Thursday, 17 November 2011

A COMPARISON BETWEEN NOVICES AND EXPERTS OF THE VELOCITY-ACCURACY TRADE-OFF IN OVERARM THROWING

A study was conducted to investigate the speed-accuracy trade off in expert and novice throwers, and the movement strategies used to execute the task of throwing. It was hypothesised that the experts would maintain high accuracy throughout the range of velocities, and that the novices would show a trade in accuracy and velocity. It was also hypothesised that a change in co-ordination strategy would be expected in the form of movement patterns leading to a throw between the different groups.

The experts, in this case were male team handball players from a Norwegian second division team, and the novices had never been involved in any organised sport that required any form of throwing activity.

The data was gathered using 3D cameras, with markers placed on the body at the shoulder, hip, elbow, wrist and the ball was also tracked. Linear velocities of these points were calculated, along with time of release and total movement time. Throwing accuracy was measured by a video camera, and a ‘hit’ was recorded when the centre of the ball hit the centre of the target, otherwise, a ‘miss’ was noted.

There were several conditions, the first was where the participants were asked to throw the ball as fast as they could, in order to record maximum velocities. The second condition was also a throw at maximum velocity, but with accuracy as an afterthought. The third condition was where velocity and accuracy were equally important. In the forth condition, accuracy was the main priority with velocity as a secondary priority, and in the final condiditon the only priority was to hit the target with velocity made irrelevant.

In summary, the throwing performance of the experts was better than that of the novices in every condition, as expected, both in terms of speed and accuracy. Also, in the experts, the velocities of most of the body segments were higher than that of the novices. However, no significant differences in absolute and intersegmental timing of the movements of the body segments was found between the two groups. Also, in terms of speed-accuracy trade off both groups performed similarly. This means that when accuracy was required, acceleration and velocities were decreased, although accuracy was not actually improved.

It was thought that the novices would show more of a speed-accuracy trade off as they were thought not to have the ability to throw the ball accurately at high speeds. Therefore, it is suggested that it is the features of the required task rather than the skill level of the subject that explains the lack of a speed-accuracy trade off in handball overarm throwing.

There were no differences in timing of body segment movements between the groups. This suggests that novices and experts may use the same general coordination pattern. The analysis suggests that in a ballistic, whole body movement the accuracy was not affected by a faster execution that was likely to have been induced by more muscle activity.

Overall, it was found that the only essential difference between novice and expert throwers was the use of a wind up or counter movement, which lead on to a stronger and shorter acceleration period. By accelerating and moving faster an expert will reach the end of motion earlier. It is not proved however, that experts use the same movement range as novices. Recent data on throwing with dominant and non-dominant arms suggest that athletes use a longer movement range with the dominant arm.

1 comment:

  1. Please add a reference to the paper, with a link to where it is online. Also tag the post with some useful labels.

    However, no significant differences in absolute and intersegmental timing of the movements of the body segments was found between the two groups.
    This is quite surprising; could you be more specific about what they tested?

    Therefore, it is suggested that it is the features of the required task rather than the skill level of the subject that explains the lack of a speed-accuracy trade off in handball overarm throwing.
    I don't understand what you're trying to say here.

    ReplyDelete