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. 2016 Jun;38(3):57.
doi: 10.1007/s11357-016-9921-2. Epub 2016 May 17.

Effects of Age and Sex on Neuromuscular-Mechanical Determinants of Muscle Strength

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Free PMC article

Effects of Age and Sex on Neuromuscular-Mechanical Determinants of Muscle Strength

Rui Wu et al. Age (Dordr). .
Free PMC article

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.

Keywords: Ageing; Muscle architecture; Muscle strength; Sex; Stiffness.

Conflict of interest statement

Compliance with ethical standards The study was approved by the University Human Research Ethic Committee, and all participants provided written informed consent to the procedures and aims of the study.

Figures

Fig. 1
Fig. 1
Ultrasound image of the vastus lateralis (VL). Ɵ, pennation angle
Fig. 2
Fig. 2
Maximal voluntary isometric contraction (MVIC) of knee extensors (KE) and flexors (KF) for young and older males and females. *p < 0.05 and **p < 0.001 significant difference between young and older males and females, respectively. Values are mean ± SD
Fig. 3
Fig. 3
Rate of torque development (RTD) for young and older males and females. *p < 0.05 and **p < 0.001 significant difference between young and older males and females, respectively. Values are mean ± SD
Fig. 4
Fig. 4
Force and surface electromyogram (EMG) obtained from vastus lateralis (VL) muscle during maximal voluntary isometric contraction (MVIC) for knee extension in one of young and older participants, respectively

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