title: The effect of HMB ingestion on the IGF-I and IGF binding protein response to high intensity military training.
abstract: Insulin-like growth factor-I (IGF-I) is a metabolic and anabolic biomarker that has been proposed to reflect physiological adaptations resulting from multistressor environments. The bioactivity of IGF-I is regulated by seven different insulin-like growth factor binding proteins (IGFBPs) which act not only as carriers of IGF-1, but also function as a modulator of IGF-I availability and activity. Supplementing with β-hydroxy-β-methylbutyrate (HMB) has been shown to enhance physiological outcomes associated with intense training, and has been reported to augment the IGF-1 response. The purpose of this study was to examine the effect of 23days of HMB supplementation on circulating levels of IGF-I and IGFBPs in combat soldiers during highly intense military training.
  
  
  
  Thirteen male soldiers from an elite infantry unit volunteered to participate in this double-blind, parallel design study. Soldiers were provided 3g·day-1of either HMB (n=6) or placebo (PL; n=7). During the study soldiers performed advanced military training with periods of restricted sleep and severe environmental stressors. Blood samples were obtained prior to (PRE) and approximately 18h following the final supplement consumption (POST).
  
  
  
  No significant differences were observed for circulating IGF-1 concentrations between HMB and PL (p=0.568). In addition, no differences were seen between the groups for IGFBP-1 (p=1.000), IGFBP-2 (p=0.855), IGFBP-3 (p=0.520), IGFBP-4 (p=0.103), IGFBP-5 (p=0.886), or IGFBP-6 (p=0.775). A significant difference was noted between HMB (169.9±23.0ng·ml-1) and PL (207.2±28.0ng·ml-1) for IGFBP-7 at POST (p=0.042).
  
  
  
  Although the results of this study do not support the influence of HMB supplementation on circulating concentrations of IGF-1 or IGFBPs1-6 during high intensity military training, it does present initial evidence that it may lower circulating IGFBP-7 concentrations. This may provide some indication of a reduced stress response, but further investigation on the physiological role of IGFBP-7 and military training is needed.
authors.affiliation: Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Redd
authors.affiliation: Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL, United States. Electronic address: jay.hoffman@ucf.edu.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Hoffman
authors.affiliation: Department of Public Health, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Yftach
authors.initials: Y
authors.lastname: Gepner
authors.affiliation: Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL, United States.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Stout
authors.affiliation: Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL, United States.
authors.forename: Mattan W
authors.initials: MW
authors.lastname: Hoffman
authors.affiliation: Israel Defense Forces, Combat Fitness Branch, Netanya, Israel.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ben-Dov
authors.affiliation: Israel Defense Forces, Combat Fitness Branch, Netanya, Israel.
authors.forename: Shany
authors.initials: S
authors.lastname: Funk
authors.affiliation: Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL, United States.
authors.forename: David D
authors.initials: DD
authors.lastname: Church
authors.affiliation: Israel Defense Force, Medical Corps, Tel Hashomer, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Avital
authors.affiliation: Israel Defense Force, Medical Corps, Tel Hashomer, Israel.
authors.forename: Yacov
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Israel Defense Force, Medical Corps, Tel Hashomer, Israel.
authors.forename: Hagai
authors.initials: H
authors.lastname: Frankel
authors.affiliation: Israel Defense Force, Medical Corps, Tel Hashomer, Israel.
authors.forename: Ishay
authors.initials: I
authors.lastname: Ostfeld
mesh_terms: D000328:Adult; D019587:Dietary Supplements; D004311:Double-Blind Method; D004435:Eating; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008889:Military Personnel; D014631:Valerates / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: C583557:IGF1 protein, human; D018969:Insulin-Like Growth Factor Binding Proteins; D014631:Valerates; C004961:beta-hydroxyisovaleric acid; D007334:Insulin-Like Growth Factor I
keywords: Endocrine; Hormones; Physical stress; Soldiers; Supplements