Muscle hypertrophy, hormonal adaptations and strength development during strength training in strength-trained and untrained men

Abstract

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.

Skeletal muscle size and strength are increased following walk training with restricted leg muscle blood flow: implications for training duration and frequency

“…In the present study, KAATSU-walk training produced a hypertrophic potential of 0.14% per session (~2% increase in muscle volume over 18 training sessions), which is similar to that observed following high-intensity resistance exercise training (Ahtiainen et al, 2003;Jones and Rutherford, 1987). The similarity in hypertrophic potential highlights the importance of the compressed training duration employed during KAATSU-walk training with very low exercise intensities.…”

“…These authors observed that 3 weeks of twice-daily KAATSU-walk training produced significant muscle hypertrophy (4-7% increase in muscle volume) and increased dynamic and isometric strength (8-10% increase) in the thigh muscles despite the very low intensity of the exercise. The magnitude of muscle hypertrophy and strength gains as well as the hypertrophic potential (percent change in muscle volume divided by the number of Skeletal muscle size and strength are increased following walk training with restricted leg muscle blood flow: implications for training duration and frequency training sessions) is comparable with previous results following HIT (Ahtiainen et al, 2003;Jones and Rutherford, 1987), although greater training effects following HIT have been reported (Akima et al, 1999;Bell et al, 1992;Seynnes et al, 2007;Tesch et al, 2004).…”

“…Maximal-intensity training 3 times a week for 5 weeks results in significant increases in muscle size (5-6%) and a hypertrophic potential of 0.3-0.5% (Akima et al, 1999;Bell et al, 1992;Seynnes et al, 2007;Tesch et al, 2004). Studies that have incorporated high-intensity (but not maximal effort) resistance training (e.g., 80% 1-RM or 10-RM) and similar training frequencies produce similar hypertrophic responses (~5% increase in muscle size; Ahtiainen et al, 2003;Jones and Rutherford, 1987).…”

Effect of resistance training on C-reactive protein, blood glucose and lipid profile in older women with differing levels of RT experience

“…Thus, a heightened anabolic environment seemingly enhances the ability for novice RT participants to achieve greater net protein accretion compared to trained individuals. In support of this hypothesis, Ahtiainen et al (Ahtiainen et al 2003) compared the quadriceps femoris crosssectional area following 21 weeks of heavy RT in untrained and trained subjects. After 21 weeks, only the untrained group demonstrated significant hypertrophy, while the trained group had reached a plateau in muscular adaptations.…”

Immunoreactive and bioactive growth hormone responses to resistance exercise in men who are lean or obese

“…For this reason, our protocol utilized large (back squat) and small (bench press and shoulder press) muscle groups. Variables that influence GH secretion include 1) the amount of muscle mass recruited, which directly affects the metabolic and hormonal responses to RE (3), and 2) the total work performed, which affects GH release (1). Still other variables include intensity, volume, rest interval between sets, and magnitude of total work done.…”