Association of circulating IGF-I and IGFBP-3 concentrations and exercise capacity in healthy volunteers: results of the Study of Health in Pomerania.

Background: Insulin-like growth factor I (IGF-I) and its binding protein 3 (IGFBP-3) are central mediators of endocrine effects of growth hormone and there is increasing evidence for an association with muscle strength and exercise capacity. The aim of the present study was to clarify the possible association of circulating IGF-I and IGFBP-3 concentrations and exercise capacity in a general adult population.
Materials and Methods: From the Study of Health in Pomerania (SHIP) 1332 subjects aged 25 to 85 years participated in a standardised symptom limited cardiopulmonary exercise test on a bicycle. Exercise capacity was characterized by oxygen uptake at anaerobic threshold (VO₂@AT), peak exercise (peakVO₂), oxygen pulse and maximum power output at peak exertion. Multivariable linear regression analyses adjusted for age, sex, body mass index, physical activity and smoking were performed.
Results: At peak exercise performance, in women IGF-I showed significant associations to peakVO₂ and maximum power output, IGF-I/IGFBP-3 ratio was associated with maximum power output. In men, this association was not consistently reproducible. Neither IGF-I nor IGFBP-3 did reveal any association to VO₂@AT in both genders.
Conclusion: Serum IGF-I concentrations are associated with peak exercise capacity in healthy women, but not in men over a wide range in ages, body sizes and activity scores.
(Copyright © 2010 Growth Hormone Research Society. Published by Elsevier Ltd. All rights reserved.)