Physical fitness is considered as a key component for optimal performance in most sports. The aim of this study was to investigate neuromuscular and functional adaptations to two different training methods. For this purpose, 14 male volunteers were divided randomly into two groups. Group A (PLYOMETRIC) trained with PLYOMETRIC training and group B (combined) trained with traditional resistance training combined with PLYOMETRIC training 3 days per week for 8 weeks. To evaluate muscle neural activity, before and after training programs, surface EMG was performed on vastus lateralis muscle. Also, to determine muscle strength and power, agility and speed of movement, 1RM, Bosco, Sargent jump, Hexagonal Obstacle and 35 m dash tests were used, respectively. Paired t-test and independent t-test were used to identify any significant differences (p£0.05). Results showed that SEMG increased in both groups (PLYOMETRIC group 30.27%, p£0.11; combined group 43.78%, p£0.05). In Bosco, Sargent jump, Hexagonal Obstacle and 35 m dash tests, PLYOMETRIC group had better results than combined group but in 1RM test combined group had better results than PLYOMETRIC group. It can be concluded that possibly, for short-term periods (8 weeks), PLYOMETRIC training alone would be more effective than combined training (resistance and PLYOMETRIC) in targeted exercise performance.

The purpose of this study was the comparison of neural and performance adaptations to PLYOMETRIC training versus combined training.22 available young soccer players (age 14.28±0.82 years, weight 41.18±7.5 kg, height 154.5±9.36, body fat 7.43±2.68%) were randomly assigned to PLYOMETRIC group (PLYOMETRIC and soccer skills training, PL) (n=8), combined group (combined PLYOMETRIC and sprint and soccer skills training, COM) (n=7) and control (soccer skills training) group (n=7) that performed 6 weeks of training (16 seasons). To assess neural adaptations surface EMG was done on vastuslateralis and vastusmedialis muscles in the static mode, pre and post training program. Hoffmann reflex was also evaluated in soleus muscle at rest. At baseline and after training, performances of players were assessed with the tests: 5-meter sprint, 10-meter sprint, 20-meter sprint, agility test, counter movement jump [CMJ], and Bosco (5 seconds). Paired test and one- way ANOVA was used to identify any significant differences and P≤.05 was accepted. Both PLYOMETRIC and combined groups were associated with significant decreases in 5-meter sprint (-5.97, -3.87%), 10-meter sprint (-4.05, -2.33%), 20-meter sprint (-2.64, -1.64%), agility (-8.99, -7.5%) and significant increases in jump height for CMJ (12.95, 7.3%) and Bosco (14.08, 13.44%). Control group showed only a significant decrease in agility (- 4.72%). PL and COM groups showed significant increase in SEMG of vastuslateralis and medialis muscles (36.54, 15.06%), respectively. In three groups H-reflex did not show significant variation. However, magnitude of changes in PL and COM groups was not significant (P≥0.05). Therefore, according to these results it seems that effects of PLYOMETRIC and sprint training is similar and PL and COM training induced similar performance adaptations, which have possibly a neural origin and may be attributable to increased motor unit recruitment and/or faster firing rates, but motor reflex does not seem to play any role in these adaptations.

Electromechanical delay (EMD) refers to the time elapsed from the onset of electrical muscle activation to the onset of force production, which reflects the electrochemical process and the mechanical process (1, 2). In the isometric contraction study, the biceps brachii of the up-per limbs (3) and the quadriceps femoris of the lower limbs (4) are mainly used as the patch site for electromyography (EMG), and efforts to indirectly examine the muscular elasticity components via the EMG and the manifested strength are made. . . .

The purpose of this study is a comparison among th effect of three models of PLYOMETRIC training (depth jump) on electromyograph indexes (Amplitude and frequancy) of Rectus femoris and Vastus medialis muscles in 16-18 year old athletes. In this study, 45 students from physical education and sport sciences high school were selected randomly and divide into 3 groups of 15 after perfroming the ability tests for participating in depth jump training. All 3 groups participated in 16 sessions depth jump training, it should be noted that the method of depth jump training was different for each group.The subjects of group A exercised bouncing Depth Jumps (BDJ) or (DJ- H/T), group B did counter movement jumps (CMJ) or (DJ-H) and as for-groupC the same exercises of group B were performed wearing weight jackets (CMWJ) or (DJ-W/H). The height of the box and vertical jump were equal for all groups (40& 70 CM .An EMG was used for measuring the electromyography indexes. This mesurements were done in three phase before training, in the middle of training ( after the 8th session) and after training. The results of the variance phase showed that regarding the aimed variables only the changed in group A that were related to the electromyography indexes were significant from a statistical point of view and there was no significant difference seen in this. index between the other groups during the above mentioned phase analysis test (ANOVA) in comparison with the average of electromyography indexes ( amplitude and frequancy of the muscles in this study) in the 3 study

Purpose: This study was accomplished to investigate the electromyographic activity of 3 PLYOMETRIC exercises (tuck jump and single leg hop in sagittal and frontal planes) to find out the appropriate procedures for strengthening biceps femoris and gluteus medius muscles.Methods: The kind of study is applied and data were collected from the supervised exercises of 15 male athletes without injury of lower extremity from Tehran University, which participated voluntarily in this research. It was assumed that subjects expend the extreme potential during their activities. Statistical analysis was made using repeated measures ANOVA to investigate the muscle activity in feed forward and feedback phases of landing with SPSS 20.Results: Significant differences (P£0.05) were found between treatments in relation to feed forward and feedback phases of muscles activities. Single leg hop in sagittal and frontal planes showed the highest activity of biceps femoris and gluteus medius in feed forward phase, respectively. Nevertheless, tuck jump demonstrated the lowest activity of these muscles in both phases.Conclusion: According to the results, single leg hop in sagittal and frontal planes could be the most appropriate exercises for improving strength and neuromuscular system of gluteus medius and biceps femoris. We should take special attention to these 2 PLYOMETRIC exercises in exercise programs. However, tuck jump in comparison with 2 other exercises show less effectiveness.