Aging, muscle activity, and balance control: physiologic changes associated with balance impairment.

Older adults demonstrate increased amounts of postural sway, which may ultimately lead to falls. The mechanisms contributing to age-related increases in postural sway and falls in the elderly remain unclear. In an effort to understand age-related changes in posture control, we assessed foot center-of-pressure (COP) displacements and electromyographic data from the tibialis anterior, soleus, vastus lateralis, and biceps femoris collected simultaneously during quiet-standing trials from elderly fallers, elderly non-fallers, and healthy young subjects. Both traditional measures of COP displacements and stabilogram-diffusion analysis were used to characterize the postural sway of each group. Regression analyses were used to assess the relationship between the COP measures and muscle activity. Elderly fallers demonstrated significantly greater amounts of sway in the anteroposterior (AP) direction and greater muscle activity during quiet standing compared with the young subjects, while elderly non-fallers demonstrated significantly greater muscle activation and co-activation compared with the young subjects. No significant differences were found between elderly fallers and elderly non-fallers in measures of postural sway or muscle activity. However, greater postural sway in both the AP and mediolateral (ML) directions and trends of greater muscle activity were found in those older adults who demonstrated lower scores on clinical measures of balance. In addition, short-term postural sway was found to be significantly correlated with muscle activity in each of these groups. This work suggests that high levels of muscle activity are a characteristic of age-related declines in postural stability and that such activity is correlated with short-term postural sway. It is unclear whether increases in muscle activity preclude greater postural instability or if increased muscle activity is a compensatory response to increases in postural sway.

[1]  C. Derouesné.  [Mini-mental state examination]. , 2001, Revue neurologique.

[2]  R. Baloh,et al.  Comparison of Static and Dynamic Posturography in Young and Older Normal People , 1994, Journal of the American Geriatrics Society.

[3]  E. Heikkinen,et al.  Postural sway during standing and unexpected disturbance of balance in random samples of men of different ages. , 1985, Journal of gerontology.

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

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

[6]  P. Holliday,et al.  The relationship of postural sway in standing to the incidence of falls in geriatric subjects. , 1982, Age and ageing.

[7]  Silvano Mior,et al.  Muscle Testing, Techniques of Manual Examination , 1985 .

[8]  Robert J. Peterka,et al.  Postural control model interpretation of stabilogram diffusion analysis , 2000, Biological Cybernetics.

[9]  C. D. De Luca,et al.  Control scheme governing concurrently active human motor units during voluntary contractions , 1982, The Journal of physiology.

[10]  Frank Moss,et al.  Noise in human muscle spindles , 1996, Nature.

[11]  R. Enoka,et al.  Reduced control of motor output in a human hand muscle of elderly subjects during submaximal contractions. , 1993, Journal of neurophysiology.

[12]  S. Sepic,et al.  Strength of isometric and isokinetic contractions: knee muscles of men aged 20 to 86. , 1980, Physical therapy.

[13]  L. Dorfman,et al.  Age‐related changes in peripheral and central nerve conduction in man , 1979, Neurology.

[14]  C. J. Luca,et al.  Open-loop and closed-loop postural control mechanisms in Parkinson's disease: increased mediolateral activity during quiet standing , 1995, Neuroscience Letters.

[15]  J. Wolfowitz,et al.  An Exact Test for Randomness in the Non-Parametric Case Based on Serial Correlation , 1943 .

[16]  M. Woollacott,et al.  Visual, vestibular and somatosensory contributions to balance control in the older adult. , 1989, Journal of gerontology.

[17]  M. Tinetti.  Performance‐Oriented Assessment of Mobility Problems in Elderly Patients , 1986, Journal of the American Geriatrics Society.

[18]  Luci Daniels,et al.  Muscle testing; techniques of manual examination , 1986 .

[19]  B R Hasselkus,et al.  Aging and postural sway in women. , 1975, Journal of gerontology.

[20]  Dennis R. Whitlow,et al.  MUSCLE TESTING: TECHNIQUES OF MANUAL EXAMINATION , 1974 .

[21]  Falls, motor dysfunction, and correlative neurohistologic changes in the elderly. , 1985, Clinics in geriatric medicine.

[22]  J. Collins,et al.  Upright, correlated random walks: A statistical-biomechanics approach to the human postural control system. , 1995, Chaos.

[23]  D. Newman,et al.  Closed-loop, estimator-based model of human posture following reduced gravity exposure. , 1996, Journal of guidance, control, and dynamics : a publication of the American Institute of Aeronautics and Astronautics devoted to the technology of dynamics and control.

[24]  J. Collins,et al.  Open-loop and closed-loop control of posture: A random-walk analysis of center-of-pressure trajectories , 2004, Experimental Brain Research.

[25]  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.

[26]  V. Vardaxis,et al.  Regulation of motor output between young and elderly subjects , 2001, Clinical Neurophysiology.

[27]  G. C. Joyce,et al.  The effects of load and force on tremor at the normal human elbow joint , 1974, The Journal of physiology.

[28]  J. Gijn.  The Babinski sign: The first hundred years , 1996, Journal of Neurology.

[29]  M. Hurley,et al.  Quadriceps function, proprioceptive acuity and functional performance in healthy young, middle-aged and elderly subjects. , 1998, Age and ageing.