Document Detail

Modeling of postural stability borders during heel-toe rocking.
MedLine Citation:
PMID:  19427219     Owner:  NLM     Status:  MEDLINE    
To maintain balance during movements such as bending and reaching, the CNS must generate muscle forces to counteract destabilizing torques produced by gravitational (position-dependent) and inertial (acceleration-dependent) forces. This may create a trade-off between the attainable frequency and amplitude of movements. We used experiments and mathematical modeling to examine this relationship during the task of heel-toe rocking. During the experiments, participants (n=15) rocked about the ankles in the sagittal plane with maximum attainable amplitude at a frequency of 0.33 Hz or 0.66 Hz. As the frequency doubled, the maximum anterior position of the whole-body centre-of-gravity (COG) with respect to the ankle decreased by 11% of foot length (from 11.9 cm (S.D. 1.6) to 9.2 cm (S.D. 1.2); p<0.001), the minimum anterior position of the COG increased by 8% of foot length (from 1.6 cm to 3.5 cm in front on the ankle; p<0.0005), and the ankle stiffness increased from 787 Nm/rad (S.D. 156) to 1625 Nm/rad (S.D. 339). However, there was no difference between conditions in the maximum anterior position of the COP (p=0.51), the minimum anterior position of the COP (p=0.23), or the peak ankle torque (p=0.39). An inverted pendulum model driven by a rotational spring predicted the measured ankle stiffness to within 0.9% (S.D. 6.8), and the maximum anterior COG position to within 1.2% (S.D. 4.0). These results indicate that COG amplitude decreases with increasing rocking frequency, due to (a) invariability in peak ankle torque and (b) the need to allocate torque between gravitational and inertial components, the latter of which scales with the square of frequency.
Chantelle D Murnaghan; Beth Elston; Dawn C Mackey; Stephen N Robinovitch
Related Documents :
21788179 - An ssvep ¿ based bci using high duty-cycle visual flicker.
22332779 - Differential effects of moderate alcohol consumption on motion and contrast processing.
11029819 - Motion pattern and posture: correctly assessed by calibrated accelerometers.
8472079 - Effect of the aircast on unilateral postural control: amplitude and frequency variables.
15473199 - Detecting postural responses to sinusoidal sensory inputs: a statistical approach.
21288249 - Magnetic field protects plants against high light by slowing down production of singlet...
3566909 - A microprocessor system for the digital synthesis of pulsed and continuous discharges o...
15916809 - Miniature telemetry system for the recording of action and field potentials.
1402869 - Photoperiod and the relationship between wing length and body weight in anopheles quadr...
Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2009-05-07
Journal Detail:
Title:  Gait & posture     Volume:  30     ISSN:  1879-2219     ISO Abbreviation:  Gait Posture     Publication Date:  2009 Aug 
Date Detail:
Created Date:  2009-07-03     Completed Date:  2009-09-24     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9416830     Medline TA:  Gait Posture     Country:  England    
Other Details:
Languages:  eng     Pagination:  161-7     Citation Subset:  IM    
Injury Prevention and Mobility Laboratory, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Ankle / physiology
Foot / physiology*
Models, Biological
Movement / physiology*
Postural Balance / physiology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Nutritional support in the treatment and prevention of pressure ulcers: An overview of studies with ...
Next Document:  Dural metastasis from prostatic adenocarcinoma mimicking chronic subdural hematoma.