Sex Differences in Fatigue Resistance Are Muscle Group Dependent

Women are often reported to be generally more resistant to fatigue than men for relative-intensity tasks. This has been observed repeatedly for elbow flexors, whereas at the ankle, sex differences appear less robust, suggesting localized rather than systemic influences. Thus, the purpose of this stu...

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Bibliographic Details
Published in:	Medicine and science in sports and exercise Vol. 42; no. 10; pp. 1943 - 1950
Main Authors:	AVIN, Keith G, NAUGHTON, Maureen R, FORD, Brett W, MOORE, Haley E, MONITTO-WEBBER, Maya N, STARK, Amy M, GENTILE, A. John, FREY LAW, Laura A
Format:	Journal Article
Language:	English
Published:	Hagerstown, MD Lippincott Williams & Wilkins 01-10-2010
Subjects:	Adult Ankle - physiology Biological and medical sciences Cohort Studies Elbow - physiology Female Fundamental and applied biological sciences. Psychology Humans Isometric Contraction - physiology Male Motor Activity - physiology Muscle Fatigue - physiology Muscle, Skeletal - physiology Pain - physiopathology Physical Endurance - physiology Sex Factors Space life sciences Torque Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports Young Adult Ankle Human Sport ISOMETRIC CONTRACTION Sex Isometric muscular contraction Fatigue Endurance Striated muscle MAXIMUM ENDURANCE TIME Elbow
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Summary:	Women are often reported to be generally more resistant to fatigue than men for relative-intensity tasks. This has been observed repeatedly for elbow flexors, whereas at the ankle, sex differences appear less robust, suggesting localized rather than systemic influences. Thus, the purpose of this study was to examine sex differences in fatigue resistance at muscle groups in a single cohort and which factors, if any, predict endurance time. Thirty-two young adults (age = 19-44 yr, 16 women) performed sustained isometric contractions at 50% maximum voluntary isometric contraction to failure for elbow flexion and ankle dorsiflexion. Pain, exertion, and muscle EMG were assessed throughout. Self-reported baseline activity was measured using the International Physical Activity Questionnaire. Women were significantly more resistant to fatigue than men at the elbow (112.3 ± 6.2 vs 80.3 ± 5.8 s, P = 0.001) but not at the ankle (140.6 ± 10.7 vs 129.2 ± 10.5 s, P = 0.45). Peak torque was greater in men than that in women (P < 0.0001) at the ankle (45.0 ± 1.7 vs 30.1 ± 1.0 N·m) and at the elbow (75.7 ± 3.1 vs 34.4 ± 2.2 N·m). Peak torque was significantly related to endurance time at the elbow (R2= 0.30) but not at the ankle (R2 = 0.03). Peak pain, rate of pain increase, peak exertion, EMG, and baseline physical activity did not differ between sexes. Sex differences in fatigue resistance are muscle group specific. Women were more fatigue resistant at the elbow but not at the ankle during a sustained isometric contraction. Further, factors that may contribute to fatigue resistance for one muscle group (e.g., sex, peak torque) may not be critical at another.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Author Justification: This project was performed by all 8 of the authors. Each author contributed to the development of the concept, design, and/or protocol. The first 7 authors performed all data collection and initial processing. The first and last authors performed all statistical analysis. The manuscript was written largely by the first and last authors, with input from the remaining 6 authors.
ISSN:	0195-9131 1530-0315
DOI:	10.1249/MSS.0b013e3181d8f8fa