Strength training is one of those activities that men love and women can be afraid of. Men love it because they want muscles like Dwayne "the rock" Johnson and women want The Rock, just not his muscles, so they can be a bit timid when it comes to strength training. Well ladies I am here to tell you that you have nothing to worry about. There are a few reasons why you can lift weights without worrying about waking up looking like the 80s version of Arnold Schwarzenegger.
First: Testosterone is the primary hormone that is responsible for making muscles bigger and women simply don't have enough of it. If you compared a man and woman using your "home testosterone measuring kit" your results, according to the National Institute of Health, would show that men have a testosterone range of 300 to 1,000 ng/dL (nanograms per deciliter) and women only have 20 to 80 ng/dL. If you do a little math you will see that men have 93% more testosterone than women.
Second: The women that you do see that have muscles on top of muscles did not get that way naturally. Women like this have to put extra chemicals in their bodies like human-growth-hormone (HGH), testosterone, and even steroids. The extra testosterone in women has noticeable side effects. Tune to a female body building competition and take a look and listen. You will probably notice that the women don't sound like women (deeper voices) or look like women (breast look more like a man's chest).
Third: To get muscles bigger you have to train a certain way. Women would have to lift extremely heavy and focus on a single muscle group for long periods of time. When training for hypertrophy (bigger muscles) the weights you lift will be so heavy that you will only be able to lift them maybe 5 times before you can do no more. So imagine going through a workout lifting heavy weights, exercising only your pectoralis muscles (chest) and calling it a day after only working out one muscle group. Women on average simply don't train this way and if they do it's because they want big muscles which of course most women do not.
Last: Don't forget that in order for anything on your body to get bigger you have to take in more calories than you burn off. I have been in the health and wellness business for 10 years and I can count on one hand how many times a woman has come to me asking to get bigger. Most women are concerned with keeping their figure slim and not adding weight to it. This means as long as your diet is one that focuses on weight loss or maintenance, getting bigger will not happen.
So ladies please pickup up dumbbells or find a weight lifting machine because unless you mix in some testosterone with your post-workout smoothie, you shouldn't worry getting too big.