Female physique examples
Want to know how to build muscle as a woman? The exact same way a man does.
Here are two women with low enough body fat that you can clearly see their muscles:
The first woman is thin (look at the frailness of her arms) and the second woman is fit.
Notice I’m not using the word “toned," which isn’t a thing. When a muscle is exercised, it responds by getting bigger. It can’t stay the same size and just get harder. So when people use the word “toned," they’re referring to the combination of (1) being thin enough that muscle definition is visible and (2) having muscles to begin with.
You might not want to get as muscular as the second woman, but getting just halfway there will still make an enormous difference in your physique.
If you only want to be muscular in certain muscle groups, this program provides a workout plan for only building your arms (biceps and triceps), abs, butt (glutes), and hamstrings. Not sure what those are? Refer to the illustration below:
Women gain muscle as fast as men
Want to know how to build muscle as a woman? The same way men do. Not with body weight, but with heavy weight progression and going to the gym every couple days.
The limiting factor to how big you can get is the broadness of your skeleton (study). So if your body is on the smaller side (e.g. high school teenager), it will be impossible to reach the same maximum muscle mass as someone much bigger than you. In other words, the average woman will ultimately gain less muscle than the average man.
But this doesn't mean women reach their maximum muscle size at a slower rate. In fact, women develop muscle at the same rate as men (study, study, study). (Hat tip to Menno Henselmans for compiling this research.) The difference is that women start with less muscle mass on average and ultimately gain less.
Even if you have an above-average sized frame, don’t be concerned about "accidentally" building lots of muscle too quickly. You’ll notice muscle gains early enough in the process to avoid getting “bulky.”
Yes, men have more testosterone, but testosterone is less important to the female muscle development process. In fact, women benefit from higher levels of IGF1 growth hormone, which is critical to muscle growth (study, study).
While there are fewer muscular women in the world, that’s a reflection of fewer women working to become very muscular — due to societal expectations. It’s not a reflection of it being more difficult for women to actually build muscle. You may have a hard time believing all this, so click on any of those studies to skim the research.
It’s important you understand that you're not at a disadvantage when bodybuilding because thinking otherwise can deter your progress. For example, one study examined the opposite scenario, where men were tricked into thinking they were taking steroids when they weren’t, and they consequently lifted 350% more in weight (study, study)!
This suggests your confidence in the gym plays a critical role in how much you can lift.
So the answer to "How do I build muscle as a woman?" is to overcome your doubt.
Getting a butt
No amount of aerobic activity, yoga, or calisthenics will build your butt ("glutes"). It's all about using heavy weight as per a proper bodybuilding program. Not aerobic bodyweight exercises. Those are a scam when it comes to building muscle mass.
Specifically, the squat exercises you'll be doing are responsible for building glutes.
There's otherwise no secret to training glutes. They respond just like every other muscle — you exercise them with 8-10 reps and use heavier weight each workout.