Conley Kevin E, Lindstedt Stan L
Department of Radiology, University of Washington Medical Center, Seattle, WA 98195-7115, USA.
J Exp Biol. 2002 Aug;205(Pt 15):2175-81. doi: 10.1242/jeb.205.15.2175.
Many mechanisms reduce the cost of muscle activity. Here, we describe a set of specializations that reduce the cost of contraction in the high-frequency twitches that are used by a wide variety of animals for either sound production or flight. Minimizing the cost of these contractions means that cellular ATP production can meet ATP demand and sustain the high contractile rate. Two classes of specialization are found that minimize the contractile cost. The first class reduces the muscle work required per contraction. Light appendages such as rattles, insect limbs and membranous wings that require little work for movement are used in high-frequency contractions. The second set of specializations involves processes that minimize energy use. High-frequency muscles tend to have a lower cross-bridge content, fewer attached cross-bridges and shorter length changes per contraction. The result is low muscle-specific forces (stress), small length changes (strain) and rapid contraction times that suggest that these muscles push the lower limit of contractile function. The consequence of function at this lower extreme of contraction is to minimize the contractile cost of high-frequency muscles. Thus, specializations that permit rapid contractions at a low rate of ATP use per twitch are the basis of a minimization strategy for energy saving in muscles contracting at high frequency.
许多机制可降低肌肉活动的成本。在此，我们描述了一组特化现象，这些特化现象降低了高频抽搐收缩的成本，高频抽搐被各种各样的动物用于发声或飞行。将这些收缩的成本降至最低意味着细胞ATP生成能够满足ATP需求，并维持高收缩率。发现了两类使收缩成本最小化的特化现象。第一类减少了每次收缩所需的肌肉功。像响尾、昆虫肢体和膜状翅膀等轻的附属物，运动时所需功少，被用于高频收缩。第二类特化涉及将能量消耗降至最低的过程。高频肌肉往往横桥含量较低，附着的横桥较少，每次收缩时长度变化较短。结果是肌肉比力（应力）较低、长度变化（应变）较小且收缩时间较快，这表明这些肌肉接近收缩功能的下限。在收缩的这个较低极限发挥功能的结果是将高频肌肉的收缩成本降至最低。因此，允许以每次抽搐较低的ATP使用率进行快速收缩的特化现象是高频收缩肌肉节能最小化策略的基础。
