I recently wrote about hamstring involvement in squats, and how both the above-parallel and below-parallel squatters are partially right and partially wrong with what they typically have to say on the matter. I'm going to do that again now, but this time on the topic of women's muscles.
So, here's how the discussion typically goes (at least on the bb.com forums).
Newbie: "Hi ladies, I'm new to fitness and need a new program. I'm looking to tone. What toning exercises should I do for my [insert body parts here; probably arms, abs and bum]? How much cardio should I do? I don't want to get all bulked up like a man!"
Veteran: "You can't tone muscles. You can only make them bigger or smaller, and gain or lose fat to change how visible they are. Women don't get bulky like men, that's a myth. Hormones, testosterone, blah blah blah. Starting Strength/NROL/read the stickies. Cardio makes you skinny-fat."
Outside of those forums, I don't want to know how the discussion goes, but from what I've observed the reply is usually full retard, and has something to do with high rep triceps kickbacks, good girl/bad girl machines, and/or yogalates on a bosu.
Okay, so, I'll attack the issue of becoming "too big/bulky/like a man" first. There are a few factors here:
1) Calorie consumption. You might be able to build some muscle mass without a calorie surplus, if you're using the energy stored in your fat to fuel the muscle growth. You don't really have much of a say in the matter of whether or not your body will recomposition itself like this, although if you are lifting heavy on an intelligently designed program with enough protein in your diet, it might happen. In this case you'll be fitter, stronger, perkier, and smaller at the same bodyweight. Most likely, though, you'll either be deliberately gaining weight in the hopes that some of it will be muscle, or losing weight in the hopes that most of it will be fat. For most people after the first 6-12 weeks of training, they will need to be consuming excess calories in order to gain weight and thus gain some muscle mass. Most women are so worried about being small and so fixated on 1200kcal/day diets that this will never happen. Never. Impossible. Forget all other factors -- if you don't eat you don't grow. But if you do happen to gain weight and thus gain muscle, and if it does happen to be more than you'd like to have gained, there's a simple solution: stop eating at a calorie surplus.
2) Hormone profile. Most people speaking in defence of women lifting weights will jump on the issue of women having jack-diddley-squat testosterone first. I feel that calorie consumption is a bigger issue, because you have to consume the calories to gain size. But testosterone will influence whether that size comes in the form of muscle or fat. Women have naturally low testosterone levels which tends to make them have less muscle mass than untrained men when they start out, gain muscle mass at a slower rate than men, and have a lower genetic potential for muscle mass than men.
3) No one gains muscle mass easily. Typically guys will eat at a calorie surplus of 500kcal/day over their maintenance levels, in order to gain about 0.5kg/week. After their first year or two of progressive training, this will typically reward them with a whopping 2.5-5kg new muscle mass per year, maybe even less. That means a lot of bulking and a lot of cutting for fairly small returns. Now refer back to points 1 and 2. Yeah. That's what I thought.
4) Toning rep ranges and exercises. Where did this idea even come from? Low reps bulk and high reps tone? What? No. Low reps build max strength, and high reps build strength endurance. In the presence of a calorie surplus, both will build some muscle mass (to varying degrees depending on the individual). In the presence of a calorie deficit, both will maintain some muscle mass (again, to varying degrees) so that the weight lost is fat. You train the muscles (or the movements that use the muscles), and you eat appropriately for your goals. On a related note, I've noticed over the years that women who don't want to get too bulky have a fitness-media-driven fixation with "lean muscles." "Oh, it's okay, I'm not going to bulk up doing this, because it'll give me lean muscles instead." I'm going to refrain from the bertstare that this sentiment thoroughly deserves for a moment, and inform you that all muscle is lean muscle. "But, what about--" no. All of it. All muscle is lean. If it's not lean, it's not muscle. Okay? Okay.
Your moment is up.
5) As Kyle says, if you did bulk up, would it really be so bad? Having extra muscle mass may or may not be pretty (in my opinion, most girls who have never done any serious strength training before would look a lot better if they did, but what's pretty to me may not always be pretty to you...you know, Eye of the Beholder Beast or whatever), but it will definitely be useful. Needing less assistance to transport your groceries to and from the car, being more capable of picking up your children/pets in your arms, and being able to outrun a cripple are all advantageous traits, and having more muscle mass will greatly enable you to acquire these traits.
Golly, them Beholders are pretty.
Now, onto the people telling you you'll never get bulky. Yes, I realise I'm now one of them after the above spiel, but there are a few misunderstandings that tend to come from the lifting crowd about our dearest newbie.
1) "Lifting a barbell won't make you accidentally wake up looking like this:"
Well, duh. Most people don't want to look like that, sure, but what makes you so certain that our dearest newbie thinks she's going to go from a petite princess to hulkzilla overnight? It's unrealistic, and I suspect even she knows this. However, she might gain 5lb in a couple of weeks, or 10lb over a couple months. This is entirely realistic, and may very well be too much in her eyes. 99.9% of the time, when asking how not to gain too much muscle, people won't tell you what "too much" is, but in a culture that seldom applauds any visible muscle on a woman, it's safe to say that the line between having pretty muscles and too much muscle is usually drawn somewhere before becoming an elite bodybuilder. For a lot of women, the concept of increasing their muscle mass by as little as 10% seems horrifying. I know, strange. But that's their issue, not yours.
2) Her goals are not your goals. This should be obvious, but often it isn't. If you can't comprehend that goals outside of your own exist, then you have no place giving training advice to anyone who doesn't want to be just like you. If you do understand that she has different goals but want to get her doing the same thing as you because you think your goals or your method is inherently better, you also have no place giving advice. I don't claim to be an expert on preparing for a full marathon, but I'm fairly confident that running Starting Strength as it's written with no additional work whatsoever is not the answer.
3) "Cardio makes you skinny-fat." Actually, no it doesn't. If you're completely untrained and deconditioned, cardio will make whatever muscles you use for it bigger. People who do nothing else but walking or running tend to have calves that put my lower legs to shame. If you haven't used a muscle before, and you start using it, it will be inclined to grow (to some extent) in order to accommodate the new activity. However, the extent to which the muscle grows will normally be significantly less if it's used for long distance low intensity activities than if it's used for short, all out efforts (such as sprints or heavy lifting). If you're an experienced lifter and you stop all lifting to do nothing but jogging every day, you probably will lose muscle mass, because weight training is better for building and maintaining muscles than cardio, however the addition of cardio on top of whatever else you've been doing is extremely unlikely to make you lose muscle mass. Now, I'm not saying that our dearest newbie shouldn't lift weights to get the body she's after (assuming that strength training will help with her goal, which it probably will), but there's no good reason to vilify cardio as a training tool, so long as it's used safely and for a sensible purpose.