At first you might think that all black workout pants are the interchangeable. Or that you can just get a pair for $20 because it doesn’t matter. Then, you’ll go for a run in what you thought were snug leggings and spent the whole run pulling them up. Or go to barre class thinking your cotton pants were a great idea, until you were on your back, in happy baby with your undercarriage on display for all to see.

There’s a reason I have 20 different pairs of workout pants. Different cuts and materials and features work for different things. And some don’t work for anything but watching TV. Here, let me break it down for you:

First some quick terminology.

PANTS: are usually for hiking, lounging, or yoga/barre/studio. They go to your ankles and are loose at least in one place.

YOGA PANTS are yoga pants. You know what they look like. Tight, crotch-showing stretchy things with a little flare leg. They’re sexy. They move with you. They’re girlie. Watch out for the flares when you’re working on machines or doing drills. Not the best for running, because you get air up your leg and the flares can get dirty.

LEGGINGS or TIGHTS are exactly what they sound like. To the ankle. And on the skin. Pros: they are definitely an “I’m serious about this workout” look. And they don’t get in the way. Cons: warmer. And there’s no hiding your shape. It’s very “Here’s what I look like. Let’s all just deal with it.” Although they’re helpful for winter walking because you can just tuck em right into your boots.

CAPRIS are any kind of pant that hits below the knee and above the ankle. My favorite cut because they cover my thighs but aren’t as warm as something that goes to the ankle. Pretty flattering for everyone. And they don’t get in the way.

KNICKERS: are pants or capri-type objects that stop around the knee. Think football pants. It mind seem kind of nitpicky to call something knickers and something else capris, but I do have two pairs that definitely are knickers, not capris, and there is a difference. As far as I can tell, the only place it would matter is in trapeze or something where you need knee protection.  (Trapeze is totally fun and not as hard as it looks, btw.) Knickers are good, simple, athletic, I’m ready to go, coach, a little less everywoman than capris, let’s kick some ass pants.

FOLD-OVER WAIST: If you’re pear-shaped like me, or any shape that has a smaller waist, these are useless. The waistband will just unfold/ roll up and be bunchy and weird. Even if you low-ride them so they stay around your hips, you’ve got muffin-top potential, and another layer of fabric to make a weird shape exactly where you don’t need it. PLUS, why do we want another pattern going on? They’re for skinny 15 year olds who wear jog bras as shirts.

SKORTS: are awkward and embarrassing for everyone. Unless they’re for biking, then they’re kind of cute. Infinitely cuter than just bike shorts. That being said, Athleta has these little ruffle-bottom ones for working out that aren’t golf-y at all, so times are a changing. But a less confused-choice is the TWO-IN-ONE: which is a pair of leggings or capris with a skirt attached. All the benefits of leggings plus a little coverage. And they look more like clothes if you have to run to the store or something.

SHORTS: I don’t deal in. Go find a skinny person and ask her. But those Nike tempo running shorts are pretty popular so they must not ride up too much? All shorts ride up on me because my thighs overlap like a venn diagram.

HOT PANTS/ BOY SHORTS: I’m about 40 pounds away from those being appropriate so, ditto. But I have to say, these are getting more mainstream by the second. So, get used to seeing girls working out in basically underwear, I guess.

NOW onto the what pants to wear for what.

RUNNING

RUNNING is fricking hard, so wear whatever you want, you viking woman, you. Just don’t wear a Tutu, please. You can wear lots of stuff to run. Running pants / leggings / capris / knickers / or even shorts. But the more you do it, the pickier you’re going to get. Which is good. At that point, you’re going to want to remember these three words:  Wicking. Tight. and High. (or WTH)

WICKING. Why? No matter what the season, you need your legs to breathe. Even thermal running tights should be breathable. Even wind-proof pants should allow moisture to escape. That means no cotton. As they say in marathon training, “Cotton is rotten.” For socks, tops, and yes, your pants. Cotton shows sweat. And if it shows sweat, that means it doesn’t wick the sweat off of your skin and into the air, so you’re running in damp clothes. Which can get heavy and sag, can make you cold, and can chafe.

TIGHT Running leggings/capris whatevers should be tight. Tighter than you would normally go for a gym workout. I’m not saying get a size too small, I’m saying look for “performance fit” or “tight fit.” Tight pants are like jog bras for your leg muscles (or in my case, saddlebags) and they also won’t fall down. “Pro” type tight pants or compression pants actually squeeze your muscles a bit for better circulation, support, and supposedly performance.

HIGH Running pants often come with a higher waist. They’re not trying to make you look gross. The higher waist is, again, so they don’t fall down. If there’s a drawstring, even better.  And yeah, if you wear shorts, the high slits on the sides or running shorts are there so they don’t ride up as you stride.

YOGA

YOGA : Remember these three things: Breathe. Bend. Butt.

BREATHE I would rather not workout than workout with visible butt sweat, so I’m all for breatheable tech fabrics and against cotton. If it’s bikram, you’re going to be dripping within five minutes (not exaggerating) so I guess you can do what you want. But tech stuff is still more comfortable. Also, in bikram you can go tighter than normal, because everything will get soaked and then stretch and sag.

BEND You need enough stretch or bagginess to accommodate deep lunges, and you don’t want to have to hike your pants up every time you do one. That’s why harem pants are kind of popular for yoga, as well as tight pants. Duh. But you also don’t want to show any crack, so…think twice about how low cut you want to go. And for shirts, something form fitting, or at least snug at the bottom will keep your shirt from going up around your face in downward dog and inversions. If you wouldn’t do a cartwheel in it, it won’t work for yoga.

BUTT Remember the see-through LuluLemon pant scandal? Well, let me tell you, all pants are see-through unless they’re not. Touch the floor and stick that ass out to make sure you can’t see anything before you buy. I’ve read the word “PINK” through some someone else’s seemingly innocent an opaque yoga pants in class. It’s not the end of the world, but it’s not exactly pro either. Also, look for sheen. Stretch the fabric horizontally and see what happens. Most companies are using black elastic thread now, which helps, but you don’t want stuff to get too shiny when it stretches because that can look see-through, too.

 STUDIO / BARRE

STUDIO / BARRE: think “Little In The Middle”

Wear whatever cut you like. But don’t go baggy in the hip or torso because your instructors need to be able to see your form. Don’t worry about your belly. You have to start somewhere, and your “corset” will never shrink if you’re hiding bad form underneath a baggy shirt. Know that you will be doing “happy baby” and have your legs up in the air with your ass out for all to see. There’s a reason people wear dark, long pants.

GYM / CROSS FIT / BOXING

There’s a little more leeway here depending on what you’re doing. Wear whatever makes you feel tough and strong. Go in there feeling like a superhero.  But something too floppy will get in the way of the equipment or your jabs. (So no capes, I guess). Especially in crossfit. It’s hard enough to do a box jump without having to worry about tripping on your own pant leg. Apparently high socks are a thing, too. I’m sure there’s a function…I’ll find out. Oh, here you go: Katy from GonePaleo explains crossfit gear well:

http://occasionalfaileo.wordpress.com/2013/06/19/crossfit-outfits-explained/

 SPIN

SPIN I shouldn’t have to tell you this, but watch out for yoga pants or anything with a wide leg. They could get caught. Go slim cut or go short. And bring a towel for eff’s sake. Gross. I’m not that serious about spin, but if you are, here’s a good article on good spin pants from Well and Good.

http://www.wellandgoodnyc.com/2010/11/08/this-is-your-crotch-on-spinning/

So there you have it. Happy shopping. I hope you don’t waste your money on cheap, see-through, butt-sweat showing pants, and you enjoy your new power outfits.