This study aimed at identifying the effect of developing the muscular balance of the arms' muscles on some of the mechanical basics and the digital level of hammer throw contestants. The researcher used the experimental method on the sample of 16 students from the Faculty of Physical Education for Boys – Alexandria University who have previously learned the hammer throw competition and have the best records. The post-measurements were conducted on them and they were divided into two equal groups, of which the first is the control group and the other is the experimental group, each one of them consisted of 8 students and had the same training program applied on them with the same size and intensity with the varied size of training given to the weak muscles, according to the strength of the anterior and posterior muscles, which was approximately 2:3, so the weak muscles were given a training size of 3:2 to the posterior muscles in the experimental group, in order to develop the muscular balance of the arms' muscles. The study was applied for 8 weeks with 4 times per-week (2, technical), (2, weights), finally the post-measurements were conducted on both groups and statistically treated.
Conclusions: Developing the muscular balance affected positively the improvement of mechanical basics and the digital level in hammer throw. The muscular balance of the experimental group was better than that of the control group, as the difference between the balance of the right arm was 20.2% and that of the left arm was 25.2%, while the balance of both arms together was 14%. The difference between the percentages of the mechanical improvement of the speed of release was 8.71%, the increase of release height was 2.50%, the release angle was 9.07%, and the difference between the improvements of the hammer throw distance was 5.54%, in favor to the experimental group.
Recommendations: Muscular balance should be developed in all parts of the body in all of the track and field events.