Overnight responses of the circulating IGF-I system after acute, heavy-resistance
exercise.
Nindl, Bradley C., William J. Kraemer, James O. Marx, Paul J. Arciero, Kei Dohi, Mark
D. Kellogg, and Gregory A. Loomis.
1Intercollege Graduate Program in Physiology, 2General Clinical Research Center at
Noll Laboratory, and 3Department of Kinesiology, The Pennsylvania State University,
University Park, Pennsylvania 16801; Divisions of 4Military Performance and 7Nutrition
and Biochemistry, United States Army Research Institute of Environmental Medicine,
Natick, Massachusetts 01760; 6Department of Exercise Science, Skidmore College,
Saratoga Springs, New York 12866; and 5Human Performance Laboratory, Ball State
University, Muncie, Iowa 47306
APStracts 8:0010A, 2001.
This study evaluated the individual components of the insulin-like growth factor I (IGF-I)
system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2
and -3, and the acid labile subunit (ALS)] in 10 young, healthy men (age: 22 ± 1 yr,
height: 177 ± 2 cm, weight: 79 ± 3 kg, body fat: 11 ± 1%) overnight for 13 h after two
conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex).
The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-
repetitions maximum sets with 90-s rest periods between sets. The Ex was performed
from 1500 to 1700; blood was obtained immediately postexercise and sampled
throughout the night (every 10 min for the first hour and every hour thereafter) until 0600
the next morning. For the first hour, significant differences (P = 0.05) were only observed
for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no
differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2
increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 µg/ml)
after exercise. The results from this study suggest that the impact that resistance exercise
exerts on the circulating IGF-I system is not in the the alteration of the amount of IGF-I
but rather of the manner in which IGF-I is partitioned among its family of binding
proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system
that can be detected in the systemic circulation.
Received 1 January 2000; accepted in final form 20 October 2000
APS Manuscript Number A147-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001