title: Early effects of ageing on the mechanical performance of isolated locomotory (EDL) and respiratory (diaphragm) skeletal muscle using the work-loop technique.
abstract: Previous isolated muscle studies examining the effects of ageing on contractility have used isometric protocols, which have been shown to have poor relevance to dynamic muscle performance in vivo. The present study uniquely uses the work-loop technique for a more realistic estimation of in vivo muscle function to examine changes in mammalian skeletal muscle mechanical properties with age. Measurements of maximal isometric stress, activation and relaxation time, maximal power output, and sustained power output during repetitive activation and recovery are compared in locomotory extensor digitorum longus (EDL) and core diaphragm muscle isolated from 3-, 10-, 30-, and 50-wk-old female mice to examine the early onset of ageing. A progressive age-related reduction in maximal isometric stress that was of greater magnitude than the decrease in maximal power output occurred in both muscles. Maximal force and power developed earlier in diaphragm than EDL muscle but demonstrated a greater age-related decline. The present study indicates that ability to sustain skeletal muscle power output through repetitive contraction is age- and muscle-dependent, which may help rationalize previously reported equivocal results from examination of the effect of age on muscular endurance. The age-related decline in EDL muscle performance is prevalent without a significant reduction in muscle mass, and biochemical analysis of key marker enzymes suggests that although there is some evidence of a more oxidative fiber type, this is not the primary contributor to the early age-related reduction in muscle contractility.
authors.affiliation: Department of Biomolecular and Sport Sciences, Coventry, United Kingdom; and tallisj2@uni.coventry.ac.uk.
authors.forename: Jason
authors.initials: J
authors.lastname: Tallis
authors.affiliation: Department of Biomolecular and Sport Sciences, Coventry, United Kingdom; and.
authors.forename: Rob S
authors.initials: RS
authors.lastname: James
authors.affiliation: School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Little
authors.affiliation: Department of Biomolecular and Sport Sciences, Coventry, United Kingdom; and.
authors.forename: Val M
authors.initials: VM
authors.lastname: Cox
authors.affiliation: Department of Biomolecular and Sport Sciences, Coventry, United Kingdom; and.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Duncan
authors.affiliation: School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Frank
authors.initials: F
authors.lastname: Seebacher
mesh_terms: D000367:Age Factors; D000375:Aging; D000818:Animals; D001835:Body Weight; D003964:Diaphragm / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D007537:Isometric Contraction; D008124:Locomotion; D051379:Mice; D018763:Muscle Fatigue; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D020127:Recovery of Function; D012119:Respiration; D055948:Sarcopenia / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D009124:Muscle Proteins
keywords: ageing; fatigue; power; sarcopenia; work loop