A study on the visco-elastic properties of the extraocular muscles

研究了家兔上直肌（SR）和球牵肌（RB）慢速纤维和快速纤维的粘弹性。整个肌肉张力的18%到19%是由SR的慢纤维产生的，1%到5%是由RB的慢纤维产生的。长时间连续收缩后，抗疲劳纤维在SR区留下残余张力，而在RB区几乎完全没有张力。采用频率响应法对动力粘弹性进行了评价。肌肉呈正弦波拉伸，在20 Hz时最大振幅为1 mm。然后检测破伤风(P)和静息（P_0）时正弦波振动的张力幅值。动刚度比（P/P_0） SR（3.1）高于RB（2.0）。结果表明，在慢纤维中肌凝蛋白和肌动蛋白丝上活化的桥的粘弹性比在快纤维中大。我们的结论是，这些特性支持慢纤维稳定眼球的假设。

We examined the visco-elastic properties of the slow and fast fibers consisting the superior rectus muscle (SR) and retractor bulbi muscle (RB) of rabbits. Eighteen to nineteen percent of whole muscle tension was produced by slow fibers in SR and one to five percent by those in RB.After long continuous contraction, fatigue-resistant fibers left residual tension in SR,but the tension was almost entirely absent in RB.The frequency response method was used to evaluate dynamic visco-elasticity. The muscle was stretched sinusoidally, with an amplitude of 1 mm at 20 Hz in Lmax. The tension amplitude to sine wave vibrations during tetanus (P) and resting (P_0) were then examined. The dynamic stiffness ratio (P/P_0) was higher in SR (3.1) than in RB (2.0). It was suggested that the visco-elasticity of the activated cross bridges at myosin and actin filaments are greater in slow fibers than in fast fibers.We concluded that these properties support the hypothesis of the slow fibers to stabilize the eye balls.