The medial gastrocnemius fascicle shortening and tendon lengthening in static standing are associated with age-related postural instability in older adults.

IF 3.3 3区 医学 Q1 PHYSIOLOGY
Taku Miyazawa, Hiroki Hanawa, Keisuke Kubota, Keisuke Hirata, Tsutomu Fujino, Naohiko Kanemura
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Abstract

Muscle-tendon unit (MTU) dynamics are involved in small body movements, including static standing. However, the effect of age-related reductions in tendon stiffness on static standing stability remains unclear. In this study, Achilles tendon stiffness was assessed in young and older adults, and muscle fascicle length and tendon length were measured during static standing with eyes open (EO) and eyes closed (EC) using ultrasonography. To isolate muscle-controlled activity, we analyzed intervals around the peak center of pressure (COP) velocity points. Fascicle length change (ΔLfas) and tendon length change (ΔLTS) during these intervals were calculated, compared by age group, and examined for their relationship to COP sway. COP was decomposed into rambling and trembling components, representing supraspinal and spinal-peripheral control processes, respectively. Results showed significantly reduced Achilles tendon stiffness and increased COP velocity and trembling in older adults (P=0.02, <0.001, and <0.001, respectively). Both age groups demonstrated fascicle shortening and tendon lengthening around peak COP velocity points, but changes were more pronounced in older adults, showing greater fascicle shortening and tendon elongation (age effect: P=0.012 and 0.031, respectively). ΔLfas amplitude positively correlated with COP velocity (EO: Young r=0.39, Older r=0.55; EC: Young r=0.71, Older r=0.44, all P<0.05) and trembling velocity (EO: Young r=0.49, Older r=0.56; EC: Young r=0.82, Older r=0.45, all P<0.001). These parameters, known to increase with age, are linked to co-contraction. This study demonstrates that excessive fascicle shortening, resulting from reduced tendon stiffness, contributes to increased postural sway in older adults.

静止站立时腓肠肌内侧束缩短和肌腱延长与老年人年龄相关的姿势不稳定有关。
肌肉肌腱单元(MTU)动力学涉及小的身体运动,包括静态站立。然而,与年龄相关的肌腱刚度降低对静态站立稳定性的影响尚不清楚。在这项研究中,评估了年轻人和老年人的跟腱刚度,并使用超声检查测量了静立、睁眼(EO)和闭眼(EC)时的肌束长度和跟腱长度。为了分离肌肉控制的活动,我们分析了峰值压力中心(COP)速度点周围的间隔。计算这些时间间隔内的肌束长度变化(ΔLfas)和肌腱长度变化(ΔLTS),按年龄组进行比较,并检查它们与COP摇摆的关系。COP分解为漫游性和颤抖性两部分,分别代表脊柱上和脊柱外周的控制过程。结果显示,老年人跟腱刚度明显降低,COP速度和颤抖增加(P=0.02, fas振幅与COP速度正相关(EO: Young r=0.39, older r=0.55; EC: Young r=0.71, older r=0.44,均P
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来源期刊
CiteScore
6.00
自引率
9.10%
发文量
296
审稿时长
2-4 weeks
期刊介绍: The Journal of Applied Physiology publishes the highest quality original research and reviews that examine novel adaptive and integrative physiological mechanisms in humans and animals that advance the field. The journal encourages the submission of manuscripts that examine the acute and adaptive responses of various organs, tissues, cells and/or molecular pathways to environmental, physiological and/or pathophysiological stressors. As an applied physiology journal, topics of interest are not limited to a particular organ system. The journal, therefore, considers a wide array of integrative and translational research topics examining the mechanisms involved in disease processes and mitigation strategies, as well as the promotion of health and well-being throughout the lifespan. Priority is given to manuscripts that provide mechanistic insight deemed to exert an impact on the field.
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