Department of Physical Therapy, University of Alabama at Birmingham, Birmingham, Alabama, USA.
J Strength Cond Res. 2012 Sep;26(9):2345-55. doi: 10.1519/JSC.0b013e3182606cc5.
The purpose of this study was to determine where stretch-shortening cycle (SSC) potentiation of force, power, velocity, and acceleration occurs across the concentric phase of ballistic leg presses. Second, we examined the influence of late eccentric phase force and length of the amortization phase on potentiated concentric phase performance variables. Twenty-one male runners (age: 31.9 ± 4.7 years) performed SSC and concentric-only (CO) ballistic leg press throws. Potentiations of concentric actions were calculated as the difference between SSC and CO contractions. An analysis splitting the concentric range of motion (ROM) into 6 equal time intervals determined force and acceleration were potentiated (p < 0.05) only during the first one-sixth time interval of concentric motion, whereas velocity and power were potentiated (p < 0.05) at all time intervals over the entire concentric motion with the exception of power over the last one-sixth time interval. A more precise analysis examining 20-millisecond time intervals across the first 200 milliseconds of concentric motion determined force was potentiated only over the first 140 milliseconds and acceleration only over the first 160 milliseconds. Eccentric force measured during the last 100 milliseconds of eccentric motion was related to potentiated force during the initial 200 milliseconds of concentric motion (r = 0.44, p < 0.05) and potentiated mean power across the full concentric ROM (r = 0.62, p < 0.01). Results indicate that in contrast to power and velocity, potentiation of force and acceleration occurs only early during the concentric phase of SSC ballistic leg presses. Correlational findings imply late eccentric phase force is important for generating force and power during the concentric phase of the SSC and thus training focusing on enhancing late phase eccentric force appears important for developing explosive force and power during SSC movements.
本研究旨在确定伸展-缩短周期（SSC）在弹道式腿举的向心阶段中增强力、功率、速度和加速度的位置。其次，我们研究了离心阶段末期力和缓冲阶段长度对增强向心阶段性能变量的影响。21 名男性跑步者（年龄：31.9±4.7 岁）进行了 SSC 和纯向心（CO）弹道式腿举投掷。将 SSC 和 CO 收缩之间的差异作为向心收缩的增强来计算。通过将向心运动范围（ROM）分为 6 个相等的时间间隔的分析确定，仅在向心运动的前 1/6 时间间隔内增强了力和加速度（p＜0.05），而在整个向心运动的所有时间间隔内（除了最后 1/6 时间间隔内的功率）均增强了速度和功率。在向心运动的前 200 毫秒内检查 20 毫秒时间间隔的更精确分析确定，仅在最初的 140 毫秒内增强了力，仅在最初的 160 毫秒内增强了加速度。在离心运动的最后 100 毫秒内测量的离心力与向心运动最初 200 毫秒内的增强力（r=0.44，p＜0.05）和整个向心 ROM 内的增强平均功率（r=0.62，p＜0.01）相关。结果表明，与功率和速度相反，力和加速度的增强仅在 SSC 弹道式腿举的向心阶段早期发生。相关发现表明，离心阶段末期力对于 SSC 向心阶段的力和功率产生很重要，因此，专注于增强后期离心力的训练对于在 SSC 运动中发展爆发力和功率很重要。
