More Evidence That Myostatin is an Important Inhibitor of Diet and Exercise Induced Muscle Gains in You & Me

Is myostatin relevant for mass monsters only, or for normal trainees, as well ?

We all know the freakish images of myostatin negative animals. We all know about the heavily marketed, but scientifically not proven myostatin inhibitors. But do we also know that myostatin is actually a major inhibitor of skeletal muscle growth in the average trainee?

I am not sure, but a recent study from the University of Padova provides further evidence that the muscle hypertrophy break myostatin may in fact be what keeps you from making the same gains you saw, when you first hit the weights (Paoli. 2015).

BFR and Hypoxia Training may decrease myostatin (Laurentino. 2012).

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In said study, Antonio Paoli et al. recruited 18 male volunteers, human movement science undergraduate students (age = 24.9 +/- 5.3 years), who responded to an invitation to participate in the study. The respondents provided written informed consent to participate in the study and were screened for the presence of diseases or conditions that would place them at risk for adverse responses to exercise.

Figure 1: Scheme of experimental design. HP, high protein; NP, normal protein; RT, resistance training (Paoli. 2015)

The subjects were healthy, nonobese, and nonsmokers, and were not taking any medications. Most importantly, however, they had never engaged in regular RT. This gave them the advantage of being strength training virgins and may explain why the supervised exercise sessions which were performed on two nonconsecutive days/week for the first 2 weeks and in 3 nonconsecutive days/week over six months triggered quite significant muscle gains in the subjects who had previously been engaged in 5–6 h/week of various team sports (soccer, volley, and basket).

The IGF-1 Promoting, Myostatin Reducing, Muscle Building Effects of PGC-1 α-4: What It Does and Why Doing Cardio Before Weights Appears to Promote It's Expression | read more.

"The exercises used throughout the program were bench press, latissimus pulldowns, seated rows, shoulder press, biceps hammer curls, and dumbbell lying external rotation. During the first week of training, subjects performed 2 sets of 9–11 repetitions at 75–80% 1RM with 2-min breaks between each set in all exercises except for hammer curl (1.5 min) and dumbbell lying external rotation (1 min). Thereafter, from second to fourth week, the training volume was elevated to three sets. 

At the fifth week the intensity of training was elevated to 80–85% 1RM with three sets of six to eight repetitions. The recovery between each set was 3 min for all exercises except for hammer curl (2 min) and dumbbell lying external rotation (1.5 min). 

From sixth to eighth week the training volume was elevated to four sets. The participants were instructed to perform the repetitions rapidly (1 sec) during the concentric phase and then return the load through the eccentric (lowering) phase at a more slow and controlled speed (1.5/2 sec). The load was adjusted every week according to the actual number." (Paoli. 2015).

In addition to being assigned to identical training protocols, the subjects were randomly assigned to consume either a high or normal protein diet. The participants were put on a fixed-menu plan with either a high (HP) or normal protein (NP) distributed across 5 meals per day. The individual daily caloric need was calculated referring to body composition and adjusted for daily activity. NP and HP diets are isocaloric regarding daily energy needs of subjects while the surplus of calories given by protein supplements were substituted by carbohydrates in diet. Thus

• the subjects in the NP group consumed 0.85 g/kg of body weight protein, while 
• the subjects in the HP group consumed 1.8 g/kg of body weight. 

In that it's important that the increased protein intake was realized via whey protein supplementation that was consumed during the warm-up (10 to 15 min prior to the beginning of training session) and 1 h after the end of the training session in form of a 250 mL of a beverage containing 15–20 g of protein, for a daily amount of 30–40 g or a placebo.

Figure 2: Changes in body composition in the high and low protein group (Paoli. 2015).

Assuming that this is not the first SuppVersity article you read, you will probably not be surprised that replacing carbohydrates with protein to achieve a protein intake of 1.8g/kg vs. 0.85g/kg body weight lead to both increases in lean mass gains and reductions in body fat. This result alone would not warrant a SuppVersity article.

Figure 3: Myostatin increases more in the HP group and it increases hand in hand with IGF-1 (small figure | Paoli. 2015).

What is really interesting, though, is the fact that the necessary increase in protein synthesis in response to the peri-workout ingestion of whey protein lead to likewise significant increases in myostatin, the muscle protein that inhibits further protein synthesis to keep the muscle domain sizes in check (learn more). And there is more: Paoli et al. are the first to demonstrate that IGF-1 and mystatin increase hand in hand (Figure 3). This is particularly interesting, because IGF-1 and its muscle-specific splice-variant MGF are responsible for the formation of new myonuclei from satellite cells and thus a decrease of the domain sizes that keeps the ever-increasing muscle mass functional.

It is thus obvious: The faster you grow - in this case due to the additional supply of whey protein, the faster will the muscular myostatin levels increase. In that, the increase in IGF-1 and the corresponding increase in satellite cell recruitement cannot keep pace with the amount of protein that could be pumped into the muscle if this would not put you at risk of ending up with the same dysfunctional monster muscles as myostatin-negative mice. Monster-muscles that look strong, but are - due to the exuberant domain sizes and lack of myonuclei - dysfunctional.

Domain sizes of EDL and soleus muscle fibers in wild-type control, myostatin negative and IGF1 overexpressing mice (Qaisar. 2012) | learn more.

Against that background it is questionable, whether inhibiting myostatin to a significant degree can actually help you to build big and strong muscles. Rather than a total inhibition of myostatin, people who strive for maximal muscle growth should rather aim for an amelioration of myostatin and a concomitant increase in IGF-1 and MGF to trigger the necessary increases in myonuclei number and domain sizes that keeps the ever-growing muscle functional. But hey, I guess the bros are already doing just that with their sometimes hilarious stacks of potent anabolics | Comment on Facebook!

References:

• Laurentino, Gilberto Candido, et al. "Strength training with blood flow restriction diminishes myostatin gene expression." Med Sci Sports Exerc 44.3 (2012): 406-412.
• Paoli, Antonio, et al. "Protein Supplementation Increases Postexercise Plasma Myostatin Concentration After 8 Weeks of Resistance Training in Young Physically Active Subjects." Journal of medicinal food 18.1 (2015): 137-143.
• Qaisar, Rizwan, et al. "Is functional hypertrophy and specific force coupled with the addition of myonuclei at the single muscle fiber level?." The FASEB Journal 26.3 (2012): 1077-1085.