title: Single muscle fiber gene expression with run taper.
abstract: This study evaluated gene expression changes in gastrocnemius slow-twitch myosin heavy chain I (MHC I) and fast-twitch (MHC IIa) muscle fibers of collegiate cross-country runners (n = 6, 20±1 y, VO₂max = 70±1 ml•kg-1•min-1) during two distinct training phases. In a controlled environment, runners performed identical 8 kilometer runs (30:18±0:30 min:s, 89±1% HRmax) while in heavy training (∼72 km/wk) and following a 3 wk taper. Training volume during the taper leading into peak competition was reduced ∼50% which resulted in improved race times and greater cross-section and improved function of MHC IIa fibers. Single muscle fibers were isolated from pre and 4 hour post run biopsies in heavily trained and tapered states to examine the dynamic acute exercise response of the growth-related genes Fibroblast growth factor-inducible 14 (FN14), Myostatin (MSTN), Heat shock protein 72 (HSP72), Muscle ring-finger protein-1 (MURF1), Myogenic factor 6 (MRF4), and Insulin-like growth factor 1 (IGF1) via qPCR. FN14 increased 4.3-fold in MHC IIa fibers with exercise in the tapered state (P<0.05). MSTN was suppressed with exercise in both fiber types and training states (P<0.05) while MURF1 and HSP72 responded to running in MHC IIa and I fibers, respectively, regardless of training state (P<0.05). Robust induction of FN14 (previously shown to strongly correlate with hypertrophy) and greater overall transcriptional flexibility with exercise in the tapered state provides an initial molecular basis for fast-twitch muscle fiber performance gains previously observed after taper in competitive endurance athletes.
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Kevin
authors.initials: K
authors.lastname: Murach
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Raue
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Brittany
authors.initials: B
authors.lastname: Wilkerson
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Kiril
authors.initials: K
authors.lastname: Minchev
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Bozena
authors.initials: B
authors.lastname: Jemiolo
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: James
authors.initials: J
authors.lastname: Bagley
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Luden
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana, United States of America.
authors.forename: Scott
authors.initials: S
authors.lastname: Trappe
mesh_terms: D056352:Athletes; D064590:Cool-Down Exercise / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D015870:Gene Expression / Q000502:physiology*; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism; D055435:Myostatin / Q000235:genetics / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism; D012420:Running / Q000502:physiology*; D000074050:TWEAK Receptor; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
chemical_list: D050884:HSP72 Heat-Shock Proteins; C583557:IGF1 protein, human; C525911:MSTN protein, human; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D055435:Myostatin; D018124:Receptors, Tumor Necrosis Factor; C000613297:TNFRSF12A protein, human; D000074050:TWEAK Receptor; D000070584:Tripartite Motif Proteins; C063403:myogenic factor 6; D007334:Insulin-Like Growth Factor I; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases