School of Medical and Health Sciences, Edith Cowan University, Joondalup 6027, Australia.
Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, V5A 1S6, Canada.
Biol Open. 2023 Sep 15;12(9). doi: 10.1242/bio.060023. Epub 2023 Sep 5.
'Muscle gear' is calculated as the ratio of fascicle-to-muscle length change, strain, or velocity. Inconsistencies in nomenclature and definitions of gear exist across disciplines partly due to differences in fascicle [curved (Lf) versus linear (Lf,straight)] and muscle [whole-muscle belly (Lb) versus belly segment (Lb,segment)] length calculation methods. We tested whether these differences affect gear magnitude during passive and active muscle lengthening of human medial gastrocnemius of young men (n=13, 26.3±5.0 years) using an isokinetic dynamometer. Lb, Lb,segment, Lf and Lf,straight were measured from motion analysis and ultrasound imaging data. Downshifts in belly gear but not belly segment gear occurred with muscle lengthening only during active lengthening. Muscle gear was unaffected by fascicle length measurement method (P=0.18) but differed when calculated as changes in Lb or Lb,segment (P<0.01) in a length-dependent manner. Caution is therefore advised for the use and interpretation of different muscle gear calculation methods and nomenclatures in animal and human comparative physiology.
肌肉装备（Muscle gear）被定义为肌束长度变化、应变或速度的比值。由于肌束[弯曲（Lf）与直线（Lf,straight）]和肌肉[整块肌肉腹（Lb）与腹段（Lb,segment）]长度计算方法的差异，不同学科之间的肌肉装备术语和定义并不统一。我们使用等速测力机测试了这些差异是否会影响年轻人（n=13，26.3±5.0 岁）内侧比目鱼肌在被动和主动肌肉拉伸过程中肌肉装备的大小。Lb、Lb,segment、Lf 和 Lf,straight 是从运动分析和超声成像数据中测量得到的。只有在主动拉伸时，肌肉拉伸时才会出现腹部装备（belly gear）的下调，而不是腹部段装备（belly segment gear）。肌束长度测量方法不影响肌肉装备（P=0.18），但当以 Lb 或 Lb,segment 的变化来计算（P<0.01）时，肌肉装备会以长度依赖的方式出现差异。因此，在动物和人类比较生理学中，对于不同的肌肉装备计算方法和术语的使用和解释需要谨慎。
