Ankle muscle co-contractions during quiet standing are associated with decreased postural steadiness in the elderly.

It has been reported that the elderly use co-contraction of the tibialis anterior (TA) and plantarflexor muscles for longer duration during quiet standing than the young. However, the particular role of ankle muscle co-contractions in the elderly during quiet standing remains unclear. Therefore, the objective of this study was to investigate the association between ankle muscle co-contractions and postural steadiness during standing in the elderly. Twenty-seven young (27.2±4.5yrs) and twenty-three elderly (66.2±5.0yrs) subjects were asked to stand quietly on a force plate for five trials. The center of pressure (COP) trajectory and its velocity (COPv) as well as the center of mass (COM) trajectory and its velocity (COMv) and acceleration (ACC) were calculated using the force plate outputs. Electromyograms were obtained from the right TA, soleus (SOL), and medial gastrocnemius (MG) muscles. Periods of TA activity (TAon) and inactivity (TAoff) were determined using an EMG threshold based on TA resting level. Our results indicate that, in the elderly, the COPv, COMv, and ACC variability were significantly larger during TAon periods compared to TAoff periods. However, in the young, no significant association between respective variability and TA activity was found. We conclude that ankle muscle co-contractions in the elderly are not associated with an increase, but a decrease in postural steadiness. Future studies are needed to clarify the causal relationship between (1) ankle muscle co-contractions and (2) joint stiffness and multi-segmental actions during standing as well as their changes with aging.

[1]  Noritaka Kawashima,et al.  Neuromusculoskeletal torque-generation process has a large destabilizing effect on the control mechanism of quiet standing. , 2008, Journal of neurophysiology.

[2]  M Hallett,et al.  Biomechanical assessment of quiet standing and changes associated with aging. , 1995, Archives of physical medicine and rehabilitation.

[3]  J. J. Collins,et al.  Age-related changes in open-loop and closed-loop postural control mechanisms , 2004, Experimental Brain Research.

[4]  William H Gage,et al.  Kinematic and kinetic validity of the inverted pendulum model in quiet standing. , 2004, Gait & posture.

[5]  Ian David Loram,et al.  Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius , 2005, The Journal of physiology.

[6]  Kelly P. Westlake,et al.  Sensory-Specific Balance Training in Older Adults: Effect on Position, Movement, and Velocity Sense at the Ankle , 2007, Physical Therapy.

[7]  J JOSEPH,et al.  A detailed study of the electric potentials recorded over some postural muscles while relaxed and standing , 1955, The Journal of physiology.

[8]  B. E. Maki,et al.  A prospective study of postural balance and risk of falling in an ambulatory and independent elderly population. , 1994, Journal of gerontology.

[9]  Jacques Duysens,et al.  Differences in foot sensitivity and plantar pressure between young adults and elderly. , 2016, Archives of gerontology and geriatrics.

[10]  D. Winter,et al.  Stiffness control of balance in quiet standing. , 1998, Journal of neurophysiology.

[11]  Motoki Kouzaki,et al.  Importance of body sway velocity information in controlling ankle extensor activities during quiet stance. , 2003, Journal of neurophysiology.

[12]  T.E. Prieto,et al.  Measures of postural steadiness: differences between healthy young and elderly adults , 1996, IEEE Transactions on Biomedical Engineering.

[13]  Kimitaka Nakazawa,et al.  Anti-phase action between the angular accelerations of trunk and leg is reduced in the elderly. , 2014, Gait & posture.

[14]  N. Benjuya,et al.  Aging-induced shifts from a reliance on sensory input to muscle cocontraction during balanced standing. , 2004, The journals of gerontology. Series A, Biological sciences and medical sciences.

[15]  Pertti Era,et al.  Force Platform Measurements as Predictors of Falls among Older People – A Review , 2006, Gerontology.

[16]  V. Zatsiorsky,et al.  An algorithm for determining gravity line location from posturographic recordings. , 1997, Journal of biomechanics.

[17]  P. Haavisto,et al.  Postural Balance in a Random Sample of 7,979 Subjects Aged 30 Years and Over , 2006, Gerontology.

[18]  G. Fuller,et al.  Falls in the elderly. , 2000, American family physician.

[19]  Kimitaka Nakazawa,et al.  Reciprocal angular acceleration of the ankle and hip joints during quiet standing in humans , 2001, Experimental Brain Research.

[20]  N Accornero,et al.  Clinical multisegmental posturography: age-related changes in stance control. , 1997, Electroencephalography and clinical neurophysiology.

[21]  Constantinos N Maganaris,et al.  Active, non‐spring‐like muscle movements in human postural sway: how might paradoxical changes in muscle length be produced? , 2005, The Journal of physiology.

[22]  Mark G. Carpenter,et al.  The influence of postural threat on the control of upright stance , 2001, Experimental Brain Research.

[23]  Andrew C Laing,et al.  The influence of ankle muscle activation on postural sway during quiet stance. , 2014, Gait & posture.

[24]  David A. Winter,et al.  Biomechanics and Motor Control of Human Movement , 1990 .

[25]  Noritaka Kawashima,et al.  Evaluation of postural control in quiet standing using center of mass acceleration: comparison among the young, the elderly, and people with stroke. , 2008, Archives of physical medicine and rehabilitation.

[26]  Vladimir M. Zatsiorsky,et al.  On the fractal properties of natural human standing , 2000, Neuroscience Letters.

[27]  Lee Nolan,et al.  Aging, muscle activity, and balance control: physiologic changes associated with balance impairment. , 2003, Gait & posture.

[28]  Motoki Kouzaki,et al.  Larger center of pressure minus center of gravity in the elderly induces larger body acceleration during quiet standing , 2007, Neuroscience Letters.

[29]  Age-related differences in the effect of a perceived threat to stability on postural control. , 2006, The journals of gerontology. Series A, Biological sciences and medical sciences.

[30]  T. Sinkjaer,et al.  Muscle stiffness in human ankle dorsiflexors: intrinsic and reflex components. , 1988, Journal of neurophysiology.

[31]  R. Kearney,et al.  Intrinsic and reflex contributions to human ankle stiffness: variation with activation level and position , 2000, Experimental Brain Research.

[32]  J. Cholewicki,et al.  Effects of external trunk loads on lumbar spine stability. , 2000, Journal of biomechanics.

[33]  J. A. Barela,et al.  Diferenças sensoriais e motoras entre jovens e idosos: contribuição somatossensorial no controle postural , 2010 .

[34]  M. Popovic,et al.  Smaller sway size during quiet standing is associated with longer preceding time of motor command to body sway. , 2011, Gait & posture.