It was 2010 that the term “mechanical tension” first hit the mainstream. Fast forward to today (2025) and it is believed that it’s the primary igniter of muscle growth (there’s two other factors involved, which I will name soon). In this article, I will tell you what mechanical tension is, explain why it’s important, and give you suggestions on rep performance that will optimize it. I will also provide nutrition and supplement guidelines. Let’s jump right in!
What Is Mechanical Tension?
I have seen multiple definitions, but ultimately, mechanical tension can be defined as the force generated by the muscles when they contract against resistance. This force will increase depending on the exercise you’re performing. There’s more to it than that, as we will soon see.
Why Is It Important
The primary reason mechanical tension is important is because it’s believed to be the key factor of hypertrophy (or muscle growth). Notice I said “the” and not “a”. Some believe it most likely affects the other two contributors to muscle growth, which are muscle damage and metabolic stress. Interestingly, and something I find fascinating, is the fact that mechanical tension also has a positive effect on the mTOR signaling pathway and protein synthesis. If you read my articles, you know I talk a lot about how important protein synthesis is to muscle growth.
How Muscles Produce Force
Ultimately, and put simply, muscles produce force through the act of muscular contraction. Muscles will generate more force if the velocity of muscular contractions is slow. This ties into the idea of using heavy weight, which by its very nature demands a slow repetition speed, even if you’re trying to lift the bar quickly.
Mechanical Tension And “Effective Reps”
It is believed that the last 4-6 reps to failure are the reps with the most mechanical tension (and therefore muscle growth potential). A popular term for these is called “effective reps”. An effective rep is a rep that recruits the fast-twitch fibers (which have the greatest growth potential). It takes a high intensity set to recruit the fast-twitch fibers. By high intensity, I mean heavy weight and optimal rep performance. Of course, it can also mean extended-set techniques, such as drop sets and rest-pause.
Rep Performance
I suggest lifting the weight explosively on the concentric phase of the rep. Now, taking into account what I said above, I don’t mean lift the weight like you’re trying to set the new land-speed record. You can lift explosively yet under control, taking a couple of seconds to get the weight up. As your set progresses, your concentric speed will slow because you’re nearing failure.
Pause and Hold
Next, when you reach the fully stretched position, pause and hold the weight for a 4 count. This should be just before the bar returns to your start position. It’s generally believed that this approach is very effective for mTOR activation, and of course, this stimulates protein synthesis.
Negative Emphasis
From there, I suggest a slow and controlled motion on the eccentric phase. This of course takes advantage of negative emphasis, a principle dating back to Arthur Jones (maybe further). Jones and especially Mike Mentzer (and later Mr. Olympia Dorian Yates) made this concept very popular. In fact Mentzer still has followers that to this day strictly adhere to his principles.
What About Rep Tempo?
So, with all this in mind, here’s your tempo: 2-4-4. That’s a 2-second concentric, 4-second pause in the fully stretched bottom position, and a 4-second eccentric. (1, 2, 3)
Other Considerations
Other considerations of rep performance include using a full range of motion. You might think that’s common sense, yet I can’t tell you how often I see lifters in the gym using half or quarter reps (some even less). Of course, these people are not really serious, and are just going through the motions. And again, I can’t emphasize enough to not rush your reps. I see that all the time too, lifters whipping out reps like a speed demon. Focus on what you’re doing!
Finally, I strongly advocate using progressive overload. While you can utilize several methods to achieve this, I advocate adding weight to the bar. Some say add a small amount of weight every week. I lean more toward the idea of adding 5% on upper body exercises, 10% on legs when you can do 2 reps over your goal rep number for 2 workouts in a row (the 2 x 2 rule). Once you’ve reached your natural strength limit, you can then explore other avenues of progression.
Nutritional Guidelines
By this time, regular readers know what I’m going to suggest. I advocate at least 1 gram of protein per pound of bodyweight evenly spaced throughout the day (for convenience). I also advocate eating 50% of the day’s carbs (and all of the day’s simple carbs) in the hours around your workout. This should be the case even if you’re following a lower carb diet.
Supplement Suggestions
Since I’m suggesting consuming all your simple carbs in the hours before and after your workout, that includes your post-workout shake. I suggest a protein powder, such as Hi-Tech Precision Protein, with some fruit mixed in. This should be your last “meal” that includes simple carbs. From there, I suggest a good pre-workout, such as Alpha Supps Pre, which is a great example of the new “Core” or “Base” type of pre-workout – streamlined yet effective and priced right. Next up, I advise adding creatine, such as Bucked Up Creatine Gummy Bucks (they’re delicious!). Finally, there’s quite a few supplement categories I haven’t mentioned, so take some time and shop illpumpyouup.com and check out all we have to offer!
Summary
In this article on mechanical tension, I covered the definition and importance of this fascinating concept. I also presented in great detail the ideal rep performance to optimize it. Finally, I gave you nutritional guidelines and supplement suggestions. Since this is the ticket to new gains, I suggest you take the tips and info presented here and run with it! See you in the gym!
References:
- Resistance exercise initiates mechanistic target of rapamycin (mTOR) translocation and protein complex co-localisation in human skeletal muscle | Scientific Reports (nature.com)
- Cheng, J., & Du, J. (2007). Mechanical stretch simulates proliferation of venous smooth muscle cells through activation of the insulin-like growth factor-1 receptor. Arteriosclerosis, thrombosis, and vascular biology, 27(8), 1744–1751.
- Morton, R. W., Oikawa, S. Y., Wavell, C. G., Mazara, N., McGlory, C., Quadrilatero, J., Baechler, B. L., Baker, S. K., & Phillips, S. M. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. Journal of applied physiology (Bethesda, Md.: 1985), 121(1), 129–138. https://doi.org/10.1152/japplphysiol.00154.2016