title: Active muscle regeneration following eccentric contraction-induced injury is similar between healthy young and older adults.
abstract: Repair of skeletal muscle after injury is a key aspect of maintaining proper musculoskeletal function. Studies have suggested that regenerative processes, including myogenesis and angiogenesis, are impaired during advanced age, but evidence from humans is limited. This study aimed to compare active muscle regeneration between healthy young and older adults. We evaluated changes in clinical, biochemical, and immunohistochemical indices of muscle regeneration at precisely 2 (T2) and 7 (T3) days following acute muscle injury. Men and women, aged 18-30 and ≥70 years, matched for gender and body mass index, performed 150 unilateral, eccentric contractions of the plantar flexors at 110% of one repetition maximum. Data were analyzed using analysis of covariance, adjusted for gender, habitual physical activity, and baseline level of the outcome. A total of 30 young (n = 15; 22.5 ± 3.7 yr) and older (n = 15; 75.8 ± 5.0 yr) adults completed the study. Following muscle injury, force production declined 16% and 14% in young and older adults, respectively, by T2 and in each group, returned to 93% of baseline strength by T3. Despite modest differences in the pattern of response, postinjury changes in intramuscular concentrations of myogenic growth factors and number of myonuclear (4',6-diamidino-2-phenylindole+ and paired box 7+) cells were largely similar between groups. Likewise, postinjury changes in serum and intramuscular indices of inflammation (e.g., TNF-α and monocyte chemoattractant protein-1) and angiogenesis (e.g., VEGF and kinase insert domain receptor) did not differ significantly between groups. These findings suggest that declines in physical activity and increased co-morbidity may contribute to age-related impairments in active muscle regeneration rather than aging per se.
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and Department of Applied Physiology and Kinesiology, College of Health & Human Performance, University of Florida, Gainesville, Florida tbuford@ufl.edu.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Buford
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and Department of Applied Physiology and Kinesiology, College of Health & Human Performance, University of Florida, Gainesville, Florida.
authors.forename: R Gavin
authors.initials: RG
authors.lastname: MacNeil
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and Department of Applied Physiology and Kinesiology, College of Health & Human Performance, University of Florida, Gainesville, Florida.
authors.forename: Launa G
authors.initials: LG
authors.lastname: Clough
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and.
authors.forename: Marvin
authors.initials: M
authors.lastname: Dirain
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and.
authors.forename: Bhanuprasad
authors.initials: B
authors.lastname: Sandesara
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and.
authors.forename: Marco
authors.initials: M
authors.lastname: Pahor
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and Department of Applied Physiology and Kinesiology, College of Health & Human Performance, University of Florida, Gainesville, Florida.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Manini
authors.affiliation: Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, Florida; and.
authors.forename: Christiaan
authors.initials: C
authors.lastname: Leeuwenburgh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000293:injuries* / Q000503:physiopathology*; D064797:Physical Conditioning, Human / Q000009:adverse effects*; D012038:Regeneration / Q000502:physiology*; D055815:Young Adult
keywords: aging; angiogenesis; inflammation; myogenesis; skeletal muscle