The science behind muscle growth: 5 myths debunked by 435 studies

Your muscles grow faster through knowledge

Myth 1: More muscle soreness means more muscle growth

The truth: Muscle soreness has no direct relationship with muscle growth (but it does give you important information).

This is probably the most widespread myth in the fitness world. Many athletes think they've only trained properly if they're sore the next day. "No pain, no gain" sounds tough, but it's not correct.

What is muscle soreness actually?

Muscle soreness is one of the sensations of muscle damage. Just like reduced strength generation due to decreased muscle fiber activation is also a consequence of muscle damage. But here's where it gets interesting: muscle damage costs the body unnecessarily high amounts of energy and proteins for repair.

The Repeated Bout Effect

Your body is smarter than you think. After a few training sessions, the so-called "repeated bout effect" occurs. This means that the amount of muscle soreness (and muscle damage) per training session decreases. Usually, you have the most severe soreness reaction at the beginning of a new program, but subsequent training sessions are accompanied by less muscle soreness.

Does this mean you're training less hard? Absolutely not. Your body simply becomes more efficient. Those proteins that can be saved by protecting the muscles from damage can be used elsewhere - for example, for extra muscle mass.

Practical application

Stop chasing extreme muscle soreness, but do aim for a little soreness the day after your workout. This signal tells you that the trained muscles received an effective muscle growth stimulus. This way, as many proteins and energy as possible remain available to build extra muscle mass, instead of being used to repair unnecessary damage.

Focus further on:

• Progressive overload - gradually increase weight, sets, or repetitions

• Stimulating repetitions - the last 5 repetitions of each set where all muscle fibers are active

• Consistency - regular training gives better results than sporadic 'killing yourself'

Myth 2: More protein means more muscle growth

The truth: 1.6 to 2.0 grams per kilogram body weight is more than sufficient for 95% of athletes.

The supplement industry tells us we need mountains of protein. The more, the better. But science tells a different story.

The magic numbers

After analyzing dozens of studies, the largest meta-analysis concludes 1.6 to 2.2 grams of protein per kilogram body weight per day. For someone weighing 80 kilograms, this means 128 to 176 grams of protein per day.

But why that range of 0.6 grams difference? A meta-analysis compares multiple studies, and each study has a different setup and different test subjects. For the average strength athlete, this isn't set in stone.

Think per meal

More important than the daily total is how you distribute it. The advice is approximately 0.4 grams per kilogram body weight per meal to make muscle protein synthesis work as effectively as possible. With four meals, you reach exactly the suggested 1.6 g/kg/day.

The 20-gram myth debunked

You often hear: "Everything above 20 grams of protein per meal isn't used for muscle building." This isn't correct. These studies looked at fast protein sources like whey protein. Whey is absorbed at about 10 grams per hour, so 20 grams is absorbed in two hours.

But what about whole foods? Absorbing 20 grams of protein from cooked eggs takes about seven hours. This slower absorption rate means that probably fewer proteins are used for other purposes than muscle building.

Practical application

• Start with 1.6 grams per kilogram body weight and evaluate your results

• Distribute over, for example, 4 meals of approximately 0.4 grams per kilogram per meal

• Choose whole food sources over supplements where possible (due to additional nutrients like fiber, vitamins, and minerals. Protein supplements aren't bad, by the way, so if a protein shake is more practically convenient, that's perfectly fine)

• Calculate in grams, not percentages of your total calories

Disclaimer: Never change your entire nutrition plan independently. Make an appointment with a dietitian for better guidance and advice.

Myth 3: Men's muscles grow faster than women's

The truth: Relatively, muscles grow equally fast; absolutely, more grows in men.

This is a perfect demonstration of how statistics can be misleading. The nuance lies in the difference between relative and absolute growth.

The numbers

Men have on average 30-40% more muscle mass than women. They also have 10-15 times as much testosterone. This sounds like men build muscle much faster, but despite these differences, men and women respond almost identically to a training stimulus.

Relative vs absolute

The muscle tissue of men and women responds approximately the same percentage-wise to an effective training program, but in absolute grams, muscle mass increases more in men.

Example: Suppose a man's muscle mass weight is 56 kilograms and a woman's is 40 kilograms. If both achieve 10% muscle growth, the man gains 5.6 kilograms and the woman gains 4 kilograms. Absolutely, there's a difference of 1.6 kilograms, despite both growing the same percentage.

Why this difference?

Besides the hormonal difference, men generally have a larger surface area of type II muscle fibers (the growth-rich fibers) than women. Women have a larger proportion of type I muscle fibers, making them more fatigue-resistant.

Practical application

For women:

• Don't expect the same absolute numbers as men, but expect the same relative progress

• Focus extra on the upper body, where the difference is greatest

• Use the same training methods - they work equally effectively

For men:

• Realize that women have to work harder for the same visual result

• The same training philosophy works for both genders

Myth 4: People over 60 cannot build muscle mass

The truth: Muscle building is possible at any age, but it does become more difficult.

This myth is not only wrong but also dangerous. It causes older adults to stop strength training, while this is precisely essential for good quality of life.

What happens with age?

Yes, muscle mass peaks between your 20th and 40th year and decreases thereafter by about 0.5% per year. From the 50th year, that goes toward 1-2% per year. But this doesn't mean growth becomes impossible.

The solution: more protein

The body responds less well to protein as you age. Total protein synthesis gradually decreases. But there's a way to partially solve this problem: by consuming more protein and specifically more leucine.

The advice differs by age:

• Younger people: 0.4 grams protein per kilogram body weight per meal

• Older people: up to 0.6 grams per kilogram body weight per meal

Strength training as 'magic pill'

Strength and conditioning training can be the so-called magic pill for aging. By continuing to train:

• You stay more mobile and coordination improves

• Your fitness stays better maintained

• There are many cognitive benefits

• The chance of diseases and conditions decreases

Practical application

For 60-plus:

• Increase your protein intake to 0.6 grams per kilogram per meal

• Stay consistently strength training - it still works

• Focus on functional strength for daily activities

• See training as an investment in your quality of life, not just appearance

Myth 5: Advanced training methods create more muscle growth

The truth: It's about stimulating repetitions, not fancy techniques.

Forced reps, drop sets, compound sets - the fitness world is full of advanced techniques that promise better results. But science shows that it ultimately comes down to one thing: the total number of stimulating repetitions.

What are stimulating repetitions?

According to Beardsley's hypothesis, each set has approximately 5 stimulating repetitions. These are the repetitions where all muscle fibers are active and the speed is slow due to either external resistance or fatigue. These are usually the last 5 repetitions per set.

The calculation example

Suppose you want to do a total of 20 stimulating repetitions for a muscle group. You can achieve this in different ways:

• 4 sets to muscle failure (4 × 5 stimulating repetitions)

• 5 sets to 1 repetition before muscle failure (5 × 4 stimulating repetitions)

• 20 sets to 4 repetitions before muscle failure (20 × 1 stimulating repetition)

The conclusion? If you're too easy on yourself, you need 20 sets to do as many effective repetitions as 4 sets to muscle failure. Do you ever do 20 sets? Probably not.

Advanced techniques vs basics

Drop sets, forced reps, and other techniques can help achieve more stimulating repetitions. But they're not magical. If you achieve the same number of stimulating repetitions with regular sets, the end result is the same.

The advantage of techniques like drop sets is that you can do more stimulating repetitions in less time. The disadvantage is that they often cause more fatigue and require longer recovery.

Practical application

• Focus on the basics: train to 1-3 repetitions before muscle failure (pro tip: this is even more effective for muscle growth than training every set to muscle failure)

• Master the concept of stimulating repetitions before using fancy techniques

• Use advanced techniques as time-saving tools or to make your training more enjoyable, not as miracle cures

The Core: Training with knowledge accelerates your growth

Ultimately, it comes down to a simple truth (simplified in this article): successfully building muscle revolves around smart choices, not chasing extremes.

The real success factors for muscle growth:

• Stimulating repetitions - Train to 1-3 repetitions before muscle failure

• Adequate protein intake - 1.6-2.0 grams per kilogram body weight

• Consistency - Regular training without interruptions

• Progressive overload - Gradual increase in training intensity

• Patience - Muscle growth is a slow process for everyone

How many sets should you do per muscle group? That's different for everyone. Aim for a little muscle soreness. Once you know where this starting point lies per muscle group, your progressive overload adventure begins there!

Stop with myths, start with science

Chasing muscle soreness, chugging protein shakes, looking for the latest training trick - it only keeps you busy. The basics work. Period.

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About the author: Sander Kers earned his Master's in Human Movement Sciences at the Vrije Universiteit of Amsterdam. As a movement scientist, author of two bestsellers, and host of the Dutch "Serious about Fitness" podcast, he has been helping people achieve their goals for 15+ years.

References

[1] Morton, R.W., Murphy, K.T., McKellar, S.R., Schoenfeld, B.J., Henselmans, M., Helms, E., …, Phillips, S.M. (2018). A systematic review, meta-analysis and meta-regression on the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Journal of Sports Medicine, 52(6), 376-384.

[2] Moore, D.R., Churchward-Venne, T.A., Witard, O., Breen, L., Burd, N.A., Tipton, K.D., Phillips, S.M. (2015). Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. The Journals of Gerontology Series A, 70(1), 57-62.

[3] Schoenfeld, B.J., & Aragon, A.A. (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15, 10.

[4-24] [Additional references as listed in the original Dutch version]