Sex disparities of human neuromuscular decline in older humans

Guo, Y, Jones, EJ, Smart, TF, Altheyab, A, Gamage, N, Stashuk, DW, Piasecki, J ORCID: https://orcid.org/0000-0001-9758-6295, Phillips, BE, Atherton, PJ and Piasecki, M, 2024. Sex disparities of human neuromuscular decline in older humans. The Journal of Physiology. ISSN 0022-3751

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Abstract

Females typically live longer than males but, paradoxically, spend a greater number of later years in poorer health. The neuromuscular system is a critical component of the progression to frailty, and motor unit (MU) characteristics differ by sex in healthy young individuals and may adapt to ageing in a sex-specific manner due to divergent hormonal profiles. The purpose of this study was to investigate sex differences in vastus lateralis (VL) MU structure and function in early to late elderly humans. Intramuscular electromyography signals from 50 healthy older adults (M/F: 26/24) were collected from VL during standardized submaximal contractions and decomposed to quantify MU characteristics. Muscle size and neuromuscular performance were also measured. Females had higher MU firing rate (FR) than males (P = 0.025), with no difference in MU structure or neuromuscular junction transmission (NMJ) instability. All MU characteristics increased from low- to mid-level contractions (P < 0.05) without sex × level interactions. Females had smaller cross-sectional area of VL, lower strength and poorer force steadiness (P < 0.05). From early to late elderly, both sexes showed decreased neuromuscular function (P < 0.05) without sex-specific patterns. Higher VL MUFRs at normalized contraction levels previously observed in young are also apparent in old individuals, with no sex-based difference of estimates of MU structure or NMJ transmission instability. From early to late elderly, the deterioration of neuromuscular function and MU characteristics did not differ between sexes, yet function was consistently greater in males. These parallel trajectories underscore the lower initial level for older females and may offer insights into identifying critical intervention periods.

Item Type:	Journal article
Publication Title:	The Journal of Physiology
Creators:	Guo, Y., Jones, E.J., Smart, T.F., Altheyab, A., Gamage, N., Stashuk, D.W., Piasecki, J., Phillips, B.E., Atherton, P.J. and Piasecki, M.
Publisher:	Wiley
Date:	10 June 2024
ISSN:	0022-3751
Identifiers:	Number Type 10.1113/jp285653 DOI 2190385 Other
Rights:	© 2024 The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Divisions:	Schools > School of Science and Technology
Record created by:	Jeremy Silvester
Date Added:	09 Aug 2024 08:55
Last Modified:	09 Aug 2024 08:55
URI:	https://irep.ntu.ac.uk/id/eprint/51954

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