title: Exercise and Regulation of Bone and Collagen Tissue Biology.
abstract: The musculoskeletal system and its connective tissue include the intramuscular connective tissue, the myotendinous junction, the tendon, the joints with their cartilage and ligaments, and the bone; they all together play a crucial role in maintaining the architecture of the skeletal muscle, ensuring force transmission, storing energy, protecting joint surface and stability, and ensuring the transfer of muscular forces into resulting limb movement. The musculoskeletal connective tissue structure is relatively stable, but mechanical loading and subsequent mechanotransduction and molecular anabolic signaling can result in some adaptation of the connective tissue, its size, its strength, and its mechanical properties, whereby it can improve its capacity by 5-20% with regular physical activity. For several of the mechanically loaded connective tissues, only limited information regarding molecular and cellular signaling pathways and their adaptation to exercise is available. In contrast to tissue responses with exercise, lack of mechanical tissue loading through inactivity or immobilization of the human body will result in a dramatic loss of connective tissue content, structure, and tolerable load within weeks, to a degree (30-40%) that mimics that of contractile skeletal musculature. This illustrates the importance of regular mechanical load in order to preserve the stabilizing role of the connective tissue for the overall function of the musculoskeletal system in both daily activity and exercise.
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery, Bispebjerg Hospital and Centre for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Electronic address: michaelkjaer@sund.ku.dk.
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
authors.affiliation: Department of Clinical Chemistry, Glostrup Hospital and University of Southern Denmark, Glostrup, Denmark.
authors.forename: Niklas Rye
authors.initials: NR
authors.lastname: Jørgensen
authors.affiliation: Institute of Biomedical Sciences, Faculty of Health and Medical Sciences and Institute of Sports Medicine, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: Katja
authors.initials: K
authors.lastname: Heinemeier
authors.affiliation: Musculoskeletal Rehabilitation Research Unit, Department of Physiotherapy and Institute of Sports Medicine, Bispebjerg Hospital, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: S Peter
authors.initials: SP
authors.lastname: Magnusson
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D002356:Cartilage / Q000378:metabolism; D003094:Collagen / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008022:Ligaments / Q000378:metabolism; D013710:Tendons / Q000378:metabolism
chemical_list: D003094:Collagen
keywords: Cartilage; Inactivity; Intramuscular connective tissue; Ligaments; Myotendinous junction; Physical training; Protein turnover; Tendon