And if you don't fall into one (or all) of those categories, going to a yoga class for the first time can be pretty intimidating.
Thankfully though, there's a revolution brewing in the world of yoga.
The activity is becoming far more inclusive, with more plus-size yogis striking a tree pose next to the yummy mummies and fitness fanatics than ever.
Don't believe us? Check out the amazing pictures on Instagram. (They're all hashtagged #PlusSizeYoga.)
Back in 2008, Dianne Bondy wrote a blog post that went viral titled Yoga: Not Just For Young, Skinny, White Girls.
In the piece, she said: "Yes, there is a Yogi stereotype and it makes me cringe. Where do I fit in? Can a size 14 black woman fit in among what the media has created as the ultimate yoga beauty standard?
"What about yoga for the rest of us? What about the non-white, size 14, over 35 year old woman, who can’t fit into anything Lululemon (well maybe the headband)?
"Whenever people meet me and I tell them I do yoga they seem shocked and even judgmental about my size. Then I kick up into handstand and I say: take that."
Following the success of her post, Bondy founded yogasteya.com - a place where anyone of any age, shape or size can practice yoga.
And Bondy isn't the only one championing yoga for all.
Michele Pernetta brought Bikram yoga to London in 1994. She's since set up Fierce Grace - a yoga system who's manifesto includes phrases like "yoga is not about perfecting a pose", "yoga is not about being flexible" and "yoga is about being happy".
Speaking to HuffPost UK Lifestyle, Pernetta explains why she thinks the current marketing around most yoga is wrong.
"Yoga is the most inclusive form of exercising. Yes later on it can be about mind and breath control, meditation and energetic awareness, but that comes later, and most people take it up for fitness and health reasons," she says.
"So that is a reason not to use these 'relaxing aspirational images' but images of people sweating, muscly, overweight, old, unattractive."
In reality, yoga is the great equaliser - a slim flexible person feels a similar challenge to a stiff person who may be a bit out of shape.
"The only difference is the former has to go a lot deeper in the pose to feel that great opening, that cathartic stretch, and the newer, stiffer person finds that place just a few inches into the pose," Pernetta adds.
"If yoga is just the human body finding its limits and stretching and breathing into those limits, then it makes no difference if you are 100lbs and 20 years old, or 250lbs and 60. Everyone has the same challenge and the same enjoyment."
Pernetta tells us that with many most sports, such as running, heavy weights or cycling, there's a risk of causing cause wear and tear on the joints.
But yoga gets you fit and strong and works on the cardiovascular system while at the same time aligning the joints correctly, resolving postural issues, and creating traction in the joints so they stay healthy.
It also helps beat stress and can help you get a better nights sleep.
With all those benefits, we're glad that yoga is finally becoming accessible for all.