Exercise-Induced Hormone Elevations Are Related to Muscle Growth

• Published in: Journal of strength and conditioning research Vol. 31; no. 1; pp. 45 - 53
• Main Authors: Mangine, Gerald T, Hoffman, Jay R, Gonzalez, Adam M, Townsend, Jeremy R, Wells, Adam J, Jajtner, Adam R, Beyer, Kyle S, Boone, Carleigh H, Wang, Ran, Miramonti, Amelia A, LaMonica, Michael B, Fukuda, David H, Witta, E Lea, Ratamess, Nicholas A, Stout, Jeffrey R
• Format: Journal Article
• Language: English
• Published: United States Copyright by the National Strength & Conditioning Association 01-01-2017; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Adult; Athletes; Endocrine system; Hormones; Human Growth Hormone - blood; Humans; Hydrocortisone - blood; Insulin-Like Growth Factor I - biosynthesis; Male; Muscle, Skeletal - blood supply; Muscle, Skeletal - physiology; Muscular system; Physical growth; Quadriceps Muscle - physiology; Resistance Training - methods; Rest - physiology; Strength training; Testosterone; Testosterone - blood; Young Adult
• ISSN: 1064-8011; 1533-4287
• DOI: 10.1519/JSC.0000000000001491

ABSTRACTMangine, GT, Hoffman, JR, Gonzalez, AM, Townsend, JR, Wells, AJ, Jajtner, AR, Beyer, KS, Boone, CH, Wang, R, Miramonti, AA, LaMonica, MB, Fukuda, DH, Witta, EL, Ratamess, NA, and Stout, JR. Exercise-induced hormone elevations are related to muscle growth. J Strength Cond Res 31(1)45–53, 2017—Partial least squares regression structural equation modeling (PLS-SEM) was used to examine relationships between the endocrine response to resistance exercise and muscle hypertrophy in resistance-trained men. Pretesting (PRE) measures of muscle size (thickness and cross-sectional area) of the vastus lateralis and rectus femoris were collected in 26 resistance-trained men. Participants were randomly selected to complete a high-volume (VOL, n = 13, 10–12RM, 1-minute rest) or high-intensity (INT, n = 13, 3–5RM, 3-minute rest) resistance training program. Blood samples were collected at baseline, immediately postexercise, 30-minute, and 60-minute postexercise during weeks 1 (week 1) and 8 (week 8) of training. The hormonal responses (testosterone, growth hormone [22 kD], insulin-like growth factor-1, cortisol, and insulin) to each training session were evaluated using area-under-the-curve (AUC) analyses. Relationships between muscle size (PRE), AUC values (week 1 + week 8) for each hormone, and muscle size (POST) were assessed using a consistent PLS-SEM algorithm and tested for statistical significance (p ≤ 0.05) using a 1,000 samples consistent bootstrapping analysis. Group-wise comparisons for each relationship were assessed through independent t-tests. The model explained 73.4% (p < 0.001) of variance in muscle size at POST. Significant pathways between testosterone and muscle size at PRE (p = 0.043) and muscle size at POST (p = 0.032) were observed. The ability to explain muscle size at POST improved when the model was analyzed by group (INTR = 0.882; VOLR = 0.987; p < 0.001). No group differences in modal quality were found. Exercise-induced testosterone elevations, independent of the training programs used in this study, seem to be related to muscle growth.