5 Factors That Determine How Much Your Muscles Will Grow in Response to Strength Training

Strength Training

If you work with weights to build strength or muscle size, you want actual results from the time you put in, and that means greater strength and muscle definition. It’s no secret that one person can develop muscle quickly while another makes much slower progress.

Some males and females have an easier time building muscle than others. Some guys gain as much as 3 pounds of muscle in 4 weeks, while others only gain a pound or two of muscle per month. On average, women gain less than men with an average muscle gain of around 1 pound per month.

Why do some people make faster muscle gains and what are the factors that influence muscle gains? If you know these answers, you can make changes that will help you advance your muscle gains. Let’s look at five factors, supported by science, that affect how much muscle you gain from weight training and why they’re important.

How You Train

You have to work your muscles against resistance to get them to grow. Muscles respond to the stress you place on them. If you challenge them and ask them to lift more weight than they’re accustomed to, they’ll adapt and become stronger. The most important principle you must follow to maximize muscle growth and strength gains is to use progressive overload.

What is progressive overload? It’s forcing your muscles to gradually work harder over time. You do this by increasing the amount of weight your muscles push or pull against, add more repetitions or more sets, increase the number of exercises, train longer, change the tempo, or otherwise alter the stimulus you place on your muscles.

The number one reason muscles fail to grow is people don’t use progressive overload and their training becomes stagnant. However, you shouldn’t increase the resistance or weight you use by over 10% every 2 weeks or so. Too much change too quickly can overload your muscles and increase the risk of injury. Plus, you should always emphasize form over resistance.

Too Little Focus on Diet

Diet matters as much as how you train for building muscle. Unless you supply your muscles with enough protein, carbohydrates, and total energy, you’ll limit your muscle growth. If you weight train, depending on how hard or often you train, you may need double the protein intake of a sedentary person. To gain muscle, get around 1 gram of protein per pound of bodyweight.

It’s also hard to build muscle if you’re restricting calories since calorie restriction sends your body into a catabolic state where you break down muscle. In fact, you’ll need to eat a slight calorie surplus to maximize muscle gains, but if you’re strength training, you’ll gain muscle, not body fat.


Men have ten times the amount of testosterone, an anabolic hormone than women do, and this is one factor in why men gain muscle easier. But don’t let lower testosterone discourage you if you’re a woman. Females can gain significant muscle through regular strength training, too.

How can women make muscle gains despite producing less testosterone? Some research shows that women release more growth hormone with weight training relative to men. Like testosterone, growth hormone is anabolic and boosts muscle growth and fat loss. The greater release of growth hormone in women may explain why women can build muscle despite having low levels of testosterone. One way to maximize growth hormone is to get enough quality sleep. Your brain releases the most growth hormone during the deepest stages of sleep.


Genetics also play a role in how quickly you can build muscle. Textbooks describe three body types: ectomorph, mesomorph, and endomorph. Ectomorphs are naturally slender with little body fat or muscle. These are the people who you might tease for never gaining weight, despite eating an indulgent diet of fast food and junk.

Endomorphs are at the opposite end of the spectrum. They tend to gain weight easily and have a higher percentage of body fat. There’s also the mesomorph, a guy or gal who is naturally muscular. They might have broader shoulders and naturally more pronounced musculature, despite not being active. It’s the mesomorphs who have the easiest time gaining muscle. Their body type is primed to put on more muscle tissue with consistent training.

Next in line is the endomorph. Although endomorphs may have a high body fat percentage, they usually have an easier time building muscle than an ectomorph, the guy or gal who’s naturally skinny. So, you may wish you were the skinny type who can eat anything and not gain weight, but you’ll also have a hard time getting your muscles to pop and may have to eat lots of calories and train hard to see any muscle growth.


Don’t forget about consistency! You’ll never maximize muscle development unless you have a plan and are consistent about executing it. It often takes a dose of patience to see significant muscle gains too. Even if you are consistent, don’t expect to see muscle gains before 4 weeks, and it may take 8 weeks to see the first sign of muscle definition. Strength gains happen faster. You might gain some strength in as little as 2 weeks as you teach your nervous system to recruit the muscles you need to lift a particular weight more efficiently. So, don’t expect change overnight or get inpatient. Good things take time!

The Bottom Line

Now you know what factors help your muscles grow. Take advantage of what you can control – training, diet, and consistency. You have less control over hormones and genetics, but if you get the other three right, you’re golden.


  • com. “When to Increase Your Weightlifting Resistance”
  • org. “Protein Intake for Optimal Muscle Maintenance”
  • Exercise Physiology. Fifth edition. McArdle, Katch, and Katch. 2001.
  • co.uk. “This is How Much Muscle You Can Gain in a Month, According to Experts”
  • com. “Protein Intake — How Much Protein Should You Eat per Day?”


Related Articles:

5 Powerful and Time-Tested Laws of Muscle Growth You Shouldn’t Ignore

Strength Training: 5 Rules for Training to Failure

What Does Research Show about Partial Reps vs. Full Reps for Strength Training?

The Repeated Bout Effect: Why You Don’t Always Get Sore When You Lift Weights

How Your Muscles Repair after a Workout and How It’s Linked with Hypertrophy

Related Cathe Friedrich Workout DVDs:

STS Strength 90 Day Workout Program

All of Cathe’s Strength & Toning Workout DVDs
Total Body Workouts
Lower Body Workouts
Upper Body Workouts

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