title: Differential basal and exercise-induced IGF-I system responses to resistance vs. calisthenic-based military readiness training programs.
abstract: The purpose of this study was to: 1) evaluate differential responses of the IGF-I system to either a calisthenic- or resistance exercise-based program and 2) determine if this chronic training altered the IGF-I system during an acute resistance exercise protocol.
  
  
  
  Thirty-two volunteers were randomly assigned into a resistance exercise-based training (RT) group (n=15, 27±5y, 174±6cm, 81±12kg) or a calisthenic-based training group (CT) (n=17, 29±5y, 179±8cm, 85±10kg) and all underwent 8weeks of exercise training (1.5h/d, 5d/wk). Basal blood was sampled pre- (Week 0), mid- (Week 4) and post-training (Week 8) and assayed for IGF-I system analytes. An acute resistance exercise protocol (AREP) was conducted preand post-training consisting of 6 sets of 10 repetitions in the squat with two minutes of rest in between sets and the IGF-I system analytes measured. A repeated measures ANOVA (p≤0.05) was used for statistical analysis.
  
  
  
  No interaction or within-subject effects were observed for basal total IGF-I, free IGF-I, or IGFBP-1. IGFBP-2 (pre; 578.6±295.7<mid; 828.6±104.2=post; 833.7±481.2ng/mL; p=0.008) and Acid Labile Subunit (ALS) changed over the exercise training (pre-; 16.2±1.3=mid-; 17.6±1.8>post-training; 14.3±1.9μg/mL; p=0.01). An interaction was observed for the RT group as IGFBP-3 increased from pre to mid (3462.4±216.4 vs. 3962.2±227.9ng/mL), but was not significant at the post-training time point (3770.3±228.7ng/mL). AREP caused all analytes except free IGF-I (40% decrease) to increase (17-27%; p=0.001) during exercise, returning to baseline concentration into recovery.
  
  
  
  Post-training, bioavailable IGF-I recovered more rapidly post-exercise. 8wks of chronic physical training resulted in increased basal IGFBP-2 and IGFBP-3, decreased ALS, increased pre-AREP free IGF-I and a more rapid free IGF-I recovery post-AREP. While total IGF-I was insensitive to chronic physical training, changes were observed with circulating IGFBPs and bioavailable IGF-I. To glean the most robust information on the effects of exercise training, studies must move beyond relying solely on total IGF-I measures and should consider IGFBPs and bioavailable IGF-I as these components of the circulating IGF-I system are essential determinants of IGF-I physiological action.
authors.affiliation: Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA 15203, United States; Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA 17063, United States.
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Nindl
authors.affiliation: Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA 17063, United States; Injury Prevention Program, Epidemiology and Disease Surveillance, U.S. Army Public Health Center (Provisional), Aberdeen Proving Ground, MD 21010, United States.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Alemany
authors.affiliation: Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA 17063, United States.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Rarick
authors.affiliation: Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA 15203, United States. Electronic address: seagle@pitt.edu.
authors.forename: Shawn R
authors.initials: SR
authors.lastname: Eagle
authors.affiliation: Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA 15203, United States.
authors.forename: Mathew E
authors.initials: ME
authors.lastname: Darnell
authors.affiliation: Neuromuscular Research Laboratory/Warrior Human Performance Research Center, Department of Sports Medicine and Nutrition, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA 15203, United States.
authors.forename: Katelyn F
authors.initials: KF
authors.lastname: Allison
authors.affiliation: Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA 17063, United States.
authors.forename: Everett A
authors.initials: EA
authors.lastname: Harman
mesh_terms: D000328:Adult; D001823:Body Composition; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008889:Military Personnel / Q000706:statistics & numerical data*; D055070:Resistance Training
chemical_list: C583557:IGF1 protein, human; C032231:IGFBP1 protein, human; C577903:IGFBP2 protein, human; C515497:IGFBP3 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I
keywords: Acute resistance; Army; Free IGF-I; IGFBPs