Semmler J G, Nordstrom M A
Department of Physiology, University of Adelaide, Australia.
Exp Brain Res. 1998 Mar;119(1):27-38. doi: 10.1007/s002210050316.
We examined motor unit (MU) discharge properties (mean interspike interval, ISI, discharge variability, short-term synchronization, common drive) and force tremor in the first dorsal interosseous (FDI) muscle of five musicians (skill-trained), five weight-lifters (strength-trained) and six untrained subjects during low-force isometric abduction of the index finger. Mean MU ISI was slightly shorter in skill-trained subjects than in untrained subjects. Discharge variability of FDI MUs did not differ significantly between groups. The mean strength of MU synchronization (expressed as the frequency of extra synchronous discharges above chance) was different in skill-trained (0.22+/-0.02 s(-1), 162 MU pairs), untrained (0.32+/-0.02 s(-1), 199 MU pairs) and strength-trained subjects (0.44+/-0.03 s(-1), 183 MU pairs). FDI MU synchrony was weak and of equivalent strength in both hands of skill-trained subjects and the dominant (skilled) hand of untrained subjects. The stronger FDI MU synchrony in the non-dominant hand of untrained subjects was equivalent to that found in both hands of strength-trained subjects. The extent of common modulation of firing rates (common drive) was assessed for a subset of MU pairs and was weaker in skill-trained subjects (0.30+/-0.04, n=14) than untrained (0.43+/-0.3, n=14) and strength-trained (0.48+/-0.03, n=21) subjects. Force tremor was quantified for each hand in the same subjects during isometric index finger abduction at target forces of 0.5 N and 3.5 N. Tremor rms amplitude and peak power in the force frequency spectrum were significantly lower in skill-trained subjects than strength-trained subjects with the 3.5-N target force. The peak tremor frequency was similar in the three groups. The relatively more independent discharge of pairs of FDI MUs in skill-trained subjects was not responsible for the reduced tremor amplitudes in these subjects. Correlations between the overall extent of MU synchrony and common drive in FDI muscles and tremor measures obtained during the same experimental session were all non-significant. Differences in the central descending command signals are the most likely explanation for the more independent discharge of FDI MUs in skill-trained hands, while neural or peripheral muscular factors may be responsible for the weaker tremor.
我们研究了五名音乐家（技能训练者）、五名举重运动员（力量训练者）和六名未训练受试者在食指低强度等长外展过程中，第一背侧骨间肌（FDI）的运动单位（MU）放电特性（平均峰间期、ISI、放电变异性、短期同步性、共同驱动）和力量震颤。技能训练受试者的平均MU ISI略短于未训练受试者。FDI运动单位的放电变异性在各组之间无显著差异。技能训练者（0.22±0.02 s⁻¹，162对运动单位）、未训练者（0.32±0.02 s⁻¹，199对运动单位）和力量训练受试者（0.44±0.03 s⁻¹，183对运动单位）的运动单位同步平均强度（以高于随机水平的额外同步放电频率表示）不同。技能训练受试者双手以及未训练受试者优势（熟练）手的FDI运动单位同步性较弱且强度相当。未训练受试者非优势手较强的FDI运动单位同步性与力量训练受试者双手的同步性相当。对一部分运动单位对的放电频率共同调制程度（共同驱动）进行了评估，结果显示技能训练受试者（0.30±0.04，n = 14）比未训练受试者（0.43±0.3，n = 14）和力量训练受试者（0.48±0.03，n = 21）弱。在目标力为0.5 N和3.5 N的等长食指外展过程中，对同一受试者的每只手的力量震颤进行了量化。在3.5 N目标力下，技能训练受试者的震颤均方根振幅和力量频谱中的峰值功率显著低于力量训练受试者。三组的震颤峰值频率相似。技能训练受试者中FDI运动单位对相对更独立的放电并非导致这些受试者震颤幅度降低的原因。在同一实验过程中获得的FDI肌肉运动单位同步性和共同驱动的总体程度与震颤测量值之间的相关性均不显著。中枢下行指令信号的差异最有可能解释技能训练的手部中FDI运动单位更独立的放电，而神经或外周肌肉因素可能是震颤较弱的原因。
