This has already been covered recently on the "Serious relationship with strong women" thread adjacent to this one.
The short answer is No.
If it were that easy, we'd all be doing it. I tried dating sites a long time ago, and while I met a lot of women, none were muscular, and it wasn't for lack of trying. Your first issue is just identifying one. It's not a simple checkbox. You're going to have to search through women that claim to lift, say they're athletic/toned, or do keyword searches like "bodybuilder." Care to guess what you get if you do that search? A couple of regular women that are looking for a male bodybuilder, and if you're lucky an FBB or two who are likely to be more than five hundred miles away. The vast majority of women that go to the gym and consider themselves sporty aren't muscular. You're going to have to wade through a lot of profiles, and the only way to be sure is by looking at their pictures.
That's not to say muscular women, including genuine FBB's, don't exist on dating sites, but they're rare, even in a populous area like where I live. My guess? If they've even tried them, they don't last long before pulling their profile. A lot of regular women can't stand the parade of clowns, let alone the extra special comments muscular women have to endure.
But let's say you do find a couple and write them? For a bunch of reasons, they might automatically eliminate you. Don't like your picture, height, politics, job/income, distance away, and in your case age. You're 18 or 19? Not a lot of age appropriate muscular women that would match you. Remember, it's not your preferences that count, it's theirs. Make it through the first ten seconds, and maybe they'll read your message.
A lot women get bombarded by men. Most of them don't have much to say. Unless there's something about your profile that catches her eye, a two sentence solicitation isn't going to cut it. I was pretty good at this part, but it's work. You've got to read and address what they've said in their profile. Not the easiest task when they've only written two sentences. Doesn't seem fair, but that's your problem.
Lucky enough to get a response that doesn't say, "You seem like a nice guy, but...?" Then there's usually a few more exchanges, followed by the phone call, and then the first date. You can fail at any point in the process before you can say she's your girlfriend. It's been done, but unless there's something extraordinary about you, odds of hooking up with a woman that uncommon on a dating site are astronomical.
I'm not telling you not to try it. But if you do, the best way to approach it is to be open to other types of women. Two reasons: At best, a muscular dream girl within a realistic distance and age range might only pop up a few times a year. If that's the only time you ever attempt to make a connection, you're probably going to fall on your face because you don't have any practice. The other reason is that you might run into somebody you're attracted to that's strong in a different way than you've got in mind, and things might end up better for you. It's the same advice I'd give if you were trying to date women in other venues. You don't want to date women you know won't work out (no pun intended) and string them along, but your parameters shouldn't be too narrow.
Good luck!