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Introduction

            Muscle quality

            The observation that muscle strength is lost at a higher rate than mass reveals that
            muscle  function  is  not  solely  determined  by  muscle  mass.  The  functioning  of  a
            muscle beyond its mass can be called muscle quality [24]. The pragmatic definition
            of muscle quality is function per mass and can be calculated as muscle strength or
            power per unit of mass, volume or cross-sectional area [24]. A more sophisticated
            way of evaluating muscle quality is to examine the determinants of relative muscle
            strength themselves [25]. Four important determinants of muscle quality are type II
            muscle fibre atrophy, mitochondrial functioning, fat infiltration, and neuromuscular
            activation (Figure 2). The bottom layer of Figure 2 shows the lifestyle factors that
            can  improve  determinants  of  muscle  quality.  These  evidence  from  randomised
            controlled trials with exercise, nutrition and bio-actives in older adults is summarised
            in Table 1-3.





































             Figure  2.  Schematic  representation  of  the  possible  influence  of  nutrition  and  exercise  on  healthy
             ageing via muscle quality-related mediators of physical performance.




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