| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Applied Physiology Research Group, School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK
2 Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Alsager ST7 2HL, UK
It has been widely assumed for nearly a century, that postural muscles operate in a spring-like manner and that muscle length signals joint angle (the mechano-reflex mechanism). Here we employ automated analysis of ultrasound images to resolve calf muscle (soleus and gastrocnemius) length changes as small as 10 µm in standing subjects. Previously, we have used balancing of a real inverted pendulum to make predictions about human standing. Here we test and confirm these predictions on 10 subjects standing quietly. We show that on average the calf muscles are actively adjusted 2.6 times per second and 2.8 times per unidirectional sway of the body centre of mass (CoM). These alternating, small (30–300 µm) movements provide impulsive, ballistic regulation of CoM movement. The timing and pattern of these adjustments are consistent with multisensory integration of all information regarding motion of the CoM, pattern recognition, prediction and planning using internal models and are not consistent with control solely by local reflexes. Because the system is unstable, errors in stabilization provide a perturbation which grows into a sway which has to be reacted to and corrected. Sagittal sway results from this impulsive control of calf muscle activity rather than internal sources (e.g. the heart, breathing). This process is quite unlike the mechano-reflex paradigm. We suggest that standing is a skilled, trial and error activity that improves with experience and is automated (possibly by the cerebellum). These results complement and extend our recent demonstration that paradoxical muscle movements are the norm in human standing.
(Received 28 September 2004;
accepted after revision 15 January 2005;
first published online 20 January 2005)
Corresponding author I. Loram: Applied Physiology Research Group, School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK. Email: i.d.loram{at}bham.ac.uk
This article has been cited by other articles:
|
|
 |
|
  C. D. Tokuno, S. J. Garland, M. G. Carpenter, A. Thorstensson, and A. G. Cresswell Sway-dependent modulation of the triceps surae H-reflex during standing J Appl Physiol, May 1, 2008; 104(5): 1359 - 1365. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Z. Z. Chew, S. C. Gandevia, and R. C. Fitzpatrick Postural control at the human wrist J. Physiol., March 1, 2008; 586(5): 1265 - 1275. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. P. Magnusson, M. V. Narici, C. N. Maganaris, and M. Kjaer Human tendon behaviour and adaptation, in vivo J. Physiol., January 1, 2008; 586(1): 71 - 81. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. D. Loram, C. N. Maganaris, and M. Lakie The passive, human calf muscles in relation to standing: the non-linear decrease from short range to long range stiffness J. Physiol., October 15, 2007; 584(2): 661 - 675. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. D. Loram, C. N. Maganaris, and M. Lakie The passive, human calf muscles in relation to standing: the short range stiffness lies in the contractile component J. Physiol., October 15, 2007; 584(2): 677 - 692. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. van der Kooij and E. de Vlugt Postural Responses Evoked by Platform Pertubations Are Dominated by Continuous Feedback J Neurophysiol, August 1, 2007; 98(2): 730 - 743. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Guigon, P. Baraduc, and M. Desmurget Computational Motor Control: Redundancy and Invariance J Neurophysiol, January 1, 2007; 97(1): 331 - 347. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Lakie and I. D. Loram Manually controlled human balancing using visual, vestibular and proprioceptive senses involves a common, low frequency neural process J. Physiol., November 15, 2006; 577(1): 403 - 416. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. D. Loram, P. J. Gawthrop, and M. Lakie The frequency of human, manual adjustments in balancing an inverted pendulum is constrained by intrinsic physiological factors J. Physiol., November 15, 2006; 577(1): 417 - 432. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. L. Onambele, M. V. Narici, and C. N. Maganaris Calf muscle-tendon properties and postural balance in old age J Appl Physiol, June 1, 2006; 100(6): 2048 - 2056. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. D. Loram, C. N. Maganaris, and M. Lakie Use of ultrasound to make noninvasive in vivo measurement of continuous changes in human muscle contractile length J Appl Physiol, April 1, 2006; 100(4): 1311 - 1323. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. van der Kooij and F. C. T. van der Helm Observations from unperturbed closed loop systems cannot indicate causality J. Physiol., December 1, 2005; 569(2): 705 - 705. [Full Text] [PDF]
|
|
|
|
|
|
I. D. Loram, M. Lakie, and C. N. Maganaris Reply from Ian D. Loram, Constantinos N. Maganaris and Martin Lakie J. Physiol., December 1, 2005; 569(2): 706 - 706. [Full Text] [PDF]
|
|
|
|
|
|
R. C Fitzpatrick and S. C Gandevia Paradoxical muscle contractions and the neural control of movement and balance J. Physiol., April 1, 2005; 564(1): 2 - 2. [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
