چکیده (انگلیسی):

The purpose of the present study was to investigate the effects of eccentric training using a multi-joint dynamometer, on the electromyographic activity of rectus femoris, biceps femoris and medial gastrocnemius during counter movement jumps, drop jumps as well as during maximal eccentric actions. Sixteen amateur soccer players was divided into equal sized groups, the control group who participated in their regular training and the training group who performed 16 sessions (in 8 weeks) of eccentric exercise using a multi joint isokinetic dynamometer. The performance of counter movement and drop jumps were evaluated on a force plate. Additionally, maximal isometric, concentric and eccentric force were assessed on the isokinetic dynamometer. After the eccentric training, the electromyographic activity during the concentric phase of counter movement jumps was found to be increased in rectus femoris (p<0.05) and reduced in biceps femoris (p<0.05). During drop jumps, electromyographic activity of the experimental group found to be increased in the pre-activation phase of gastrocnemius (p<0.05). Additionally, during the takeoff phase of the drop jumps smaller angles for hip and ankle joints were observed (p<0.05). Finally, the electromyographic activity during eccentric strength evaluation were found to be elevated in rectus femoris (p<0.05) and decreased in gastrocnemius (p<0.05). The eccentric training which can cause neural adaptations, faster recruitment of motor units as well as changes in the architecture in muscle tendon system may also cause the alterations in electromyographic activity of leg muscles as observed in the present investigation.