title: Composition and adaptation of human myotendinous junction and neighboring muscle fibers to heavy resistance training.
abstract: The myotendinous junction (MTJ) is a common site of strain injury and yet understanding of its composition and ability to adapt to loading is poor. The main aims of this study were to determine the profile of selected collagens and macrophage density in human MTJ and adjoining muscle fibers, and to investigate whether heavy exercise loading would alter this profile. Fifteen individuals scheduled for anterior cruciate ligament repair surgery were randomized into three groups: control, acute or 4 weeks heavy resistance training. MTJ samples were collected from the semitendinosus and gracilis muscles and were sectioned and stained immunohistochemically for collagen types I, III, VI, XII, XIV, XXII, Tenascin-C and CD68. Macrophage density and distribution was evaluated and the amount of each collagen type in muscle and MTJ was graded. Collagen XXII was observed solely at the MTJ, while all other collagens were abundant at the MTJ and in muscle perimysium or endomysium. The endomysial content of collagen XIV, macrophages and Tenascin-C increased following 4 weeks of training. These findings illustrate the heterogeneity of collagen type composition of human MTJ. The increase in collagen XIV following 4 weeks of training may reflect a training-induced protection against strain injuries in this region.
authors: Section for Sports Traumatology M51, Department of Orthopaedic Surgery, Bispebjerg Hospital, Copenhagen, Denmark.
authors: J R
authors: JR
authors: Jakobsen
authors: Institute of Sports Medicine, Department of Orthopaedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.|Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors: A L
authors: AL
authors: Mackey
authors: Section for Sports Traumatology M51, Department of Orthopaedic Surgery, Bispebjerg Hospital, Copenhagen, Denmark.
authors: A B
authors: AB
authors: Knudsen
authors: Institute for Dental Research and Oral Musculoskeletal Biology, and Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany.
authors: M
authors: M
authors: Koch
authors: Institute of Sports Medicine, Department of Orthopaedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors: M
authors: M
authors: Kjaer
authors: Section for Sports Traumatology M51, Department of Orthopaedic Surgery, Bispebjerg Hospital, Copenhagen, Denmark.
authors: M R
authors: MR
authors: Krogsgaard
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000601:surgery; D015703:Antigens, CD / Q000502:physiology; D015214:Antigens, Differentiation, Myelomonocytic / Q000502:physiology; D003094:Collagen / Q000502:physiology; D005260:Female; D006801:Humans; D008264:Macrophages / Q000166:cytology; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D055070:Resistance Training; D019063:Tenascin / Q000502:physiology; D013710:Tendons / Q000502:physiology*; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D003094:Collagen; D019063:Tenascin; C067980:CD68 antigen, human; D000097382:CD68 Molecule
keywords: Injury prevention; Nordic Hamstring; extracellular matrix