Growth hormone levels after flywheel ergometer exercise: correlation with independent variables.
BACKGROUND
In-flight muscle mass and strength losses are likely exacerbated by low growth hormone (GH) concentrations. Factors associated with exercise may foretell resultant GH levels and thereby help blunt future mass and strength losses.


METHODS
To assess the ability of variables to predict GH variance from resistive exercise done on a flywheel ergometer (FE) designed for in-flight exercise, subjects (N=17) performed three types of workouts on the device. With a randomized design, subjects performed the workouts with the intent to determine if changes in post-exercise GH concentrations are impacted by contractile mode and workload. Body mass, blood lactate (BLa-) concentrations, and peak angular velocity (PAV), average power (AP), and total work (TW) from workouts attempted to predict GH variance. Pre-exercise blood draws, and at 1 and 30 min after workouts, were used to determine GH concentrations. BLa- levels were measured before workouts and at 5 min post-exercise. Delta (8, post-pre) and 30-min post-workout GH levels served as criterion variables.


RESULTS
Multivariate regression with an alpha < or = 0.05 yielded the following significant prediction equation: deltaGH = 13.64 - 0.014 (body mass) - 0.607 (post-exercise BLa-) + 0.659 (deltaBLa-) - 0.624(PAV) + 0.653(TW) + 0.147(AP).


CONCLUSIONS
Univariate correlations show body mass, deltaBLa-, and TW were the best predictors of deltaGH variance. Future research should also attempt to identify additional variables that account for the unexplained GH variance from FE workouts.
Caruso
John F
JF
Exercise and Sport Science Program, Department of Chemistry and Biochemistry, The University of Tulsa, OK, USA. john-caruso@utulsa.edu
Coday
Michael A
MA
Monda
Julie K
JK
Ramey
Elizabeth S
ES
Hastings
Lori P
LP
Marshall
Mallory R
MR
D000328:Adult; D000704:Analysis of Variance; D015992:Body Mass Index; D016552:Ergometry; D015444:Exercise / Q000502:physiology*; D005260:Female; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D015999:Multivariate Analysis; D053581:Muscle Strength Dynamometer; D012044:Regression Analysis; D013997:Time Factors
D019382:Human Growth Hormone; D019344:Lactic Acid