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

本文研究了兔眼上级直肌（SR）和眼球牵开肌（RB）的慢纤维和快纤维的粘弹性。SR中慢肌纤维产生的张力占总张力的18 ~ 19%，RB中慢肌纤维产生的张力占总张力的1 ~ 5%，长时间连续收缩后，SR中抗疲劳纤维有残余张力，RB中几乎无张力。将肌肉正弦拉伸，振幅为1 mm，Lmax为20 Hz。然后检测强直（P）和静息（P_0）时正弦波振动的张力振幅。动刚度比（P/P_0）SR（3.1）高于RB（2.0）。结果表明，在慢纤维中，肌球蛋白和肌动蛋白丝处激活的横桥的粘弹性大于快纤维，这些性质支持了慢纤维稳定眼球的假说。

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.