| 英文摘要 |
Introduction: The human being exists a feedforward mechanism to response the load extremely under the external condition of anticipation or unanticipation. The muscle pre-activation of bounce drop jump is one kind of the important characteristics. However, the intramuscular coordination of reaction muscle is affected by the magnitude of impact force and the sequence of movement. The purpose of this study was to compare the differences for lower extremity muscle under the manipulations of height of drop jump, and to investigate the muscle activation characteristics of the mechanism of pre-stretch and self-defense during landing. Methods: The participants (body height: 167.3 ± 5.4 cm, weight: 65.1 ± 5.5kg, age: 21.7 ± 1.9 years old) were ten physical education students. They were asked to perform hop and drop jump (15 cm, 50 cm, and 100 cm). The Biopac MP 150 system (2000 Hz) was used to record and to analysis the muscle activation patterns of lower extremity. The electromyography signals after root mean square processing were compared the statistical difference in repeated measure one way ANOVA and HSD post hoc test. Results: The results showed the phenomena of pre-stretch and the gastrocnemius mechanism of self-defense in the activation patterns were observed clearly with the increasing stretching loads (p < .05, η2 = .28, power = .72). During pre-landing and initial contact phase, the vastus medialis demonstrated no significant difference among hop, 15 cm, 50 cm, and 100 cm. The vastus medialis showed mainly activation muscle during descending phase (p < .05, η2 = .38, power = .90). The gastrocnemius and soleus muscles demonstrated no significant difference during descending phase. Conclusion: It indicated that the muscle activation patterns of leg extensors were enhanced following the load increasing of stretch, but the intramuscular coordination mechanism that the activation of neuromuscular was inhibitory appeared to serve as the function of self-defense mechanism. |
