title: Strength training increases the size of the satellite cell pool in type I and II fibres of chronically painful trapezius muscle in females.
abstract: While strength training has been shown to be effective in mediating hypertrophy and reducing pain in trapezius myalgia, responses at the cellular level have not previously been studied. This study investigated the potential of strength training targeting the affected muscles (SST, n = 18) and general fitness training (GFT, n = 16) to augment the satellite cell (SC) and macrophage pools in the trapezius muscles of women diagnosed with trapezius myalgia. A group receiving general health information (REF, n = 8) served as a control. Muscle biopsies were collected from the trapezius muscles of the 42 women (age 44 ± 8 years; mean ± SD) before and after the 10 week intervention period and were analysed by immunohistochemistry for SCs, macrophages and myonuclei. The SC content of type I and II fibres was observed to increase significantly from baseline by 65% and 164%, respectively, with SST (P < 0.0001), together with a significant correlation between the baseline number of SCs and the extent of hypertrophy (r = -0.669, P = 0.005). SST also resulted in a 74% enhancement of the trapezius macrophage content (P < 0.01), accompanied by evidence for the presence of an increased number of actively dividing cells (Ki67(+)) post-SST (P < 0.001). GFT resulted in a significant 23% increase in the SC content of type II fibres, when expressed relative to myonuclear number only (P < 0.05). No changes in the number of myonuclei per fibre or myonuclear domain were detected in any group. These findings provide strong support at the cellular level for the potential of SST to induce a strong myogenic response in this population.
authors.affiliation: Institute of Sports Medicine, Department of Orthopaedic Surgery M, Bispebjerg Hospital, and Centre for Healthy Ageing, Faculty of Health Sciences,University of Copenhagen, Denmark. abigail.mackey@gmail.com
authors.forename: Abigail L
authors.initials: AL
authors.lastname: Mackey
authors.forename: Lars L
authors.initials: LL
authors.lastname: Andersen
authors.forename: Ulrik
authors.initials: U
authors.lastname: Frandsen
authors.forename: Gisela
authors.initials: G
authors.lastname: Sjøgaard
mesh_terms: D000328:Adult; D059350:Chronic Pain / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D006984:Hypertrophy / Q000473:pathology; D019394:Ki-67 Antigen / Q000378:metabolism; D007797:Laminin / Q000378:metabolism; D008264:Macrophages / Q000166:cytology*; D008875:Middle Aged; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism / Q000473:pathology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism / Q000473:pathology; D009135:Muscular Diseases / Q000378:metabolism / Q000473:pathology*; D059352:Musculoskeletal Pain / Q000378:metabolism / Q000473:pathology*; D024461:Myosin Type I / Q000378:metabolism; D009334:Neck Muscles / Q000378:metabolism / Q000473:pathology*; D051763:PAX7 Transcription Factor / Q000378:metabolism; D055070:Resistance Training; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology* / Q000378:metabolism
chemical_list: D019394:Ki-67 Antigen; D007797:Laminin; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; D024461:Myosin Type I