Noonan Alex M, Oxland Thomas R, Brown Stephen H M
Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada.
Department of Orthopaedics, The University of British Columbia, Vancouver, Canada.
Eur Spine J. 2022 Mar;31(3):783-791. doi: 10.1007/s00586-022-07120-2. Epub 2022 Jan 28.
Various aspects of paraspinal muscle anatomy, biology, and histology have been studied; however, information on paraspinal muscle contractile function is almost nonexistent, thus hindering functional interpretation of these muscles in healthy individuals and those with low back disorders. The aim of this study was to measure and compare the contractile function and force-sarcomere length properties of muscle fibers from the multifidus (MULT) and erector spinae (ES) as well as a commonly studied lower limb muscle (Extensor digitorum longus (EDL)) in the rat.
Single muscle fibers (n = 77 total from 6 animals) were isolated from each of the muscles and tested to determine their active contractile function; all fibers used in the analyses were type IIB.
There were no significant differences between muscles for specific force (sF) (p = 0.11), active modulus (p = 0.63), average optimal sarcomere length (p = 0.27) or unloaded shortening velocity (V) (p = 0.69). However, there was a significant difference in the rate of force redevelopment (k) between muscles (p = < 0.0001), with MULT being significantly faster than both the EDL (p = < 0.0001) and ES (p = 0.0001) and no difference between the EDL and ES (p = 0.41).
This finding suggests that multifidus has faster cross-bridge turnover kinetics when compared to other muscles (ES and EDL) when matched for fiber type. Whether the faster cross-bridge kinetics translate to a functionally significant difference in whole muscle performance needs to be studied further.
人们已经对椎旁肌的解剖学、生物学和组织学的各个方面进行了研究；然而，关于椎旁肌收缩功能的信息几乎不存在，这阻碍了对健康个体和患有下背部疾病的个体中这些肌肉的功能解读。本研究的目的是测量并比较大鼠多裂肌（MULT）、竖脊肌（ES）以及常用作研究对象的下肢肌肉（趾长伸肌（EDL））的肌肉纤维的收缩功能和力-肌节长度特性。
从每块肌肉中分离出单根肌肉纤维（共77根，来自6只动物）并进行测试，以确定其主动收缩功能；分析中使用的所有纤维均为IIB型。
各肌肉之间在比力（sF）（p = 0.11）、主动模量（p = 0.63）、平均最佳肌节长度（p = 0.27）或无负荷缩短速度（V）（p = 0.69）方面无显著差异。然而，各肌肉之间在力重建速率（k）方面存在显著差异（p = < 0.0001），多裂肌的力重建速率显著快于趾长伸肌（p = < 0.0001）和竖脊肌（p = 0.0001），而趾长伸肌和竖脊肌之间无差异（p = 0.41）。
这一发现表明，在纤维类型匹配时，与其他肌肉（竖脊肌和趾长伸肌）相比，多裂肌具有更快的横桥转换动力学。横桥动力学更快是否会转化为整块肌肉性能上的功能显著差异，还有待进一步研究。
