Bampouras Theodoros M, Reeves Neil D, Baltzopoulos Vasilios, Maganaris Constantinos N
Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Alsager, United Kingdom.
Muscle Nerve. 2006 Dec;34(6):740-6. doi: 10.1002/mus.20610.
Activation capacity has traditionally been assessed using the interpolated twitch technique (ITT) and central activation ratio (CAR). However, the quantitative agreement of the two methods and the physiological mechanisms underpinning any possible differences have not been fully elucidated. The aim of this study was to compare and assess the sensitivity of the ITT and CAR to potential errors introduced by (1) evoking inadequate force, by manipulating the number of stimuli, and (2) neglecting differences in series elasticity between conditions, by manipulating joint angle. Ten subjects performed knee extension contractions at 30 degrees and 90 degrees knee-joint angles during which the ITT and CAR methods were applied using 1, 2, 4, and 8 electrical stimuli. Joint angle influenced the ITT outcome with higher values taken at 90 degrees (P < 0.05), while the number of stimuli influenced the CAR outcome with a higher number of stimuli yielding lower values (P < 0.05). For any given joint angle and stimulus number, the CAR method produced higher activation values than the ITT method by 8%-16%. Therefore, in the quantification of voluntary drive with the ITT and CAR methods consideration should be given not only to the number of stimuli applied but also to the effect of series elasticity due to joint-angle differences, since these factors may differently affect the outcome of the calculation, depending on the approach followed.
传统上，激活能力是通过内插单收缩技术（ITT）和中枢激活率（CAR）来评估的。然而，这两种方法的定量一致性以及支撑任何可能差异的生理机制尚未完全阐明。本研究的目的是比较和评估ITT和CAR对以下因素引入的潜在误差的敏感性：（1）通过操纵刺激次数诱发力量不足；（2）通过操纵关节角度忽略不同条件下串联弹性的差异。10名受试者在膝关节角度为30度和90度时进行膝关节伸展收缩，在此期间使用1、2、4和8次电刺激应用ITT和CAR方法。关节角度影响ITT结果，90度时的值更高（P < 0.05），而刺激次数影响CAR结果，刺激次数越多值越低（P < 0.05）。对于任何给定的关节角度和刺激次数，CAR方法产生的激活值比ITT方法高8%-16%。因此，在用ITT和CAR方法量化自主驱动时，不仅应考虑所施加的刺激次数，还应考虑由于关节角度差异导致的串联弹性的影响，因为这些因素可能会根据所采用的方法不同地影响计算结果。
