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: 101/4/1036    most recent 00103.2006v1 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 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 Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Hunter, S. K. Articles by Taylor, J. L. Search for Related Content PubMed PubMed Citation Articles by Hunter, S. K. Articles by Taylor, J. L.

Supraspinal fatigue does not explain the sex difference in muscle fatigue of maximal contractions

¹Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin; ²Prince of Wales Medical Research Institute, Sydney; and ³Discipline of Physiology, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia

Submitted 26 January 2006 ; accepted in final form 17 May 2006

Young women are less fatigable than young men for maximal and submaximal contractions, but the contribution of supraspinal fatigue to the sex difference is not known. This study used cortical stimulation to compare the magnitude of supraspinal fatigue during sustained isometric maximal voluntary contractions (MVCs) performed with the elbow flexor muscles of young men and women. Eight women (25.6 ± 3.6 yr, mean ± SD) and 9 men (25.4 ± 3.8 yr) performed six sustained MVCs (22-s duration each, separated by 10 s). Before the fatiguing contractions, the men were stronger than the women (75.9 ± 9.2 vs. 42.7 ± 8.0 N·m; P < 0.05) in control MVCs. Voluntary activation measured with cortical stimulation before fatigue was similar for the men and women during the final control MVC (95.7 ± 3.0 vs. 93.3 ± 3.6%; P > 0.05) and at the start of the fatiguing task (P > 0.05). By the end of the six sustained fatiguing MVCs, the men exhibited greater absolute and relative reductions in torque (65 ± 3% of initial MVC) than the women (52 ± 9%; P < 0.05). The increments in torque (superimposed twitch) generated by motor cortex stimulation during each 22-s maximal effort increased with fatigue (P < 0.05). Superimposed twitches were similar for men and women throughout the fatiguing task (5.5 ± 4.1 vs. 7.3 ± 4.7%; P > 0.05), as well as in the last sustained contraction (7.8 ± 5.9 vs. 10.5 ± 5.5%) and in brief recovery MVCs. Voluntary activation determined using an estimated control twitch was similar for the men and women at the start of the sustained maximal contractions (91.4 ± 7.4 vs. 90.4 ± 6.8%, n = 13) and end of the sixth contraction (77.2 ± 13.3% vs. 73.1 ± 19.6%, n = 10). The increase in the area of the motor-evoked potential and duration of the silent period did not differ for men and women during the fatiguing task. However, estimated resting twitch amplitude and the peak rates of muscle relaxation showed greater relative reductions at the end of the fatiguing task for the men than the women. These results indicate that the sex difference in fatigue of the elbow flexor muscles is not explained by a difference in supraspinal fatigue in men and women but is largely due to a sex difference of mechanisms located within the elbow flexor muscles.

transcranial magnetic stimulation; central fatigue; voluntary activation; gender; elbow flexor muscles

This article has been cited by other articles:

				T. Yoon, M. L. Keller, B. S. De-Lap, A. Harkins, R. Lepers, and S. K. Hunter Sex differences in response to cognitive stress during a fatiguing contraction J Appl Physiol, November 1, 2009; 107(5): 1486 - 1496. [Abstract] [Full Text] [PDF]

				S. K. Hunter, G. Todd, J. E. Butler, S. C. Gandevia, and J. L. Taylor Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions J Appl Physiol, October 1, 2008; 105(4): 1199 - 1209. [Abstract] [Full Text] [PDF]

				R. C. I. Wust, C. I. Morse, A. de Haan, D. A. Jones, and H. Degens Sex differences in contractile properties and fatigue resistance of human skeletal muscle Exp Physiol, July 1, 2008; 93(7): 843 - 850. [Abstract] [Full Text] [PDF]

				D. Farina, M. Pozzo, M. Lanzetta, and R. M. Enoka Discharge Variability of Motor Units in an Intrinsic Muscle of Transplanted Hand J Neurophysiol, May 1, 2008; 99(5): 2232 - 2240. [Abstract] [Full Text] [PDF]

				J. L. Taylor and S. C. Gandevia A comparison of central aspects of fatigue in submaximal and maximal voluntary contractions J Appl Physiol, February 1, 2008; 104(2): 542 - 550. [Abstract] [Full Text] [PDF]

				R. M. Enoka and J. Duchateau Muscle fatigue: what, why and how it influences muscle function J. Physiol., January 1, 2008; 586(1): 11 - 23. [Abstract] [Full Text] [PDF]

				B. K. Barry and R. M. Enoka The neurobiology of muscle fatigue: 15 years later Integr. Comp. Biol., October 1, 2007; 47(4): 465 - 473. [Abstract] [Full Text] [PDF]

				J. L. Taylor Magnetic muscle stimulation produces fatigue without effort J Appl Physiol, September 1, 2007; 103(3): 733 - 734. [Full Text] [PDF]

				G. Todd, J. L. Taylor, J. E. Butler, P. G. Martin, R. B. Gorman, and S. C. Gandevia Use of motor cortex stimulation to measure simultaneously the changes in dynamic muscle properties and voluntary activation in human muscles J Appl Physiol, May 1, 2007; 102(5): 1756 - 1766. [Abstract] [Full Text] [PDF]

				M. B. Martin Can supraspinal/central fatigue explain the lesser muscle endurance of men compared with women? J Appl Physiol, October 1, 2006; 101(4): 1015 - 1016. [Full Text] [PDF]