Male and Female Strength and Muscle Growth: Do Men and Women Gain the Same?

Male and female muscles get bigger and stronger by lifting weights. But is it harder for women to build muscle? Do males have more muscle mass than women? Those are just two questions we’ll answer in this article.


Male and Female Muscle: Similar but Different

Men and women have many things in common. However, subtle but important things separate us when it comes to building muscle.

Many things have a say in how much muscle you can gain and how fast. Anabolic hormones and enzymes in our muscles tell our bodies to flip the switch and add muscle mass. Lifting weights increase muscle gain and muscle breakdown, and when the gain is larger than the breakdown over time, your muscles grow bigger and stronger.

Males and females are quite different in some of these areas, and many people probably think that the advantage is in the male corner. The weights don’t care about your sex, though. We all benefit from strength training. We get bigger and stronger, and healthier.

Is it a myth that females have a harder time gaining muscle mass and strength, or can you expect to gain the same regardless of your sex?

Male and Female Muscle Differences

Contrary to popular belief, you would be hard-pressed to find any differences in muscle protein synthesis rates between men and women. We build muscle at the same rate when we are at rest. The same goes for the post-exercise period after a gym session. Both training and protein-rich feedings stimulate our muscle protein synthesis similarly.1

Our basal muscle protein synthesis is not the only thing determining the rate at which we build muscle over time. Neither is what happens right after you lift weights or eat. Looking at the amount of new muscle tissue created by an intense strength training session, there are no significant sex differences.2 3

female muscle growth

A single study stands out from the others. In that study, the scientists saw higher muscle protein synthesis rates in women.4 However, that’s the only time anyone has shown this. You can assume that men and women respond to strength training the same way.

After a strength training session, you build about 50% more muscle compared to normal for several hours. 5 That’s without any meal before or after the training session. If you eat some protein after your workout, you increase the muscle-building effect dramatically. There are no sex differences there either, though.6

Do males have more muscle mass than females?

The answer to that question is yes. On average, women have less total muscle mass than men, both in absolute and relative terms. The differences in muscle mass between the sexes appear sometime during puberty and remain throughout our lives.

Both men and women gain muscle mass through long-term strength training, regardless of age. 7 Men gain more than twice the total amount of muscle mass from heavy strength training than women.8

Male and Female Muscle Growth

However, keep in mind that women have less muscle mass to begin with. If you consider that, women gain just as much muscle as men.9 10

A large-scale study with 585 subjects, 58% of which were women, did not find any sex differences in relative muscle mass after 12 weeks of biceps curls.11

Biceps muscle growth rate

These findings might sound like either good news or bad news, depending on your training goals.

Many women don’t want to become as muscular as a man. If that’s you, don’t worry. You won’t wake up one day looking like a bodybuilder. That takes years of hard work and dedication. Females can’t develop as large muscles as males.

One study found that the biceps of competitive male bodybuilders were twice as large as those of competitive female bodybuilders after years of training.12 Also, the male bodybuilders had a larger number of muscle fibers, meaning more building material to start with. Your muscle fibers increase in size when you lift weights, not in numbers. This means that females can’t catch up, everything else being equal.

If you want to gain a lot of muscle as a woman, you can. At least if you have the genes for it. Genetics and what you do inside and outside the gym are what’s important, not your sex.

In conclusion:

  • Women respond to strength training just as well as men and gain just as much muscle, relative to how much muscle mass they started with.
  • Females do not have as much muscle mass, to begin with. This means that, in absolute terms, men gain more muscle mass from strength training, expressed as kg or lbs of body weight.
  • Testosterone likely explains a large part of any differences in muscle mass gains. Even though strength training’s acute effects are not dependent on hormones, you will gain more muscle mass in the long run with higher testosterone levels.

And speaking of testosterone…

Male and Female Hormones

Hormones control the size of your muscles, telling your body to break them down or grow them bigger. The most well-known of these is probably the male sex hormone testosterone. Testosterone helps regulate both muscle protein synthesis and muscle protein breakdown. If you have a lot of testosterone, you likely also have more muscle mass and strength and less body fat. 13

Men have about 10 times more testosterone than women.14 It’s easy to assume that it is much easier for men to gain muscle mass because of that.

However, female sex hormones also help build muscle.

  • Estrogen builds muscle and prevents muscle breakdown. This has been documented in several studies.15
  • Progesterone stimulates muscle protein synthesis just as musch as testosterone.16

Most people associate testosterone with strength and big muscles. You probably don’t think of female sex hormones when you think about gaining muscle. However, those hormones help women gain as much muscle as men when they lift weights, even though their testosterone levels are far lower.

You might be able to use these hormones to boost your training. Females have access to a form of natural “doping” called the menstrual cycle. Throughout the menstrual cycle, your hormone balance shifts dramatically. During the first two weeks, the cycle is dominated by estrogen. A recent meta-analysis found the scientific evidence too weak for any definite conclusions. Still, some studies show that you can gain more muscle from strength training during the first two weeks of the menstrual cycle. Go heavy and hard when you have the help of your hormones.17 18

Also, there seems to be a relationship between growth factors like IGF-1 and strength and muscle mass in females.19 That’s not the case for men. Women also produce up to 80 times more growth hormone than men.20

In summary, testosterone might be the more well-known anabolic hormone, but females have several other hormonal advantages for building muscle.

Male and Female Age Differences

When you get older, male and female muscle differences start to appear. Getting old, in general, means less muscle mass. You don’t build as much muscle when you eat protein like you did when you were younger. Men are at an advantage here, as this process happens faster for women.

However, basal muscle protein synthesis rates in elderly females are higher than those in age-matched males. In other words, older women build more muscle tissue 24/7 than older men do. This is likely because males have been exposed to high testosterone levels their entire life. Testosterone might be anabolic per se, but a lifetime of male testosterone levels diminish the anabolic sensitivity to the hormone.

Despite the higher basal muscle protein synthesis rates in women, females lose significantly more muscle mass than males during the aging process. Several factors influence this difference.

  • An increased rate of muscle protein breakdown.
  • Gene expressions that counteract muscle growth following menopause.
  • A diminished anabolic response to both a protein-rich meal and strength-training sessions post-menopause.

Each meal stimulates muscle protein synthesis less than before menopause.. Each training session results in less new muscle tissue. Older women are at a double disadvantage here compared to men of the same age. That happens because your estrogen levels are lower than they used to be. You don’t have the help of higher testosterone levels, and your previous estrogen advantage that helped you maintain muscle mass is gone.

This sounds worse than it is! There is a medicine to be had, and that medicine is strength training.

When you get older, you don’t build as much muscle from a strength-training session as you once did. However, lifting weights still prevents or at least slow muscle loss. Strength training is essential to maintain muscle mass as you age. By engaging in strength training and keeping most of your muscle mass, you maintain your mobility and quality of life, regardless of sex. This means that strength training is even more important for females than males, once past the age of 60.

Despite this, females are at a disadvantage compared to men when trying to gain muscle mass at an advanced age. Here is where sex differences in the capacity to build and maintain muscle mass become noticeable.21

Strength

Everyone knows that testosterone is important, if not critical, for muscle growth. However, the (in)famous male sex hormone probably plays an even more prominent role if you are training for strength.22 In general, males are stronger than females, in absolute terms. It is easy to think this means an advantage in the gym when it comes to getting stronger.

Lower Body

Females often have similar lower body strength as males. Again, not in absolute terms, but after adjusting for total body mass, the differences go away. More studies compare lower body strength between the sexes than upper body strength.

When women train the same way as men, their strength increases just as much.23 No significant sex differences there, in other words.

Upper Body

Your upper body muscles might have a larger number of anabolic receptors compared to your lower body. Therefore, it seems logical to assume that men, with their 10-fold higher testosterone levels, might respond better to strength training and gain upper body strength faster.

This does not seem to be the case.

In one study, 44 young men and 47 young women performed leg presses, leg curls, chest presses, and lat pulldowns twice a week for 10 weeks.24 Strength tests did not show any differences between males and females. The men improved by 11.61% on average, while the women improved by 11.76%.

These results match those of an earlier study. That study investigated the time course for strength gains following high-intensity strength training. Seventeen young and 20 middle-aged men and women engaged in strength training 3 days per week for 12 weeks.25 Both the males and the females increased their absolute strength similarly in both the upper and lower body. In relation to their total body mass, the females actually had a slight edge.

Let’s Take a Look at a Recent Meta-Analysis

More than 60 studies investigate and compare strength training effects on male and female strength and muscle mass. Up until recently, no meta-analyses or systematic reviews have compiled the results of these studies.

In May 2020, the publication of the meta-analysis Sex Differences in Resistance Training: A Systematic Review and Meta-Analysis fixed that. For the first time, we got a good look at whether males or females gain more muscle mass and strength gains by lifting.26

The results can be broken down into a few highlights:

  • Ten studies with 12 outcomes found that males and females gain muscle mass pretty much at the same rate.
  • The researchers analyzed 17 studies and 19 outcomes and found that females gain upper-body strength a little easier than men.
  • When it comes to lower-body strength, analyzing 23 studies did not reveal any sex differences.
  • Males and females gain just as much muscle mass and lower-body strength by lifting weights. Looking at upper-body strength relative to body size, females actually improve more.

Untrained females might be able to gain upper-body strength faster than untrained males. The available research can’t explain why this difference is only apparent in the upper body. Sex differences in muscular, neural, and motor learning, maybe? Hopefully, future studies will investigate and reveal more. It might even be that the studies are too short for any reliable conclusions.

The More Muscle Mass You Have, the Harder It Is to Gain Even More

When you have been strength training long enough to leave your beginner’s gains behind, additional gains come slower and slower. Over the years, the flood of gains slows down to a trickle.

In this regard, there are no apparent differences between men and women. It becomes harder for all of us to keep making progress. In one study, male and female competitive bodybuilders stopped gaining muscle mass after a certain point. Sooner or later, you will likely find yourself refining and adding quality to your physique rather than quantity. The very experienced bodybuilders did not increase their muscle fiber size after 24 weeks of monitored training in the study.27 They even used anabolic steroids, and they still didn’t gain any more. The capacity for muscle growth definitely decreases the more experienced you get.

In Summary

Contrary to popular belief, females respond just as well as males to weight training. Maybe even better during the beginner’s stage. Despite much lower levels of the anabolic hormone testosterone.

Male testosterone levels allow them to grow a larger total amount of muscle mass naturally. However, this does not mean an easier time gaining muscle and strength in the gym. Several factors, like hormones and genes, control muscle mass and strength. In several instances, these favor females.

In absolute terms, men do build more muscle mass. If you take an 80-kilogram male and a 60-kilogram woman, and they both manage to increase their muscle mass by 10%, the man will have gained more muscle tissue. However, compared to their starting point, females gain similar amounts of muscle as males, as a rule.

Women looking to gain as much muscle as men have to train the same way as men. If you are female and want to gain as much muscle as possible, you have to train to gain. This means high-intensity strength training for years. Plenty of women out there in the gyms train just a hard as any man. At the same time, some women use light weights and don’t challenge themselves when they train. Then they wonder why they don’t see the results they want from all the time they spend in the gym.

Conclusion: Males and Females Aren’t So Different, After All

Despite the fact that men and women are quite different on a physiological level, from hormones to genes, we have one thing in common. We all get more muscular and stronger by hitting the weights. Males develop more muscle mass than females in absolute terms, but in relative terms, female muscle grows just as fast.

References

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  2. Acta Physiol (Oxf). 2010 May;199(1):71-81. Resistance exercise increases leg muscle protein synthesis and mTOR signalling independent of sex.
  3. J Appl Physiol (1985). 2009 Oct;107(4):1308-15. No major sex differences in muscle protein synthesis rates in the postabsorptive state and during hyperinsulinemia-hyperaminoacidemia in middle-aged adults.
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  16. The Journal of Clinical Endocrinology & Metabolism, Volume 99, Issue 1, 1 January 2014, Pages 256–265. Testosterone and Progesterone, But Not Estradiol, Stimulate Muscle Protein Synthesis in Postmenopausal Women.
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