title: Endurance training-induced changes in the GH-IGF-I axis influence maximal muscle strength in previously untrained men.
abstract: In this study we have determined the effects of 20weeks of endurance running training on the GH-IGF-I axis changes in the context of the skeletal muscle performance and physical capacity level.
  
  
  
  Before and after the endurance training program a maximal incremental exercise tests, a 1500m race and a muscle strength measurements were performed and the blood samples were taken to determine both resting as well as end-exercise serum growth hormone (GH), insulin-like growth hormone-I (IGF-I), insulin-like growth hormone binding protein-3 (IGFBP-3) and plasma interleukin-6 (IL-6) concentrations.
  
  
  
  20weeks of endurance running training improved power output generated at the end of the maximal incremental test by 24% (P<0.012), 1500m running time by 13% (P<0.012) and maximal muscle strength by 9% (P<0.02). End-exercise IGF-I/IGFBP-3 ratio was decreased by 22% after the training (P<0.04) and the magnitude of IGF-I/IGFBP-3 ratio decrease (ΔIGF-I/IGFBP-3ex) was 2.3 times higher after the training (P<0.04). The magnitude of the exercise-induced changes in IGFBP-3 concentration was also significantly higher (P<0.04) and there was a trend toward lower end-exercise IGF-I concentration (P=0.08) after the training. These changes were accompanied by a significantly higher (30%) end-exercise IL-6 concentration (P<0.01) as well as by a 3.4 times higher magnitude of IL-6 increase (P<0.02) after the training. Moreover, there were strong positive correlations between changes in resting serum IGF-I concentration (ΔIGF-Ires) and IGF-I/IGFBP-3 ratio (ΔIGF-I/IGFBP-3res) and changes in muscle strength (ΔMVC) (r=0.95, P=0.0003 and r=0.90, P=0.002, respectively).
  
  
  
  The training-induced changes in the components of the GH-IGF-I axis may have additive effects on skeletal muscle performance and physical capacity improvement.
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Al. Jana Pawla II 78, 31-571 Krakow, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Grandys
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Al. Jana Pawla II 78, 31-571 Krakow, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Majerczak
authors.affiliation: Department of Physical Education and Corrective Gymnastics, Institute of Health Protection, The State Higher School of Vocational Education, Ul. Mickiewicza 8, 33-100 Tarnow, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Kuczek
authors.affiliation: Department of Clinical Biochemistry of Pediatric Institute, Faculty of Medicine, Jagiellonian University, Ul. Wielicka 265, 30-663 Krakow, Poland.
authors.forename: Krystyna
authors.initials: K
authors.lastname: Sztefko
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Al. Jana Pawla II 78, 31-571 Krakow, Poland; Department of Nursing, Institute of Health Protection, The State Higher School of Vocational Education, Ul. Mickiewicza 8, 33-100 Tarnow, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Duda
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Al. Jana Pawla II 78, 31-571 Krakow, Poland. Electronic address: jerzy.zoladz@awf.krakow.pl.
authors.forename: Jerzy A
authors.initials: JA
authors.lastname: Zoladz
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D055815:Young Adult
chemical_list: C583557:IGF1 protein, human; C515497:IGFBP3 protein, human; C508600:IL6 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D015850:Interleukin-6; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I
keywords: Insulin-like growth factor; Interleukin-6; Muscle strength; Running; Training