Reading the trajectory
A real skill
Trajectory reading is involved in all anticipation-coincidence tasks requiring to catch a moving object. Studies show that this type of skill is needed in many sports but also in every day life activities.
The mechanisms are many and involve at the same time a head movement, an eye movement, the cooperation of eyes, central or surround vision, the perception of the targeted object's dimensions.
We have demonstrated that experience is essential to make this calculation performing and predict with precision the exact place and moment when the ball will pass in the trajectory.
This means that the volume of practice and diversity of conditions participate in the elaboration of this perceptive skill.
A three dimensional problem
Trajectories can vary from right to left, from top to bottom and in length. The mechanisms at play are not the same and it is in fact quicker and easier to adapt to left / right variations than to variations in length.
Up / down variations are detected but the inexperienced player does not immediately relate to the fact that high = long and low = short, which is however right in most cases. As trajectory length appreciations are less accurate, he is often badly placed on trajectories that are shorter or longer than he anticipated. Refinement in the appreciation of the speed and the long / short variations rests on experience and practice.
Consequently, by favouring an intervention zone "in front of you" much more easily adjustable we facilitate the adaptation and success of the hit.
Trajectories close to the ground are more appreciated than those which fly high. However, volley-ball happens up there! This requires a reorganisation of the visual perception field.
The player placed "under the ball" finds himself under very particular conditions to appreciate the ball's speed and distance.
On a two hand hit he adapts thanks to a coincidence between the hands course and that of the ball (hands and ball converge on a same course with "timing" imprecision).
In the case of a spike the player is offset relative to the ball and the hand's trajectory has to cut the ball's trajectory at some point.
Construction of the "ball / hand meeting point " which is the pplayer's ow, hitting space requires a longer training. We notice hits "from fingertips" or "from the wrist" which are indicators of an earliness or delay in the hit.
If the spike player places himself under the ball to facilitate his access, he finds it impossible to hit effectively.
Developing visual information gathering strategies
In ball sports it appears that information gathering strategies are different between expert players and beginners.
To put it simply, experts are at the same time precise in their prediction of the landing point and of the instant of the ball's fall and are able to share their information by briefly detaching their eyes from the ball during the trajectory with quick glances. This way they can gather information on the changes in the context while ensuring interception of the ball.
We could say that, in volley-ball, we learn to use our eyes at the same time as we learn to use our hands.