Arampatzis Adamantios, Mademli Lida, De Monte Gianpiero, Walsh Mark
German Sport University of Cologne, Institute of Biomechanics and Orthopaedics, Carl-Diem-Weg 6, 50933 Cologne, Germany.
J Biomech. 2007;40(14):3193-200. doi: 10.1016/j.jbiomech.2007.04.011. Epub 2007 Jun 27.
The purpose of this study was to investigate the effect of the differences between the actual fascicle length during a voluntary contraction and the fascicle length at rest of the triceps surae muscle on the determination of the voluntary activation (VA) by using the interpolated twitch technique. Twelve participants performed isometric voluntary maximal (MVC) and submaximal (20%, 40%, 60% and 80% MVC) contractions at two different ankle angles (75 degrees and 90 degrees ) under application of the interpolated twitch technique. Two ultrasound probes were used to determine the fascicle length of soleus, gastrocnemius medialis and gastrocnemius lateralis muscles. Further, the MVCs and the twitches were repeated for six more ankle angles (85 degrees , 95 degrees , 100 degrees , 105 degrees , 110 degrees and 115 degrees ). The VA of the triceps surae muscle were calculated (a) using the rest twitch force (RTF) measured during the same trial as the interpolated twitch force (ITF; traditional method) and (b) using the RTF at an ankle angle where the fascicle length showed similar values between ITF and RTF (fascicle length consideration method). The continuous changes in fascicle length from rest to MVC affect the accuracy of the assessment of the VA. The traditional method overestimates the assessment of the VA on average 4% to 12%, especially at 90 degrees ankle angle (i.e. short muscle length). The reason for this influence is the unequal force-length potential of the muscle at twitch application by the measure of ITF and RTF. These findings provide evidence that the fascicle length consideration method permits a more precise prediction (an improvement of 4-12%) of the voluntary contraction compared to the traditional method.
本研究的目的是通过使用内插单收缩技术，探讨比目鱼肌在自主收缩期间的实际肌束长度与静息时肌束长度的差异对自主激活（VA）测定的影响。12名受试者在应用内插单收缩技术的情况下，于两个不同的踝关节角度（75度和90度）进行等长自主最大收缩（MVC）和次最大收缩（20%、40%、60%和80%MVC）。使用两个超声探头测定比目鱼肌、腓肠肌内侧头和腓肠肌外侧头的肌束长度。此外，在另外六个踝关节角度（85度、95度、100度、105度、110度和115度）重复进行MVC和单收缩。比目鱼肌的VA通过以下两种方法计算：（a）使用与内插单收缩力（ITF；传统方法）在同一次试验中测量的静息单收缩力（RTF）；（b）使用在肌束长度在ITF和RTF之间显示相似值的踝关节角度处的RTF（肌束长度考虑法）。从静息到MVC期间肌束长度的持续变化会影响VA评估的准确性。传统方法平均高估VA评估4%至12%，尤其是在踝关节角度为90度时（即肌肉长度较短时）。这种影响的原因是通过测量ITF和RTF在施加单收缩时肌肉的力-长度潜力不相等。这些发现提供了证据，表明与传统方法相比，肌束长度考虑法能够更精确地预测自主收缩（提高4-12%）。
