A great number of studies showed in the last years that static stretching performed immediately before athletic activity has negative effects on lower extremity performance during athletic activities like vertical jump and sprint. All of this research associated with static stretching evaluated performance in the agonist musculature. The co-activity of the antagonist muscles, on the other hand, is also important when an activity is performed or during joint stabilisation. Changes in the activity of the antagonist muscles, either decrease or increase during sports can influence the related athletic performance. There is limited number of published studies in the literature investigating the effects of stretching the antagonist muscles on agonist muscle activity during jump performance. Therefore, the aim of this study was to investigate the effects of static stretching of the muscles that acts as antagonists in relation to the more agonist muscles during jumping on biomechanical data, vertical jump height and electromyographic (EMG) activity of the agonist muscles during vertical jump performance.
Eleven healthy elite female athletes (mean age, 23.0 ± 6.2 years; mean height, 176.2 ± 9.1 cm; mean body mass, 67.5 ± 12.4 kg) participated to this study. All of the subjects performed the protocols for stretching intervention, non-stretching (control) and static stretching, in a randomised order on different days within one week. Static stretching, which comprised four consecutive repetitions, was held for 30 seconds in the hip flexor, knee flexor and ankle dorsi-flexor muscles. To determine if stretching intervention of the antagonist muscles affects performance, subjects carried out a squat jump test before and immediately following the intervention. Vertical jump height, EMG activity of the hip extensor, knee extensor and ankle plantar-flexor muscles of both legs, joint flexion angle of the hip, knee and ankle as kinematic and power analysis as kinetic variable was tested during the squat jump. The EMG activity in total of 12 muscles from both legs was recorded from the following exact points; (a) at which each subject began the concentric phase of the jump, (b) between the start of jump and take-off, (c) at take-off, (d) between take-off and landing, (e) at landing where the fingers contacted the ground and (f) at the contact of heel with the ground.
There were no significant EMG activity differences between the stretching and control intervention in the hip extensor, knee extensor and ankle plantar-flexor muscles of both legs at the measured six vertical jump phases (p > 0.05). Similarly, the hip, knee and ankle range of motion during the squat jump divided to ten timelines did not represent significant differences between the stretching and control group (p > 0.05). In contrast, according to the 2 × 2 repeated measures ANOVA model, the vertical jump height following the static stretching of the antagonist muscles showed a significant stretch type x time interaction (stretching group: before 161 ± 18 mm, after 167 ± 21 mm; control group: before 169 ± 20 mm, after 166 ± 19 mm; p = 0.019).
Although the statistical significant difference for the vertical jump height following stretching, the 6 mm increase is not clinical meaningful. Therefore, according to the results of the present study it seems that static stretching of the antagonist muscles involved in the squat jump activity does not affect the squat jump performance evaluated with EMG activity, kinematic and kinetic analyses.
Acknowledgement The authors would like to express appreciation for the support of the Department of the Scientific Research Projects of Uludag University (Project Number = HDP(T)−2016/13)
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