Department of Exercise Science and Sport Management, Kennesaw State University, Kennesaw, GA 30144, United States of America.
Department of Exercise Science and Sport Management, Kennesaw State University, Kennesaw, GA 30144, United States of America.
Exp Gerontol. 2019 Oct 1;125:110677. doi: 10.1016/j.exger.2019.110677. Epub 2019 Jul 30.
Little evidence exists regarding the contribution of torque and velocity to the age-related decrease in peak power (PP) for the plantar flexors (PFs). A comprehensive assessment of PF neuromuscular function is necessary to elucidate age-related changes, especially between middle-aged and older adults, in order to identify early, age-related decrements. Thus, the purpose of this study was to examine neuromuscular function of the PFs in middle-aged and older males, and identify predictors of PP. Twenty-eight healthy, middle-aged (n = 13; 45.1 ± 2.7 yrs) and older (n = 15; 65.3 ± 3.2 yrs) males performed concentric isotonic PF contractions ranging in intensity from 20% to 70% isometric strength using a dynamometer. PP in addition to velocity and torque at the moment in time PP occurred, as well as the rate of velocity, torque (RTD), and power (RPD) development were recorded. The rate of electromyography rise (RER) was derived from the linear slope of the normalized electromyography signal. Isometric and concentric dynamic strength were assessed, as well as cross-sectional area and muscle quality (i.e., echo intensity) of the PFs via panoramic ultrasonography. The relationship between serum c-terminal agrin levels and select variables was examined to explore the potential role of neuromuscular junction deterioration. Appendicular lean mass and physical activity level were similar between groups (p > 0.05), and only PP (p = 0.046; d = 0.79), RPD (p = 0.026; d = 0.90), RTD (p = 0.022; d = 0.91), and RER (p = 0.010; d = 1.04) were lower in older males. When groups were collapsed, RTD was the only significant predictor of PP, while c-terminal agrin levels were not associated with any variables. Our findings indicate that PP and time-dependent parameters of muscle activation and contractile function of the PFs are dramatically diminished in older adults compared to middle-aged adults. PP is produced at the same velocity and relative intensity in middle-aged and older males, and RTD is most influential for PP. The inability of the PFs to be rapidly activated appeared to be influential for the age-related impairment in PP and time-dependent contractile parameters.
对于跟年龄相关的足底屈肌峰值力量（PP）下降，扭矩和速度的贡献，证据很少。为了阐明与年龄相关的变化，尤其是在中年和老年人之间，需要对足底屈肌的神经肌肉功能进行全面评估，以识别与年龄相关的早期衰退。因此，本研究的目的是检查中年和老年男性的足底屈肌神经肌肉功能，并确定 PP 的预测因子。28 名健康的中年男性（n=13；45.1±2.7 岁）和老年男性（n=15；65.3±3.2 岁）使用测力计进行了从 20%到 70%等长强度的向心等速足底屈肌收缩。记录了 PP 以及在发生 PP 时的速度和扭矩、速度（RTD）和功率（RPD）发展的速率。从归一化肌电图信号的线性斜率得出肌电图上升的速率（RER）。通过全景超声评估等长和向心动态强度以及足底屈肌的横截面积和肌肉质量（即回声强度）。检查血清 C 端凝集素水平与选定变量之间的关系，以探讨神经肌肉接头恶化的潜在作用。四肢瘦体重和身体活动水平在两组之间相似（p>0.05），只有 PP（p=0.046；d=0.79）、RPD（p=0.026；d=0.90）、RTD（p=0.022；d=0.91）和 RER（p=0.010；d=1.04）在老年男性中较低。当两组合并时，RTD 是 PP 的唯一显著预测因子，而 C 端凝集素水平与任何变量都没有关联。我们的研究结果表明，与中年男性相比，老年人的 PP 以及足底屈肌肌肉激活和收缩功能的时变参数明显降低。中年和老年男性的 PP 是在相同的速度和相对强度下产生的，而 RTD 对 PP 的影响最大。足底屈肌快速激活的能力下降似乎对与年龄相关的 PP 及时变收缩参数损伤有影响。
