Bobbert M F, Harlaar J
Department of Functional Anatomy, Faculteit Bewegingswetenschappen, Vrije Universiteit, Amsterdam, The Netherlands.
Med Sci Sports Exerc. 1993 Feb;25(2):251-9.
The purpose of this study was to challenge the notion that the relationship of moment of force to angular velocity, determined in isokinetic knee extension tests, reflects the force-velocity relationship of human knee extensors. For this purpose, maximum-effort isometric knee extension moments were collected at seven different knee joint angles, and maximum-effort isokinetic knee extension moments were measured as a function of knee joint angle at angular velocities of 30, 60, 120, and 210 degrees.s-1. For the isokinetic contractions two protocols were used with a different threshold moment, i.e., the minimum knee extension moment that had to be reached isometrically before knee extension was initiated. In one protocol (LTM, for low threshold moment) the threshold was set at 5% of the maximum isometric knee extension moment produced at the starting angle of 85 degrees (180 degrees being full knee extension), in the second protocol (HTM, for high threshold moment) it was set at 95% of this isometric moment. During all contractions, electromyograms were recorded from m. vastus medialis, m. vastus lateralis, m. rectus femoris, and m. biceps femoris. The EMG signals were rectified and smoothed to yield SREMG. Two hypotheses were specifically tested. The first was that the threshold moment does not affect knee extension moments in the middle of the range of motion. Between knee angles of 100 degrees and 145 degrees, no differences were found between moments produced in the HTM protocol and those produced in the LTM protocol. Thus, the first hypothesis was supported. The second hypothesis was that subjects achieve the same level of muscle excitation at different speeds.(ABSTRACT TRUNCATED AT 250 WORDS)
在等速膝关节伸展测试中确定的力矩与角速度的关系反映了人类膝关节伸肌的力-速度关系。为此，在七个不同的膝关节角度收集了最大努力的等长膝关节伸展力矩，并在角速度为30、60、120和210度·秒⁻¹时测量了最大努力的等速膝关节伸展力矩作为膝关节角度的函数。对于等速收缩，使用了两种具有不同阈值力矩的方案，即膝关节伸展开始前必须等长达到的最小膝关节伸展力矩。在一种方案（低阈值力矩，LTM）中，阈值设定为在起始角度85度（全膝关节伸展为180度）产生的最大等长膝关节伸展力矩的5%，在第二种方案（高阈值力矩，HTM）中，阈值设定为该等长力矩的95%。在所有收缩过程中，记录了股内侧肌、股外侧肌、股直肌和股二头肌的肌电图。肌电信号经过整流和平滑以产生SREMG。具体测试了两个假设。第一个假设是阈值力矩不影响运动范围中间的膝关节伸展力矩。在膝关节角度100度至145度之间，HTM方案产生的力矩与LTM方案产生的力矩之间未发现差异。因此，第一个假设得到支持。第二个假设是受试者在不同速度下达到相同水平的肌肉兴奋。（摘要截至于250字）
