Responses of insulin-like growth factor-i to endogenous increases
in growth hormone after heavy resistance exercise.
Kraemer, William J., Brian A. Aguilera, Mitsuyo Terada, Robert U.
Newton, James M. Lynch, Gonny Rosenthal, Jeffrey M. McBride, Scott E.
Gordon, and Keijo H[umlaut]akkinen.
Center for Sports Medicine, The Pennsylvania State University,
University Park, PA 16802
APStracts 2:0221A, 1995.
The purpose of this investigation was to examine the effects of a
heavy resistive exercise protocol known to dramatically elevate
immunoreactive growth hormone (GH) on circulating insulin-like growth
factor (IGF-I) following the exercise stimulus. Seven men (23.1 +/-
2.4 yrs) volunteered to participate in this investigation. Each
subject was asked to perform an eight station heavy resistance
exercise protocol consisting of 3 sets of 10 repetition maximum
resistances with 1 minute rest between sets and exercises followed by
a recovery day. In addition a control day followed a non-exercise day
to provide baseline data. Pre-exercise and post-exercise (0, 15 and
30 minutes) blood samples were obtained and analyzed for lactate,
creatine kinase, GH and IGF-I. Post-exercise values for lactate and
GH were significantly (p<0.05) elevated above pre-exercise and
resting baseline values. The highest mean GH concentration following
the heavy resistance exercise protocol was 23.8 +/- 11.8 [mu]g x L-1
observed at the immediate post-exercise time point. Significant
increases in creatine kinase were observed after the exercise
protocol and during the recovery day. No significant relationships
were observed between creatine kinase and IGF-I concentrations. No
significant changes in serum IGF-I concentrations were observed with
acute exercise or between the recovery and control days. Thus, these
data demonstrate that a high intensity bout of heavy resistance
exercise which increases circulating GH did not appear to affect IGF
-I concentrations over a 24 hour recovery period in recreationally
strength trained and healthy young men.
Received 2 November 1994; accepted in final form 18 May 1995.
APS Manuscript Number A1126-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.