HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 91/1/172    most recent 00613.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (16) Citing Articles via Google Scholar Google Scholar Articles by Sosnoff, J. J. Articles by Newell, K. M. Search for Related Content PubMed PubMed Citation Articles by Sosnoff, J. J. Articles by Newell, K. M.

Aging and Rhythmical Force Output: Loss of Adaptive Control of Multiple Neural Oscillators

¹ Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania 16802; ² The Gerontology Center, The Pennsylvania State University, University Park, Pennsylvania 16802; ³ Department of Movement Sciences, University of Illinois at Chicago, Chicago, Illinois 60608; ⁴ Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois 60608

Submitted 27 June 2003; accepted in final form 18 September 2003

The current study examined the influence of aging on the oscillatory activity of a population of motor units during rhythmical force production. Previously, it has been shown that aging humans have greater low-frequency and less high-frequency electromyographic (EMG) activity during constant and slow ramp force contractions. We hypothesized that more rapid force contractions would reverse the established finding of reduced high- and greater low-frequency EMG activity to greater high- and reduced low-frequency EMG activity in older adults. Intramuscular EMG activity and effector force were recorded while 45 human subjects (20–31 and 60–88 yr of age) rhythmically produced force at four distinct frequencies (1–4 Hz) and two force levels (5 and 25% maximal voluntary contraction). Spectral and coherence analyses were performed on the force output and EMG activity. In the 3- and 4-Hz targets, the older adults had greater 35- to 50-Hz and reduced 0- to 5-Hz EMG activity compared with the young adults. There was greater EMG-force coherence in the 0- to 5-Hz bandwidth for the young subjects. No systematic age difference in the phase relationship between the EMG and force signals were found. Higher frequency force contractions reversed the previously established aging differences in the relative contribution of low- and high-frequency EMG activity. Thus the frequency properties of the task goals channel the relative contribution of low and high EMG activity. Furthermore, it is proposed that aging humans lose the adaptive capability to coordinate the excitatory and inhibitory activity of multiple neural oscillators.

This article has been cited by other articles:

				E. A. Christou, B. Poston, J. A. Enoka, and R. M. Enoka Different Neural Adjustments Improve Endpoint Accuracy With Practice in Young and Old Adults J Neurophysiol, May 1, 2007; 97(5): 3340 - 3350. [Abstract] [Full Text] [PDF]

				M. V. Sale and J. G. Semmler Age-related differences in corticospinal control during functional isometric contractions in left and right hands J Appl Physiol, October 1, 2005; 99(4): 1483 - 1493. [Abstract] [Full Text] [PDF]

				M. M. Sturman, D. E. Vaillancourt, and D. M. Corcos Effects of Aging on the Regularity of Physiological Tremor J Neurophysiol, June 1, 2005; 93(6): 3064 - 3074. [Abstract] [Full Text] [PDF]

				J. G. Semmler, M. V. Sale, F. G. Meyer, and M. A. Nordstrom Motor-Unit Coherence and Its Relation With Synchrony Are Influenced by Training J Neurophysiol, December 1, 2004; 92(6): 3320 - 3331. [Abstract] [Full Text] [PDF]