No sex differences in evoked contractile properties after fatiguing isometric and isotonic exercise for the plantar flexors

Females tend to fatigue less than males after isometric exercise, but less is clear for isotonic exercise. Further, there have been relatively few sex comparisons for fatigability of the plantar flexors (PFs). We sought to investigate potential sex differences in contractile properties after a susta...

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Published inJournal of musculoskeletal & neuronal interactions Vol. 22; no. 4; pp. 504 - 513
Main Authors Ha, Phuong L, Dalton, Benjamin E, Alesi, Michaela G, Smith, Tyler M, VanDusseldorp, Trisha A, Feito, Yuri, Hester, Garrett M
Format Journal Article
LanguageEnglish
Published Greece International Society of Musculoskeletal and Neuronal Interactions 01.12.2022
Subjects
Adolescent
Adult
Exercise Therapy
Female
Humans
Isometric Contraction
Male
Muscle Contraction
Muscle Fatigue
Original
Sex Characteristics
Young Adult
Gender Differences
Fatigue
Plantar Flexors
Nerve Stimulation
Peripheral Fatigue
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Summary:Females tend to fatigue less than males after isometric exercise, but less is clear for isotonic exercise. Further, there have been relatively few sex comparisons for fatigability of the plantar flexors (PFs). We sought to investigate potential sex differences in contractile properties after a sustained maximal voluntary isometric contraction (MVIC) and isotonic contractions. Twenty-seven physically active males (n=14; 22±2 yrs) and females (n=13; 21±2 yrs) randomly performed a 2 min MVIC and 120 concentric isotonic (30% MVIC) contractions for the PFs on separate visits. Before and after each fatiguing task, muscle activation was obtained from brief MVICs, which was followed (~2 sec) by tibial nerve stimulation at rest. Contractile properties including peak twitch, absolute and normalized time to peak twitch, and half relaxation time were calculated. No sex differences existed for fatigue-induced changes in muscle activation (p=0.09-0.41; =0.33-0.69) or contractile properties (p=0.19-0.96; =0.06-0.94). Peripheral fatigue, as indicated by contractile parameters, did not differ between sexes after isometric or isotonic exercise. The PFs similar fiber type proportions between sexes or greater fiber type heterogeneity may explain why sex differences in fatigability, though common in other muscle groups (e.g., knee extensors), were not expressed in this muscle group.
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ISSN:1108-7161