Ohio Musculoskeletal and Neurological Institute (OMNI), Ohio University, Athens.
Department of Biomedical Sciences, Ohio University, Athens.
J Gerontol A Biol Sci Med Sci. 2021 Mar 31;76(4):692-702. doi: 10.1093/gerona/glaa157.
Weakness is a risk factor for physical limitations and death in older adults (OAs). We sought to determine whether OAs with clinically meaningful leg extensor weakness exhibit differences in voluntary inactivation (VIA) and measures of corticospinal excitability when compared to young adults (YAs) and OAs without clinically meaningful weakness. We also sought to estimate the relative contribution of indices of neural excitability and thigh lean mass in explaining the between-subject variability in OAs leg extensor strength.
In 66 OAs (75.1 ± 7.0 years) and 20 YAs (22.0 ± 1.9 years), we quantified leg extensor strength, thigh lean mass, VIA, and motor evoked potential (MEP) amplitude and silent period (SP) duration. OAs were classified into weakness groups based on previously established strength/body weight (BW) cut points (Weak, Modestly Weak, or Not Weak).
The OAs had 63% less strength/BW when compared to YAs. Weak OAs exhibited higher levels of leg extensor VIA than Not Weak OAs (14.2 ± 7.5% vs 6.1 ± 7.5%). Weak OAs exhibited 24% longer SPs compared to Not Weak OAs, although this difference was insignificant (p = .06). The Weak OAs MEPs were half the amplitude of the Not Weak OAs. Regression analysis indicated that MEP amplitude, SP duration, and thigh lean mass explained ~62% of the variance in strength, with the neural excitability variables explaining ~33% of the variance and thigh lean mass explaining ~29%.
These findings suggest that neurotherapeutic interventions targeting excitability could be a viable approach to increase muscle strength in order to reduce the risk of physical impairments in late life.
虚弱是老年人（OA）身体功能受限和死亡的一个风险因素。我们试图确定与年轻成年人（YA）和无临床意义虚弱的 OA 相比，是否存在临床意义上的腿部伸肌无力的 OA 存在自愿失活（VIA）和皮质脊髓兴奋性测量值的差异。我们还试图估计神经兴奋性和大腿瘦体重指数在解释 OA 腿部伸肌力量的个体间变异性方面的相对贡献。
在 66 名 OA（75.1 ± 7.0 岁）和 20 名 YA（22.0 ± 1.9 岁）中，我们量化了腿部伸肌力量、大腿瘦体重、VIA、运动诱发电位（MEP）幅度和静息期（SP）持续时间。OA 根据先前建立的力量/体重（BW）切点（弱、适度弱或不弱）分为弱组。
OA 的力量/BW 比 YA 低 63%。弱 OA 的腿部伸肌 VIA 水平高于非弱 OA（14.2 ± 7.5%比 6.1 ± 7.5%）。弱 OA 的 SP 持续时间比非弱 OA 长 24%，尽管差异无统计学意义（p =.06）。弱 OA 的 MEP 幅度是非弱 OA 的一半。回归分析表明，MEP 幅度、SP 持续时间和大腿瘦体重解释了约 62%的力量变异性，其中神经兴奋性变量解释了约 33%的变异性，大腿瘦体重解释了约 29%的变异性。
这些发现表明，针对兴奋性的神经治疗干预可能是增加肌肉力量以降低晚年身体功能障碍风险的可行方法。
