Muscle hypertrophy, hormonal adaptations and strength development during strength training in strength-trained and untrained men.
Hormonal and neuromuscular adaptations to strength training were studied in eight male strength athletes (SA) and eight non-strength athletes (NA). The experimental design comprised a 21-week strength-training period. Basal hormonal concentrations of serum total testosterone (T), free testosterone (FT) and cortisol (C) and maximal isometric strength, right leg 1 repetition maximum (RM) of the leg extensors were measured at weeks 0, 7, 14 and 21. Muscle cross-sectional area (CSA) of the quadriceps femoris was measured by magnetic resonance imaging (MRI) at weeks 0 and 21. In addition, the acute heavy resistance exercises (AHRE) (bilateral leg extension, five sets of ten RM, with a 2-min rest between sets) including blood samples for the determination of serum T, FT, C, and GH concentrations were assessed before and after the 21-week training. Significant increases of 20.9% in maximal force and of 5.6% in muscle CSA in NA during the 21-week strength training period were greater than those of 3.9% and -1.8% in SA, respectively. There were no significant changes in serum basal hormone concentrations during the 21-week experiment. AHRE led to significant acute decreases in isometric force and acute increases in serum hormones both at weeks 0 and 21. Basal T concentrations (mean of 0, 7, 14 and 21 weeks) and changes in isometric force after the 21-week period correlated with each other (r=0.84, P<0.01) in SA. The individual changes in the acute T responses between weeks 0 and 21 and the changes in muscle CSA during the 21-week training correlated with each other (r=0.76, P<0.05) in NA. The correlations between T and the changes in isometric strength and in muscle CSA suggest that both serum basal testosterone concentrations and training-induced changes in acute testosterone responses may be important factors for strength development and muscle hypertrophy.
Ahtiainen
Juha P
JP
Neuromuscular Research Center and Department of Biology of Physical Activity, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland. ahtiainen@sport.jyu.fi
Pakarinen
Arto
A
Alen
Markku
M
Kraemer
William J
WJ
Häkkinen
Keijo
K
D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001823:Body Composition; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006984:Hypertrophy; D007537:Isometric Contraction / Q000502:physiology; D007866:Leg / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology*; D013739:Testosterone / Q000097:blood*; D014891:Weight Lifting / Q000502:physiology*
D013739:Testosterone