La vision and ball sports such as tennis, squash, baseball or cricket, are the sports where the visu-motor system is put to the most radical test. The speed of the ball is a challenge for vision. In most cases, the ball reaches us in a maximum of 500 msec and we must detect it, see the movement that follows and move, adjusting our movement, to respond with a precise hit.
Other sports, such as soccer or rugby, have to intercept a ball, which implies being in the right place in the right way, that is, running to where we think the ball will go and arriving with the arm in the correct position to catch it. without falling or with the leg to cut off an opponent's pass.
Look good for ball sports
The first point to take into account is the fact that in all sports, as in this case, ball sports, where it is necessary to “identify” a mobile object, it will be essential that the athlete's vision is the best possible.
This seems obvious, it turns out that in practice it is not so. It is necessary to start from the basis that an athlete must check his vision and that in case of alterations in refraction, the possible ametropia is corrected, neutralized, in addition to recommending the type of glasses (materials and types of frames), contact lenses or even assess the refractive surgery.
Key factors in vision and ball sports
In a throw as in rugby, the ball follows a parabola in which its acceleration and the path it describes must be calculated. Chapman in 1968, proposed that to arrive at the right point at the right time, the angle of elevation of the ball during flight "α", with respect to the player running after it, must be that in which the acceleration of the tangent of “α”, must be equal to zero (see figure).
We make this adjustment with the stimuli sent by the head when lifting it and turning it to look for the ball, together with the follow-up with the gaze of the curve that the ball describes in the parabola of flight, the speed with which it approaches us (tangent of α ). To this we must add the fact that the ball does not usually fly vertically with respect to the one that runs, that is, the parabola must be adjusted to a lateral displacement, independent and obviously related adjustment mechanisms (McLeod 2006).
The key point in receiving the ball is the precise adjustment of the contact, the basis for being able to catch it correctly and not escape.
For this fine adjustment, the visual system uses two mechanisms: the radial expansion of the ball in the retina (collision time) and the disparity of the ball in the binocular vision, In the stereopsis, during the approach in the last 20 m.
The two mechanisms offer us information for the fine adjustment of the time and point of arrival of the ball (Regan and Gray, 2000).
Retinal expansion and binocular disparity
Studies carried out with different sports show that retinal expansion is more useful in those sports that use large balls, such as soccer, while if the ball is small, such as in ping-pong, binocular disparity will be more useful.
Vision in sports with small balls
At tennis or Baseball, Savelsbergh and Whiting (1996), showed that after the signals that we can obtain from the player who serves or throws the ball, the next step to catch it or answer with a racket or bat, is the visual information that we have in the 450 msec prior to the ball. contact, from this time the precision of the response will be reduced, with a time limit of 125 msec, after which we can no longer vary the response that we had planned, we can no longer rectify the programmed movement.
Let us remember that in a tennis serve or a baseball pitch, even in cricket, the ball takes a maximum of 500 msec to arrive, and at the speed it travels we can only make a maximum of two saccadic eye movements and, much less movements. fine tracking. That is why it is important to intuit the type of serve that he will make and predict where the ball will be so that, in one or two serves, he directs his gaze to that point close to us, where we have already moved to answer. We only have time to adjust the capture movement where we think the ball will go (see figure), that's why training in these sports should be aimed at studying the opponent's movements to intuit the type of serve, the visu-motricity to go for the ball and visual fine-tuning: collision time and binocular disparity, to confirm the arrival of the ball at that point and place the hand or racket accurately (Lopez Miller, 2007).
vision and attention
Anticipation is basic and we see it with special intensity in the squash, where the ball, in addition to going very fast, bounces off several walls.
The player must carry out a very sophisticated response strategy. In studies carried out with an eye-tracker system, we see how after the serve, when the ball bounces off the wall and goes to the second wall (see figure), the player who answers goes from fixing the ball on the first wall to locate it in the middle of the route to the second wall, by means of a saccade and from here, with a new saccade, it looks for the ball in what will be half the distance from the second wall to the racket, point in which a finer tracking, based on retinal ball expansion and binocular disparity. It can be seen how in most of the movement of the ball, we do not see it, we only try to locate it at points where we assume it should be (Mckinney, 2008).
During the taken ones we do not see, that is why we must take advantage of the sack during the trajectory of the ball in the phase that "nothing happens".
In most ball sports, there is a limited repertoire of throws, with defined and predictable trajectories, for this reason it is important to guess what type of throw they will make, so once the ball comes out, we disregard the route in the intermediate phase, since only we can make a saccade in which we invest 140 – 200 msec, that is, we can only go to look for the ball at a point close to us, where we can only confirm its direction and adjust the fine visual-motor control to impact it.
The physiology of visual perception determines that we stop seeing the ball during most of its trajectory, although this does not imply the impossibility of being able to answer a serve or hit correctly. It is necessary to use other mechanisms, such as the intuition of the trajectory.
Visual tracking of the ball
It is not recommended to try to visually track the ball throughout its trajectory as fine tracking takes too long, 100 msec to start up and has a limit on the speed of the moving object, not beyond 40 km /h. When the tennis ball travels at more than 200 km/h, which means losing it completely, without time to establish an effective search saccade that locates the ball again.
That is why the recommendation of many coaches to insist on "looking closely at the ball" is not effective, it is simply impossible, we have to guess where it will be when it arrives and go look for it, it is what is called "playing in the area".
You have to train the types of shots and the quick take-off to search for the ball at a close point to, then, yes, follow it more precisely in the final phase prior to contact.
vision and tennis
In tennis we also have the bounce of the ball. The player who responds establishes the direction and time of arrival of the ball according to visual information in the shot made by the opponent, foresees where the ball will bounce and makes a serve to go look for the bounce point and then follow the ball with a movement fine-tuning, based on information from retinal expansion y binocular disparity.
The studies carried out show that "knowing how to read" the type of pitch is the key to a good response (Muller and Abernethy, 2006).
Vision in throwing sports
In other sports where the throwing of a ball must be very precise, such as golf, basketball, darts, etc., the visu-motor process is different. In the first phase it is basic to calculate the direction and distance. It takes a few seconds for the player to process this information, with the 350msec prior to launch being crucial (Vickers, 2002).
The adjustment of the shot must be combined with the vision of the ball. In golf we must combine the information of the distance to the hole with the precision of the shot, we must see the ball and the hole, which implies one more point of difficulty for the effectiveness of the shot.
vision and cricket
In England, where cricket is one of the most popular sports, vision researchers, and surely cricket fans, saw that there are twelve types of ball releases and the batsman has 100 msec to start the ball preparation movement, based on the visual analysis of the movements executed by the thrower.
The ball arrives in 500 msec and it is not enough to finely track it and adjust the motor system to make the correct hit. Before the ball is thrown, we already have to infer the type of throw it will make and adjust our movements based on the path we think the ball will follow.
We know that with this system of deciphering the type of throw, we can predict the trajectory of the ball and we can infer where it will be a few milliseconds before it arrives, so we can look directly at that point, neglecting the previous path, go find the location of the ball at that point, to confirm the trajectory that we have predicted and validate the adjustment of the previous movements for the correct hitting.
vision in ball sports
As we can see, in sports where you have to control a moving ball, it is essential to understand that we cannot "follow" the entire trajectory of the ball, therefore it is necessary to carry out training that allows us to intuit the type of launch or trajectories that it will follow. the ball, rapid eye movements (saccades), punctual location of the ball, and rapid sensory-motor activation to move to the "zone" and adjust the catch or response movement with the racket, for example, in tennis.
A good visual training allows to greatly improve the efficiency in this type of sports.
