BODY SIZE, MUSCLE POWER OUTPUT AND LIMITATIONS ON BURST LOCOMOTOR PERFORMANCE IN THE LIZARD DIPSOSAURUS DORSALIS
BODY SIZE, MUSCLE POWER OUTPUT AND LIMITATIONS ON BURST LOCOMOTOR PERFORMANCE IN THE LIZARD DIPSOSAURUS DORSALIS
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发表时间：
1993
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通讯作者：
T. P. Johnson;S. Swoap;A. F. Bennett;R. Josephson
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作者：
T. P. Johnson;S. Swoap;A. F. Bennett;R. Josephson
采用振荡工作环技术，在35℃下测量了沙漠鬣蜥(Dipsosaurus Dorsalis)髂腓肌(IF)快速糖酵解(FG)肌纤维的功率输出。为了模拟跑步过程中肌肉长度的周期性变化，分离的纤维束在应变周期中受到正弦长度变化和相位刺激。在恒定应变(12%)下，调整刺激的持续时间和时间(阶段)以最大化功率输出。以4-8g的幼鱼和15-70g的成鱼为材料，用回归分析的方法描述了种内IF长度和收缩特性的异速生长。等长力最大处的肌长(L0，mm)随体质量(M，g)呈几何级数增加(L0=5.7M0.33)。最大功率输出和缩短过程中产生的力量与身体大小没有显著关系；最大化功率所需的每周功输出(Wopt，J kg-1)确实随着身体大小的增加而增加(Wopt=3.7M0.24)。抽动持续时间(Td，ms)，从用力产生到50%松弛，随体质量的增加而增加(Td=12.4M0.18)。爆发式跑步时的肢体骑行频率(文献中报道的f)和体外最大功率输出所需的频率(Fopt)随着身体尺寸的增加而减少，两者都与身体质量的0.24次方成正比。这些发现表明，肢体骑行频率可能受抽搐收缩动力学的限制。然而，尽管与身体大小成比例，爆发式跑步时肢体骑行的频率比最大化功率输出所需的骑行频率低约20%。文中还讨论了IF在体外和体内收缩性能的差异，涉及到重力施加的限制以及肌肉、神经和骨骼系统的设计。
The power output of fast-glycolytic (FG) muscle fibres isolated from the iliofibularis (IF) muscle of desert iguanas (Dipsosaurus dorsalis) was measured at 35 sC using the oscillatory work-loop technique. To simulate cyclical muscle length changes during running, isolated fibre bundles were subjected to sinusoidal length changes and phasic stimulation during the strain cycle. At constant strain (12 %), the duration and timing (phase) of stimulation were adjusted to maximise power output. Using both hatchlings (4–8 g) and adults of varying sizes (15–70 g), the intraspecific allometries of IF length and contractile properties were described by regression analysis. The muscle length at which isometric force was maximum (L0, mm) increased geometrically with body mass (M, g) (L0=5.7M0.33). Maximum power output and the force produced during shortening showed no significant relationship to body size; work output per cycle (Wopt, J kg-1) under conditions required to maximise power did increase with body size (Wopt=3.7M0.24). Twitch duration (Td, ms), measured from the onset of force generation to 50 % relaxation, increased allometrically with body mass (Td=12.4M0.18). Limb cycling frequency during burst running (f, reported in the literature) and the frequency required to maximise power output in vitro (fopt) decreased with body size, both being proportional to body mass raised to the power 0.24. These findings suggest that limb cycling frequency may be limited by twitch contraction kinetics. However, despite corresponding proportionality to body size, limb cycling frequencies during burst running are about 20 % lower than the cycling frequencies required to maximise power output. Differences in the contractile performance of the IF in vitro and in vivo are discussed in relation to constraints imposed by gravitational forces and the design of muscular, nervous and skeletal systems.