| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands
2 Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands; Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Cheshire, United Kingdom
* To whom correspondence should be addressed. E-mail: C_J_DE_RUITER{at}FBW.VU.NL.
We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60 and 90° knee angle. Experiments were performed in subjects (n=7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions (MVCs). During maximal electrical nerve stimulation (8 pulses at 300 Hz) the maximal rate of torque development (MRTD) and torque-time-integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60°). At each knee angle voluntary MRTD and stimulated MRTD were similar (P<0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent (p>0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects the averaged (across knee angles) values ranged from 10.3 ± 3.1 % to 83.3 ± 3.2 %, and were positively related (r2=0.75, p<0.05) to the knee extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of MVC, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.
This article has been cited by other articles:
|
|
 |
|
  A. de Haan, K. H. L. Gerrits, and C. J. de Ruiter Counterpoint: The interpolated twitch does not provide a valid measure of the voluntary activation of muscle J Appl Physiol, July 1, 2009; 107(1): 355 - 357. [Full Text] [PDF]
|
|
|
|
|
|
A. M. Horstman, R. M. Enoka, O. Girard, N. Babault, W. Herzog, S. Racinais, O. Girard, J. Duchateau, D. G. Behm, J. Lexell, et al. Maximal rate of force development can represent a more functional measure of muscle activation. J Appl Physiol, July 1, 2009; 107(1): 359 - 360. [Full Text] [PDF]
|
|
|
|
|
|
A. de Haan, K. H. L. Gerrits, and C. J. de Ruiter Last Word on Point:Counterpoint: The interpolated twitch does/does not provide a valid measure of the voluntary activation of muscle J Appl Physiol, July 1, 2009; 107(1): 368 - 368. [Full Text] [PDF]
|
|
|
|
|
|
T. M. Altenburg, A. de Haan, P. W. L. Verdijk, W. van Mechelen, and C. J. de Ruiter Vastus lateralis single motor unit EMG at the same absolute torque production at different knee angles J Appl Physiol, July 1, 2009; 107(1): 80 - 89. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Spanjaard, N. D. Reeves, J. H. van Dieen, V. Baltzopoulos, and C. N. Maganaris Gastrocnemius muscle fascicle behavior during stair negotiation in humans J Appl Physiol, April 1, 2007; 102(4): 1618 - 1623. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. J. de Ruiter, M. D. de Boer, M. Spanjaard, and A. de Haan Knee angle-dependent oxygen consumption during isometric contractions of the knee extensors determined with near-infrared spectroscopy J Appl Physiol, August 1, 2005; 99(2): 579 - 586. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
