How many reps? The ultimate guide to fast muscle growth

Update: Since publishing this article I’ve written a more complete guide to muscle hypertrophy here, I recommend you go and check that out first and foremost.

One of the most common topics I see debated about on the internet is the repetition parameter. There are many very useful tables and charts out there for determining the right repetition range for your specific goal. This article assumes that your primary goal is muscle hypertrophy.

To put it simply, as a rule of thumb, to support your goal of muscle hypertrophy, you need to go above and beyond what your muscles feel comfortable doing in any given workout, and you need to get a combination of enhanced blood flow through the muscle, and the accumulation of lactic acid. I’ll explain the science of why this is the case in a couple of paragraphs.

That moment at the end of a set, after about 10 or so reps, when you squeeze out another two or three extra reps, is where you will best stimulate muscle growth. What separates the big guys from the small guys (apart from calories and creatine, obviously, but that’s another story) is that drive to squeeze out the extra repetition or two that seem almost impossible at the end of a set.

The big picture to have in your head is that the complete exhaustion of the muscle tissue in each set spurs a response from the body to repair and improve the muscle tissue.

When smashing out a set of any lift, the muscles working the action get a locally increased blood flow, so the cells of the muscle tissue can receive more oxygen and nutrients, and transport away any waste products. This increases the amount of blood plasma surrounding the muscle cells.

During the work, and especially towards the end of a set, lactic acid and other chemicals accumulate, which combined with the increase blood plasma around the cells creates a gradient between the muscle tissue and the blood, causing the cells to suck water from the blood, through a process called osmosis (similar to how a vacuum cleaner works). We call this phenomenon of increasing the muscle cell volume the “pump”, and it’s why your muscles look bigger after a difficult set :-)

A lot of further chemistry happens at this point, which isn’t completely necessary to understand, but I would suggest to the more academically curious among you search for “muscle sodium gradient” on Google. Men and women who have many years of academic experience in this area have written detailed articles and papers on the specific chemistry, and they’re easily found in the search engines.

The result of the complicated chemical exchange mentioned above is a sodium gradient across the cell membrane (the outside limit, or “fence” of the muscle cell), which in turn results in amino acid uptake, the key to protein synthesis = muscle tissue growth. Of the amino acids, the branched chain amino acid leucine is by far the most important for triggering protein synthesis.

So you see, as long as there is an adequate intake of protein before and after the workout, the extra-hard work we put in for those final repetitions is the best way to turn on protein synthesis and muscle growth. Placing a volumised (pumped) cell under high mechanical tension for a sufficient amount of time directly increase protein synthesis (study for the curious).

To reiterate the points at the beginning, the way we can apply this to our workouts to enhance muscle hypertrophy is to go for high reps, squeezing out those last one or two reps. Lactic acid is your friend! Time under tension builds bigger muscles.

Example chest workout:

  • Bench press, 4 pyramid sets working up in weight to a max, 1 minute rest, then one burnout set for 20+ reps
  • Lying dumbbell flies, 3 sets of 12+ reps, 1 min rest

Nutrition: a meal of brown rice, broccoli, and a glass of whole milk before the workout. During and after the workout, 10g of a BCAA supplement mixed with cordial or diluting juice. After the workout, a meal of beef mince, boiled pasta, and white mushrooms.

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