The medial gastrocnemius fascicle shortening and tendon lengthening in static standing are associated with age-related postural instability in older adults.
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引用次数: 0
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.
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.