Hirono Tetsuya, Takeda Ryosuke, Nishikawa Taichi, Okudaira Masamichi, Kunugi Shun, Yoshiko Akito, Ueda Saeko, Yoshimura Akane, Watanabe Kohei
Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan; Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan.
Arch Gerontol Geriatr. 2024 Jan;116:105151. doi: 10.1016/j.archger.2023.105151. Epub 2023 Aug 1.
Muscular dysfunctions involving a decline in muscle strength are often induced by loss of muscle mass in older adults. Understanding neural activation in older adults in addition to muscular characteristics may be important to prevent such age-related dysfunctions. This study aimed to investigate the difference in motor unit firing patterns between community-dwelling older individuals with normal and low skeletal muscle mass. Sixty-six older adults (62-90 years) performed muscle strength and function tests. On conducting high-density surface electromyography of the vastus lateralis, individual motor unit firing properties were assessed. Individual motor units were divided into three different recruitment threshold groups and their firing rates were compared. The skeletal muscle quantity and quality were assessed using bioimpedance methods and ultrasound images. They were divided into two groups according to sarcopenia criteria: a normal group (n = 39) and presarcopenia group with low skeletal muscle mass but normal physical functions (n = 21). Skeletal muscle mass and muscle thickness were greater and echo intensity was lower in the normal group than presarcopenia group. Motor units in normal older adults fired at different rates with a hierarchy depending on their recruitment threshold, observed as a normal phenomenon. However, motor units in the presarcopenia group fired without showing the hierarchical pattern. The results suggest that older adults with low skeletal muscle mass exhibited an abnormal neural input pattern, in addition to declines in muscle quantity and quality.
涉及肌肉力量下降的肌肉功能障碍在老年人中通常是由肌肉量减少引起的。除了肌肉特征外，了解老年人的神经激活情况对于预防此类与年龄相关的功能障碍可能很重要。本研究旨在调查骨骼肌量正常和较低的社区居住老年人之间运动单位放电模式的差异。66名老年人（62 - 90岁）进行了肌肉力量和功能测试。在对股外侧肌进行高密度表面肌电图检查时，评估了个体运动单位的放电特性。将个体运动单位分为三个不同的募集阈值组，并比较它们的放电率。使用生物电阻抗方法和超声图像评估骨骼肌的数量和质量。根据肌肉减少症标准将他们分为两组：正常组（n =3=39）和骨骼肌量低但身体功能正常的肌肉减少症前期组（n = 21）。正常组的骨骼肌量和肌肉厚度更大，回声强度低于肌肉减少症前期组。正常老年人的运动单位根据其募集阈值以不同的速率分级放电，这是一种正常现象。然而，肌肉减少症前期组的运动单位放电时没有表现出分级模式。结果表明，骨骼肌量低的老年人除了肌肉数量和质量下降外，还表现出异常的神经输入模式。
