Differential effects of aging and physical activity on corticospinal excitability of upper and lower limb muscles.
Differential effects of aging and physical activity on corticospinal excitability of upper and lower limb muscles.
复制标题
衰老和体力活动对上肢和下肢肌肉皮质脊髓兴奋性的不同影响。
DOI：
10.1152/jn.00077.2019
复制
发表时间：
2019
影响因子：
2.5
通讯作者：
Hunter,SandraK
中科院分区：
文献类型：
--
作者：
Rozand,Vianney;Senefeld,JonathonW;Sundberg,ChristopherW;Smith,AshleighE;Hunter,SandraK
皮质脊髓束兴奋性可因年龄、体力活动(PA)以及可能的性别而改变，但这些影响在上肢和下肢肌肉之间是否有所不同尚不清楚。我们通过比较运动诱发电位(MEP)的刺激-反应曲线，确定了年龄、PA和性别对次最大收缩时上肢和下肢肌肉皮质脊髓兴奋性的影响。采用经颅磁刺激(TMS)方法，从主动运动阈值(AMT)以下逐渐增加刺激器强度，直到MEP波幅达到平台值，从而在活动肌肉中诱发刺激-反应曲线。对30例青年(23.9 ± 3.8岁)和33例老年(72.6 ± 5.6岁)的第一背侧骨间(FDi)和13例青年(23.2 ± 2.2岁)和25例老年(72.7 ± 5.5岁)的股外侧肌(VL)的刺激反应曲线进行了分析。通过用四参数S型曲线拟合曲线并计算最大斜率(Slopemax)来确定皮质脊髓的兴奋性。用三轴加速度计评估PA，并将参与者分为高PA组(10,000步/天，n=15)和低PA组(<；10,000步/天，n=43)。在TMS强度较高(120-150%AMT)和斜率较大时，年轻人的fDMEP波幅(复合肌肉动作电位最大波幅的百分比)大于老年人(P<；0.05)，但高PA组和低PA组之间没有差异(P>；0.05)。然而，高PA组的VL MEP波幅和斜率最大值低于低PA组，没有年龄或性别差异。这些数据表明，与下肢相比，年龄和PA对投射到上肢肌肉的皮质脊髓束的兴奋性有不同的影响。经颅磁刺激评估投射到第一背侧骨间的皮质脊髓束的兴奋性随着年龄的增加而降低，但与个体的常规体力活动(步数/天)和性别无关。相比之下，股外侧肌的皮质脊髓兴奋性不受年龄的影响，但在达到推荐的每天10,000步体力活动的个体中，其兴奋性会降低。年龄和活动对上肢和下肢肌肉的皮质脊髓兴奋性有不同程度的影响。
Corticospinal tract excitability can be altered by age, physical activity (PA), and possibly sex, but whether these effects differ between upper and lower limb muscles is unknown. We determined the influence of age, PA, and sex on corticospinal excitability of an upper limb and a lower limb muscle during submaximal contractions by comparing stimulus-response curves of motor evoked potentials (MEPs). Transcranial magnetic stimulation (TMS) was used to evoke stimulus-response curves in active muscles by incrementally increasing the stimulator intensity from below the active motor threshold (AMT) until a plateau in MEP amplitudes was achieved. Stimulus-response curves were analyzed from the first dorsal interosseous (FDI) of 30 young (23.9 ± 3.8 yr) and 33 older (72.6 ± 5.6 yr) men and women and the vastus lateralis (VL) of 13 young (23.2 ± 2.2 yr) and 25 older (72.7 ± 5.5 yr) men and women. Corticospinal excitability was determined by fitting the curves with a four-parameter sigmoidal curve and calculating the maximal slope (slopemax). PA was assessed with triaxial accelerometry, and participants were dichotomized into high-PA (>10,000 steps/day,n= 15) or low-PA (<10,000 steps/day,n= 43) groups. Young adults had larger FDI MEP amplitudes (% maximum amplitude of compound muscle action potential) at higher TMS intensities (120–150% AMT) and greater slopemaxthan older adults (P< 0.05), with no differences between high- and low-PA groups (P> 0.05). VL MEP amplitudes and slopemax, however, were lower in the high-PA than low-PA participants, with no age or sex differences. These data suggest that aging and PA, but not sex, differentially influence the excitability of the corticospinal tracts projecting to muscles of the upper compared with the lower limb.NEW & NOTEWORTHYExcitability of the corticospinal tract projecting to the first dorsal interosseous assessed with transcranial magnetic stimulation was reduced with age but independent of regular physical activity (steps/day) and sex of the individual. In contrast, corticospinal excitability of the vastus lateralis was not affected by age but was reduced in individuals achieving more than the physical activity recommendations of 10,000 steps/day. Aging and activity differentially affect corticospinal excitability of upper and lower limb muscles.