"Go Hard or Go Home?" Study Reveals Different Anabolic Signalling in Response to "Heavy" vs. "Medium" Intensity Leg Extensions at Different Times Under Tension

Working out ain't child's play, right? "Go Heavy or Go Home!" this is the mantra of true champions, but is it also the mantra of skeptical scientists?

I guess, it's important to say this first: The results of the study Daniil V. Popov et al. conducted at the Institute of Biomedical problems of Russian Academy of Sciences in Moscow need to be interpreted to have any relevance in terms of the question all of you keep asking yourselves: "What is the best training intensity to make fabulous gains?"

The data the Russian researchers offer is acute, not chronic. It's not based on muscle size measurements, but on the measurement of anabolic signalling proteins and the expression of MyoD, IGF-1, myostatin & co. We know that all of them are involved in the process of skeletal muscle hypertrophy, but even if all of them are elevated, this is not identical to muscle size increases as you would measure them in a long(er)-term study.
I hope that the previous elaborations were detailed and convincing enough to increase your awareness of the limitation of the data I am about to cite.

Figure 1: Toque and angle during knee extensions in the high intensity (HI), medium intensity (MI) and medium intensity continuous tension trial (MIR) - the subjects did bilateral leg extensions (Popov. 2014)

Data that was recorded with 10 strength-trained athletes who performed high-intensity [HI, 74% of 1 repetition maximum (RM)], middle-intensity (MI, 54%1RM), or middle-intensity (54% 1RM) no-relaxation exercise (MIR; continous tension on the trained muscle).

Figure 2: Changes in p21, MyoD, myostatin and MGF in response to each of the three training regimen (Popov. 2014)

The previously mentioned parameters were measured before, 45 min, 5h, and 20 h after exercise - you can see the results in Figure 2. The lactate concentration, which is not shown in Figure 2 was approximately 2-fold lower in the MI vs. the MIR & HI. It was the highest in the MIR session, and would thus coincide with the expression of the pro-anabolic protein p21 and the maximal early reduction in myostatin.

Over the course of the 24 study period, however, the high intensity trial yielded distinctively more pronounced anabolic effects.

A more pronounced and sustained elevation in p21, a maximal increase in MyoD, a marker of satellite cell (muscle precursor cell) activity, a significantly more pronounced increase in the intramuscular isform of IGF, i.e. MGF (learn more) and, last but not least, a sustained reduction of the muscle growth break myostatin.
References:

• Popov, Daniil V., et al. "The Influence of Resistance Exercise Intensity and Metabolic Stress on Anabolic Signaling and the Expression of Myogenic Genes in Skeletal Muscle." Muscle & nerve (2014).