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Supraspinal fatigue does not explain the sex difference in muscle fatigue of maximal contractions.
J Appl Physiol (1985). 2006 Oct; 101(4):1036-44.JA

Abstract

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.

Authors+Show Affiliations

Exercise Science Program, Department of Physical Therapy, PO Box 1881, Marquette University, Milwaukee, WI 53201, USA. Sandra.Hunter@marquette.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16728525

Citation

Hunter, Sandra K., et al. "Supraspinal Fatigue Does Not Explain the Sex Difference in Muscle Fatigue of Maximal Contractions." Journal of Applied Physiology (Bethesda, Md. : 1985), vol. 101, no. 4, 2006, pp. 1036-44.
Hunter SK, Butler JE, Todd G, et al. Supraspinal fatigue does not explain the sex difference in muscle fatigue of maximal contractions. J Appl Physiol (1985). 2006;101(4):1036-44.
Hunter, S. K., Butler, J. E., Todd, G., Gandevia, S. C., & Taylor, J. L. (2006). Supraspinal fatigue does not explain the sex difference in muscle fatigue of maximal contractions. Journal of Applied Physiology (Bethesda, Md. : 1985), 101(4), 1036-44.
Hunter SK, et al. Supraspinal Fatigue Does Not Explain the Sex Difference in Muscle Fatigue of Maximal Contractions. J Appl Physiol (1985). 2006;101(4):1036-44. PubMed PMID: 16728525.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Supraspinal fatigue does not explain the sex difference in muscle fatigue of maximal contractions. AU - Hunter,Sandra K, AU - Butler,Jane E, AU - Todd,Gabrielle, AU - Gandevia,Simon C, AU - Taylor,Janet L, Y1 - 2006/05/25/ PY - 2006/5/27/pubmed PY - 2006/10/20/medline PY - 2006/5/27/entrez SP - 1036 EP - 44 JF - Journal of applied physiology (Bethesda, Md. : 1985) JO - J Appl Physiol (1985) VL - 101 IS - 4 N2 - 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. SN - 8750-7587 UR - https://www.unboundmedicine.com/medline/citation/16728525/Supraspinal_fatigue_does_not_explain_the_sex_difference_in_muscle_fatigue_of_maximal_contractions_ L2 - https://journals.physiology.org/doi/10.1152/japplphysiol.00103.2006?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -