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High Intensity Training Mesterolone Yield Muscle and Fiber Type Specific Size Gains Of Up To 100 More

Want to learn more about fiber types? ➫ review past SuppVersity articles

I am not telling you a secret, when I say that testosterone alone - in the absence of training - will lead to significant increases in skeletal muscle mass (if you think that sounds like a secret you must have missed my previous article from the "Intermittent Thoughts on Building Muscle" series | read more). To a certain extend, the same is true for DHT (learn more), and - as a recent 6-week rodent study by Karina Fontana, Gerson E. R. Campos, Robert S. Staron and Maria Alice da Cruz-Höfling shows even by the structurally similar, orally bioavailable derivative Mesterolone (aka Proviron), which produces pretty drastic, fiber-type specific increases in muscle size, when it is administered in super-physiological doses for 6 weeks (Fontana. 2013).

AAS +/- HIT = ?

Basically the question the researchers from the universities of Campinas (Brazil) and Ohio had in mind, when they came up with their study protocol was: Do anabolic steroids exert direct effects on the fiber type composition and cross-sectional area of skeletal muscle fibers of sedentary and high-intensity, aerobically-exercised transgenic mice.
As the scientists point out, the aim of the study was thus "to investigate the role of mesterolone in a supposed catabolic environment" (Fontana. 2013) and answer the following detail questions:

• Does the interaction of anabolic hormone treatment and high-intensity aerobic exercise produce an increase in muscle mass and redistribution of skeletal muscle fiber types? 
• Are muscles with distinct metabolic and contractile properties (i.e., fast/glycolytic vs. slow/oxidative) differently modulated by the anabolic androgenic steroid treatment combined with a high-intensity, endurance-type training program? 
• As such, three skeletal muscles were studied under these experimental conditions: soleus (SOL), tibialis anterior (TA) and gastrocnemius (GAS). 

To be able to do so, assigned their transgenic mice (these mice have been "modified" so that they have a lipid metabolism thats closer to the one of human beings) to four different groups, i.e.

Table 1: Overview of the incremental exercise program the rodents in the "EX-" (=exercise) groups performed on a treadmill 5x per week

• Sed-C - sedentary control
• Sed-M - sedentary + 3x2mg/kg* Mesterolone per week
• Ex-C -5x/week HIT exercise + gum arabic placebo
• Ex-M - 5x/week HIT exercise + 3x2mg/kg* M per week

After 6 weeks, the animals were sacrificed, their muscles harvested and an analysis of the entire range of pure and hybrid fiber types was conducted.
Just in case you dont remember all the details youve learned about the different fiber types in previous SuppVersity articles, keep in mind that type I fibers are mainly oxidative, they use fat as a "preferred" substrate and will get you from A to B when you walk or jog. The type II fibers, on the other hand are "glycolytic", this means, that they rely heavily on glucose. Their prerogative are explosive / fast contractions and they carry the lions share of the weight you through around at the gym.

Figure 1: Muscle weight and body weight (in g) at the end of the study (Fontana. 2013)

Against that background its quite telling that the tibialis, the muscle with the largest amount of Type IIA and Type II AD fibers, fast twitch fibers that can use both, glucose and fat as fuel, is the only muscle where we dont see the following relation between the muscle weight: EX-M > EX-C > SED-M > SED-C.

Figure 2: Detailed analysis of the changes in fiber type composition of soleus, tibialis and gastrocnemius muscle; all data expressed relative to sedentary control (Fontana. 2013)

If you take a closer look at the detailed fiber type analysis the researchers conducted (Figure 2), you will see that a similar trend can be observed in the "intermediate" muscle, the gastrocnemius (see grey arrow). The effects the DHT clone had on the "oxidative" soleus, on the other hand, were in no instance more pronounced than those of the 20-60min treadmill running regimen (see Table 1, for details).
References:

• Fontana, Karina, et al. "Effects of Anabolic Steroids and High-Intensity Aerobic Exercise on Skeletal Muscle of Transgenic Mice." PloS one 8.11 (2013): e80909. 
• Itil, Turan M., et al. "Male hormones in the treatment of depression: effects of mesterolone." Progress In Neuro-Psychopharmacology 2.4 (1978): 457-467. 
• Ly, Lam P., et al. "A double-blind, placebo-controlled, randomized clinical trial of transdermal dihydrotestosterone gel on muscular strength, mobility, and quality of life in older men with partial androgen deficiency." Journal of Clinical Endocrinology & Metabolism 86.9 (2001): 4078-4088. 
• Saartok, Tönu, Erik Dahlberg, And Jan-Åke Gustafsson. "Relative binding affinity of anabolic-androgenic steroids: comparison of the binding to the androgen receptors in skeletal muscle and in prostate, as well as to sex hormone-binding globulin." Endocrinology 114.6 (1984): 2100-2106.
• Singh, Keerti, Asha Singh, and A. K. Sarada. "Assessment of mesterolone therapy in oligospermic males." www.ijpsi.org Volume 2 Issue 3 March 2013.

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