Shortening velocity and power output of muscles that produce ballistic movements

缩短产生弹道运动的肌肉的速度和功率输出

• 批准号: 0240349
• 负责人: Kiisa Nishikawa
• 金额: $ 34.83万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0240349&HistoricalAwards=false
• 关键词: Shortening; velocity; power; output; muscles

New insights in biology have often come from studies of animals that exhibit some extreme of performance. In such animals, principles of function common to all animals are exaggerated, and are therefore observed and studied more readily. Ballistic tongue projection in toads represents one such extreme. During ballistic tongue projection, toad tongues can leave the mouth at accelerations of 2500 m/s2. Previous and ongoing research in the laboratories of these investigators has focused on elucidating mechanisms by which mouth opening muscles of toads produce the power required for this extremely rapid movement. The work in this project will focus on understanding the force-velocity relationships and power output of two muscles that are involved in powering ballistic movements: 1) the m. depressor mandibulae, which is solely responsible for mouth opening during tongue projection ; and 2) the m. semimembranosus, which along with other muscles, extends the hind limb during jumping. The proposed studies will use the classic load clamp or quick release technique to quantify the biphasic shortening behavior of these muscles during the transition from isometric tetanus to isotonic shortening. In the load clamp technique, an activated muscle is stimulated to develop tension while contracting against a load that prevents it from shortening. When the load is reduced, the muscle first shortens rapidly and then decelerates to a slower shortening velocity. In contrast to most recent studies which measure only the velocity of shortening during the slow phase, these investigators measured velocity of shortening during the initial fast phase as well. Four important new aspects of the shortening behavior of muscle have been discovered. During the fast phase: 1) shortening velocity can be high (up to nearly 100 times Vmax), and it differs between jaw and hind limb muscles; 2) external work performed contributes to total power output, although the magnitude of the contribution varies between the jaw and hind limb muscles; 3) shortening velocity increases with the duration of isometric pre-stimulation; and during the slow phase 4) shortening velocity also increases with the duration of isometric pre-stimulation, at least in some muscles. These results are consistent with a model in which a series elastic component within the sarcomere is stretched by the contractile elements during isometric tetanus, and the degree of stretch increases with the duration of isometric pre-stimulation. Preliminary data suggest that muscles differ adaptively in how kinetic energy is distributed between the fast and slow phases of shortening. A mechanism, such as phosphorylation of the thick and/or thin filaments, that controls the distribution of kinetic energy between the fast and slow phases would likely be important in controlling muscle power output during ballistic movements. The proposed studies will extend these preliminary studies. Specifically, the investigators will: 1) compare biphasic shortening of anuran jaw and hind limb muscles in species of anurans that differ in feeding and jumping performance; 2) quantify the effects of duration of isometric pre-stimulation and muscle length on biphasic shortening; and 3) examine the relationship between movement velocity and duration of muscle pre-activation in freely behaving animals. The proposed studies are likely to demonstrate: 1) that a significant amount of elastic potential energy, stored during isometric pre-stimulation, is converted to kinetic energy at the instant of release to isotonic shortening; and 2) that muscles differ in their strategies for distributing this kinetic energy between the fast and slow phases of shortening, thereby optimizing their power output during shorter vs. longer contractions. In these ways, the proposed studies have the potential to change our concept of how muscles shorten, especially at the high velocities that occur during ballistic movements.

生物学的新见解通常来自对表现出极端性能的动物的研究。在这样的动物中，所有动物共有的功能原理被夸大了，因此更容易观察和研究。蟾蜍中的弹道舌头投影代表着如此极端。在弹道舌头投射过程中，蟾蜍的舌头可能会以2500 m/s2的加速度离开嘴。这些研究人员的实验室的以前和正在进行的研究都集中在阐明蟾蜍肌肉张开肌肉的机制上，从而产生了这种极快运动所需的力量。该项目的工作将集中在理解弹道运动的两种肌肉的力 - 速度关系和功率输出：1）m。下颌骨，这是舌头投射过程中张开的完全负责的； 2）m。半膜与其他肌肉一起在跳跃过程中延伸后肢。拟议的研究将使用经典的载荷夹或快速释放技术来量化这些肌肉从等距破伤风转向等渗缩短过程中这些肌肉的双相缩短行为。在负载夹技术中，激活的肌肉被刺激以产生张力，同时与阻止其缩短的负载收缩。减少负载时，肌肉首先缩短，然后减速至较慢的缩短速度。与最新的研究相反，这些研究仅测量缓慢阶段的缩短速度，这些研究者也测量了初始快速阶段缩短的速度。已经发现了肌肉缩短行为的四个重要新方面。在快速阶段：1）缩短速度可能很高（vmax近100倍），下颌和后肢肌肉之间有所不同； 2）执行的外部工作有助于总功率输出，尽管下颌和后肢肌肉之间的贡献程度有所不同。 3）缩短速度随着等距预刺激的持续时间而增加；在缓慢的阶段4）缩短速度也随着等距预刺激的持续时间的增加，至少在某些肌肉中。这些结果与一个模型一致，在该模型中，肌膜中的串联弹性成分在等距破伤风中的收缩元件拉伸，并且随着等距预刺激的持续时间，伸展程度随着伸展程度而增加。初步数据表明，肌肉在动能的快速和较慢较短阶段之间的分布方式适应性差异。控制厚和/或细丝的磷酸化的机制，该机制控制在快速和慢期之间的动能分布对于在弹道运动过程中控制肌肉功率输出可能很重要。拟议的研究将扩展这些初步研究。具体而言，研究人员将：1）比较Anuran颌骨和后肢肌肉的双相缩短，而Anurans物种的进食和跳跃性能有所不同； 2）量化等距预刺激和肌肉长度持续时间对双相缩短的影响； 3）检查自由表现动物的运动速度与肌肉预活化的持续时间之间的关系。拟议的研究很可能证明：1）在等距预刺激期间存储的大量弹性势能在释放时在释放时转化为动能； 2）肌肉在缩短的快速和慢速阶段之间分配这种动能的策略有所不同，从而在较短的收缩和更长的收缩期间优化了其功率输出。通过这些方式，拟议的研究可能会改变我们对肌肉如何缩短的概念，尤其是在弹道运动过程中发生的高速度。