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Growth Horm IGF Res. 2017 Feb;32:33-40. doi: 10.1016/j.ghir.2016.12.001. Epub 2016 Dec 6.

Differential basal and exercise-induced IGF-I system responses to resistance vs. calisthenic-based military readiness training programs.

Author information

1
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.
2
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.
3
Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA 17063, United States.
4
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.
5
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.

Abstract

OBJECTIVE:

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.

DESIGN:

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.

RESULTS:

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.

CONCLUSION:

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.

KEYWORDS:

Acute resistance; Army; Free IGF-I; IGFBPs

PMID:
27979730
DOI:
10.1016/j.ghir.2016.12.001
[Indexed for MEDLINE]

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