Numerous studies have shown that static stretching compromise a muscle’s ability to produce strength either isometric or isokinetic, and dynamic stretching, on the other hand, may improve muscle strength performance. When the studies were scrutinised, it is obvious that the strength measurements were performed only in the stretched muscles. It is known that during sport activities antagonist muscle co-contractions on the opposite direction are common to prevent overloading to a joint. At the same time, the net external force applied during a movement is proportional to the force produced by the antagonist muscles. Therefore, the aim of this study was to investigate if static and dynamic stretching exercises of the knee muscles (quadriceps and hamstring muscles) have any effects on concentric and eccentric isokinetic peak torques and electromyographic amplitudes (EMG) of the contrary muscles.
Twenty healthy male athletes (age between 18-30 years) voluntarily participated in this study. All of the subjects visited the laboratory to complete the following intervention protocol in a randomised order (a-b-c-d-e, b-e-c-d-a, d-c-a-e-b, ……) on 5 separate days; (a) non-stretching (control), (b) static stretching of the quadriceps muscles, (c) static stretching of the hamstring muscles, (d) dynamic stretching of the quadriceps muscles, and (e) dynamic stretching of the hamstring muscles. Static stretching exercises either for the quadriceps or the hamstring muscles were carried out at the standing and sitting positions. Subjects performed four successive repetitions of each stretching exercises for 30 seconds in both stretching positions. Similar to static stretching exercises two different stretching modes were designed for dynamic stretching exercises. Concentric and eccentric isokinetic peak torque for the non-stretched contrary quadriceps or hamstring muscles at angular velocities of 60°/sec and 240°/sec and their concurrent electromyographic (EMG) activities recorded with a portable 8-channel EMG device were measured before the intervention protocol and immediately after.
Isokinetic peak torques of the hamstring and quadriceps muscles did not represent any significant (p > 0.05) differences following static and dynamic stretching exercises of the quadriceps and hamstring muscles, respectively. Similarly, the EMG activities of the agonist muscles exhibited no significant alterations (p > 0.05) following both stretching exercises of the antagonist muscles.
In light of the results of the present study it is possible to state that antagonist stretching exercises either in the static or dynamic modes do not affect the isokinetic peak torques and the EMG activities of the contrary muscles.
Acknowledgement The authors would like to express appreciation for the support of the Department of the Scientific Research Projects of Uludag University (Project Number = OUAP(T)−2014/3)
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