Department of Musculoskeletal Biology, Institute of Aging and Chronic Disease, University of Liverpool, The William Henry Duncan Building, 6 West Derby Street, Liverpool L7 8TX, UK.
Department of Biosciences, University of Durham, South Road, Durham DH1 3LE, UK.
Proc Biol Sci. 2022 Jun 8;289(1976):20220622. doi: 10.1098/rspb.2022.0622. Epub 2022 Jun 1.
Muscle spindle abundance is highly variable within and across species, but we currently lack any clear picture of the mechanistic causes or consequences of this variation. Previous use of spindle abundance as a correlate for muscle function implies a mechanical underpinning to this variation, but these ideas have not been tested. Herein, we use integrated medical imaging and subject-specific musculoskeletal models to investigate the relationship between spindle abundance, muscle architecture and muscle behaviour in the human locomotor system. These analyses indicate that muscle spindle number is tightly correlated with muscle fascicle length, absolute fascicle length change, velocity of fibre lengthening and active muscle forces during walking. Novel correlations between functional indices and spindle abundance are also recovered, where muscles with a high abundance predominantly function as springs, compared to those with a lower abundance mostly functioning as brakes during walking. These data demonstrate that muscle fibre length, lengthening velocity and fibre force are key physiological signals to the central nervous system and its modulation of locomotion, and that muscle spindle abundance may be tightly correlated to how a muscle generates work. These insights may be combined with neuromechanics and robotic studies of motor control to help further tease apart the functional drivers of muscle spindle composition.
肌梭数量在个体内和个体间存在高度变异性，但我们目前还不清楚这种变异的机械原因或后果。以前将肌梭数量作为肌肉功能的相关指标表明这种变异性存在机械基础，但这些想法尚未得到验证。本文使用整合的医学成像和特定于个体的肌肉骨骼模型来研究人类运动系统中肌梭数量、肌肉结构和肌肉行为之间的关系。这些分析表明，肌梭数量与肌纤维束长度、绝对肌纤维束长度变化、纤维拉伸速度以及行走时的主动肌肉力量密切相关。还发现了功能指标与肌梭数量之间的新相关性，在行走过程中，具有高肌梭数量的肌肉主要作为弹簧起作用，而具有较低肌梭数量的肌肉主要作为制动器起作用。这些数据表明，肌肉纤维长度、拉伸速度和纤维力是中枢神经系统及其对运动的调节的关键生理信号，而肌梭数量可能与肌肉产生功的方式密切相关。这些见解可以与运动控制的神经力学和机器人研究相结合，以帮助进一步梳理肌梭组成的功能驱动因素。
