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

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 98/6/2072    most recent 01149.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted 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 (26) Citing Articles via Google Scholar Google Scholar Articles by Kornatz, K. W. Articles by Enoka, R. M. Search for Related Content PubMed PubMed Citation Articles by Kornatz, K. W. Articles by Enoka, R. M.

Practice reduces motor unit discharge variability in a hand muscle and improves manual dexterity in old adults

Department of Integrative Physiology, University of Colorado, Boulder, Colorado

Submitted 12 October 2004 ; accepted in final form 28 January 2005

A steadiness-improving intervention was used to determine the contribution of variability in motor unit discharge rate to the fluctuations in index finger acceleration and manual dexterity in older adults. Ten healthy and sedentary old adults (age 72.9 ± 5.8 yr; 5 men) participated in the study involving abduction of the left index finger. Single motor unit activity was recorded in the first dorsal interosseus muscle before, after 2 wk of light-load training (10% maximal load), and after 4 wk of heavy-load training (70% maximal load). As expected, the light-load training was effective in reducing the fluctuations in index finger acceleration during slow shortening (0.25 ± 0.12 to 0.13 ± 0.08 m/s²) and lengthening contractions (0.29 ± 0.10 to 0.14 ± 0.06 m/s²). Along with the decline in the magnitude of the fluctuations, there was a parallel decrease in the coefficient of variation for discharge rate during both contraction types (33.8 ± 6.8 to 25.0 ± 5.9%). The heavy-load training did not further improve either the fluctuations in acceleration or discharge rate variability. Furthermore, the manual dexterity of the left hand improved significantly with training (Purdue pegboard test: 11 ± 3 to 14 ± 1 pegs). Bivariate correlations indicated that the reduction in fluctuations in motor output during shortening (r² = 0.24) and lengthening (r² = 0.14) contractions and improvement in manual dexterity (r² = 0.26) was directly associated with a decline in motor unit discharge rate variability. There was a strong association between the fluctuations in motor output and manual dexterity (r² = 0.56). These results indicate that practice of a simple finger task was accompanied by a reduction in the discharge rate variability of motor units, a decrease in the fluctuations in motor output of a hand muscle, and an improvement in the manual dexterity of older adults.

contraction type; first dorsal interosseus; manual dexterity; steadiness; strength training

This article has been cited by other articles:

				H. B. Olafsdottir, V. M. Zatsiorsky, and M. L. Latash The effects of strength training on finger strength and hand dexterity in healthy elderly individuals J Appl Physiol, October 1, 2008; 105(4): 1166 - 1178. [Abstract] [Full Text] [PDF]

				T. Manini, M. Marko, T. VanArnam, S. Cook, B. Fernhall, J. Burke, and L. Ploutz-Snyder Efficacy of Resistance and Task-Specific Exercise in Older Adults Who Modify Tasks of Everyday Life J. Gerontol. A Biol. Sci. Med. Sci., June 1, 2007; 62(6): 616 - 623. [Abstract] [Full Text] [PDF]

				B. K. Barry, M. A. Pascoe, M. Jesunathadas, and R. M. Enoka Rate Coding Is Compressed But Variability Is Unaltered for Motor Units in a Hand Muscle of Old Adults J Neurophysiol, May 1, 2007; 97(5): 3206 - 3218. [Abstract] [Full Text] [PDF]

				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]

				C. A. Knight and G. Kamen Modulation of motor unit firing rates during a complex sinusoidal force task in young and older adults J Appl Physiol, January 1, 2007; 102(1): 122 - 129. [Abstract] [Full Text] [PDF]

				J. Duchateau, J. G. Semmler, and R. M. Enoka Training adaptations in the behavior of human motor units J Appl Physiol, December 1, 2006; 101(6): 1766 - 1775. [Abstract] [Full Text] [PDF]

				J. J. Sosnoff and K. M. Newell Aging, visual intermittency, and variability in isometric force output. J. Gerontol. B. Psychol. Sci. Soc. Sci., March 1, 2006; 61(2): P117 - P124. [Abstract] [Full Text] [PDF]

				M. Shinohara, C. T. Moritz, M. A. Pascoe, and R. M. Enoka Prolonged muscle vibration increases stretch reflex amplitude, motor unit discharge rate, and force fluctuations in a hand muscle J Appl Physiol, November 1, 2005; 99(5): 1835 - 1842. [Abstract] [Full Text] [PDF]

				C. J. Mottram, E. A. Christou, F. G. Meyer, and R. M. Enoka Frequency Modulation of Motor Unit Discharge Has Task-Dependent Effects on Fluctuations in Motor Output J Neurophysiol, October 1, 2005; 94(4): 2878 - 2887. [Abstract] [Full Text] [PDF]