Acute Effects of Countermovement Jumps with Post-activation Potentiation Utilizing Additional Elastic Resistance during Eccentric Stretching Phase

Abstract

<p>目的：本研究欲探究下蹲階段輔以彈性阻力之反向跳預先活動，對於6分鐘恢復時間後之跳躍表現的活化後增益效應。方法：本研究招募11名國立大學體育相關科系男性學生為受試對象，施以2循環、每循環5次的反向跳預先活動，且於下蹲制動階段介入外加彈性阻力，阻力強度分為0% BW、15% BW、30% BW三種情境，並於預先活動介入前與介入後第6分鐘後進行前測與後測。以兩塊測力板擷取前測與後測之反向跳過程中垂直地面反作用力值與時間，並計算發力率、跳躍高度、修正式反應力量指標以及下肢勁度。以相依樣本 t-test 進行統計檢驗，統計水準訂為 α = .05，比較前測與後測的下肢動態力量特徵之參數是否有差異。結果：本研究結果顯示，三種介入模式皆顯著提升反向跳制動末點力值 (p < .05)。15% BW與30% BW的介入模式顯著提升制動期與推蹬期發力率 (p < .05)。30 % BW的介入模式顯著提升反向跳下肢勁度、修正式反應力量指標，並縮短制動期時間 (p < .05)。結論：本研究之介入應有助於增進牽張反射機制之效益，尤其是在離心制動階段的肌力特徵表現上，因此，建議在進行具備牽張反射機制之動作執行前，可透過反向跳下蹲階段輔以30% BW彈性阻力進行下肢動態肌力活化之預先活動，以助於後續之運動表現。</p> <p> </p><p>Purpose: The current study aimed at exploring the immediate effect of pre-activities of countermovement jumps, with elastic resistance and 6 minutes of recovery time, on post-activation potentiation during squatting phase. Method: Eleven male college students recruited from the Physical Education department at National Dong Hwa University were asked to perform pre-activities of countermovement jumps (2 cycles, 5 repetitions for each cycle), with elastic resistances (0% BW, 15% BW, and 30% BW) during the squatting phase, followed by pre-tests and post-tests before and after six minutes of recovery time. Two AMTI force plates were used to collect data on vertical ground reaction force and time during countermovement jumps for pre- and post-tests. Rate of force development, jump heights, reactive strength index modified, and lower extremity stiffness were calculated accordingly. Dependent sample t-test was conducted (α=.05) to determine if there were significant differences in the parameters related to lower extremity dynamic strength between the pre- and post-tests. Results: Pre-activities with all three interventions significantly increased the ground reaction forces during the breaking phase (p < .05). Pre-activities with elastic resistances of 15% and 30% BW significantly elevated the rates of force development during the breaking and propulsive phases (p < .05). Pre-activities with 30% BW elastic resistance significantly led to increased lower extremity stiffness, reactive strength index modified, and decreased breaking time (p < .05). Conclusion: The added elastic resistance enhanced the benefits of stretch reflex mechanism, especially the muscle strength characteristics during the eccentric breaking phase. Based on our finding, countermovement jumps with pre-activity with elastic resistance of 30% BW is recommended prior to performing movements concerning stretch reflex mechanism.</p> <p> </p>