High-affinity growth hormone binding protein and acute heavy resistance exercise.
OBJECTIVE
The purpose of this investigation was to examine the influence of resistance training on circulating concentrations of growth hormone binding protein (GHBP) in response to acute heavy resistance exercise.


METHODS
Using a cross-sectional experimental design, a group of resistance-trained men (RT, N=9, 7.9+/-1.3 yr resistance training experience) and a group of untrained men (UT, N=10) performed an acute heavy resistance exercise protocol (AHREP) consisting of 6 sets of 10 repetition maximum parallel squats. Blood samples were obtained 72 h before exercise, immediately before exercise, and 0, 15, 30, 45, and 60 min after exercise.


RESULTS
Significant increases (P<0.05) in GHBP, immunoreactive growth hormone (iGH), and IGF-1 were observed in both subject groups after AHREP. There were no differences (P>0.05) between groups in GHBP at rest or after AHREP. However, RT exhibited a significantly greater iGH response to AHREP than UT subjects, and significantly higher IGF-1 values at rest and after exercise. Significant positive correlations were found between GHBP and BMI, body fat, and leptin in both groups. A significant positive correlation also was observed between resting leptin and GHBP values in UT but not RT subjects.


CONCLUSIONS
In summary, these data indicate that resistance training does not increase blood GHBP. Nevertheless, the increases observed with IGF-1 concentrations in the resistance-trained subjects do suggest an apparent adaptation with the regulation of this hormone. If there was in fact an increase in GH sensitivity and GH receptor expression at the liver that was not detected by blood GHBP in this study, it may be possible that factors contributing to the circulating concentration of GHBP other than hepatocytes (e.g., leptin and adipocytes) may serve to mask training-induced increases in circulating GHBP of a hepatic origin, thus masking any detectable increase in GH receptor expression.
Rubin
Martyn R
MR
Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
Kraemer
William J
WJ
Maresh
Carl M
CM
Volek
Jeff S
JS
Ratamess
Nicholas A
NA
Vanheest
Jaci L
JL
Silvestre
Ricardo
R
French
Duncan N
DN
Sharman
Matthew J
MJ
Judelson
Daniel A
DA
Gómez
Ana L
AL
Vescovi
Jason D
JD
Hymer
Wesley C
WC
D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002352:Carrier Proteins / Q000097:blood*; D003430:Cross-Sectional Studies; D002149:Energy Intake / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D019344:Lactic Acid / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D012146:Rest / Q000502:physiology; D014891:Weight Lifting / Q000502:physiology*
D001786:Blood Glucose; D002352:Carrier Proteins; D020738:Leptin; D019382:Human Growth Hormone; D019344:Lactic Acid; D007334:Insulin-Like Growth Factor I