The aim of this study was to find out how changes in object size and weight alter during the process of learning to throw, and also how do these factors affect throwing once the skill has been aquired.
This was done by testing 18 female students, who were capable, but had little previous experience of overarm throwing. They were split into 3 groups, each having a different set of objects to throw, one group had objects of constant density, one group objects of constant size, and the other threw objects of constant weight. The study involved a pre-test, training period, and post-test throwing trials. Three criteria were measured; Throwing distance, angle of release and speed of release.
The results of this study state that overall, in all 3 categories, throwing distance improved, although the way in which they improved was varied. Throughout practice, the increasing distances being thrown were affected by the objects in the practice set. This suggests that the physical properties of the objects did play a part in the outcome of the distances thrown.
The angle of release results did not show significant mean changes in angle of release. The average angles of release remained close to 33 degrees in all categories, through all training and testing, which is in turn close to the optimal angle of 36 degrees as found in previous studies.
However, upon examining the variability of the angle of release showed that angle of release did become more consistent throughout practice. This was calculated by the standard deviations from the first and last weeks of practice, and a 3 - way mixed design ANOVA conducted on them.
In constant the density and constant weight categories, the smaller the object showed a greater variability in release angle. The constant size group showed only variations in object weight and showed no object effect, showing that the size of the object played little part in angle of release.
Finally, speed of release increased up to 50% throughout practice but each category displayed a different pattern. Separate ANOVAs were performed in order to determine the effect of objects on release speed in each category and practice week. With practice, release speeds were increasingly affected by objects for all groups. Tukey HSD post-hoc analyses showed that consistently greater release speeds came from the lighter objects in the constant density and size categories. The lightest object was thrown with the highest speed. In the constant weight group however, release speed increased consistently regardless of the size of the object. This suggests that release speed varied with object weight but not object size.
It was found that improvements in throwing performance were mainly due to an increase of release speeds. Analysis found that release speeds varied with object weight but not size.