Another result indirectly indicating the possibility of noninvasive fiber typing derives from the experiments of Merletti et al. and Hara et al. who demonstrated that, when isometric force level increases from low (20–50% MVC) to high (80–100% MVC) values, an increment of CV and MDF or MNF is observed. This increment is higher in younger subjects and lower in elderly subjects in agreement with bioptic findings indicating a progressive decrement of size or number of type II fibers with age. In addition, the rate of decrement of CV during a sustained contraction is higher in young subjects providing evidence which further supports this hypothesis .
间接表明非侵入性纤维分型的可能性的另一个结果来自Merletti等人的实验。和Hara等。他们证明了,当等轴测力水平从低(20-50%MVC)增大到高(80-100%MVC)值时,会观察到CV和MDF或MNF的增加。与活检结果一致,该增加在年轻受试者中较高,而在老年受试者中较低,这表明随着年龄的增长,II型纤维的大小或数量逐渐减少。此外,年轻受试者在持续收缩过程中CV的降低率较高,这提供了进一步支持这一假设的证据。
图6 在30 pps刺激相应神经时,从三只大鼠肌肉的神经肌肉制剂中体外获得的中值频率(MDF)的标准化值(八只大鼠的测量值的平均值和标准偏差)。请注意,与不同类型的纤维类型(按面积计)有关的不同的递减率。对于传导速度观察到相似的结果。经许可从Kupa等人重画