title: Muscle structural assembly and functional consequences.
abstract: The relationship between muscle structure and function has been a matter of investigation since the Renaissance period. Extensive use of anatomical dissections and the introduction of the scientific method enabled early scholars to lay the foundations of muscle physiology and biomechanics. Progression of knowledge in these disciplines led to the current understanding that muscle architecture, together with muscle fibre contractile properties, has a major influence on muscle mechanical properties. Recently, advances in laser diffraction, optical microendoscopy and ultrasonography have enabled in vivo investigations into the behaviour of human muscle fascicles and sarcomeres with varying joint angle and muscle contraction intensity. With these technologies it has become possible to identify the length region over which fascicles and sarcomeres develop maximum isometric force in vivo as well as the operating ranges of fascicles and sarcomeres during real-life activities such as walking. Also, greater insights into the remodelling of muscle architecture in response to overloading and unloading, and in ageing, have been obtained by the use of ultrasonography; these have led to the identification of clinical biomarkers of disuse atrophy and sarcopenia. Recent evidence also shows that the pattern of muscle hypertrophy in response to chronic loading is contraction-mode dependent (eccentric versus concentric), as similar gains in muscle mass, but through differing addition of sarcomeres in series and in parallel (as indirectly inferred from changes in fascicle length and pennation angle), have been found. These innovative observations prompted a new set of investigations into the molecular mechanisms regulating this contraction-specific muscle growth.
authors.affiliation: University of Nottingham, Division of Medical Sciences and Graduate Entry Medicine, School of Medicine, Faculty of Medicine and Health Sciences, MRC-ARUK Centre of Excellence for Musculoskeletal Ageing Research, Derby Royal Hospital, Derby DE22 3DT, UK marco.narici@nottingham.ac.uk.
authors.forename: Marco
authors.initials: M
authors.lastname: Narici
authors.affiliation: University of Nottingham, Division of Medical Sciences and Graduate Entry Medicine, School of Medicine, Faculty of Medicine and Health Sciences, MRC-ARUK Centre of Excellence for Musculoskeletal Ageing Research, Derby Royal Hospital, Derby DE22 3DT, UK.
authors.forename: Martino
authors.initials: M
authors.lastname: Franchi
authors.affiliation: Research Institute for Sport and Exercise Sciences, Faculty of Science, Liverpool John Moores University, Liverpool L3 3AF, UK.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Maganaris
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D001696:Biomechanical Phenomena; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology
keywords: Atrophy; Hypertrophy; Muscle contraction; Sarcopenia; Skeletal muscle