to change ball flight or adjust for it.
It is not uncommon for a swimmer to shave his entire body and even scrub the palms of his hands with sandpaper to improve sensitivity. His freshly sensitized hands provide elevated tactile sense, which enhances his ability to find still water for optimal stroke performance. Freshly shaved skin enhances his awareness of drag, allowing him to manipulate body position for optimal hydrodynamics.
- Chek, P. Scientific Back Training
- Juhan, D. Job’s Body, Station Hill Press, 1987
- Schmidt, R. Motor Learning and Performance