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: 99/2/570    most recent 00198.2005v1 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 (7) Citing Articles via Google Scholar Google Scholar Articles by Mork, P. J. Articles by Westgaard, R. H. Search for Related Content PubMed PubMed Citation Articles by Mork, P. J. Articles by Westgaard, R. H.

Long-term electromyographic activity in upper trapezius and low back muscles of women with moderate physical activity

Norwegian University of Science and Technology, Norwegian University of Science and Technology, Trondheim, Norway

Submitted 17 February 2005 ; accepted in final form 1 April 2005

The habitual activity patterns of trapezius and postural back muscles (multifidus, iliocostalis, longissimus) of 23 female subjects with moderate physical activity were studied. Bilateral surface electromyographic (sEMG) recordings from start of work until bedtime were analyzed. The activity level was calibrated as percentage of root mean square-detected muscle activity at maximal voluntary contraction (EMG_max). Sixty-six previous trapezius recordings of women with moderate physical activity were included in some analyses to pursue the full range of variation in trapezius activity. Twenty-six of these were recorded twice, separated by 16–28 mo. Median activity level and duration of periods with sEMG activity of <0.5% EMG_max ("rest time"; only trapezius) and exceeding 2 ("burst time"), 10, 30, and 50% EMG_max was determined. The trapezius median activity level ranged from 0.6 to 8.8% EMG_max, burst time from 9 to 84%, and rest time from 2 to 84%. The activity patterns of the back muscles showed similar large interindividual variation. Repeated trapezius recordings of the same subject showed high consistency; intraclass correlation coefficients ranged from 0.62 to 0.79 for different sEMG variables. Periods with high sEMG amplitude were of short duration; 7% of the trapezius recordings did not present time intervals (0.2-s duration) above 50% EMG_max. The activity patterns of the postural muscles, despite large interindividual variability, were distinctly different from activity patterns of upper and lower limb muscles reported by others (e.g., mean burst time 40–50 vs. 10–20%). We conclude that postural trunk muscles show idiosyncratic activity patterns with large interindividual variation. High-threshold motor units are activated to a very minor extent.

postural muscles; habitual muscle activity; long-term recording

This article has been cited by other articles:

				T. Grunheid, G.E.J. Langenbach, A. Zentner, and T.M.G.J. Van Eijden Duty Time of Rabbit Jaw Muscles Varies with the Number of Activity Bursts. J. Dent. Res., December 1, 2006; 85(12): 1112 - 1117. [Abstract] [Full Text] [PDF]

				P. J. Mork and R. H. Westgaard Low-amplitude trapezius activity in work and leisure and the relation to shoulder and neck pain J Appl Physiol, April 1, 2006; 100(4): 1142 - 1149. [Abstract] [Full Text] [PDF]