title: COX Inhibitor Influence on Skeletal Muscle Fiber Size and Metabolic Adaptations to Resistance Exercise in Older Adults.
abstract: Common cyclooxygenase (COX)-inhibiting drugs enhance resistance exercise induced muscle mass and strength gains in older individuals. The purpose of this investigation was to determine whether the underlying mechanism regulating this effect was specific to Type I or Type II muscle fibers, which have different contractile and metabolic profiles. Muscle biopsies (vastus lateralis) were obtained before and after 12 weeks of knee-extensor resistance exercise (3 days/week) from healthy older men who consumed either a placebo (n = 8; 64±2 years) or COX inhibitor (acetaminophen, 4 gram/day; n = 7; 64±1 years) in double-blind fashion. Muscle samples were examined for Type I and II fiber cross-sectional area, capillarization, and metabolic enzyme activities (glycogen phosphorylase, citrate synthase, β-hydroxyacyl-CoA-dehydrogenase). Type I fiber size did not change with training in the placebo group (304±590 μm(2)) but increased 28% in the COX inhibitor group (1,388±760 μm(2), p < .1). Type II fiber size increased 26% in the placebo group (1,432±499 μm(2), p < .05) and 37% in the COX inhibitor group (1,825±400 μm(2), p < .05). Muscle capillarization and enzyme activity were generally maintained in the placebo group. However, capillary to fiber ratio increased 24% (p < .1) and citrate synthase activity increased 18% (p < .05) in the COX inhibitor group. COX inhibitor consumption during resistance exercise in older individuals enhances myocellular growth, and this effect is more pronounced in Type I muscle fibers.
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana. ttrappe@bsu.edu.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Trappe
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Ratchford
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Brooke E
authors.initials: BE
authors.lastname: Brower
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Sophia Z
authors.initials: SZ
authors.lastname: Liu
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Kaleen M
authors.initials: KM
authors.lastname: Lavin
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Chad C
authors.initials: CC
authors.lastname: Carroll
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Bozena
authors.initials: B
authors.lastname: Jemiolo
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors.forename: Scott W
authors.initials: SW
authors.lastname: Trappe
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage*; D000222:Adaptation, Physiological; D000368:Aged; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage*; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D052097:Quadriceps Muscle / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology*; D055070:Resistance Training; D055948:Sarcopenia / Q000188:drug therapy* / Q000378:metabolism*
chemical_list: D016861:Cyclooxygenase Inhibitors; D000082:Acetaminophen
keywords: Cyclooxygenase; Fiber-type specific; Prostaglandin; Sarcopenia
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