title: Effects of age and sex on neuromuscular-mechanical determinants of muscle strength.
abstract: The aim of this study was to concurrently assess the effect of age on neuromuscular and mechanical properties in 24 young (23.6 ± 3.7 years) and 20 older (66.5 ± 3.8 years) healthy males and females. Maximal strength of knee extensors (KE) and flexors (KF), contractile rate of torque development (RTD) and neural activation of agonist-antagonist muscles (surface EMG) were examined during maximal voluntary isometric contraction (MVIC). Tissue stiffness (i.e. musculo-articular stiffness (MAS) and muscle stiffness (MS)) was examined via the free-oscillation technique, whereas muscle architecture (MA) of the vastus lateralis and subcutaneous fat were measured by ultrasonography. Males exhibited a greater age-related decline for KE (47.4 %) and KF (53.1 %) MVIC, and RTD (60.4 %) when compared to females (32.9, 42.6 and 34.0 %, respectively). Neural activation of agonist muscles during KE MVIC falls markedly with ageing; however, no age and sex effects were observed in the antagonist co-activation. MAS and MS were lower in elderly compared with young participants and in females compared with males. Regarding MA, main effects for age (young 23.0 ± 3.3 vs older 19.5 ± 2.0 mm) and sex (males 22.4 ± 3.5 vs females 20.4 ± 2.7 mm) were detected in muscle thickness. For fascicle length, there was an effect of age (young 104.6 ± 8.8 vs older 89.8 ± 10.5 mm), while for pennation angle, there was an effect of sex (males 13.3 ± 2.4 vs females 11.5 ± 1.7°). These findings suggest that both neuromuscular and mechanical declines are important contributors to the age-related loss of muscle strength/function but with some peculiar sex-related differences.
authors.affiliation: School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Republic of Ireland. rui.wu.1@ucdconnect.ie.
authors.forename: Rui
authors.initials: R
authors.lastname: Wu
authors.affiliation: School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Republic of Ireland.|Institute for Sport and Health, University College Dublin, Dublin, Republic of Ireland.
authors.forename: Eamonn
authors.initials: E
authors.lastname: Delahunt
authors.affiliation: School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Republic of Ireland.|Institute for Sport and Health, University College Dublin, Dublin, Republic of Ireland.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Ditroilo
authors.affiliation: School of Electrical, Electronic and Communications Engineering, University College Dublin, Dublin, Republic of Ireland.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Lowery
authors.affiliation: School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Republic of Ireland.|Institute for Sport and Health, University College Dublin, Dublin, Republic of Ireland.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Vito
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D012737:Sex Factors; D055815:Young Adult
keywords: Ageing; Muscle architecture; Muscle strength; Sex; Stiffness